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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
I have a 1985 Z28 with the TPI with about 95,000 miles on it, the other day I started stalling when breaking, sometimes its right before I get to a complete stop others will stall while Im still at 20-30mph just depends on how fast Im going. I checked the break booster by putting on the e-break, putting it in drive, and punching the break but it idles like normal. I couldnt find a vacuum leak on any of the hoses as well. I do have a check engine light when I idle. I dont really know what else to check so Im coming to you guys. Any guesses?
This is how to check for error codes on the ECM if you don't have a code reader.
The ALDL or DLC is located behind a plastic cover under the steering wheel.
Diagnostic Mode
If the "Test" terminal is grounded (Jump pins A and B) with the ignition "ON" and the engine stopped, the system will enter the Diagnostic Mode. In this mode the ECM will:
1. Display a code "12" by flashing the "CHECK ENGINE" light (indicating the system is operating). A code "12" consists of one flash, followed by a short pause, then two flashes in quick succession. This code will be flashed three times. If no other codes are stored, code 12 will continue to flash until the "Test" terminal is ungrounded:
On fuel injected engines, codes can only be obtained with the engine stopped. Grounding the "test" terminal with the engine running gives the "field service mode".
2. Display any stored trouble codes by flashing the "CHECK ENGINE / "SERVICE ENGINE SOON" light.
Each code will be flashed three times, then code "12" will be flashed again.
On a fuel injected engine, if a trouble, code is displayed, a Diagnostic Code Chart from the service manual is to be used to find a problem.
If you do not have a service manual let us know what code(s) you have and we will look them up for you.
This is how to check for error codes on the ECM if you don't have a code reader.
The ALDL or DLC is located behind a plastic cover under the steering wheel.
Diagnostic Mode
If the "Test" terminal is grounded (Jump pins A and B) with the ignition "ON" and the engine stopped, the system will enter the Diagnostic Mode. In this mode the ECM will:
1. Display a code "12" by flashing the "CHECK ENGINE" light (indicating the system is operating). A code "12" consists of one flash, followed by a short pause, then two flashes in quick succession. This code will be flashed three times. If no other codes are stored, code 12 will continue to flash until the "Test" terminal is ungrounded:
On fuel injected engines, codes can only be obtained with the engine stopped. Grounding the "test" terminal with the engine running gives the "field service mode".
2. Display any stored trouble codes by flashing the "CHECK ENGINE / "SERVICE ENGINE SOON" light.
Each code will be flashed three times, then code "12" will be flashed again.
On a fuel injected engine, if a trouble, code is displayed, a Diagnostic Code Chart from the service manual is to be used to find a problem.
If you do not have a service manual let us know what code(s) you have and we will look them up for you.
Will this still work if my ECM isnt holding any codes? Because the check engine light goes away after I start driving it again.
The only way to catch that code that’s probably not related to the stalling is to watch a scanner or use winaldl see what malfunction code throws. Your stalling could be iac related or fuel related like a sudden pressure drop. Might start by cleaning the iac and setting iac minimum speed then double check tps setting if you adjust the throttle body screw.
It is also possible that your fuel pump relay has failed and the oil pressure switch is what is keeping the engine running. When you slow down the oil pressure may be dropping low enough to drop out as well, depriving the engine of fuel and stalling the motor.
Replace the fuel pump relay and if the problem goes away, you will have found the cause.
Then you will have to find out why your oil pressure is dropping so low. The oil pressure switch should be closed from about 6psi. and higher.
It is also possible that your fuel pump relay has failed and the oil pressure switch is what is keeping the engine running. When you slow down the oil pressure may be dropping low enough to drop out as well, depriving the engine of fuel and stalling the motor.
Replace the fuel pump relay and if the problem goes away, you will have found the cause.
Then you will have to find out why your oil pressure is dropping so low. The oil pressure switch should be closed from about 6psi. and higher.
? your saying oil pressure is suddenly dropping under 4psi ?
i didn’t see a mention of hard start or no pump prime.Taking a parts cannon isn’t a good way to diagnose.
A parts cannon is a bad way to troubleshoot, but I don't know how many tools the OP has, and a $30 fuel pump relay is a cheap and easy fix.
Stalling while driving is a problem I would want to fix as soon as possible and this eliminates a possible cause.
You can TEST a relay. Don't need to buy one to TEST the theory.
I agree that the symptoms that have been shared, do not point to the FP relay. To that end, I think if the OP is getting less than 4 PSI oil pressure while decelerating (or any time), he's got bigger problems than a relay.
OP needs to buy a <$100 OBD I SCAN TOOL so he can have a relationship w/his ECM and "see" what is going on.
It is also possible that your fuel pump relay has failed and the oil pressure switch is what is keeping the engine running. When you slow down the oil pressure may be dropping low enough to drop out as well, depriving the engine of fuel and stalling the motor.
Replace the fuel pump relay and if the problem goes away, you will have found the cause.
Then you will have to find out why your oil pressure is dropping so low. The oil pressure switch should be closed from about 6psi. and higher.
I replaced the oil pressure switch a few months ago. Ill check the relay.
Vacuum leak thru the brake booster, maybe. Had a similar issue yearsss ago. Turned out, the diaphragm in the booster ripped, every time i pressed the brake pedal the engine would stall.
See if the car still stalls with the booster line disconnected/plugged.
