92 c4 idle problems
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92 c4 idle problems
ok guyz heres my story. month ago picked up a 92 C4 with 124K miles. at the time it looked fantastic and ran good. so I took it ion for an inspection at a vette shop and they noted it needed front shocks, front pads and a cooling temp sensor. The person I got it from had replaced the opti-spark and on-board computer so that was outta the way.
I just did the shocks and front pads also the cooling temp sensor. I mostly replaced the CTS cuzz the car was idleing rough in drive when stopped at a light, but drove down the road real good! Right after the CTS was replaced I had thought the idle problem was gone but it came back. The guy that replaced it showed me the scan readout before and after the change which showed great improvement! but still the idle problem was still their and still is now.
I did the injector "screw driver test" and all 8 seem to be pulsing ata steady rate, so don't think that could cause the bad idle, but not sure, I bought a can of BG44 in hopes it might make a difference, isn't here yet so will see.
Anyway am needing suggestions what could be causing the problem.
Once again the problem is the car wants to pulsate when in gear and stopped at a light but runs fine goin down the road. BTW its an automatic
I just did the shocks and front pads also the cooling temp sensor. I mostly replaced the CTS cuzz the car was idleing rough in drive when stopped at a light, but drove down the road real good! Right after the CTS was replaced I had thought the idle problem was gone but it came back. The guy that replaced it showed me the scan readout before and after the change which showed great improvement! but still the idle problem was still their and still is now.
I did the injector "screw driver test" and all 8 seem to be pulsing ata steady rate, so don't think that could cause the bad idle, but not sure, I bought a can of BG44 in hopes it might make a difference, isn't here yet so will see.
Anyway am needing suggestions what could be causing the problem.
Once again the problem is the car wants to pulsate when in gear and stopped at a light but runs fine goin down the road. BTW its an automatic
Last edited by lectroglide; Jul 25, 2014 at 09:45 PM.
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Joined: Sep 2013
Posts: 97
Likes: 2
From: Simi Valley CA
ok guyz heres my story. month ago picked up a 92 C4 with 124K miles. at the time it looked fantastic and ran good. so I took it ion for an inspection at a vette shop and they noted it needed front shocks, front pads and a cooling temp sensor. The person I got it from had replaced the opti-spark and on-board computer so that was outta the way.
I just did the shocks and front pads also the cooling temp sensor. I mostly replaced the CTS cuzz the car was idleing rough in drive when stopped at a light, but drove down the road real good! Right after the CTS was replaced I had thought the idle problem was gone but it came back. The guy that replaced it showed me the scan readout before and after the change which showed great improvement! but still the idle problem was still their and still is now.
I did the injector "screw driver test" and all 8 seem to be pulsing ata steady rate, so don't think that could cause the bad idle, but not sure, I bought a can of BG44 in hopes it might make a difference, isn't here yet so will see.
Anyway am needing suggestions what could be causing the problem.
Once again the problem is the car wants to pulsate when in gear and stopped at a light but runs fine goin down the road. BTW its an automatic
I just did the shocks and front pads also the cooling temp sensor. I mostly replaced the CTS cuzz the car was idleing rough in drive when stopped at a light, but drove down the road real good! Right after the CTS was replaced I had thought the idle problem was gone but it came back. The guy that replaced it showed me the scan readout before and after the change which showed great improvement! but still the idle problem was still their and still is now.
I did the injector "screw driver test" and all 8 seem to be pulsing ata steady rate, so don't think that could cause the bad idle, but not sure, I bought a can of BG44 in hopes it might make a difference, isn't here yet so will see.
Anyway am needing suggestions what could be causing the problem.
Once again the problem is the car wants to pulsate when in gear and stopped at a light but runs fine goin down the road. BTW its an automatic
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Joined: Sep 2013
Posts: 97
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From: Simi Valley CA
It may very well be something else. I merely stated that my '94 presented the same symptoms. Replacing the opti-spark remedied the problem. Do a search of this forum. You'll find that a new opti-spark can go wrong just like one with 50,000 miles on it. They are the twitchiest component to our LT-1 engines.
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It may very well be something else. I merely stated that my '94 presented the same symptoms. Replacing the opti-spark remedied the problem. Do a search of this forum. You'll find that a new opti-spark can go wrong just like one with 50,000 miles on it. They are the twitchiest component to our LT-1 engines.
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Joined: Oct 2011
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From: Dallas Texas
2025 C4 of the Year Finalist - Modified
Rough idle, my guesses are opti or plug wires. On the 40th Ruby I bought, the opti was recently replaced. It died on me 3 weeks ago. Looked good visually, but the shaft made a grinding noise when I'd turn it by hand. Was also hard to turn it. Good luck
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thanx for the reply, just had it out today but now the problem is intermittent so somethings changed. another question is why the rough idle when in gear and stopped but not going down the hiway?
Race Director
Joined: Oct 2011
Posts: 16,087
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From: Dallas Texas
2025 C4 of the Year Finalist - Modified
on these lt1 engines, have a rough idle and it's their nature.
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Melting Slicks
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Yes, post them up.
JFYI, batch fire just means that all the injectors fire at the same time. Not sure if you knew that or not. It works just fine.
Does it idle fine in Park? What is the IAC count at idle in gear? Is it in closed loop or open loop when idling in gear? What was the guy using to look at the CTS?
JFYI, batch fire just means that all the injectors fire at the same time. Not sure if you knew that or not. It works just fine.
Does it idle fine in Park? What is the IAC count at idle in gear? Is it in closed loop or open loop when idling in gear? What was the guy using to look at the CTS?
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Joined: Jul 2014
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Yes, post them up.
JFYI, batch fire just means that all the injectors fire at the same time. Not sure if you knew that or not. It works just fine.
Does it idle fine in Park? What is the IAC count at idle in gear? Is it in closed loop or open loop when idling in gear? What was the guy using to look at the CTS?
JFYI, batch fire just means that all the injectors fire at the same time. Not sure if you knew that or not. It works just fine.
Does it idle fine in Park? What is the IAC count at idle in gear? Is it in closed loop or open loop when idling in gear? What was the guy using to look at the CTS?
Melting Slicks
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From: Delta B.C. Canada
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Another thing to try is removing the throttle body and giving it a good cleaning, including the orifices to the IAC. It also might be the IAC itself.
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