we go together lol hes way to compicated
'86 Idle and Stalling Problem
Thread Starter
Instructor
Joined: Feb 2004
Posts: 126
Likes: 3
From: Bloomingburg NY
'86 Idle and Stalling Problem
My 86 with 170k miles is having a problem at idle. It's an intermittant problem. It will be idling fine for about 30 seconds and then it will drop down to about 300-400 rpm. A couple times when it has done this it stalled.
Today I put the scan tool on it. No codes. I did notice however that the car was in closed loop but seemed to be constantly running lean. The O2 counts were zero for a period of time (15-25 seconds) and then it would go back to cycling between lean and rich. I thought maybe the sensor was cold even though the car was up to operating temperature but it didn't change even after driving it with the scan tool on it. Could this be a bad O2 sensor?
I didn't have time to take the throttle body off to clean it but I did try to clean it from the front without removing it. It looked pretty dirty inside since I haven't cleaned it in a year or two. Would this cause it to actually stall or just run rough?
I can make the idle stumble if I hold the brake in drive and blip the throttle. It will speed up and then stumble down to about 300-400 rpm. The IAC looked ok via the scan tool but I haven't actually pulled it.
I looking for ideas.
Thanks,
Andy
Today I put the scan tool on it. No codes. I did notice however that the car was in closed loop but seemed to be constantly running lean. The O2 counts were zero for a period of time (15-25 seconds) and then it would go back to cycling between lean and rich. I thought maybe the sensor was cold even though the car was up to operating temperature but it didn't change even after driving it with the scan tool on it. Could this be a bad O2 sensor?
I didn't have time to take the throttle body off to clean it but I did try to clean it from the front without removing it. It looked pretty dirty inside since I haven't cleaned it in a year or two. Would this cause it to actually stall or just run rough?
I can make the idle stumble if I hold the brake in drive and blip the throttle. It will speed up and then stumble down to about 300-400 rpm. The IAC looked ok via the scan tool but I haven't actually pulled it.
I looking for ideas.
Thanks,
Andy
Instructor
Joined: Dec 2005
Posts: 197
Likes: 0
From: Woodland California
Clean your throttlebody, then adjust the idle & IAC according to the repair or service manuel. If the o2 sensor has not been replaced in many miles, replace it. Its cheap & easy with an o2 sensor removal socket.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Based on the scan, I'd suspect an air flow problem. Either the MAF isn't sending a correct # to the ECM or there's an air leak beyond it. With either situation, the ECM can't match fuel delivery to actual air flow and you get the lean condition the scan revealed to you. Start by disconnecting the MAF. If the stall goes away, you need a new one. If not, examine the rubber connection for rips or tears and make sure there's a good seal between the MAF and the plenum. Apply a soapy solution to the plenum and runners and look for bubbles while it's running. Check vacuum lines for cracks. Run a plumber's welder with the propane turned on (but not lit!) along both sides of the intake and if it speeds up, you need to redo the gaskets.
Corvette172002: Your might have a MAF problem too - but you also have an IAC circuit that isn't working. If you had the throttle body off and the IAC was removed, depress the accelerator slightly and start it up. Let it run for 10 seconds, then off for 5 seconds, then restart it. If the idle isn't correct, a scan would provide you with some key info. For starters, need to know the TPS signal voltage, Targeted RPM, Coolant Temp, and IAC counts.
Corvette172002: Your might have a MAF problem too - but you also have an IAC circuit that isn't working. If you had the throttle body off and the IAC was removed, depress the accelerator slightly and start it up. Let it run for 10 seconds, then off for 5 seconds, then restart it. If the idle isn't correct, a scan would provide you with some key info. For starters, need to know the TPS signal voltage, Targeted RPM, Coolant Temp, and IAC counts.
Advanced
Joined: Jan 2006
Posts: 62
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Maf Quiestion
got 86 vette on my maf sensor i got a screen on the front and the back if i cut em off will it still work fine or wht need info pronto thx oh yea and on my intake box where the filter is the metal cover.....it covers theh whole filter can i cut the middle part out and leave the sides so the filter wont move so i can get more air in lol i need horsepower baddly 
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Instructor
Joined: Dec 2005
Posts: 197
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From: Woodland California
Originally Posted by corvette172002
well i hope ur right tpi i dont wanna screw this up but the screen cutting is there a certain way or what
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Originally Posted by corvette172002
I HAVE NO IDEA WHAT THE HELL U JUST SAID IM ONLY SEVEENTEEN AND IMA STREET RACER SO YEA ITS REALLY SCRWEING ME OVER 
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Originally Posted by dennis50nj
im 51 and dont now either 
Big deal, I'm 54. Go to Borders (use your AARP card for a 10% discount) and buy Ben Watson's Chevy Fuel Injection. When mastered, you'll be able to respond to most of the questions asked here and better yet, you'll also be able to fix your Buick.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Too bad - Here's an oversimplification of how it works: Electronic Fuel Injection is nothing more than a means of supplying fuel delivery to meet the demands of the engine. That means enough fuel to support an air fuel ratio of 14.8/1 or 1 part fuel for every 14.8 parts of air. In order to do this, it needs to know how much air is coming into the engine. The MAF (or Mass Air Flow Sensor) provides that info. Mounted in front of the Intake Plenum, it has a wire that is heated by a voltage. As air is sucked pass the wire, it cools off. To maintain the desired temp of the wire, it's voltage is increased. This rise in voltage is seen by the ECM (Electronic Control Module or computer) and whatever the voltage difference is, the ECM translates into air flow. It then pulses (opens) the injectors (in miliseconds) to give the engine the precise amount of fuel. If the voltage rise is wrong, then so is fuel delivery, and you get a crappy running engine.
