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Old 11-07-2013, 01:52 PM   #12
OldNuc
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Join Date: Apr 2008
Location: Far Southwestern Iowa
Posts: 64,635
 

1998 SC2
Default Re: Warm 98 SL2 Engine Hesitation when changing throttle position upward

Check the exhaust by allowing the entire system to reach room temperature and then pressurize from an external low pressure source and spray down every inch of the pipe with soapy water between the head and CAT inlet. The remainder of the system will not cause this problem. You can not hear the size of leak you are looking for. Low pressure source is a shop vac that will blow, leaf blower, or large fan.

This has noting to do with closed loop at all ever, what happens is the base mixture changes to a leaner setting when the engine warms up and this lean mixture causes the hesitation to become apparent.

Buy new plug wires instead of fiddling around with a swap that will prove nothing. Plug wires do not last forever.

Did not think the EGR was the problem here to start with.

Quote:
Originally Posted by climbski View Post
Tested the EGR and that didnt change anything.

Checked for exhaust leaks somewhat. No leak at block or other side of exhaust manifold. No audible leak in front or back of either cat but that may not be conclusive.

There is a small leak after at the back end of the muffler.

The wires on my 00 SW2 are a pain to remove so didnt have time to swap them (if they even fit on the 98)

A question. This problem seems related to closed loop operation. But I replaced and checked the ects and plug..I did plug it in backwards at first which intantly caused problems and the service engine light. Then I put it on right and reset. No problem.

Have not checked front O2 sensor.

Could a loose timing chain cause this problem only in closed loop?

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