2.8 wont idle and oil pressure low

nicky gio88gt · Post by **nicky gio88gt** » Wed Dec 20, 2006 1:01 pm

Ok I just put a cone filter on the end of my maf sensor til I get a real intake. Now before I did any of this the car was running great no problems starts right up. I had to disconnect my battery to remove the air box. So of course when you disconnect the battery you reset the cpu. So just today I decided to do that(let it idle with the heater on, let the fans kick on and off, drove it around the neighborhood a little bit.) but now the car doesnt want to idle Ill start the car and it will shut right off, and my oil pressure gauge is saying my pressure is low Im getting plenty of juice my volt gauge says about 13-14 volts, however in the process of bolting the battery up I kinda stripped the negative terminal a little bit(dont know if that makes a diference but I want to give as much info as possible). Also upon cleaning out the engine bay of my car I found a factory sticker that says it was apparently programmed for speed density in 1989.(once again dont know if that matters but I want to give as much info as posssible). Im just trying to be like marvin gaye and try to find out whats goin on here so any help would be appreciated to the fullest extent.
Thanks,
-Nick

ozzy · Post by **ozzy** » Wed Dec 20, 2006 1:19 pm

not sure if this is realted or not..but my kids s-10 2.8 wouldnt hold an idle and stall out..turned out to be the temp control sensor...seems the ecm was setup to run the fuel delivery thru that sensor....hence bad sensor no fuel......juts a thought

nicky gio88gt · Post by **nicky gio88gt** » Wed Dec 20, 2006 7:03 pm

I forgot to add that it only does this when the motor is hot.

Jeff P · Post by **Jeff P** » Thu Dec 21, 2006 1:16 am

It might be a good idea to check for codes first. I doubt it set one, but with luck...Does the negative cable seem like it is secure and getting a good connection? Is your MAF plugged in securely? How's that vacuum line next to the battery? By the way, how easy was it to remove the MAF from the airbox? Just curious, I've never tried it. I don't know how much room is available at the neck of your cone filter, but since you've got the speed density update you could get rid of your MAF and use an IAT sensor instead if you wanted to. It would give you less restriction, anyway.

Man, what's with the million questions?

nicky gio88gt · Post by **nicky gio88gt** » Thu Dec 21, 2006 8:56 am

Removing the maf sensor is very easy theres a regular hose clamp on one end and the other clamp(that attaches to the airbox) was a little bit more trickier because it wasnt like a regular hose clamp it looks like you need like a special tool to get it off but I just wedged a flathead screwdriver in there and gently pryed it from the maf sensor. Theres also a 13mm bolt that connects the maf sensor to a metal support bracket. The airbox was also easy to remove and taking all that metal crap out shaved like 5 pounds from the car . Anyway my negetive terminal is pretty secure and my vacum line is in tact, however I just noticed this morning that I overtighten the 13mm bolt on the support bracket and cracked my maf sensor, fortunetly one of my friends has a brand new maf sensor in his totaled cutass ciera that I can get for free. So hopefully thats the culprate. Anyway, thanks for the help guys.

nicky gio88gt · Post by **nicky gio88gt** » Fri Dec 22, 2006 9:18 am

Just did the maf sensor, its still doin the same thing. When it gets hot, it wont idle when I put it in gear, and when I try to restart it, it shuts right off.

Jeff P · Post by **Jeff P** » Fri Dec 22, 2006 11:47 am

After it shuts off on its own, unplug the oxygen sensor and try to start the car again. This will cause it to run in open loop and if it keeps running will pretty much narrow it down to a sensor problem (or something that is actively regulated, anyway). This may set a code, by the way. You might try disconnecting the battery and doing another idle relearn. It sounds like your car is an automatic, so this time block the wheels, engage the e-brake, and put the car in Drive for the first cycle. Then put the car in Reverse for the 2nd cycle. Turn all accessories, even the heater, off. Anyway, it's worth a try. Sorry the new MAF didn't work. I'm wondering if your IAC valve might be the problem. I take it the oil level is okay?

Edit: How low is it showing the oil pressure?

nicky gio88gt · Post by **nicky gio88gt** » Fri Dec 22, 2006 8:07 pm

Oil level is good, but once it warms up pressure drops to about 15-20 psi, Ive also noticed it takes awhile for my temp gauge to show a reading, I think my o2 sensor is goin bad because after awhile at idle my ses light comes on but usually when your o2 sensor goes it just makes your car run rich or lean not make the car not idle in gear once warm. Im definetly going to try what you said about letting it hang out in gear for the idle relearn and thank you once again hopefully I can nip this thing in the butt.

Scanman88GT · Post by **Scanman88GT** » Fri Dec 22, 2006 10:39 pm

Just so you know, 15-20 PSI at idle is not considered "low". According to GM, the 2.8's can idle at 9 PSI without problems. There was a perceived customer issue with low oil pressure in the 2.8's, which prompted GM to issue a bulletin stating that 9 PSI was considered "normal".

My 2.8 in my 88GT idles at around 30-35 PSI, but I had installed a Melling high flow oil pump before I put the junkyard 2.8 back in, along with a new timing gear/chain set.

Mr Goodwrench · Post by **Mr Goodwrench** » Sun Dec 31, 2006 12:53 am

some of the 2.8 an 4.3 had a special maf relearn or reflash of your ecm to new specs. But i havnt seen or done one in years

Mr Goodwrench

nicky gio88gt · Post by **nicky gio88gt** » Thu Jan 04, 2007 11:40 am

I did the idle relearn that jeff p told and it worked it'll idle in gear now after it warms up, my ses light still comes on though but I think its just my o2 sensor. Thanks once again for the info everyone.

Jeff P · Post by **Jeff P** » Sat Jan 06, 2007 12:51 am

Sounds like good news, Nick, I hope it works out for you

nicky gio88gt · Post by **nicky gio88gt** » Sat Jan 06, 2007 3:31 pm

unforunetly ive now run into a new problem. I just got done doin a few laps around my block and then out of no where my car stalls, and whenever I restart it idles perfectly in park and neutral but as soon as i put it into gear the car shut completly off I couldnt get it in gear without it shutting off. I eventually jammed it into 2nd and got the car home but as sooon as i got into the driveway it stalled out in that gear also. Im thinkin throttle position sensor but I just dont know why though, when i first got this car in june this car was perfectly fine but ever since I put the cone filter on the end of my maf sensor and disconnected my battery its been one thing after another.

1988GTU · Post by **1988GTU** » Sat Jan 06, 2007 4:41 pm

Unplug that blue plug circled in yellow.

It is located right in that area and goes into the trans. Let us know what happens.

metalheadchic3 · Post by **metalheadchic3** » Sun Jan 14, 2007 4:38 am

Yep, sounds like the TCC to me. My '89 2.8 GT was doing the same thing - starting just fine then dying when I put it in gear. Unplugged the TCC and its fine now, just runs a little richer.

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