C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

l98 idle surging

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Old Jul 9, 2011 | 10:32 AM
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Default l98 idle surging

i have developed a new problem with my car. my engine begins to surge after it becomes warm. also if i have the car in drive and am at a stop with the brake on dose not surge as bad if at all. from what i have found on the search there many different things to look for. i have checked TPS - good, i did not find any obvious vacuum leaks or borken tubes. i have replaced MAP and o2 previously. last year did complete tune, plugs, wires, rotor, cap, fuel filter. i have pulled IAC, was really nasty, im thinking i should pull it again and clean it, bu not sure that is the problem, how can i test the IAC for function? thanks for any help.
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Old Nov 28, 2011 | 11:20 AM
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Originally Posted by sharp90
i have developed a new problem with my car. my engine begins to surge after it becomes warm. also if i have the car in drive and am at a stop with the brake on dose not surge as bad if at all. from what i have found on the search there many different things to look for. i have checked TPS - good, i did not find any obvious vacuum leaks or borken tubes. i have replaced MAP and o2 previously. last year did complete tune, plugs, wires, rotor, cap, fuel filter. i have pulled IAC, was really nasty, im thinking i should pull it again and clean it, bu not sure that is the problem, how can i test the IAC for function? thanks for any help.
Were you able to figure out what was causing the surging problem? I have the same problem on a 1990.

Thanks!
-Terry
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Old Nov 28, 2011 | 01:40 PM
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I'm working on the same issue with my L98. See my other threads, lots of good suggestions of items to check.
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Old Dec 1, 2011 | 12:04 PM
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Originally Posted by sharp90
i have pulled IAC, was really nasty, im thinking i should pull it again and clean it, bu not sure that is the problem,

how can i test the IAC for function? thanks for any help.
Did you pull the entire Throttle Body and the IAC housing and clean everything up?

Got a scanner?
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Old Dec 2, 2011 | 08:54 AM
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Originally Posted by sharp90
i have developed a new problem with my car. my engine begins to surge after it becomes warm. also if i have the car in drive and am at a stop with the brake on dose not surge as bad if at all. from what i have found on the search there many different things to look for. i have checked TPS - good, i did not find any obvious vacuum leaks or borken tubes. i have replaced MAP and o2 previously. last year did complete tune, plugs, wires, rotor, cap, fuel filter. i have pulled IAC, was really nasty, im thinking i should pull it again and clean it, bu not sure that is the problem, how can i test the IAC for function? thanks for any help.
I had a similar problem yrs ago with my '91. I checked the injectors (resistance) and several were out of spec.....replaced them and corrected the problem. IF you have originals still in place they are known to cause these types of issues and need to be replaced. Their is a vendor on the forum that many have used. I can not remember his name (John???)

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Old Dec 2, 2011 | 08:56 AM
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Originally Posted by vetteman42
I had a similar problem yrs ago with my '91. I checked the injectors (resistance) and several were out of spec.....replaced them and corrected the problem. IF you have originals still in place they are known to cause these types of issues and need to be replaced. Their is a vendor on the forum that many have used. I can not remember his name (John???)

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Corvette Injectors: http://corvetteinjectors.com/
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Old Dec 2, 2011 | 01:02 PM
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I have a similar problem, only its the reverse of the OPs. My L98 surges until it warms up. Once up to temp, it appears to smooth out.

Have not looked into it since its not affecting driveablitly, however Im assuming it has something to do with the car going from open to closed loop.... since it disapears with temp. Maybe the Ops is opposite....
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Old Dec 2, 2011 | 01:52 PM
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Originally Posted by popo8
I have a similar problem, only its the reverse of the OPs. My L98 surges until it warms up. Once up to temp, it appears to smooth out.

Have not looked into it since its not affecting driveablitly, however Im assuming it has something to do with the car going from open to closed loop.... since it disapears with temp. Maybe the Ops is opposite....
Sounds like compensation to me by the ECM. Should be looked into
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Old Dec 2, 2011 | 01:55 PM
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Originally Posted by aklim
Sounds like compensation to me by the ECM. Should be looked into
My problem or the OPs?

Sorry, hard to think when I look at that avatar you have, lol...
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Old Dec 2, 2011 | 02:12 PM
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Originally Posted by popo8
My problem or the OPs?

Sorry, hard to think when I look at that avatar you have, lol...
Both of you. What it means is that it is outside the parameters of the open loop program but when it is at closed loop, it still has adjustment capability. Sooner or later, it might fall out of that adjustment window

That is the old Jenna Jameson. Too bad she doesn't look like that anymore.
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Old Dec 2, 2011 | 02:16 PM
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Originally Posted by aklim
Both of you. What it means is that it is outside the parameters of the open loop program but when it is at closed loop, it still has adjustment capability. Sooner or later, it might fall out of that adjustment window

That is the old Jenna Jameson. Too bad she doesn't look like that anymore.
Lol... Im sure shes still "dirty" hot.

and ok..... Unfortunately, Im the guy who does not worry about fixing stuff till its broke, so till then..... lol
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Old Dec 2, 2011 | 02:52 PM
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Originally Posted by popo8
Lol... Im sure shes still "dirty" hot.

and ok..... Unfortunately, Im the guy who does not worry about fixing stuff till its broke, so till then..... lol
Not really from the latest pics I have seen

Then you are also the guy that will spend more later on in general. Remember, when something goes, it rarely goes by itself. It usually tries to take something else out with it.
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Old Dec 2, 2011 | 02:55 PM
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Originally Posted by aklim
Not really from the latest pics I have seen

Then you are also the guy that will spend more later on in general. Remember, when something goes, it rarely goes by itself. It usually tries to take something else out with it.
lol....
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