Bad stalling, idling... here is my problem...

When I slow down or come to a stop, or when it is idling about 500 RPM, the car jerks bad, and I either have to come to a stop quickly and probably kick it in neutral and give it gas, or keep it moving steady at about 1000 RPM, or else it usually dies.
It does this after about 20 minutes of driving, or maybe when the spark turns on or whatever.

I replaced fuel pump, ignition coil, ignition module.... No error codes are coming up, so probably not a sensor, and maybe not the ECM, yet still think this may be the problem... The car reads low voltage, so I was told by the mechanic that its either coil or bad ECM, but I changed coil, so we think its ECM.
Is there anyway I can check my coil, just in case, at home???
What are symptoms of bad ecm??
It did this a while back, and thats when it was the ignition coil, but it seems to be doing it again but worse... Any help appreciated....

Auto or manual? Cuz I know my car never really goes down the 500 rpm

it only acts up at idle??? if so there are some things to try before the ECM. My 89 IROC had a very similar problem, the same low idle stumble, rough running in gear, and absolutely nocodes, and it was the ICM, or the ignition control module. its a small electronic control module inside the distrubutor that controls spark advance and retard. To get to it, remove the distributor cap, and look under the rotor, the black module, with three connectors is what you are looking for, unplug the three connectors, and undo the two hold down screws, and pull it out, there really isnt any way to test it, but its not very expencive, i think 47 bucks from www.gmpartsdirect.com. Another thing it could be is the IAC, or idle air control valve, sometimes the valve can get gummed up or coated in fuel deposites, i reccomend either doing, or having done an induction service with a throttle body cleaning. i did this and noticed a drastic increase in throttle responce and idle quality. id try those things first, and go from there.

I had some rough idle and took off my EGR (by accident lol), musta shook somethiin out cuz it ran fine after I put it back on

Hey jafowler49, what is the year and motor style of you car?

89 firebird according to his profile

i've had bad MAF sensors cause the same problem. try cleaning it with some carb cleaner. dont change the ecm unless it's a last resort. i'd bet it's not the problem unless it's been induced to a voltage spike or severe vibration.

Car is 89 Trans Am 5.7 Liter, Automatic. Could it be the spark plugs?? The module was changed, when the coil was changed. What is the EGR and IAC, or more specifically where are they??

A diagnostic check read low voltage also... but remember I changed coil and module, and battery seems good.... And problem happens after like 20 minutes of driving or during normal driving temps

well the EGR is the exhaust gas recirculation valve, it is located under the plenium, the "spider legs" of the intake runners kinda wrap around it. you have to remove the plenium to get to it.

the IAC is the idle air control valve. it is basicly a computer controlled adjustment that on the carburator is the idle speed screw. it is located in the passenger side of the throttle body, and will have a four pin connector. you will need a 1.25in socket or wrench to take it off.

A diagnostic check read low voltage also... but remember I changed coil and module, and battery seems good.... And problem happens after like 20 minutes of driving or during normal driving temps


do you mean the system voltage(as in not charging enough) was low, or the voltage to a module or sensor was low? cause a weak alternator could cause this problem

why does your car is it carbuetor or efi?

low voltage to module/coil, not charging system. Replaced alternator. It is fuel injected. Not a sensor problem because no check engine lights coming on

just because the check engine light isn't on doesn't mean that a sensor isn't on it's way out, the MAF sensor in particular