88' vze idles rough and dies when i open the throttle

[Roadtripper]

Hey everyone, im having problems with 88 3.0 vze 4runner. As the title says it starts up and idles... kinda rough and if I open the throttle it chokes itself out until it dies. If i let go of the throttle before it dies then it goes back to idle. I brought it to a shop which found that the fuel pressure was half of what it should be so they replaced the fuel pump and it ran.... for 2 days (same problem came back.) I pulled off the throttle position sensor and it ran again so i replaced that... 2 days later the same problem came back. I pulled off the tps again but it didnt fix it so i pulled off the MAF sensor which caused the truck to die. Plugged it back on and the truck ran again...for 2 days. I brought it to a shop which said the MAF is fine so they dont know whats happening. Any ideas? Thanks everyone

 

[Brownfaux]

Seems like something is intermittent, the only thing I have had that seemed like what you are experiencing is my coolant temperature sensor when it was acting up. I replaced it but I didn’t need to. The problem was in the wiring harness, it was Brittle and the contacts were staying in contact with the sensor. Wish I had more of an idea for you.

I just got done wrestling with my circuit opening relay and fuel pump.


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[Roadtripper]

mini update:

the problem is intermittent which is hard because i need it to stop working to diagnose it.

I checked all the connections and voltages on the ECU and that is all ok which tells me all the wires and sensors are working. There is little resistance between the ground ECU connections and the body ground when checking ohms with a multimeter so the grounds should be good. I also shorted the fuel pump connection at the diagnostics port with no change so its not the Open Circuit Relay or the Air Flow Meter. A shop also replaced the Air Flow Meter with no change. I changed the main relay just because and its not that.

On to the NEXT!!

When the first shop replaced the fuel pump they said the pressure was 13 psi (half what it should be.) So now I am focused on that. My main thought is the Fuel pressure regulator, maybe a vacume line connected to it (but probably not because I dont see how that would be intermittant) or a problem/blockage in the fuel line.

I will update... let me know if anyone has any thoughts.. Thanks

 

[Roadtripper]

The pressure runs at maybe 20 psi. If i step on the gas it goes all the way down to zero. Without the engine running i can get the pressure all the way to 50psi but once it starts idleing it goes down to 20.

I changed the fuel preasure regulator and the fuel filter. No luck. No obvious kinks in the lines. Exhaust smells fuel rich and sometimed backfires. Is it possible one of the injectors is dumping fuel?

 

[COMTB]

The pressure runs at maybe 20 psi. If i step on the gas it goes all the way down to zero. Without the engine running i can get the pressure all the way to 50psi but once it starts idleing it goes down to 20.

I changed the fuel preasure regulator and the fuel filter. No luck. No obvious kinks in the lines. Exhaust smells fuel rich and sometimed backfires. Is it possible one of the injectors is dumping fuel?

I don't know a ton about the fuel system on these trucks so the pressure drop is weird, and leads me to believe it's an injector or maybe an O-ring went on an injector.

I've had similar issues when I replaced my air filter and accidentally disconnected a vacuum line. It would barely turn-over and wouldn't run. if I did get it running it was extremely rough.

Good Luck!

 

[Ahlem]

If you take the rubber boot off the intake and spray starter fluid in BRIEFLY and start it does it run well for a moment? Will it continue to run if you continue to spray? BIG DISCLAIMER... SAFETY FIRST. An independent shop did this to ours outside near nothing else. The diagnosis was clogged fuel injectors. They were right. We had 3 so clogged they wouldn't spray. After that it's been running well-ish for 3 years. You can also get a spark tester from Harbor Freight and see if you have interrupted spark.