surging idle

[BerettaMN]

So my car off and on had a surging idle off and on, I coluldnt find vac leaks, so I cleand the idle air control valve. It seemd to work. Then I drove the car for 10 min yesterday no problem. Shut it off went to start it and it would fire and just kill. I took the map sensor off blew it out cut some vac line off then re attatched it. Started no problems. Got to work today shut the car off. Tried restarting it, started then died. Again now it seems to just die after getting to temp and restarting no surge. Any ideas on if its the map or how to test it? Its a 91 3.1 auto

[Koots]

What year of car is this? what engine/transmission?

Just some extra information that would help anyone looking at this thread

[scd88ga]

Stalling once up to temp is usually a bad CPS (crankshaft Position Sensor) or ICM (Ignition Control Module). You can have the ICM tested at an auto parts store, but those aren't always accurate.

[BerettaMN]

I don't think its the cps it did it the whole way home after sitting 9 hours. Except at freway speeds. Got it home killed started it back up killed. Started it again idled fine. I cleaned my iacv so looks like next step is to maybe hit the junkyard grab some egr and map sensors maybe see if its one of them without having to buy new ones just to see

[berettaboi]

i have yet to find the culprit for this issue... but haven't tried too much to be honest... would love to hear if someone has solved the issue.

mine happens in really warm weather usually, switching between reverse and drive fairly quickly... it wont catch idle, will just drop and stall. i know that i need to clean my EGR ports in the intake. the IAC (idle air control) could likely use a much more direct cleaning as well. not TCC tranny sensor... my car finds torque converter lock up and pops out of it fine on the hwy, and usually not an issue on the newer 4spd trannys.

crank sensor will likely give you more issues, like not allowing restarts when hot. ICM can go out in several different fashions, usually causing misfires or lack of power above a certain throttle position.

[scd88ga]

I don't think its the cps it did it the whole way home after sitting 9 hours. Except at freway speeds. Got it home killed started it back up killed. Started it again idled fine. I cleaned my iacv so looks like next step is to maybe hit the junkyard grab some egr and map sensors maybe see if its one of them without having to buy new ones just to see

I guess if your going to throw the wrong parts at it, they might as well be cheap used parts from non-running cars! Let us know how that goes.

[BerettaMN]

Ive pulled sensors before at the yard that work perfectly fine. Anyways the crank position sensor was cracked so I bought a new one put it in, started the car let it get to temp, shut off, tried re starting it it didnt wanna stay running. no vac leaks, cleaned idle air controle valve, cleaned throttle plate and inside it, all my grounds look good, starting to become very annoying, no stored codes or ses light either.

[3X00-Modified]

Time to try swapping out the ICM or coils... or have them all tested.

[felixGTU]

When I first bought my GTU it had the same problem. For me it was the injectors. I checked them and the resistance in some of them were low. So they where bad. After I put other used injectors it worked perfect. Check the resistance with a multi-meter or take them to a parts store to have them checked. Good luck.

[BerettaMN]

Maybe Ill do that and have my uncle, (a mechanic) test the icm/coils for me. Today the check engine light came on for a while so I pulled the codes and it was 44, and 45. Lean exhaust condition and rich exhaust condition. I replaced the o2 sensor a couple mos back though and wiring was good. any ideas on that? thanks for the help so far guys

[BerettaMN]

Well I tried like 6 dif map sensors from the junk yard, none helped it. I checked for spark after it gets warm and doesnt want to start, it has spark, I guess next thing is to hook a fuel pressure guage up to it?

[berettaboi]

it could be your fuel pump, is it noisy? usually a telltale sign it's in need of replacement. good idea to check how much flow you are getting. i'm not sure how you rule out the fuel pressure regulator as well, but i suspect that would not be effected by heat really... the pump will. you may find the car runs perfect with a full tank of gas, but you have more starting problems when you are 1/4 or less... the fuel pump is immersed in the gas to keep it cool as well.

scd88ga mentioned the CPS crank sensor as well, they are greatly effected by heat when they are worn out. it may provide weak or no signal to the ecm, so then no spark from the icm/coils

[BerettaMN]

already replaced the cps last week, even thought the old one had a crack, it didnt change anything. The car has a full tank of gas now. before it was cold starting fine. now its not wanting to even do that unless you pump the gas. I can hear the gas pump cycling when you turn the key but its not noisy I was listening with the gas cap off. Going to harbor freight after work tomorrow grab a cheap fuel pressure guage tester. Then we will see what the pressure is.

[berettaboi]

pumping the gas before or while starting the MPFI or SFI motors (or just about all fuel injected motors) will not have really any effect. while it is opening the throttle plate, allowing the option of more air, the ECM is not sending more than a specifically programmed/set amount of fuel for start up. once it's started then a few of the sensors start to send signals and the fuel/air mixture is kept as close to specs as possible.

actually, sticking the accelerator pedal right down will not allow you to start the engine at all... in most cars that tells the injectors not to spray at all

[BerettaMN]

Well pumping it to flip the throttle plate/letting in more air helps start it so it is doing something haha cuz just cranking wont start it. But cranking and doing that will start it. Anyways Im about at the end of my rope with this thing. Alldata Pro says Turning the key ON a couple times to cycle the pump should put it at 40.5psi - 47psi. It sits right at 40. when started and running on its own with no help it drops to around 30psi idling.