rough idle / randomly stalls

Hello I have a 96 Geo Tracker LSi 4dr 4WD. I am having a problem with it idling. When I first start the car cold in the morning it idles perfectly fine but after a few minutes of driving it starts to idle really low around 500 rpms when I come to a stop but after a few seconds the idle will slowly stablize back up to about 800 rpms where it should be. After the car is up to fully operating temperature it gets really bad, the idle will drop too low and bounce like crazy between like 400-700rpm and sometimes it stalls. Sometimes it takes many cranks to turn over when it's at operating temperature and when it does it will stall immediately after starting. So I'll have to start it again and keep my foot on the accelerator as I switch from park to reverse to drive etc. When I came home from work today it was shaking really badly and when I pulled in the driveway I put it in park and let it sit there and idle roughly and after about 2 mnutes the idle all of the sudden stabilized itself to a steady 800rpms like nothing was wrong? I don't understand how it idles perfectly sometimes other times it bounces all over the place and stalls. It seems to get worse as the car warms up and the worst when it's at fully operating temperature. In the last few months although not all at the same time I have replaced the spark plugs, ignition wires, cap, rotor, air filter, and pcv valve but it still does it. It doesn't misfire while driving. I need to figure it out before I end up getting into an accident because of it. What could it be? My check engine light is on, I don't know the exact number of the code but I had it checked at AutoZone and they said it was EGR flow. Do you guys think the EGR is the problem or something else? How do I figure out what is wrong with the EGR?

it sounds to me like its the ECM. i could be wrong. i would take it to the shop and get them to run some test on the ECM. If it is the ECM it might be able to be re-programmed, if it can be re-programmed then you looking at a costly problem.

What is the ECM is that the ECU? How much do they run? Easy to replace by myself?

the ECM stands for the Electroninc Computer Mod. its the computer of the car.

the ECM stands for the Electroninc Computer Mod. its the computer of the car. very costly. probably have to get a shop to put it on because the would have to run diagnostics on it.

im sorry i ment to say Engine Control Module and ECU stand for Engine Control Unit..... same thing

breezinintime, for future reference, you can edit posts by clicking the edit/delete link just below the post.. saves confusion some of the time :biggrin:

I found one on rockauto.com for around $150. Do you think the problem could be clogged fuel filter. Car has 97K on it and it has never been changed. My friend's dad said it could be the fuel filter clogged or the throttle position sensor. I was thinking it could also be the throttle cable freeplay?

did you check your egr valve and the componets that make it work such as the egr sv valve which opens and closes egr valve which is controlled by the ecm the manifold differial presuure MDP sensor and the EGRB(EGR BYPASS) VALVE.these two components are used by ecm to check for blockage in the erg system. i got this info from chilton manual. if you rev engione the egr goes on way then when you deaccelorate the valve goes the other way.

Well I got the fuel filter changed, and the problem is worse. The damn thing stalls constantly now. How can changing the fuel filter make it worse? I hate this car it's retarded.

my tracker is giving me problems too. they are a pain in the ass but damn they are neat offroad. especially at the beach. ive grew up at the beach and did nothing but offroad on the beach and ive got to say that these little things are great. umm i think that dgee has something with the egr valve.. i heard about that before but i cant remember where. thanks for the tip dgee.

i had a problem with mine i found the FI fuse was in but the prongs were not making good contact with the fuse i bent fuse a little bit and tighten prons a little bit also do the same for ign coil fuse.have not stalled since this morning original program started with ign coil fuse blowing left fuse cover off i think i found the problem with ign coil fuse blowing it might have had something to do with the torque converter and the speed sensor went to putthe fuse cover back on and engine stalled i found the prongs on the FI fuse to be a little loose . let me know if this helps.

stupid question did you put filter in right direction.and did the old filter have a lot of stuff inside of it that it could have gotten into the injectors.

could it be the temperature sensor .

Yeah filter is on right direction. Are you talking about the Engine Coolant Temp Sensor? Wouldn't it throw a code? The only CEL I have is P0400 EGR Flow. On a side note my water pump is leaking, but I refill the coolant all the time. Do you think the sensor is getting a false reading because of the coolant being low sometimes?

it could just be giving you the wrong readings i think you can test the sensor.i have to get back to you tommorrow on how to check it im at work and book at home.also my engine is all over the place but never stalls it will go down to first line if i stopquicklyand slowly build back up to 800 or so.when the engine is hot its been doing that since i bought it two years ago.also the egr info came from the chilton book.

to check sensor use thermometer and ohm meter. and a pot of water.at 68 degreesthe resistance should be2.21-2.69 kilo ohms at 104 should be 1.14 kilo ohms at 140 it should be .58 kilo ohms at 176 it should be at .29-.35 kiloohms .use terminals a and b if you have three prongs sensor still use a and b. and i think it is more temp.than how much coolant is in the system. perform test with sensor out of car.also sensor in intake manifold.

Well I changed the water pump this weekend....so that eliminates the Engine Coolant Temp sensor not getting a reading from low coolant since the coolant stays full now and the car is still stalling constantly. It seems to be getting harder to start....after it stalls....it will crank for like 5 seconds before it turns over. My friend's dad who helped me change the water pump said we'll have to check the timing with a timing light. I still think the P0400 EGR Flow code is the problem. I'm betting the EGR ports are clogged up or the valve too, but could that cause the car to have trouble starting when the engine is hot? The car seems to turn over fine when cold. I don't think it's fuel related because if I leave the key in ON position for about 10 seconds you know and let the fuel pump run, it doesn't turn over any quicker. Maybe the distributor is goin bad. I think the problem may be spark related since it has trouble turning over when hot. Any way to test the distributor? Oh and I was reading some other similiar threads where someone said they cleaned their IAC valve and that fixed it, but I don't think that could be the problem here because if I turn the AC it makes no difference the car still stalls out.

did you check the egr system.is it operating properly also there is an ATS air temperature sensor on the intake manifold on the TFI (throttle body fuel injection)motor or on the air cleaner on the MFI (multiport fuel injection)this also control idle. to check this senor use ohm meter and thermometer and water . put end into water and put ohm meter across terminal. at 68 degree 2.28-2.87 k ohms at 140degree .53 to .70 k ohms.at 212degree .29-.39 k ohms. also there is a throttle positoin sensor.
personallly i would check the egr system since it did get an error code.first see if it is not stuck and if it is moving back and forth while revving the engine . if not stuck pull it out check passage.make sure not clogged.

one other valve the IAC (idle air controll valve. function 1 to maintain specific engine idle speed at all time. 2 to improve engine starting 3 to compensate the air fuel mixtureduring decelerationand 4 to improve drivablity when engine is at normal operating temp.