RedRooster527

Ok my 88 pickup is having issues and I'm about to pull my hair out. It starts/idles fine but after 10 or so miles and its warm it starts 2 backfire and acts like its running out of fuel. If u stay 1/4 or less throttle it actually builds power and runs fine but anything over 1/4 or so it starts doing it. I would like to think its lack of fuel of some sort but the fact it starts/ idle fine and only after it warm it does it doesn't make sense to me. Ive already installed and adjusted new tps with no luck, checked for spark and plug gap, ohmmetered injectors, new battery, checked vacuum lines. Next ill check the fuel pressure from pump and filter but as said before the symptoms dont really point to it. Any suggestions?

RedRooster527

I forgot to mention the check engine light has never been shown but does illuminate with the key on which doesn't make sense to me either

Rerunn

The cel is always going to illuminate with key on. I'd lean towards fuel issue. Your pressure could be fine but if your not getting the correct amount of volume issues will arise.

RedRooster527

Well I mean it hasnt thrown any codes when should have. The only time the cel has been on since I got the truck is when u turn the key on

RedRooster527

Is there anyway it could be fuel pump or something related if it runs fine tell warm. I would think if it was something in the fuel system time or temperature shouldn't matter. It should do all the time not just when it gets warm. And I checked the cat. and muffler to see if one was plugged up. The cat. has been hollowed by the previous owner and guts bout out of the muffler as well. Also the o2 sensor is lose in the pipe and looks ate up with rust so that's something else that should make the cel go off

Rerunn

These things don't kick codes like that. They aren't that sensitive

RedRooster527

Ok so what would make it go off? And what did u mean by getting the right pressure but not volume?

85TurboRunner

Your issue sounds very similar to what my old '85 4Runner was doing.

It would start up, idle great and was able to be driven up until it reached operating temp. Then it would fall on its face, sputtering and backfiring. Then it would just die.

After letting it sit and cool down a bit it would re-start then be able to be driven till it warmed up again.

I came to the conclusion it was an electrical issue and decided to change out the engine harness for a different one.

That fixed the problem and I never had any issues afterwards. I still don't know what the actual problem was but harnesses were pretty cheap and easy to find back then.

JROCK3R

85 turbo runner. My 91 22re is doing the same as yours. It started just every once in a while it would die out. Now I have to stay on the gas at the red light to keep the motor running. I changed the plugs and wires but didn't help. Can you help me step by step on how to fix this problem or find out what's wrong @85turborunner

RedRooster527

Where could I get a harness at, besides salvage yard?

RedRooster527

Whats the chances of the afm causing this?

JROCK3R

I found my problem. It was the plastic intake boot to the manifold. It had a hole sucking in air causing the mass air flow sensor to misread. Cleaned the throttle body and patched the hole runs like a champ.

RedRooster527

Well I got the fuel system pressure tested. When cold it holds 35-38 psi as normal but once its warmed up if you're past 1/4-1/2 in the throttle It drops to 15 psi. Just a weak fuel pump or should I look at something else?

85TurboRunner

I really can't help ya. I never knew the exact cause of the problem. I am electrically inept.

I just came to the conclusion it was somewhere in the engine harness and I was right.

As far as where I found a harness it was C-list. I've also found them at various pick and pulls.

I never pass on a chance to get a complete wire harness since it seems the older these trucks get the more wiring issues pop up.