My 3.1 MPFI is having idle issues, when comming to a stop it will stall, has anyone solved this kind of problem?

 

Does it happen all the time? Or, does it only happen when it's warm? Does it only happen when it's warm, and you come to a stop after going higher than 40 mph? (Example, you can drive around town all day at 25 mph, but as soon as you go above 40, and then come to a stop, the car stalls?)

Automatic trans or manual?

 

it has come to stall at any speed and temp.

 

I have changed the IAC,CTS. i do get codes 44-45-32. new rotor,cap, wires and plugs.

 

MAF? Try unplugging it and see what happens. Make sure batt disconnected first to be on the safe side.

 

91-92 is MAP.

Have you tried resetting the ECM. That can clear alot of problems on its own.

You said you replaced the IAC. You do know there are like 4 different ones right? meaning 4 different types of IAC for the 90-92.
You changed spark plugs and wires cap rotor.
How old is the fuel filter?
How is the Fuel pressure?
While they are probly not culprits, you may want to check them anyway.

90-92 stalling can be EGR related.
I eventually had to disconnect my EGR (Triangle shapped plug on passanger header)
Wait untill the engine is cold, dead colt. The valve "Should" be closed. unplug it. Yes you will have to deal with anoying SES light, but if the problem stops, you found the problem.

On 90-92 the only other thing that causes that would be a faulty vacuum signal to the MAP, or a vacuum leak. Cracked hose , or broken seal somewhere.
There are three behind and under the throttle body.
One goes to coolant valve on passanger frame rail.
One goes to a "T" and branches to go to the charcoal canister, and the other goes to the fuel pressure regulator.
I cannot recall where the third one goes at the moment.
There are two that come off the rear on the intake manifold.
Big one goes to the brake booster.
The other to the MAP sensor.

As far as checking the gaskets, I recomend water in a spray bottle. 1. will not catch fire. 2. that little amount will not harm the engine.
Spray, sit. If and when it studders, last area you sprayed has the leak.

 

thank you for the repsonse , i will try these.

 

I am unaware of 4 different IACs.

 

When I went to get one for my EX-92 they said which one cause there are 4.

 

Hey whatsup, just saw some of the posts to this thread. I figured that maybe someone could be of some help. I am just trying to find out where the vacuum lines for a 3.1L go. Theres three lines behind the throttle body and two lines behind the plenum. If someone could just tell me where each one goes. Also if you could say if its like the line on the drivers side or the passenger side, so I don't hook up anything wrong. Thanks for any help on this.

 

Try reading my reply... I knew where all but 1 went.

 

I did see that. I am just trying to figure out where they all go. I am not trying to like start an argument or anything. I just thought that theres someone out there with a 3.1L and has all their lines hooked up and would be able to share that info. Thats it man.

 

Should only be one IAC motor for 90-92's... I did some internet poking, and just found different brands-

AC/delco, 217-437
OEM GM, 17112349 (v6)
Borg Warner, 21812
Standard, AC28
KEM, 150-121

V6sucker, do you know the part # of the one you bought? Does it match with any of these?

But I agree with resetting the computer; 90ekm, those three error codes might not be the "current" list. If you pull the negative battery cable, wait a few seconds, then reconnect the negative cable, and then go for a drive- drive 1/2 hour away at 55-65 mph, and a 1/2 hour back home at the same speed. By the time you get home, the SES light should've turned on. Turn the car off and check the error codes- hopefully just One error code will come up. I'm betting that 2 of those codes are "old" ones that are just sitting around in memory.

 

then they may have meant 4 diff part numbers... As far as what I got I have no clue. It was choice number 3 is all I remember. This was years ago. The first one idled at 4300. 2nd at 3400. 3rd right on.

 

I did reset ecm, got another code for lean. and problem just got worse, stalling at everylight, stop.

 

Fuel pump. Fuel filter. O2 sensor. Fuel pressure regulator. Fuel injectors. Clog in fuel line. Vacuum leak. EGR open.

I still say the latter.

 

well, car is now in a shop, they tell me all that stuff mentioned above checks out, even tried a new ecm. it is getting way to much gas, going to pull injectors.

 

CHECK YOUR TRANNY...

Mine does this too, i'm 99% sure it's the TCC (torque converter clutch). It locks the input and output of the torque converter to "increase efficency". Another one of GM's cool ideas gone bad. Basically think of hitting the brakes in a manual car without hitting the clutch, is this what yours is doing?

 

when comming to a stop it would feel like that, but even at idle it would just run like sh@#, when it would stall, i would have to pump the gas and and if i let it idle it will stall. strong gas order in exhaust is another clue. shop has told me they ran the car unpluging each item (egr,map etc.) and come to try injectors.

 

latest, not fuel injectors.

 

V6sucker,
with engine cold,egr valve should be closed, how should engine run with this disconnected?

And with this disconnected should it only be a emissions issue?

thanks

 

well for testing, it will need to be functional. But you can get a replacement before the test.

It should run fine if the egr is functioning propperly, but if it is sticking as I suspect, it basically creates a massive vacuum leak and severly leans the AFR.

The disconnect trick is just to see if the problem goes away. If it does, you found the problem. But leave it off for more then a day or so. Just to make sure.

 

only disconnect at the header?

 

the plug.
or remove and put a metal plate there. your choice.
I just unplugged mine and it solved the problem.

 

how does it sound with it unplugged?

 

The same thing happened to me...it was the ECm there was a fault in the O2 sensor circuit. Caused the code 44 (which doesn't mean you're running lean, it means the computer is doing the LEAN STEP, which is to add more fuel (which is fouling your plugs, causing a miss, and the fuel odor and the intermittent stalling). Get you an ECM from the junkyard, pop it in and see if the code goes away (your problems with it). I'm 90% sure this is whats causing your problems. Believe me, I went through ALL of the stuff you are, then I finnally figured it out.

 

repair shop tried a ecm and did not cure the problem.

 

no different.

 

Odd..... I would guess mechanical next then, assuming all of the above was ruled out. Do a compression test, see what that looks like I guess.....I'm dumbfounded...

 

i have not tried the egr test you suggested, car is still in shop. shop tells me that not mechanicle

 

got car back from shop today, I am going to try the egr removel tip and will let you know what happens.

note: when drove car home from shop,ran good, parked, when started back up it ran like %$#@. did notice battery guage drop a little then back to normal.

 

good luck on that bro, i had my car act up like that a few weeks ago, brought to shop and just died on me , thank *** i got in there at least ....mechanics say it was electrical..500 dollars later and she ran again..a week later the same ****..i went back to shop and the master mechanic whom worked on my car is on vacation...i am studying my haynes manual and testing/changing parts that i can think of that causes my car to stall...tomorrow im doing the fuel filter ..so far i replaced the map sensor, plugs and cables, and CTS..good luck man and make sure that shop will haul ur car to the shop if it acts up again ..

 

thanks, shop says it is just getting way to much gas.

 

 

hey at least its stalling and not blowing up

 

update, having block of plate made for egr.

 

LOL... Good luck man.

 

UPDATE! placed block off plate at EGR and car now runs fine. did a test run and no stall or up/down idle

will do long term update.

Many Thanks to V6sucker for the tip

 

What can ya say, when your right your right.
LOL nice to hear man.

 

You can't be serious?? The TCC is a great device and GM isn't the only one that uses it.

 

i have been trouble shooting my tcc setup for some time now, it is a good idea but not very well placed or worked out on our cars, try what they said man, worked for me on another type of problem

 

the TCC lock up would bog the engine. If the system works right the IAC should compensate and raise the idle RPM.
A symptom of the TCC is very low driving RPMS, as it would always be locked up.
The car would fight to rev, It would rather smoothy rev, but just take forever to get anywhere on the scale.

 

If it was locked up, then the engine would stall at idle and not restart until it unlocked.

 

Thats why I said if the ENTIRE system was running correctly, the ECM would see the pressure drop, and send a command to the IAC to open more. Hense bringing the idle back up.

Edit, ok not the entire system, cause then the problem would not exsist, but if the engine system worked corretly.

 

i used to have the same problem, it came from me disconnecting my battery, some how it reset something in my computer, but after a week of so the problem would eventually work itself out and it would no long do that, i guess for now just double foot it

 

The problem was solved by him blocking off the EGR, the last few posts have been about someone else' TCC lock up.

 

Long term update,

car was runing very well at first, the stalling problem would happen again one time untill reaching operating temp then would run very well. example, in the morning 7am it would stall once. then after work 5pm it would run fine, no stalling.

 

Have you gotten any new codes?

Mine would have some issues when it was dead cold out, like below 45-50, but as soon as it warmed up it would pass.

Did you also block of the EGR intake port by the throttle body?

Have you reset the ECM since blocking the EGR? If not, try that as well.

 

i have not blocked off the EGR at the throttle body, i got a 32,44-45 codes, not sure if they are old but check engine has come on, while driving the speedometer would drop to zero and come back up, tried starting this morning and would not run, had to floor it for engine to start, once i moved the car i tried restarted but did not drive it, got p#$@!.

 

ok, 1st, block the plate at the T/B. That is letting in excess air, and basically giving a smaller problem the EGR was creating.

If you removed the EGR, you should have a plate on the manifold, and the T/B.

codes are...
32- EGR, supposed to be there.
44/45 lean/rich exhaust perspectively. This is created by the T/B EGR not being blocked as well.
I will surmise that the Idle is a little high as well? Maybe even a little eratic?

Basically by leaving the T/B EGR port open, is you have a 3/8" hole that is allowing in excess air. That is why I just recomended unpluging the EGR once it is known to be closed. Either a small piece of sheet metal, or layers of fiber gasket material and some layers of cardbaord should cure the problem.

EDIT- Yes once the EGR plug/system has been removed, it will throw on the SES light. However, you do know now what is the matter with the car. The EGR, if you ever decide to fix...