Idle Surg
Thread Starter
Racer
Joined: May 2009
Posts: 342
Likes: 1
From: Cutler Ohio
Ohio Events Coordinator
St. Jude Donor '09
Idle Surg
I'm new to the C4 and the L98, and very new to this problem. I did a search but didn't actually know what to search for. I'll try to describe my problem/concern. When cold idle is smooth, after a normal warmup idle is slightly surging or rolling. While driving everything is good. After speed is reached, as long as it is free idling all is well, however when idling against the compression of the motor such as downhill picking up speed but not giving gas/throttle you will get a bucking type surge. Not at all opposed to changing any part or making any adjustment just want some opinions that will prevent a wild goose chase. Thanks in advance. "pear"
Le Mans Master
Joined: Jul 2009
Posts: 6,381
Likes: 66
From: SF bay area C.A.
C4 of the Year Finalist
Check your IAC also clean around your butterfly on the throttle with TB cleaner to make sure it doesnt hang up . Dist. cap , rotor could be arching.
Last edited by kimmer; Jan 17, 2011 at 03:35 PM.
Thread Starter
Racer
Joined: May 2009
Posts: 342
Likes: 1
From: Cutler Ohio
Ohio Events Coordinator
St. Jude Donor '09
It's an 89, I have not scanned for codes as I'm still looking for an old type scanner. Working this week so I'll have little time to find one or even act on suggestions made to this point, but I'll report back as I proceed and try what I have had, for suggestions... Thanks "pear"
Drifting
Joined: Jun 2010
Posts: 1,853
Likes: 8
From: Westerly RI
It's an 89, I have not scanned for codes as I'm still looking for an old type scanner. Working this week so I'll have little time to find one or even act on suggestions made to this point, but I'll report back as I proceed and try what I have had, for suggestions... Thanks "pear"
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Given the symptoms, no load cruise, I'd suspect the Evaporative Emissions System. Tank should stop venting when you take your foot off the throttle, but if it isn't or if the solenoid is funky, the extra fuel causes the surge. Should be easy to rule out. Clamp off the hose from the Cannister at the throttle body and see if it goes away.
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Thread Starter
Racer
Joined: May 2009
Posts: 342
Likes: 1
From: Cutler Ohio
Ohio Events Coordinator
St. Jude Donor '09
Cleaning the IAC and runing higher grade fuel than the last guy seems to be helping, but not curing yet. MUCH!! improved though. I'll update later as we go. Work and weather have made this a challenge. Thanks guys, "pear"