Ok so to set minumum air I would need a #20 Torx and to have the car running at normal operating temperature.

Next I need to remove the metal cap that goes on the top of the screw head, but I've tried and had no luck getting it off.

How am I supposed to get it off so I can adjust the screw?

I'm sick and tired of the car idling so incredibly fast, and I know I don't have a vacuum leak anywhere, I've been over the system many many times and havent found any leaks.

I just fixed the TPS...... AGAIN, every now and again it gets out of spec and makes the car idle ridiculously high(~2500-3750RPM) but when it is in spec, the best that I can get the car to idle has been around 1100 and I KNOW that the engine's minimum air is set supposed to be set to 450RPM, and most of the time I idle about 3 times as fast......

I'm getting tired of idle problems.....

 

How did you fix the TPS? That would be the first thing to check.

As for the idle stop, you might need a ***** punch (looks kind of like an awl) and a hammer, seeing as how it hasn't been removed in about 19 years...

 

All I did was take off the torx screws and while the engine was running, based off the sound of the engine(quieter=slower, louder=faster) adjust it to be as quiet as I could, its a new BWD engine management TPS, my old one was making the car surge, but once I got that set to give the best reading and to be right on with the closed throttle plate I replaced the screws.

But I need to find something to get that little cover off, I tried to do it in these blizzard like conditions here in central PA, but after about 5 minutes of toying with it I shut the hood and went back inside. I tried a pair of needle nosed plyers and opened them as far as I could and tried to twist it off but it wouldn't work....

All of a sudden the car decided it wanted to start idling really fast again and when the TPS is out of spec it wants to keep the engine surging on idle, and well it made it stall once, so I just wanted to fix it, and I'm just trying to fix the idle now too while I'm at it.

 

Take the TPS out and bring it in the house to look at under decent light. You'll notice that there are 2 elongated ridges around each of the mounting holes, that look kind of like bananas. You need to remove the plastic in these shapes to make the TPS adjustable. The reason you're idling high with the new TPS is because the ECM is looking for a lower signal than the TPS is putting out (probably around .7VDC instead of the .55 it's supposed to be if it's like my BWD one was). I hope you have a Dremel or something because drilling alone doesn't work too well.

:edit: And no, I don't understand why the 90-92 ECMs do that. They're not supposed to. According to my 92 FSM, the ECM is supposed to accept a steady signal under .96VDC as the idle signal when the engine is first started.

 

You guys do know that the 7730 ecm doesn't need the TPS adjusted, right? They sense the start up position as throttle closed, and base the throttle position off of that voltage. Adjustment of the position does absolutely nothing as it's forgotten the next time you start the car.

 

Like I said:
Had the same problem with the 730 as I do with the 302 needing adjustment. Either way, I've found that more often than not, it's the TPS output causing the high idle on most systems that don't have a vacuum leak or something stuck. That's why I recommend the adjustment, especially if the idle speed can't be set no matter what the person does, potentially setting a code 35 (I think that's the one for "I can't set the idle to 1200 RPM because something is either preventing me from doing so or I am going based on what I see from sensors."). Especially with the problems people have been having lately with their 730 (and late 302 with the later style TPS) systems starting and running about 2700 RPM before they rev the engine and the ECM "accepts" the high signal from the TPS as being the idle signal.

 

I've had to adjust mine numerous times, so yes it does need to be adjusted, and Maverick H1L can back that up.

I'm going to try to get that cap off tomorrow, school has a 2-hr delay aready so that gives me time to try and get it off, if not then I can do it tomorrow afternoon.

 

Yeah, that's why GM redesigned the TPS to be non-adjustable, even though they already had an adjustable TPS on the shelves. Go ahead and knock yourselves out if you think it works, but it's pretty clear that you're compensating for a problem somewhere else. On a stock engine that hasn't been changed you shouldn't have to reset the throttle stop anyway, but hey like I've said before, ignorance is bliss. There's a right way and a wrong way to fix every problem, and adjusting things that are non-adjustable on a stock setup is definitely the wrong way to fix this problem.

 

Well then lets hear what you are proposing, what do you suppose the problem is, I'm not trying to be an *** hole here........

 

... You said it yourself. If he doesn't have any vacuum problems and all that had been replaced recently was the TPS, wouldn't one assume that something isn't right with it, especially if the idle stop screw is still set to FACTORY settings? Or, my minimum air rate is correct, but I replace the TPS and even with the engine at operating temp, running on MINIMUM AIR, the idle speed is still 500+RPM OVER what it should be, and the only thing I've replaced is my TPS, with no vacuum leaks, what would you think was wrong there?

 

At this point I'm willing to try anything, I think to re-adjust the Minimum Air screw as just another thing to try and toy around with and see if I can't at least improve the situation, plus who knows, maybe something got messed up over 20 years from bumps and daily driving conditions, even though I doubt it.....

I just want it to idle at factory speed with out surging to 1250 and then dropping to factory idle speed and then surging again.....its really annoying.....

 

Where are you located in PA? Im in Norristown and I can't ever get mine out of the parking spot, and I have a posi. I got easily 18+ inches of snow.

Also, it kinda sounds like a vacuum leak to me.

 

Montgomery, Pa, its right over the mountain from Williamsport Killert, we got like 7, but we had 3 or 4 still on the ground from before, so we have about a foot or so on the ground.

I have open gears and surprisingly, if I started off in 2nd, I didn't really have problems getting around today, just have to be careful.

I had always thought it was a vacuum leak too, but I've checked all my lines, replaced some, gotten a new MAP sensor, IACV, TPS, Intake Temperature Sensor, had the VSS tested, got new Intake Manifold gaskets installed, top and bottom, adjusted all my sensors numerous times, and asked many many people from all over all about it, and after I've told them all what I've done, they're just as dumb founded as me.

So maybe does anyone else have any ideas on what to do to double, triple, quadruple, what ever time this is......recheck for vacuum leaks?

 

Get a can of carb cleaner (make sure it's flammable) and spray around lines. If the idle changes you found it. And check the EGR gasket, when I was putting mine back together after I cammed it, the EGR valve gasket moved about 1/2 inch and it was a sucking chest wound.

 

Did all that.

 

Brake booster leaking? Throttle body gasket maybe?

 

I bought an intake manifold gasket set which had upper/lower gaskets, plenum gaskets, throttle body gaskets, EGR vavle gaskets and for the flex pipe as well, so all of the gaskets have to be good. They aren't even a year old yet.

As for vacuum lines, in the summer I found some behind the intake that just crumbled in my hand when I touched them and replaced them, and thats when I got the new MAP sensor as well.

Then I traced all of my vaccum lines and cut off the ends of some of the ones that were questionable, and it still did nothing.

Also, I'm pretty sure that I've used a whole can of carb cleaner try to find leaks before, and I check it all the time, so I'm lost....

I don't know where else to look for leaks.......

 

I guess I do have one question about the brake booster, when I step in the brake in Park the idle speed of the engine will increase, but when I release it will surge a bit more and then return to idle speed, is that what I'm looking for?

I've had that vacuum line off many times and inspected it and could find nothing that would raise a red flag to make me think I would have to replace it, so yeah....haha

 

Contrary to popular belief, I don't reply just to hear myself type or to make an *** out of myself. If I reply it's intended to help and inform. Now that that's out of the way...

If the idle is obviously way off, I'd be looking in the same areas, but I wouldn't just start adjusting things that aren't intended to be adjustable. If the idle is high something is wrong. The correct way to fix it is find the problem and fix it, not create another problem. If the TPS has been changed, and suddenly there's a problem, I'd probably start by testing the TPS, and if all else fails I'd probably buy an AC Delco, GM replacement to insure that it's not just faulty discount auto parts.

If I were fighting with an idle problem, I'd start with the IAC. Simply cleaning the IAC and passages, and the throttle body, including the back side of the throttle blade, and behind the throttle blade (carb cleaner and scrub with an old toothbrush), usually cures 90% of MPFI/TPI idle problems. If the car is stock (stock cam, heads, intake) then the factory set position of the throttle stop is going to be close, if not exactly where it should be.

In this case, I'd probably start by doublechecking that by putting the throttle cable on the throttle body lever post intended for the cruise control, and making it tighter to increase throttle response, you aren't accidently keeping the throttle from closing completely. In fact, why don't you disconnect all the cables from the throttle body and see if it idles lower.

 

Check the flex tube for cracks. I've seen a couple have very small cracks, but big enough for a vacuum leak.

 

Thanks for the advice, I'll go out and disconnect all the cable from the throttle body, but I had worse idle problems before I put the throttle cable on the cruise control bracket or whatever, so I don't know.

The car is completely stock, and I have cleaned the throttle plate many many times as best I could, as well as the IACV.

Thanks Killert, I'll check it over again and see if I can't find crack or imperfections or anything.....

ugh....here we go again with trying to find the source of my idle problems....

 

Ok so I just got done finishing up on what you guys told me to do:

Drew, disconnected everything from the throttle body and nothing happened

Maverick H1L: Nail punch worked got the cap off of the screw, but I don't have a torx bit small enough to fit where it needs to go

Killert: Removed the brake line booster and found no cracks anywhere in the assembly

Furthermore: Sprayed carb cleaner all over the engine, every place that I could think of to spray, and nothing changed

So now what, lol.

 

The screw is a T20, IIRC. Mine works with a 1/4" bit on a ratchet.

Sounds to me like it's time to adjust the TPS... Trust me, the ECM will like you better if you do. I guarantee you'll have 3000 RPM running until you step on the gas a couple of times after starting, even with the minimum air rate set properly, unless you adjust the TPS.

 

I might be suggesting something stupid, as you would probably notice and have checked, but check what shape your throttle plate is in, its possible that if it somehow(yes it's highly unlikely, but worth a shot for the 5s it takes to check) got damaged and is missing a chunk of metal, or chipped or something, air could be slipping past it which would have the same effect as it being open more. I figure its something no one mentioned, so worth a shot...And I can't think of anything else =/ Well, actually, maybe your wiring harness for the TPS?

 

Ok, do you have any codes? Are you basing the high idle diagnosis off a factory tachometer? I seem to remember my 3.1 idled at around 1k rpm in park. It was definitely higher then 450rpm in gear. It was closer to 800rpm idling in drive. Do you really have a problem?

Next, adjusting the TPS should not effect idle. The reason that the TPS needs to be adjusted on earlier cars when setting minimum air has nothing to do with the idle, it has to do with the position of the throttle blade changing as you adjust how far open it needs to be to allow the minimum air to enter the engine, which then throws off the tps. However, it doesn't even apply to later cars because the computer doesn't care where the TPS is adjusted. That's why it's not adjustable. The TPS and CTS determine the A/F ratio, not the idle.

Moving on, the IAC controls the idle. The computer opens the valve to let air into the engine as necessary to modulate the throttle and prevent stalls. It operates based on battery voltage, coolant temp, engine load, and engine RPM. Just to clarify, you'll notice throttle position isn't even in that list. If the IAC can't control the idle, it'll set a code 35. Unfortunately on the 3.1 there aren't really any easy ways to test the IAC. If you disconnect the battery, the computer will TRY to relearn the correct position. The same thing happens if you unplug the IAC while the engine is running. The book says it can take 7 minutes for the computer to relearn the proper idle position. In some rare cases, it has to be reset with a special tool called the GM Tech I scan tool. If you haven't already, reset the computer and try letting it relearn. Sometimes it can take a few tries.

You can read all about how the system works in the GM/Helm Service Manual. Flip to page 6E3-C2-1 and start reading. You'll also read other fun facts, like the ECM cuts fuel above 6200rpm, while in gear to prevent engine damage, and above 115mph to keep from damaging tires. It kind of shoots holes in some of the BS that gets posted regularly on this forum. You'll also read that the only time the throttle stop should be adjusted is when installing a new throttle body.

IF the throttle stop is set too far open or closed, it'll cause the IAC to bottom out. It won't even effect the idle if the IAC is within it's operating range.

So I'll say it again... You're putting a bandaid on a virus. It might make you feel better, it might even compensate (for a short time) for the problem, but it's not a fix.

 

Ok, it does give a code, code 24 but I believe it to be intermittent because it shows up all the time and always goes away.

When the car will idle down it will idle at around 1150-1250 but when I put it in gear, it will try to idle down to about 700-800rpm and then it messes up and starts to stall but most of the time before it does it will open the IACV and revv the engine up to about 1250-1500, and then it will repeat this cycle.

I have had the idle set before by a dealer with a TECH-II but it didn't do anything and I've ended up resetting the ECM numerous times.

Unfortunately, I don't have a manual to look at either....

Do you guys think it would be a good idea to just rebuild the entire throttle body and its assemblies?

I'm about out of ideas as to what it could be, but it has to be something either electrical like the wiring harness or the sensors themselves or something isnt correct with my throttle body.

And I have looked at the throttle plate, but not lately and last time I did, it was completely fine with no chips or anything.

 

Code 24 is a VSS problem. Either a damaged harness, mis adjusted or faulty neutral safety switch, or the sensor is going dead. I've replaced three of them because they tend to go bad, so it wouldn't surprise me. If the VSS itself is bad, your speedometer will start getting flaky and then eventually die.

If it were me, I'd start isolating the problem, and then replace parts only when I'm almost positive the part in question is the problem. You can bypass the IAC completely by plugging it's port in the throttle body. It could be a wiring problem, but you'll need a digital voltmeter, and a manual to troubleshoot it.

If you plan on keeping your car for any length of time, get on ebay and spend the $40-50 on a used GM service manual. It's the 3-4" thick monster bible that explains how nearly everything on the car works, with charts and instructions to guide you through resolving various issues. It's indispensable. The cheapskate version is the Chiltons which has some pages directly lifted from the GM manual, but it's missing most of it. Haynes are garbage.

 

Drew, I'm not real familiar with the V6 and their ECM in the Third Gen application, but would a VSS issue impact idle on this application?

I do know for a fact that in some applications, the VSS signal does play a role in idle control (idle mode, lean cruise).

I'd probably be also looking at the IAC counts in a scan tool to see if the ECM is trying to command a lower idle, or if the ECM is actually holding the high idle. Either would help direct where the issue might be.

 

I would think that the VSS does play a role because the ECM looks at vehicle speed to determine when to switch to idle spark and fuel control (2 MPH, as I've seen a lot).

And I agree about the scan tool... The results should be interesting, especially if he looks at the TPS signal percentage...

I'll take a look at my 92 FSM, which I should probably get in the house from the back porch (where the 91 harness is at current so I can work on it), and see what it says about this sort of thing. Other than the obvious vacuum leak crap, of course.

 

I know that the code is for a bad VSS, well it says defective or short circuiting but I've had that same VSS in the car the entire time that I've had it.

And well everytime that I've gotten pulled over the VSS and the radar have been dead on.

The speedo does kinda creep up the and like jolt and not increase smoothly but it's always been that way.

I guess it's time to go on eBay and buy a "Bible" though, it will definately be worth the money.

 

Ok so today when I started up the car for the first time, it was idling again at 3250RPM, and when I popped the hood and forced the throttle plate all the way back to the adjustment screw it idled down to 1500, which is about where it always idles until its warm, but its still doing the same surging thing on idle, I haven't bought a new VSS yet though. The car was used for 500 miles this weekend.

 

I'll tell you one thing... Prices for the VSS have probably gone up since I had to get the one for my T5 back 4 years ago, and it was $30 then, and yours could possibly be more. If I knew where the one was I pulled out of my 700R4 a while ago for the gears I'd throw it in with the TCC solenoid.

Anyways, I'd still hook the ECM to a scanner and look at the TPS% at cold start. Also, have you cleaned the IAC passages and especially the throttle plate itself, along with the bore? You'll probably want to get a throttle body gasket kit and take the top cover off of the TB to clean the carbon and junk out of the IAC passages. Also, make sure that if you have replaced the IAC at any point that it has the o-ring on it.

 

Oh yeah the price definitely went up, I forget how much but I know it isn't no $30 bucks, haha.

I've had all the gaskets replaced and cleaned the entire throttle body actually just recently but I guess I'm going to be doing it again here real soon.

 

Ok so I'm sitting in my car trying to teach it how to idle again and I disconnected the ECM from power for about a minute, plugged it back in, and started her right on up. It started at 1750 and well its not going down, its slowly climbing. Its about ready to kick on the fan so I'll be moving to the next step here soon.


Ok, fan came on, shut off then I shut the car off. Started it back up and now its idling at like 1350RPM or so, so thats a little bit better.

I'm doing the steps off of 60degreev6.com and now im supposed to let it idle for 5 minutes and then it should be done.

But after I turn it off for the last time, I'm going to go for a little drive and see how she does.

I'm starting to think that the car doesn't even go into closed loop but only a code scan tool can tell me that, and I don't currently have one

Ok so I took the car around the block and now it wants to idle 1100-1200, but its really nice and steady, its just a few hundred RPMS fast.

On the other hand, it seems like it was time for an ECM reset, the whole car drives nicer, and the transmission was shifting soooo nice and smooth and crisp and fast, and no jerking from the car, and I could barely tell that it was shifting, Maverick you'll have to help me out there, is it possible that the TCC Solenoid just needed to relearn everything?

I mean I didn't have the car to speeds that it would have locked up but I know it plays a role the entire time that the car is in motion. But then again, until I get my service manual I won't know much, but thats going to change!

 

At any point have you replaced the IAC?

If it were me, I'd probably go pull a complete throttle body off a 3.1 in the junkyard. If I remember correctly FWD 3.1's used the same throttle body. It could be the arm on the your throttle body is bent, in which case the throttle stop might not be touching when it should. If nothing else you'll get a different TPS and IAC as well as different gaskets, seals, and potentially less worn moving parts. Go to a you-pull-it yard and you can probably get the entire assembly for under $20.

 

FWD TB won't fit. And yes, I know you're referring to a GenII TB. I've tried. The cable attachments are on the wrong side and hit the alternator's upper bracket that runs to the one bolt on the tensioner. IIRC, the back plate is different as well.

FireInMe, it could be that the ECM just needed a reset, but if you have a code 24, that will screw with the TCC engagement, as the ECM reads the VSS to tell the TCC to lock.

 

I have both a new IACV and a new TPS, and its all clean, it drove perfectly and then later tonight it started to surge again....

So I'm starting to think its an electrical problem, either somethings not grounded right or somethings shorting out, or maybe the TPS that I bought is bad. I still have the old IACV too, and its pretty clean but I just wanted to replace it anyway, I'll try to put it back on and see what happens.

I'll see if I get any codes as well. None yet.

 

Probably a dumb question, but when was the last time you did a full tune up?

I have had an IAC fail right out of the package. Couldn't return an eBay item, so I just chucked it (another waste of $45). Went to the junkyard of all places, got 3 of them for $10, and got a good one. Same with the MAP.

 

Well the thing with getting the car back up and running was going to be gradual replacement of sensors and other various parts that would need attention and inevitable replacement. I think that I've done a pretty good job addressing the things on the car that need attention in the time that I have owned it and its cost me about 5 grand to do so at this point but it was worth it every penny.

First when I got the car I needed to get fluid and filters changed of course, so I got new oil, new transmission fluid, a new oil filter, a new transmission fluid filter, and a new air filter. Then from there to get it to pass PA State Inspection, the problem was exhaust and emissions, which it did not really have a hard time passing. I needed a few gaskets and a new EGR vavle because it was leaking. That was taken care of.

This was about a month after the car was bought, and not really being driven yet.

Then when I could start to drive it, I started to get a good feel for how it should be and how I wanted it to be, and what I myself had to do to get it there.

Some of the first things that I did was replace the fuel filter, after it started to get clogged up from sediments in that tank from it sitting for nearly 4 years.

Then along came sensors. I started to replace sensors left and right and I think I did pretty good diagnostics on what was wrong and researching the cars symptoms.

Then I asked around until I would buy, and replace the sensors in question.

Next I started to learn about ways to clean the engine and keep it going strong. So, I cleaned out the throttle body and such. Things like STP products got dumped into the gas tank door to try and clean the fuel system, and it really made a difference.

Then a few months into owning the car, I replaced the igntion system. New from the distributor up all the way to the spark plugs.

That also made a great difference in the way that the car acted and responded.

And then for a long period of time I became interested in appearance and waxing/polishing it all the time, and this only came because the car was running in a way that I felt was exceptional, and met my desires for how the car should run, and what I thought it ran when it was new(er).

Until recently, its proved to be a tough winter for the car, and with me losing my job for nearly 8 weeks, I didn't have a lot of money to get the car the things that it needed.

And thats where I'm stuck now, but I start work next week, and I will once again have cash to spend on my car, and get things done.

So I have done a full tune-up, and even though its been gradual, its happened. Its a pretty good tune up I should say, I've replaced just about everything that could have been replaced, and really, along the way I've learned a lot about cars and my car, before I started all of this, I knew nothing about how a car worked.

 

Hmm. I don't know if it would apply to your '90, but 91 V6 cars tended to have a problem with the wiring to the ignition module causing intermittent problems and stalling. There is some info in the DFI/ECM section on this, I think. It had to do with wires shorting in the ignition circuit because of bad insulation, and some other problems, eventually leading to even a MEMCAL replacement.

At least you have something worth waxing and polishing. Maybe one of these days I'll get lucky enough to find a decent full-time job and actually be able to afford paint. Mine was in such bad shape when I bought it, and it's only marginally better in the body department now. Problem is, I only make enough to fix the cheap stuff. I can't exactly afford to replace EVERY single suspension bushing, removable body panel, and get the car repainted. Heck, like I mentioned in another thread, I have a $5K parts list, and that doesn't count the almost $4k in body work I'm expecting to have done (weatherstripping, replacement of pass side rear quarter, both front fenders and front and rear bumper covers, realignment of all body panels and glass, rust removal, and finally the paint). I figure that by the time the car is finished, finally, I'l have spent as much as the guy who bought it back in '87 did, about $12K.

See, I learned to read with some DIY books. The favorite was the Reader's Digest Complete Car Care Manual, which covered cars, foreign and domestic, up to 1980. I can find out how to do things most guys either don't know or have forgotten how to do. I started wrenching with lawn and garden equipment when I was about 8, and cars is just another step. I'm hoping that someday I can step up to being FAA airframe and powerplant maintenance and repair certified, but I have to get through the ASE certs first. If I can ever get a job in a shop.

 

Well best of luck to you Maverick H1L, I know that everybody on this forum really appreciates the help that you've given then day in and out. I at least know that I do.

Its a lot of work, but these cars deserve it.

I'm going to continue working on this and I should get my service manual tomorrow.

 

after replaceing the iac and tps did you happen to do an idle relearn ?

 

Yes sir I did.

 

Ok so it definitely has to be the VSS, even after a computer reset it still gives a code for a bad VSS.

Plus, tonight I adjusted the minimum air screw on the throttle body and then it didn't idle at anything above 1500RPM, which it hasn't done on a cold start for a while....

But the thing that confirms the bad VSS for me is that when the car isn't moving, it idles perfectly. But when its rolling, the engine surges.

And I still haven't gotten my service manual yet

Today was a good day though, tore apart my dash as well and installed new speakers, cleaned out the vents, tightened the dash, and fixed the dash pad

 

mine gave a intermitten bad vss code a while back. i just unplugged the connector and cleaned it and plugged it back in has not been back since. id just check the connection first. simple instead of changing the sensor. if you do change the sensor. clean the connection also.

 

Good idea, I'll be working on the car again tomorrow, hopefully I get my service manual in the mail, but I doubt I'll need it to remove and reset a connection for a sensor, haha.

 

Make sure that when you replace the VSS that you jack the REAR of the car as high as possible to minimize trans fluid loss... That thing has a HUGE hole in the trans housing. Your connector is different from his... It should be a weatherpack, like the rest of them in the engine bay, so it might not be as dirty, if it is at all.

Good news is that my idle is fixed (still have a slow IAC, but right now, I don't care). The replacement MAF came in the mail yesterday and I don't have a code 45 anymore.

I still think your TPS could use the adjustment...

 

Here are two links with good info in them:

https://www.thirdgen.org/forums/v6/1...dle-learn.html
https://www.thirdgen.org/forums/v6/8...-you-have.html

If the stock Multec injectors are still in the engine, you may want to replace them.

RBob.

 

Congrats Maverick H1L, hopefully that MAF doesn't go back tooI(*knock on wood)

I remember I was having problems with my old IACV and I cleaned out the plugs and straightened them out and just even doing that gave the car a better idle. So who knows, maybe it will help, maybe not.

I still have to get under there and replace the transmission mount and everything too, I still have a few more days until I can't take the one mount back though.

 

Four of the six Multecs are still in the engine, two of them died and got replaced, but I didn't have money to get all of them replaced....

It died last summer and I didn't know how to fix it, and it ended up costing me ~$1800 to get it fixed.