1995 Corolla DX 1.8 Stalls once engine warm

[jborris]

I have a 1995 Corolla DX 1.8 with 94,000 miles. The car runs almost flawlessly when cold. Once the car warms up, it has trouble idling when in gear. If I accelerate normally or especially when if I accelerate hard from a stop, the car will stall. If I press the accelerator slowly, the car will increase RPMs slowly and drive fine at higher speeds/RPMs. As the car changes gears, in the lower RPMs again if I press on the accelerator hard, the car will stall. If I press gently, once the car reaches a higher RPM 1200 or so (guessing no Tach in the car), the car drives fine. If in DRIVE (3rd Gear) and car not moving very fast, car will stall as I press on the gas too hard. I have to shift to 2nd gear so car will be running in higher RPMs, then it will accelerate better, then shift to Drive, now that the car is moving faster.

Things I have tried/Done:

New Fuel Pump
New Fuel Filter
New IAC (Idle Air Control Valve)
Tested IAT (Air Temperature Sensor) hot water and voltmeter per manual
Replaced Ignition Rotor (Cap did not look bad)
Bought new coil but it reported same values as installed one, so returned. Car actually ran worse when installed. Did not appear to be a Denso part.

Ideas?

[zythr]

Originally Posted by jborris

I have a 1995 Corolla DX 1.8 with 94,000 miles. The car runs almost flawlessly when cold. Once the car warms up, it has trouble idling when in gear. If I accelerate normally or especially when if I accelerate hard from a stop, the car will stall. If I press the accelerator slowly, the car will increase RPMs slowly and drive fine at higher speeds/RPMs. As the car changes gears, in the lower RPMs again if I press on the accelerator hard, the car will stall. If I press gently, once the car reaches a higher RPM 1200 or so (guessing no Tach in the car), the car drives fine. If in DRIVE (3rd Gear) and car not moving very fast, car will stall as I press on the gas too hard. I have to shift to 2nd gear so car will be running in higher RPMs, then it will accelerate better, then shift to Drive, now that the car is moving faster.

Things I have tried/Done:

New Fuel Pump
New Fuel Filter
New IAC (Idle Air Control Valve)
Tested IAT (Air Temperature Sensor) hot water and voltmeter per manual
Replaced Ignition Rotor (Cap did not look bad)
Bought new coil but it reported same values as installed one, so returned. Car actually ran worse when installed. Did not appear to be a Denso part.


Ideas?

Have you tested the fuel injectors?

[speedy25]

From your description I would test the TPS. Especially since you are having trouble when opening the throttle.

Idle problems are 99% IAC caused but I see you installed a new one. Did you clean out the manifold where the IAC is attached?

-SP

[Bitter]

if you unplug the primary oxygen sensor, besides a check engine light how does it run?

hows the trans fluid level? will the trans shift on its own normally in D?

[jborris]

Zythr, Speedy, Bitter, thanks for your comments.

Injectors: I listened with a screwdriver-Ear to see if they were clicking, all four were. I added 5 gallons of Super (93 octane gas and a bottle of Lucas injector cleaner one day ago)

TPS: I have not tested the TPS yet. I will ASAP, but leaning towards quitting and taking to the shop.. Grrrr

O2 Sensor: Disconnecting the O2 sensor? Primary or Secondary? What would that do. I would think the computer would enter into loop mode or something if it detected a O2 sensor failure and used some pre-fixxed values to determine right fuel mixture?

Tranny: The Transmission is fine. It shifts smoothly. I shift manually because I need to delay the shifts some.

New Info: I replaced the Engine Coolant Temperature Sensor. (for ECM) The car ran better at first, then ran awful. Would not drive over 40, car sounds like it is flooding and kept stalling when pressing on the gas. The car stalled and would not restart. I disconnected battery fro 5 minutes to reset the ECM computer. It started after a few tries and ran like shyt. Car stopped again and would not start, I decided to put old temp sensor back. It ran better with the old one. Car finally start and runs awful. I almost had to call AAA to get home, but car started at the last minute and I barely got home.

[Bitter]

if the O2 sensor was bad and staying stuck indicating a lean condition it would cause the engine to run like poop in closed loop (once its warm). unplug the primary O2 sensor, see how it runs. The computer doesn't really have anything to check the O2 sensor against and may not throw a code if the sensor is sticking at a reasonable value. The computer is pretty basic when it comes to self diag on these OBD1 cars, pretty much will only tell you if something is open or shorted. In closed loop (warmup) the engine is running off the IAT and MAP sensors and some basic calculations to roughly figure out air/fuel ratio and timing. Once the engine has warmed some it switches to closed loop and compares against the oxygen sensor to run close to 14.7:1 air/fuel ratio and adjusts timing more closely.

Its not impossible that the primary sensor is bad and sending a signal like 800mv or 50mv which is within reasonable readings for a running engine, but not correct. It should swing between rich and lean except on engine accel or engine decel (closed throttle it goes lean, harder acceleration it goes rich). It should look like its just bouncing between rich and lean all the time at idle, if its not then its probably bad and the cause of your problem. when you unplug it the computer obviously ignores the O2 sensor input and goes back to running closed loop. if it runs fine in closed loop then runs bad when its plugged back in and restarted you can be reasonably sure its the O2 sensor. Use a Denso sensor if you replace it.

[jborris]

Great information Bitter. Thanks. I will take a look at the O2 sensor.

[kmenzel]

My 94 Corolla was having the same problems. Based on some ideas elsewhere in the 7th generation forums, I reset the ECM, and since then the car has been running very well, that has been for about 5 days. I simultaneously ran through a tankful of gas treated with Lucas injector cleaner, so the fix could have come from either source. Can't say more as I am currently doing battle with the driver's side CV axle... The contrast from cold to warm running was pretty dramatic, super smooth and powerful for cold and absolutely crap when warm. Very odd. Good luck!

[jborris]

Thanks you everyone that replied to this thread. The problem was a bad distributor and the wire connecting the TPS (Throttle Position Sensor) had a short in it. The car runs great now.