89 idle issues
Thread Starter
Instructor
Joined: Apr 2011
Posts: 160
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From: Edinburg Tx
89 idle issues
quick question, my 89 for some reason starts great and will drive great but after warming up when in park or stopped at light it will idle anywhere from 500-1100 rpms. again this is only when warmed up, when i first start its an even idle at 800rom. exhaust fumes really burn the ol eyes. also noticed that i can disconnect the TPS and car idles exactly the same. hopefully i can get some feedback. Thanks
Le Mans Master
Joined: Aug 2007
Posts: 8,735
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From: WV
Sounds like the car is running rich after it goes into closed loop. The car runs off a set of perameters in the computer when in open loop, when it goes into closed loop somewhere around 140 degrees it starts using all the sensors to determine fuel and air delivery.. It sounds like one of those sensors is not working correctly..My guess would be you have a bad O2 sensor, but the only way to tell for sure is to hook it up to a scanner to see which sensor isn't working properly. The O2 sensor should be changed every few years as part of preventive maintance anyway..You don't want to throw parts at the problem but if the O2 sensor hasn't been changed for awhile that would be a good place to start......WW
Last edited by WW7; Feb 21, 2012 at 08:55 AM.
Thread Starter
Instructor
Joined: Apr 2011
Posts: 160
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From: Edinburg Tx
replaced both, same issue. they told me it could be idle air control valve but it was replaced not too long ago by PO. looks brand new. anyone have any ideas?? seems as WW7 had it right w/ the loop thing. any one think maybe the egr? also noticed that it build pressure up quickly in tank.
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Instructor
Joined: Aug 2011
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From: London, Ontario
Throttle position sensor. If it runs the same when not plugged in I would guess it might not be working. I changed one not too long ago with similar issues and it cured my problems. Scanner is the way to go for sure.
Thread Starter
Instructor
Joined: Apr 2011
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From: Edinburg Tx
TPS is also new. just pulled the fuel pump and man it has a funky smell, also a little dirty in the tank. the sending unit had some rust near the tank and the little valve is completely rusted through. ill post pics. think this could be my issue?
Thread Starter
Instructor
Joined: Apr 2011
Posts: 160
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From: Edinburg Tx
no clue y it would change, maybe heat up and fail a bit?? well today i decided to run some seafoam through it, well seems that the intake has a leak since i saw some smoke coming out near the runners on the back on passenger side. do u guys think it is the intake gaskets? looks like i know what will be happening this weekend. work on new house, have a bday bbq, work on the vette! sounds like fun to me
Thread Starter
Instructor
Joined: Apr 2011
Posts: 160
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From: Edinburg Tx
while removinf runner on side of which seafoam was leaking, i saw a small threaded hole in the middle right under injectors. all three are plugged except for that rear one, anyone know what that threaded hole is or does?
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Racer
Joined: Nov 2010
Posts: 476
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My 89' was doing the EXACT same thing as your's. After a ton of work and $$$$ in parts (Fuel pump, fuel lines, fuel filter, FPR, ERG, TPS, AIC, F.I.C injectors, & complete tune up)......simply changed the ECM and it's ran great since.
Racer
Joined: Mar 2011
Posts: 304
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From: Victoria Australia
Mine did this and also was a bad ECM/EPROM. However, don't jump to conclusions. I found out mine was bad when I tested it through the ALDL connection and it was not completing the 12, 12, 12 code check.
Previous symptoms where a constant sys on the dashboard and my mpg instant would not read. Also when connecting to a scanner it would not read. And yes like yourself, the random high idling and occasional almost stalling low idle. I actually changed the IAC but no luck.
Final nail in the coffin, it got so bad that the car would cut out completely then on restart my speedo would show 0km/h.
Previous symptoms where a constant sys on the dashboard and my mpg instant would not read. Also when connecting to a scanner it would not read. And yes like yourself, the random high idling and occasional almost stalling low idle. I actually changed the IAC but no luck.
Final nail in the coffin, it got so bad that the car would cut out completely then on restart my speedo would show 0km/h.
Thread Starter
Instructor
Joined: Apr 2011
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From: Edinburg Tx
manifolds came off, appears water was seeping through into air ports as well as drivers side rear was somehow shut with some type of paper/cardboard material that formed almost a rock. broke it down w/ a flathead and vacuumed the junk out of head. im hoping that that bad gasket was my issue, tomorrow will be a put back together and see what she does. so far new fuel pump, ecm, maf sensor, iac, and TPS.