Irregular engine speed - Team Camaro Tech
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post #1 of 8 (permalink) Old Feb 26th, 01, 06:26 PM Thread Starter
 
Join Date: Feb 2001
Location: Hazard,Ky. USA
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I have a 1986 Iroc 305 tune port.
When I come to a stop me engine speed goes up and down when I back off the throttle. Also at idle, my engine speed goes up and down from 700rpm to 300rpm and sometimes stalls unless I hold the throttle down.

I have replaced MAF,IAC,TPS, fuel pump, and did a complete tune up.

I would really appreciate any help.
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post #2 of 8 (permalink) Old Feb 27th, 01, 06:12 PM
 
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did you check you for and codes on the computer? and i would buy some throttle body cleaner and clean it out.
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post #3 of 8 (permalink) Old Feb 28th, 01, 04:42 AM
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sounds like it could be a vaccuum leak...a co-worker has a 85 'vette with a tpi 350 and his did the same thing when he bought it...we replaced the leaking tpi runner gaskets and it ran like a champ afterwards.

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post #4 of 8 (permalink) Old Feb 28th, 01, 05:00 PM Thread Starter
 
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Thanks to 86 Camaro and Travis. I will check these things out in the next few days and let you know what I find.
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post #5 of 8 (permalink) Old Feb 28th, 01, 11:56 PM
 
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[Try to check the timing if it is not on 0*top dead center idle will fluxuate up and down,it can be up to 3* before the computer will act up like that,did you reset the IAC VALVE measure from bottom of threads to the tip of the pendulume,before doing that plug key in diagnostic terminal {top two ports},turn key to the on position ,wait 15 seconds,go unplug the IAC VALVE,go back into the car and turn the ignition off,now crack the car the idle should be real low about 150 to 200 rpm,get your cars repair manual to get the min-idle speed,it should be around 400rpm for 350 L98,305 should be close to that,stick shift will be set a little higher.after you do that turn off car.when you crank it back it it might still be idled low ,don't woory just drive it down the road above 40 mph the IAC will reset itself.If you have the idle cop off the throttle body you can reset the base idle when you are through,if it is off a little :ALL OF THESE THINGS WILL CAUSE THIS! It will take a little time but make sure ALL of you sensors are set write it will run great!

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post #6 of 8 (permalink) Old Mar 1st, 01, 12:10 AM
 
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<BLOCKQUOTE>quote:</font><HR>Originally posted by T/A GTA:
[Try to check the timing if it is not on 0*top dead center idle will fluxuate up and down,it can be up to 3* before the computer will act up like that,did you reset the IAC VALVE measure from bottom of threads to the tip of the pendulume,before doing that plug key in diagnostic terminal {top two ports},turn key to the on position ,wait 15 seconds,go unplug the IAC VALVE,go back into the car and turn the ignition off,now crack the car the idle should be real low about 150 to 200 rpm,get your cars repair manual to get the min-idle speed,it should be around 400rpm for 350 L98,305 should be close to that,stick shift will be set a little higher.after you do that turn off car.when you crank it back it it might still be idled low ,don't worry just drive it down the road above 40 mph the IAC will reset itself.If you have the idle cap off the throttle body you can reset the base idle when you are through,if it is off a little :ALL OF THESE THINGS WILL CAUSE THIS! It will take a little time but make sure ALL of you sensors are set write it will run great!
GET a good servce manual it will have all the specs of all sensors,if bad replace sensor there is not to many,yours should have 1-knock sensor,maf,iac,speed sensor,try checking the ignition module will make miss like crazy,oxygen sensor,coolant fan sensor,coolant-temp sensor will also cause it trouble if it reads low temp the computer will stay rich mixture mode,it might cause it burn real rich,egr silinoid,egr,maf burn-off relay,speed sensor controls mixture and other settings also,i may have forgot one or two,but i listed the major ones.GOOD LUCK!

<HR></BLOCKQUOTE>



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post #7 of 8 (permalink) Old Mar 1st, 01, 03:49 PM
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Give this a try, pull the vac hose off your egr valve and drive it.
You may get some pinging under cruse because the valve is supposed to partially open then. The spark knock sensor will sense the knock and retard the spark and you may feel this loss of power. If you have good gas this may not be noticable.

If the problem is gone, the egr valve needs to be replaced. There is a passage inside the valve that goes through the stem of the valve and it carbons up and starts the valve opening too far, too soon, even at idle or cranking.
I just finished changing one on a pickup, had two more go bad in the last year.

If pulling the hose doesn't fix it the EGR is fine.
David

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[This message has been edited by davidpozzi (edited 03-01-2001).]

[This message has been edited by davidpozzi (edited 03-01-2001).]
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post #8 of 8 (permalink) Old Mar 6th, 01, 04:36 PM Thread Starter
 
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Thanks again to everyone. I am still checking things on my days off from work. As soon as I get it right I will let you know.
BILL
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