TomP

Yeah well I kinda fixed it... I decided for the hell of it to get 89 octane gas instead of 93 octane, and now the car doesn't stall when it's cold. It still does the rev-high-rev-low thing, but not as drastically, and the idle evens out faster.

I can just imagine what kinda shape my ignition system is in! That's all I can figure; lower octane = easier to ignite.

And that's also the most work I've done on my car in months... sigh...

martyr

I have the high rev search / stall problem too. 350 motor but same symptoms...guess what? It doesn't seem as bad with a full tank of gas!!! Does that seem strange or what?

TechSmurf

Thank the lord I have this problem not, but if you guys figure it out, lemme know... I tend to see someone with it at least twice a year.. be nice to be able to fix it...

IROC57TPI

Have you guys ever entertained the idea of the IAC being dirty?

Just a thought...

martyr

I've cleaned and reset the IAC. Could try it again.....but what do you think about the full tank of gas partially alleviating the problem?

I could have other issues too. My car will overheat if it sits too long and the alternator drops below 12v at the same time.

firechicken_-54

it could also be the fuel pump, less octane = less viscosity, and the less the pump has to work.

TomP

When it first started, I checked fuel pressure; it's fine. The pressure gauge did show a leaking injector, though, which I have to fix one of these years. Just found it interesting that lower octane gas made the problem less severe. IROC57, I'd heard that about the IAC; haven't cleaned it since the summer tuneup- and I bet it's full of carbon (especially w/the leaking injector). This weekend, if I can escape from my desk at work, I'm going to give my car a mini-tuneup/repair job-

oil change/lube job
pcv valve/clean tb/clean iac
read & clean & regap spark plugs
check & clean distributor cap/rotor contacts
buy & install a rebuilt p/s pump
fill the rear diff (it's leaking, I'm sure it's low)
check the trans fluid level
add more antifreeze
replace the headlight connector
put the new January registration on my car (oops!)
check air pressure/air shock pressure
try to clean out the back seat

Quick_Trans_Am

iTrader: (2)

could someone please explain what the rev high/low thing is?

1991tealRSt-topGuy

can i be the inquisitor and ponder why you were using 93 octane in the first place

2.8's have nowhere near enough compression to warrant that grade of gas

remember, the lower the octane, the better the gas actually is
high octane is actually a downgrade (doesnt burn as easily) to prevent high compression/ worn engines from pinging/knocking/dieseling

its hard to grasp, buts it kinda like a catch 22, especially the way hi-octane gas is marketed

funstick

theres a black tube that runs form the TB to the base manifold on the MAF 2.8s its tends to crack cuasing slight vacum leaks that cuase surging hook up a scanner and if the blm is above 130 id highly sugest taking a look at that tube. now for a good fix. ahhh

get the intake manifold uppr lower middle from a 3.1 camaro and go ahead and toss the silly cold start injector. or just swap the top and use the lter 3.1 tb and plug the vacum post for the IAC on the base manifold and keep the cold start injector. you will need to swap the IAc conncetor and the TPS connector but that very simple to do. i hgihly suggest doing this as it solves 90% of the idleing problems ive seen on the maf cars. good luck have fun

TomP

Sure, you can inquire! I wouldn't say "the lower the octane, the better the gas is". Anyone remember 86 octane? And yeah, lower octane is more "explosive", but, until recently I guess, my ignition system's been strong enough to ignite the 93 (MSD 6AL, MSD Blaster SS coil). And actually, before I did the MSD box, I couldn't run 94 octane gas- or ANY Sunoco gas; my car ran like crap. After the MSD box, I put Sunoco in because I was running on fumes one day- and wow! The car loved it! So ever since then it's been Sunoco 93. And if I'm not around a Sunoco, I still use 93 octane, just because I can afford it.

Funstick, I'll check out that tube. Wouldn't it affect idle all the time though? Do you know if there's any way to check to see which injector is leaking without yanking the whole damn rail out? This weekend I'm going to try priming the pump a few times on a cold motor, then pull the spark plugs, and see if one is wet with fuel. I have the tools to perform an injector balance test; but that won't help me if one is stuck open.

1991tealRSt-topGuy

your right tom,i shouldnt have said that the lower the octane, the better it is...........its hard to explain, because the way hi-octane is marketed, it makes it look like it does so much more for your engine than it actually does

to the average person, hi-octane seems better, thats what i should have said

funstick

pulling the injectors is easy. take off the top manifold and there they are. two bolts and the rail is out. id replace all 6 not just one. best bet is to find a 3.1 and pimp the injectors and replace the plenum top and swap the IAC and the TPS while your at it. it works well. trust me itll fix the wierd idle problems. that black tube is the IAC feed on teh maf cars and if it leaks the ECM wont read the air. hence the lean out and surging

Gumby

Sunoco cheap 86 is really 87.3 and so on and so fourth. all their gas is under rated a point or so.


Also for 17 bucks eastwoodcompany.com has a fuel injector diagnostic kit for all cars and systems.

part # 46150

6SPEED84Z28

iTrader: (1)

there is a GM bulletin for a problem like this (#87-108 stalls, hesitates after cold start). it says to check for air leaks and basic troubleshooting and if nothing is found replace the PROM.

6SPEED84Z28

iTrader: (1)

there is a GM bulletin for a problem like this (#87-108 stalls, hesitates after cold start). it says to check for air leaks and basic troubleshooting and if nothing is found replace the PROM with a new updated one for your application.

6SPEED84Z28

iTrader: (1)

sorry for the double post computer error