Guest j.w. Posted January 28, 2015 Share Posted January 28, 2015 good afternoon folkson a cold am when starting the 1996 century(fuel injection)-it high idles like crazy.I have to drive about 4 miles for the idling to come downwhen the car is just in drive it is going about 35 mph, not even stepping on the gaswhat do you thing the problem is ??many thanks Link to comment Share on other sites More sharing options...
leosdad Posted January 29, 2015 Share Posted January 29, 2015 Check for a code,but my symptoms on a 93 LeSabre were the same.A new throttle position sensor fixed it Link to comment Share on other sites More sharing options...
NTX5467 Posted January 29, 2015 Share Posted January 29, 2015 (edited) With an appropriate scan tool, you can check the TPS percentage, BUT it could also be a sticking stepper motor in the throttle body. It's the stepper motor which regulates air bypassing the throttle plate when it's closed, at idle. It might well be that a good cleaning of the throttle body could take care of the issue, but some GM throttle bodies are either not cleanable, with a reasonable degree of success, so replacement is the only real option, in that case (regarding the internal passages which the stepper motor control). On some throttle body assemblies, the PCV "gasses" are added to the intake manifold tract just behind the throttle plate, which can also allow them to migrate into the throttle body passages under certain conditions . . . why the throttle body might need to be removed for inspection and cleaning of the internal idle passages. What you might investigate would be to get the throttle body internal passages cleaned, the throttle body "plate" area cleaned, then let it sit overnight at the repair shop and have them check for proper operation AND also the TPS signals to the ECM (that the indicated %s match actual throttle opening %s). With the cold engine, you can also check (as it warms up) the signals from the ECM's engine temp sensor, which can possibly have a modulation of the idle speed as the engine warms up. If the temp sensor is "lazy", it might delay the ECM knowing the engine can tolerate slower idle speeds after the cold start.Sometimes, too, a "deposited" EGR circuit can prevent the EGR valve from fully seating at idle (or other times it should be closed). But I would suspect that would set a code.Worst case scenario, it might be an intake manifold leak that closes as the engine warms up. Try the easiest and least expensive things FIRST, though.Just some thoughts,NTX5467 Edited January 29, 2015 by NTX5467 (see edit history) Link to comment Share on other sites More sharing options...
TxBuicks Posted January 30, 2015 Share Posted January 30, 2015 I had the same problem with my 1991. As Leosdad said, the throttle position sensor was the issue. They are not that expensive and easy to change out. Link to comment Share on other sites More sharing options...
Guest j.w. Posted January 30, 2015 Share Posted January 30, 2015 in terms of the throttle position sensorwould the car have to be high idlin g in order to get the code ??when the idle returns to normal-then if using the scannner-would the code still show up ?? Link to comment Share on other sites More sharing options...
leosdad Posted January 31, 2015 Share Posted January 31, 2015 To be honest with you j.w.my Buick never set a check engine code.I changed the TPS on a mechanics advice Link to comment Share on other sites More sharing options...
TxBuicks Posted February 3, 2015 Share Posted February 3, 2015 Mine didn't have the Check Engine light on, and never had a code, either. I just read in the repair guide what the symptoms were and everything pointed to the TPS first. Link to comment Share on other sites More sharing options...
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