AmpleUnicorn88

So when searching Google and on here I can't seem to find the answer to this. I believed my IAC to be bad and I took it off and cleaned it and then put it back in and it idled differently. Rough and almost stalling out and then smoothened out but then idling high at like 1300 rpms. I put a new IAC in and it now runs at 1700 rpms. When I read through tons of tutorials on how to make adjustments, it refers to a torx screw. I didnt have a torx screw on my old IAC and there isn't one one the new one I got, there also isn't one on the TB. There are torx screws holding the TPS on but thats it. Is there some other way to adjust it? I cant find any other way to searching online. I know people hate when somebody doesn't use the search function but I tried that and can't seem to get a good answer as to where this screw is supposed to be, and why I wouldnt have it, unless I just haven't looked in the right spot. I replaced the TPS months ago and didnt do anything else to it. Just bolted a new one in.

1988 305 TBI 5 speed

AmpleUnicorn88

Update:

So I discovered that the spot the screw was in was blocked by a plug. When I originally tried using a punch on it it didn't do anything so I didn't want to mess with it. I ended up breaking that cap apart and found the screw. So I followed the steps on here and other sites. I jumped the A and B terminals, turned the key on for 30 seconds, then unplugged the IAC pigtail, then started it. Once started, I adjusted it to where I wanted, shut it off, and hooked everything back up and took the jumper out of the pins. Then restarted it and it started idling at 1800 rpms. So I did it again, this time it idled about where I set it, 600-700 rpms. Then I turned it off and restarted it, just to make sure it was good, and it went right back up to 1800 rpms. So I disconnected the negative cable for about 30 minutes, then redid all of it again. Same results. Did it, set the idle where I wanted, shut it off, hooked it all back up then restarted it, and it idled fine. Then turned it off and then started it again to test it and again, it went back up to 1800 rpms. I'm about out of ideas on what to do now. I didn't notice any vacuum lines broken or disconnected. My TPS is not adjustable and it is a newer one as of a few months ago. J don't have a meter to check it, so I don't know if maybe the issue is now my TPS?
King of at a loss here and not sure what to start checking.

Not sure if this matters, but when I jump the A and B pins, my SES light doesn't light at all, an UPSHIFT light lights up and stays lit up. When I pull the jumper wires out of the A and B pins it goes out. I am jumping the 2 top right pins which I thought were the A and B pins, so maybe that's my issue?

henryd3

iTrader: (128)

Perhaps you're setting the idle too high before plugging the IAC back in. This bit from the how-tos section worked for me
https://www.thirdgen.org/tpimod2/
Also make sure the pintle in the IAC is pushed in far enough

Tuned Performance

iTrader: (92)

The Tbi base gaskets are known for leaking over time as well .

AmpleUnicorn88

I am thinking now that I have to check the TPS voltage. I don't have an adjustable TPS. I have read in some threads that 90-92 don't have adjustable ones but the years prior came with them. I'm assuming if you have a non adjustable TPS then it should just be the correct voltage, and if it's not than it's bad. My TPS is a newer one as of a few months ago. I replaced all the gaskets on and around the TB a little over a year ago with ons of those rebuild kits. I checked vacuum lines and none immediately appear to be cracked or broken. The vacuum lines on my egr are new.
I was able to set the idle, then turn it off, hook everything back up, then start it again with everything hooked up, and it idled where I had set it. If I turn it off again and then restart it, the idle jumps right back up to being above 1500 rpms. I'm wondeeing if go through the process again, then turn it off and hook it all back up, start it, and then drive it around for awhile that would work. Not sure if maybe the PCM has to relarn the driving or not.

I have read that some people have drilled out where the Allen screws are to make their TPS adjustable. Wondering if there is any downsides to that.

henryd3

iTrader: (128)

You shouldn't need to do that. Did you set the idle down to 450 before shutting it off and reconnecting the IAC?

AmpleUnicorn88

I set the idle to around 700 rpms. What I have been reading is manuals you set between 600-700 rpms. If I set it to 450, it would probably be close to stalling out.

henryd3

iTrader: (128)

Yes, but the IAC will fix that.
READ THIS, i's in the How-Tos section on here
https://www.thirdgen.org/tpimod2/

AmpleUnicorn88

I read that and was following it but I was reading in other places that manuals you have to set between 600-700 rpms. I will try setting it to 450 and then see if that bring the idle to around where it needs to be once it's all hooked up.

henryd3

iTrader: (128)

And have the engine fully warmed up when you do this

DynoDave43

iTrader: (11)

henryd3, just curious...that url ends in tpimods2. Is that a TPI only procedure, or will it work for both, or is the URL misleading?

henryd3

iTrader: (128)

I have no idea. I have a TBI and this worked in my case. Have no idea if this also works for TPI. Never paid any attention to the URL name, oops how
unperceptive is that?

henryd3

iTrader: (128)

So, did it work out?

AmpleUnicorn88

Nope. I redid everything multiple times. I did make sure it was up to temp before every time. If I follow that procesure to a T it doesnt work. I just read another post somebody made on here a cew years back that said in addition to removing the IAC plug before starting, to also removed the "set timing connector" as well, and then start it. Seems odd to me because if you unplug the distributor I'm not sure how it will start. I haven't checked the voltage on the TPS yet but it is a non adjustable one so maybe it's bad? When it idles, it doesnt fluctuate or run like crap, it just idles high. It's still driveable but the throw out bearing will sometimes grind when trying to shift because of it.
The TB has had every gasket replaced and it was cleaned thoroughly while it was apart. It was out back together properly. As far as I can see, I do not have a vacuum leak. The vacuum port on the front drive side of the TB is plugged with a cap because I have an aftermarket air filter assembly. When I removed it it didn't seem to change much only slightly. So in a sense, I created a vacuum leak real quick and then plugged it back up.
I would just go get another TPS but it was hard to find one a few months ago when I got it and it was almost $100. I bought one thinking it was it and then it ended up being the wrong one. The TBI one seems to be hard to come by. I have thought about borrowing my buddies off his 91 TBI that's adjustable and seeing if that works. I'm going over there tomorrow so I will try that tomorrow afternoon or Tuesday sometime, assuming I still have the car. I have it listed for sale for pretty cheap so it might not last long.

I'm not selling because of this problem. I just bought a 97 f250 powerstroke and I now have 4 vehicles and need to start downsizing before I move.

AmpleUnicorn88

One thing I forgot to mention again is that when I jump A and B my SES light doesn't illuminate. All the way to the right, basically directly above the pins is an "UPSHIFT" light that lights up when I jump it. Could this maybe have something to do with it? Mg understanding is the reason you're jumping the pins is to have it in closed loop and then that pushes the pintle out in the IAC and then when you start it and adjust it, turning it off leaves it extended out. Then when you plug it back in the ECM takes over and adjusts accordingly.
So if it isn't actually jumping it, then could that be the problem?

RBob

iTrader: (1)

Time for a few quick tests. Do a key-on, engine-off while observing the SES light. The SES light should turn on briefly, blink off, then remain on solid.

Can repeat the test after 10 seconds of key-off. The blink off is what to look for, unless it does the blink the ECM is in limp mode. Go no further until you get the SES blink.

If the blink occurs, then jump A & B on the ALDL connector and do a key-on, engine-off. You should be able to hear and feel the IAC being stepped closed.

Also, the SES should now be blinking out any stored codes. It will start with code 12, blink it three times then move on to any other codes. If no codes then just 12 gets blinked out.

Do these tests first, as if they fail then no use in playing with sensors and actuators.

RBob.

AmpleUnicorn88

Just went out and did that. SES light never illuminates even briefly. Right next to the SES light is the UPSHIFT light. That illuminates when I jump A and B on the ALDL. When jumping it it does not light up the SES light at any time.

AmpleUnicorn88

Right after posting my response to this, I just saw another thread on here I found through Google that you responded to when somebody was asking about their SES light not coming on when they jumped it. You recommended unplugging the ECM, then key on no start, and if the SES light comes on, that could indicate a bad ECM.

I do know that the SES light at some point did work. It was on and turned off a few times the first 6 months I owned it. Never did any work or tried pulling the codes, just left it alone. No I see with how the car was running. Haven't seen it come on in a year now. So could be the bulb is bad, but, when I jump the aldl the UPSHIFT light lights up. I have an aftermarket gavuge cluster and my buddy did fix the wiring issue I had when I first got the car, but it ran fine for over a year after that and didn't have any issues. When this high idling issue first appeared, turning it off and starting it back up would remedy it. Eventually, I would have to turn it off and start it again 2 or 3 times and it would go away. Then, it got to the point where it just never went away probably 3 or 4 months ago. I have run seafoam through it (through the booster line) and that seemed to fix it for about 10 minutes once the seafoam worked its way through. Then it went back to idling high.

Tuned Performance

iTrader: (92)

You can always use a test light as the mil. If the one end of a test light is hooked to power and the probe end is inserted into a5 (brown/wht) wire at the ecm.

RBob

iTrader: (1)

That is true of electronic carb'd vehicles. They use a lamp driver module for the SES/CEL light.

The EFI vehicles do not, unplug the ECM and the SES/CEL will stay off.

Is this car subject to moisture/water issues? Pull the ECM down and unplug it. Then in good light check the ECM harness connector pins. Any green at all and you need a new ECM. Heavy white corrosion is also bad, as it is on the ride to green corrosion.

RBob.

Schurkey

Do I have this right? You jump the terminals at the ALDL, and a light comes on on the instrument cluster. It's not the MIL spot on the cluster, but it's also an aftermarket cluster.

What are the chances that the aftermarket cluster either has defective wiring, is incorrect for the vehicle, or it wasn't installed properly?

Any chance that the ALDL has had it's pins swapped around?

Does the UPSHIFT light blink like the MIL is supposed to?

AmpleUnicorn88

sofry for taking so long. I just bought another vehicle and have been doing stuff with it so I sort of put this on hold. I never got a notification people responded to this either which is weird.

Anyways, I havent checked the ECM yet. I will do that today or tomorrow. I havent tried running through the steps again but I don't think it's going to do me any good. If I jump the ALDL and the SES light isn't coming on then I'm guessing I have another issue I need to solve first.

AmpleUnicorn88

I probably should have specified on the cluster. I realise now that could he confusing. I have an intellitronix digital gauge cluster. It goes in place where all the gauges go, but all the factory warning lights on those strips to the left and right of the steering wheel remain untouched. I did the swap pretty soon after I bought the car and I know I have seen the SES light come on at least once after it has been installed. I was having it turn on under heavy acceleration. That was over a year ago and it hasn't turned on in about that long.

My buddy put the gauge cluster in for me. He's on this forum as he has a 91 he has also out the same gauge cluster in. He wired it so the gauge cluster is easily removable and can put the stock one back in if wanted. Something to do with the back of the cluster where it hooks up to the wires. He didnt actually cut and splice the cluster in.

The light I am referring to is on that warning light strip directly above the port to jump the aldl. It is the far right light. The first time I have seen it light up is when I first jumped the aldl a few weeks ago when trying to figure out this idling issue. With the A and B pins jumped, as soon as I turn the key on, it lights up, and stays lit up until I turn the car off. No other warning light comes on. I kind of thought maybe the bulb was swapped because when I did notice the SES light coming on, it was under heavy acceleration, so maybe that was the shift light telling me to shift. But, it didnt always come on under heavy acceleration, just some times. So that may or may not mean it was swapped. If it wasn't swapped, then I am guessing there is another issue going on, because I havent found a single source anywhere online that says what it means if you jump the Aldl and the UPSHIFT light comes on and stays on.

I do have a manual transmission so an UPSHIFT light isn't the craziest thing to imagine. But, I had never heard of there being one until I jumped the aldl on my camaro. When I googled this stuff this thread actually comes up, and a few other threads on other forums pop up but it involves how to get it to light up or how to remove the bulb so it doesn't light up.

I guess my next question in all this is, besides the bulbs being swapped around, is there another reason why the UPSHIFT light would come on when jumping the aldl? If wiring is correct and there are functioning bulbs, does that point to the ECM as the source of the issue?

RBob

iTrader: (1)

The SES on heavy acceleration is likely due to the forced knock test failing. That would set code 43 and pull timing. Can usually feel the lower timing as a lower level of engine power. But as you mention it did show that the SES works.

As for the way the engine is acting, idle wise and so on. Along with the up shift light illuminating with A & B jumped. My guess is that the ECM is bad, it is likely in limp mode. Can you borrow an ECM to try?

RBob.

AmpleUnicorn88

I'm sure my buddy will let me use his. His is for a 1991 305 TBI. But, he bought a new one that has the usb cable port installed to hook up to a computer from somebody on here to do the EBL tuning stuff so I don't know if it will work in mine or not. I'm going to his place today so I can ask. He is actually about to start an engine swap in his so it will be down for a week,or 2 once he starts pulling the engine.

RBob

iTrader: (1)

His stock ECM won't run your engine (VATs), but will show whether the SES light now works. IOW, if his ECM shows the SES blink while yours doesn't, that is enough to verify that your ECM is bad.

RBob.

Ron U.S.M.C.

Towards the end I could not get passed a stop light without stalling.
Here's what I did.

"Setting Minimum Idle Speed".

This step includes the IACV.

1) Jump the A to B terminal under the dash
2) Turn the key on but do not start it.
You should hear a slight ticking coming from the IAC valve.
What 45 seconds then unplug the IAC Valve with the ignition still on.
3) Disconnect the EST wire and remove the jumper.
Start the car.
It may be necessary to hold the throttle open slightly to prevent the engine from stalling.
4)Allow the engine to reach normal operating temperature.
5) Connect a tachometer. I used a digital timing gun with RPM feature.
6) Adjust the minimum idle speed using the throttle stop screw.
7) My Chilton’s says set it to 700rpm in park on an 89 TBI 5.0 auto.
8) When done shut the car off and reconnect the EST wire.
9) Plug the IACV back in.
At this point you drive the car normally/take it easy for a while so the ECM will relearn its parameters.

If you use a paperclip to jump the A to B Terminal be sure to look at the clip very closely because they sometimes put a "very" thin coating of clear plastic on it that's almost impossible to see. That needs to be removed or it will be a very long day indeed.

I also had the ECM E-PROM changed a little including removal of VATS.

After those two things were finished the car runs like a champ now.

vinny R

I fought the same problem for months or longer Did the IAC multiple times, Checked sensor voltages, used a bunch of seafoam and no matter what I did it only cured the problem for at most only one day. My car is an auto and sometimes would end up idling @ 1500 when in drive with my foot holding the brake, I could drive 30 mph without my foot on the gas! My fix.....new AC DELCO TPS. Even though the voltage test I did checked out upon further inspection of the TPS it was an aftermarket. It was only a few months old when I bought the car, the previous owner shopped at a discount auto store. I purchased a new AC Delco from Rock Auto for a total of $60. Did the IAC one more time and it has been perfect for 2 weeks. Mine is a TPI but I saw Rock Auto had the ones for TBI also. You did say you bought an aftermarket sensor also,

AmpleUnicorn88

Yeah I replaced the TPS on it a few months back. Within the same 6 month period this issue started, so I suppose it could be the potential culprit. The problem is every time I looked up the TPS for my car, it just showed the tpi. Like an idiot, I just ordered one, and when I got it, it was the wrong one. So I searched for an hour and found a place that had one that looked identical to the one installed on my car, so I bought that. It was like almost $90 for it though. If somebody has an exact part number of an OEM TPS for a 305 TBI in an 88 (I think in 90+ they were adjustable) I would love to see that and maybe pick one up.

I still havent tried the ECM I borrowed from my buddy. Because my data port isn't jumping correctly, I'm assuming I at the very least have an issue with something else, if it isn't whats causing the issue.

I have been so incredibly busy the last month. Between doing the clutch on my f250, and other stuff as well as working on my dads f350, my girlfriends car, and then school being difficult for me this semester, as well as moving this month, I have basically given up everything except eating, going to the bathroom, and sleeping. I haven't worked out in a few weeks which is really throwing my whole day off. I am moving soon, and am just going to tow the camaro to the new house and then start messing with it. Nobody is interested in it even at as low of a price I have it listed for, and have told people, that I think people just arent buying third gens right now. So I am back to possibly keeping it if I can't even get $2,000 for it.