What is up with this?? I just got the ECM changed, the timing corrected, the solenoid replaced and a new starter! Everything was fine for a while, and now everytime I come to a stop the RPM's go down real low, below 400, then they jump back up again, then back down, and so on and so on.

I don't have a problem when the RPM's are high or I'm on the road, just when I come to a stop. Is it air related perhaps? New air filter? I just got a K @ N about 6-7 months ago, that thing better not need replaced already! Any ideas what the heck this is?

Oh BTW, I was outbid on some nice 91-92 style wheels in the LATS 3 SECONDS on Ebay!! RRRRR that ruined my day yesterday, oh well.

Thanks

 

check for a vacuum leak. I had this problem too after I had the heads done. There was a port on the lower part of the intake back by the distributer where the pipe from the IAC went in. When I put the engine back together i forgot that there was an extra port that wasn't used for anything on my car(was plugged when I took it apart).I think it was for a vacuum line to the Automatic trans that was available?Dunno. Anyways, I forgot to put the plug back on and it caused major idle rpm problems. i bought a new plug and it fixed me right up. Now I have other problems...hehehe.

 

Does sound like vacuum..try listening for it. If you hear a steady HISS noise, it's vacuum. I removed the vacuum line from my manifold going to my cruise control box, and put some elecrical tape over the end on the manifold. When the tape came off, I heard a HISSSSSS when I was driving...but the leak was minor enough that the engine compensated for it by raising rpms...my idle got way quick.

 

not sure if this will help, but my 90 3.1 firebird had this same exact problem, I changed the fuel filter, coolent temperature sensor and the oxygen sensor(s) and it ran great... I would try the CTS coolent temperature sensor first, that seemed to be my biggest problem. I wish they would just get rid of all those damned sensors!

 

As much as I hate sensors, I really do love em. I wouldn't know what to do with a sensorless engine. I'm so used to them...

 

Check the distributor. If you can wiggle the cap and get any movement at all, then the "base plate" has loosened from the distributor shaft. My son's 88 V6 Fbird was acting much the same way. Ended up brazing the plate back onto the shaft housing. The tach was all over the place too (bouncing hi and low).

See the listed link below.

https://www.thirdgen.org/techbb2/sho...tributor+shaft

 

Check the distributor. If you can wiggle the cap and get any movement at all, then the "base plate" has loosened from the distributor shaft. My son's 88 V6 Fbird was acting much the same way. Ended up brazing the plate back onto the shaft housing. See the listed link below.

https://www.thirdgen.org/techbb2/sho...tributor+shaft

:D

 

Mine has done that several times.
the prob was the connection to the battery was weak.
It actually popped off once.

 

Alright, now that it is a little warmer out I can go and check out those things that might be wrong. Vacuum leak, distributor and perhaps the coolant temperature, then I'll get back. Thanks for the advice, I don't know what I would do without you guys. Probaby I would get ripped off by some mechanic!!!

 

did it start acting up when the temperature outside became cold, or before? that could help isolate the problem

 

To an extent yes, a similar problem occurred (I don't know if it was the same) and it started just when it started to get cold. We fixed the O2 sensor and put a new ECM in and that fixed the problem RPM's bouncing up and down. Car then started stalling, so we fixed the fuel filter and the fuel line, fixed that. Car then wouldn't turn on, and I got the celonoid fixed, it seemed fixed. For about a week that is, the car seemed fine then the engine wouldn't crank anymore, so I had to get the celonoid fixed somewhere else, then it wouldn't turn on again. Engine wouldn't crank again so I took it to another shop where they put in another starter, hopefully that will solve that. However now, the RPM's will bounce down to less than 400 when I come to a stop from about a 30-40 mph and higher roll. The RPM's don't fluctuate when I put down past 2000-3000, and they only flutter lightly at idle. I don't have a problem most of the time, it happens just when I come to a stop from a 30-40 roll. It is annoying however, ESPECIALLY at turns, the car likes to stall.

 

Sounds like a sticking IAC valve to me....but not 100%....

 

On the '90-'92 models every time the battery power is removed from the ECM the idle has to be re-learned. If this procedure is not done the symptoms you describe will occur. It is a royal PITA. Stalling, rev'ing (alomst rear ending other cars), sputtering, stumbling, basically runs like !@#$%^&*()).

First time I cycled power to the ECM the engine/car was a nightmare to drive. It was three weeks of daily driving before it learned the idle on it's own.

It's funny that everytime I post this info no-one believes me. If you are interested in how to do the idle learn procedure say so and I'll dig up the info and post it. It takes ~ 20 minutes to do it. I now do it everytime power has been removed from the ECM.

RBob.

 

Your car must have drastically different requirements than what are programmed into the ECM as default. My car requires no learning. It's a 91 RS..even with power killed to the ECM, only thing it does is stall out immediately after the first start; just the IAC learning where it is... But after that...idle all the way up to WOT are completely normal.

 

Hmmm, after the ECM and O2 sensor was changed it would idle really high, but at least it wasn't sputtering like it used to. It went for this for a while, then it just went back to normal. That is what I figured too, it had to "relearn" the normal idle. Should I wait a couple for a little while longer before I go ahead and go searching for problems, like the stuck IAC?

 

RBob, if you could post that idle learn procedure, I'd appreciate it! I always tell guys to go for a 1/2 hour drive away from their house, at highway speeds, and then drive 1/2 hour home at highway speeds. I have to do that after pulling the battery, or my car will run like crap.

 

Your car does require learning wheather you realize it or not. On most/all 2.8/3.1's the motor needs to set a "minimum air rate" or a 'learned IAC position". Fortunately for me, I can use the Tech1 (scantool) to do this so I never learned the proper procedure without a scantool.......

 

wow, thats really good info, cuz my car used to do that all the time, took 2 days to fix, I thought it was just my car

 

Let me rephrase... Yeah, the car does require learning, but it doesn't have to learn much in terms of how to operate the car properly. Soon as I start it up, even after the ECM has been cleared, car runs just fine...you'd never know it ever had power cut to it. Guess I'm a lucky one...

 

Is your by any chance a stick? The reason I ask is I've heard from others with a stick the same, no real problems.

RBob.

 

The idle learn procedure.

Idle Learn Procedure for 3.1L V6:

Disconnect battery, wait one minute, and reconnect.

Turn off A/C.
Turn off Backlight Heater (rear window defroster).

Do Not Touch The Throttle at Any Point.
Do Not Touch The Steering Wheel at Any Point.

Set parking brake and chuck tires.

Start engine, let settle a bit and put trans in drive.

Let engine run until fan cycles on then off.

Turn off engine.

Wait five minutes.

Start engine and place in gear.

Let idle for five minutes.

Shut off engine.

End of procedure.


If the throttle is touched at anytime during this you have
to start from the 'disconnect battery' again.

If the steering wheel has pressure applied you have
to start from the 'disconnect battery' again.

If the engine stalls at any point just restart and place
back into gear.

--

RBob.

 

i have a 3.1 and i am hearing continuous hissing sound from the engine and my rpms are bouncing

i recently have disconnected and connected my battery several times to install a stereo system that was shortly after stolen so i disconneted and reconnected again

after reading this post i have come to the conclusion that it is a vaccum leak although here in pittsburgh its been too cold to actually check

when i do get a chance to check and if it is a vaccum leak then should i still perform the idle learn procedure. please define "chuck tires" and after fan cycles on then off should i place in park before i turn off and is it ok to touch brake pedal

 

Chuck tires. Just not too far, need to put them back on when you are done .

Actually I mean to block them with something so that the car doesn't take off on you. After the fan cycle I usually slide the shifter into neutral for the shut off and restart. Foot on brake is no problem (just don't hit the steering wheel with your knee).

The reason for no A/C, no defroster, no steering wheel pressure, and no throttle change is because these actions change the IAC position. In doing so it upsets the learn process.

This is the same learn procedure that other GM cars require. Even the FWD 3.1l cars (IE: Buicks, Z24) require this.

RBob.

 

Ok, I just got finished checking for vacuum leaks. From what I can see, there are none. I also took apart the intake system to see if anything was clogged, sure enough nothing was. So, what about the IAC? Unfortunetely I am very ignorant of auto mechanics and as you all know, the search button is down. How can I check to see if there is a problem with the IAC?

 

IAC....look at your THROTTLE BODY. Passenger side..it's got a connector clipped upside down into it, and 2 Torx screws, one on either side. Engine off..disconnect connector. Take Torx screws out and carefully pop the sucker out. It does have an O-ring around it so be careful not to rip that. Slide the IAC out..it's probably covered in black crud and crap. Spray it down with carb cleaner and wipe it thoroughly, but be careful..try to wipe it bottom to top I believe, and avoid side to side movement..you don't want to move the pintle up or down, or worse-release it..the spring is very strong and will probably send the sucker flying never to be seen again. After you're done cleaning it, get some carb cleaner on a rag and clean everything you can reach INSIDE the area where the IAC valve sits. Clean all that out, and you might as well clean the throttle body and butterfly while you're at it..but use TB cleaner for the throttle body. Carb cleaner only for the IAC stuff...I'd probably use throttle body cleaner for the area where the IAC sits too, and reserve the carb cleaner only for the IAC. Reason being..carb cleaner is a big no-no for EFI engines...messes them up quite nicely. Pop the sucker back in nice and snug, and make sure the o-ring is in properly...put the screws back in and clip it back on..start the car and let it idle for a few mins..will probably run just a little 'off' for a few before the car adjusts/finishes inhaling and disposing of the carb and TB cleaner vapors. Hope that helps!

 

OK, that was what I was looking for. Thanks for your help!

 

Any time...

 

Hmm, thanks for that info RBOb, i'm going to try that and see if it helps any, my car is doing somthing very similar.

 

just download freescan and use the iac reset. key on engine off. works every time for me

 

Think it took me long enough to respond to this?? Lol, and no RBob, it's not a stick.

 

hold the phone.

there are 3 different relearn procedures. one for the trans, one for the accessories and one for the computer

the one for the trans requires a**** load of stuff. the one mentioned before is for the accessories with the computer, the engine relearn has to be done by a mechanics computer. i went to work and looked it up on out mitchell On Demand, and it didnt give the procedure, it said that it had to be done through a computer. my battery died recently so i went thought all this.
you can however go for a half hour drive and thatll tune it up abit. every time you start up your car, it remembers alittle bit.

just when you drive on it, jump on it sometimes from a stop, and go easy on it from a stop etc etc so the computer gets used to all types of driving

 

How can the tranny learn? It has no computer controls, just hydraulics and cables..?

 

just what mitchell said. ford has the same thing. after you re install an automatic transmission in a ford, you gotta go through a relearn procedure to get its shift points and pressures back i guess...just what i heard. i knwo trans just got cables and clutches. not tryin to start any crap, but its just what i read.

 

Hmm....I'd like to see their explanation on how to teach a non electronic, non computer controlled transmission. I mean shift points and pressures are controlled by several things, among them the TV cable....that's a hydraulic thing...how is hydraulic pressure going to change or anything based on any sort of procedure...it's all a complicated set of springs and plates and all this other crap that gives me a headache just thinking about...

I'm not starting anything with you man, don't worry..I just don't believe your manual.

 

Check your timing with a timing light.

 

 

my manual was Mitchell on demand 4. we use it in my shop, it has been known to be wrong in the past. but its a proven shop program. that and All Data

 

Yeah I've heard about those....seems like a pretty damn cool program to have...I mean I'm sure it's right 99% of the time, and the convenience added with it.....every manual just has its wacky points..I'm thinking that the tranny learn procedure might've been for 93 and later F-Bodies, the 4th gens with electronic trannies.

But yeah...my Haynes manual is wrong quite frequently, in stupid little things such as part/sensor locations...that was for my V6. My V8 Mustang, well, the FIRST thing I did by the manual, it was wrong already...it said to unplug a thing with a single wire connector to get my base timing, but there was none...the correct thing to unplug had a dual wire.

 

We have here a perfect example of why I do copious internet research on major message boards rather than paying attention to a manual once I become confused. It's amazing, really.. every major car out there has a board similar to thirdgen.org... rx7club.com, for some odd reason, seeing as their are far less RXs on the road than third-gens alone, has 2.5x our userbase, and I've seen 600 people browsing the forums at a given time.. same with fox body sites. We *are* the shop manuals of the future =)

 

well now nixon you we love to follow eachother around on posts now dont we? haha this is the 3rd i have seen man! haha

the manuals are wrong on alot of occasions...
i have been trying to look for a crack of mitchell or something for my personal computer. they are very convieniant. and i think mitchell on demand 5 is 100% better than 4.

 

Ha ha...yeah man..guess we like the same kinda posts... Or one of us is a stalker.

 

i thought i saw you outside my house you treejumper

hahahaha

 

Actually, I didn't jump...I fell...which is why you haven't seen me lately........