Mechanics

TRUCK STALLS WHEN ENGINE HOT (AFTER 15 MIN OF DRIVING 45+MPH) AND THEN SLOWING DOWN OR IDLING AT STOP SIGN

1990 Toyota 4Runner • 170 miles


It always stall when same conditions exist (engine hot, slowing down or idling at stop sign. (This can't be called intermittent problem)so why no code is recorded for this problem?

The very first time it occurred, I found the inlet hose connected to the throttle body was cracked. Replaced it and it worked fine for 2 weeks and then it kept on stalling.

Engine light works, reports other faults (disconnected O sensor, it was detected, error code was recorded and I was able to read the code from engine light)

Verified and adjusted idle speed (Cold start 1700, gradually rpm drops to 800 in park and 600 in Drive). Timing is set to 10.
PCV is has been a major suspect but the location makes it unreachable unless half parts under the hood are removed but I did heat up the engine and sprayed Throttle cleaner in the valve a few times with no results.

So far done the following:
Used Fuel Injector cleaner and it run fine for 60 miles before it stalled. Inspected all related hoses, cleaned air inlet path, Verified functionality for canister, Dash Pot, Pressure Regulator, EGR Modulator, VSVs and Check Valve per Toyota Shop repair manual instruction. Removed, cleaned and reinstalled Throttle body, Mass Airflow sensor, and EGR valve. Replaced Spark Plugs, Oxygen sensor and Catalytic Converter. Won't make it to the dealer (too far) so I took it to local auto repair shop. They replaced vacuum switch and also killed my battery in the process (total $350) and still problem exists. I have owned this truck for over 20 years and depend on it. Please help!
So far I have spent $787. If my problem is resolved I will most definitely donate to this site.
Avatar
Hadia
February 22, 2012.




I see you've verified that the pressure regulator is working, but have you checked the actual fuel pressure yet?

Rivermikerat
Feb 22, 2012.
Thanks for the reply. No I have not. It could be that it may require another tool to buy and I hesitate to spend any more money unless it really helps. If this test can be done with minimal cost please provide instruction and I will give it a try. For my knowledge, may I ask how (technically)the gas pressure would cause the stall at the situation I am explaincing? And also, why no fault code is recorded?
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Tiny
Hadia
Feb 22, 2012.
You can rent or borrow a fuel pressure gauge at most chain parts stores, like Advanced, Autozone, and O'Reilly.

Rivermikerat
Feb 22, 2012.
To test the Fuel pressure on this 4Runner, the fuel gauge tester requires Banjo fittings and banjo adapter. Unfortunately I can neither find one tester set equipped with these parts to rent nor to buy locally. If I was sure of these parts' size specification I would buy them separately from hardware store. If I find a gauge set online, I would not know if the adapter and fitting that comes with it will be the right size for my needs. Still searching.

Tiny
Hadia
Feb 26, 2012.
Still, if anyone out there can tell me what conditions would make this stall problem not to be picked up by ECU as a fault I appreciate it. (Knowing that ECU can report other faults.)

Tiny
Hadia
Feb 26, 2012.
Have you checked for vacuum leaks? Also check and clean the IAC and EGR, if so equipped.

Rivermikerat
Feb 27, 2012.
As I wrote in the introduction of this thread, among other things, I have inspected all hoses, replaced vacuum switch, removed and cleaned EGR and Throttle body. In this car, I believe the IAC is a build in part of Throttle body and not sure if it can be removed as separate part. The Toyota repair shop Manuel does not mention IAC separately and an internet search for an IAC for this truck ends up with "no results found.". If I am wrong please let me know.

Tiny
Hadia
Feb 27, 2012.
The why no code question is probably because the problem isn't bad enough to cause engine or emissions system damage, just driveability issues.

I don't see where you say you've checked for vacuum leaks, just checked a 'switch' for operation. That doesn't say whether a vacuum leak, which can cause your problem, is present.

Not being able to test the fuel pressure also hurts the ability to diagnose this type of problem. If the pump isn't delivering enough pressure, you can experience vapor lock after the engine compartment heats up. This is where the liquid fuel boils and vaporizes in the fuel lines, and is no longer able to be pumped through the system.

Rivermikerat
Feb 27, 2012.
I have checked all vacuum hoses and other hoses related to EC and EFI systems for wear and tear, cracks and brakes. I have performed any vacuum test that the Toyota Shop repair Manuel calls for (not requiring any special tool except a vacuum gauge).
Of all this work, the vacuum switch is the only thing that Auto Repair shop diagnosed and replaced.
One way or another I will test the fuel pressure and report the results.

Tiny
Hadia
Feb 27, 2012.
Ok. We'll be here.

Rivermikerat
Feb 29, 2012.

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