ok so i bought a 91 pickup 3.0 4x4 5speed it will start right up in the morning or when its cold out run ok bouncy idle for bout 10 mins then wont idle at all if your foot is not on the gas it will die and will take a good 30-40 sec to start and wont start without giving it gas

any1 have any idea of what could cause this im thinking my maf or it fell out of timing

 

Sounds like the idle air by-pass circuit is clogged/restricted. Or you just need to turn the screw out to let more air in at idle.



It's probably not the AFM(your engine doesn't have a MAF). Though it might be a vacuum leak between the AFM and throttle body. You might want to check for codes just to be on the safe side there too. But there's no way it would ever "fall out of timing". So you don't need to worry about. Of course, it wouldn't hurt to check that the ignition timing is set correctly. Though I highly doubt it would cause this issue even if it was set incorrectly.

And, FYI, when you push on the gas pedal while you're starting the engine, all you're giving it is air. Not gas. It doesn't have a carburetor.

 

K ill try and clean that but the air should be clean that's after the filter

didn't know bout the afm

ive had vehicles come out of timing and ya i worded the gas thing wrong lol thanks

 

I doesn't necessarily need cleaned, not if you can still adjust the idle with the Idle Speed Adjusting Screw. But it could, if you can't adjust the idle speed with the screw, because the throttle body is down stream from the PCV ventilation/breather hose. Which means that at times blowby flows from the crankcase through the ventilation/breather hose, discharging into the air intake hose directly in front of the TB. Which is why throttle bodies need to be cleaned occasionally. They are part of the PCV system.

See pages 2-5 here.

 

I'd be willing to bet, if you take the intake hose off, (the big one that's clamped to the throttle body) and turn it upside down, and look carefully, you will find a large crack that allows un-metered air into the intake. It gets worse as the engine warms up, cuz it expends...

 

That's what I meant by "it might be a vacuum leak between the AFM and throttle body".

Unmetered air, unmeasured air, vacuum leak, false air entry into the air intake/induction system. It all means the same thing in my book.

See page 12.
http://autoshop101.com/forms/h21.pdf

 

Ok so i adjusted that bypass screw till the idle was stable but it at 600rpms and still does not want to start without pushing down the gas pedal

 

Definitely a vac leak maybe bad head gasket