My engine has 255,000 kms on it now. It is the 5spd model. My engine doesn't idle very well anymore, it would stall out quite a bit before but i slightly increased the idle speed and it helped, as it hasn't stalled since I have done that last fall, but the idling is very weird. It will idle around 900-1000rpm but slowly rev up to like 2000 or 2200 then kinda choke down to 1000 then up to 2 then down to 1, and repeat as long as its idling. It does this most of the time. Any ideas? I have engine error codes sometimes, something about intake air temperature, but I've checked the air filters and such. (K&N)

Thanks for any info u can give me. I try to be mechanically inclined but my knowledge base is fairly low, so please be descriptive.

 

Start by looking for vacuum leaks. With the engine running spray some carb cleaner around if the car revs you have found a leak. Keep in mind though this is not the "safest" method . Take care not to spray too much and try to avoid the exhaust manifolds all together.

 

Sounds like your IAC passageway (and IAC motor's pintle) is clogged up with years of carbon. The IAC lets a controlled amount of air go around your throttle body's intake plate; so when your foot's off the gas, the IAC lets some air slip by.

If you remove your air intake hose to the top front of the engine, you'll see the TB's butterfly plate. Look directly to the passenger side of the plate; you'll see a "dark" area; looks like a side of an oval; in that area's a hole- that's where the bypassed air comes through. Now, look to the top passenger side of the back outside of the TB- you'll see a black cylinder poking into there, with a 4-pin square connector going to it. That's the IAC motor.

Anyway, search for "IAC" on this message board and you'll find my instructions on how to clean both the motor and the passageway... all you need is a can of "throttle body and intake cleaner for fuel injected engines" (like carb cleaner, but safe for fuel injected motors), a big adjustable wrench to get the IAC out, a flat screwdriver to remove the intake tube, and 10 minutes.

Aw hell, here's the message... welcome to the website! https://www.thirdgen.org/messgboard/...ML/001539.html


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Tom and HIX5000 have good points, I endorse thaose ideas, also.
BUT
You have a bad/worn timing chain.
Check it this way.
Take off the cap.
Twist the engine crank. Watch how long it takes to move the distrib rotor.
Your engine is worn, that's obvious, but, this is part of the problem which can cause other parts to appear worn and lead them to become worn out.
You have some work to do, to bring your engine back to life or a major transplant (another engine).
Been there.
I gave mine a transplant after I worked on the 2.8.

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Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA

 

I was going to say how if he's got 255000 km on the car, that's 159,000 miles- and my car was running great when I replaced my timing chain at 185,000 miles (298,000 km's). But, then again, I don't know how well his car's been maintained...

He should check all the easy stuff first, then go after the timing chain.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Ok, I couldn't find any vaccuum leaks, but probably because I am inexperienced in what to look for. I did clean out the IAC (and its place in the TB) as directed and I *think* it solved the problem. I will have more extensive test driving to do first. Could anyone take a whack at why I had to (like 6 months ago) slightly increase my idle speed to avoid stalling? Would it be becasue of the same reasons as above?

Thanks