erratic cold idle

bob brady

3 black cars
on cold start, my buick races from 1000 rpm to 2000 rpm rhythmically for 30 seconds or so. makes a metalic noise the sounds like a gas ping! i have replaced the IAC, and the MAF with no results. could it be a fuel pressure regulator with a bad diaphram leaking gas into vacuum line and actually make the motor knock?
 

NY Twin Turbo

All the good stuff.....Times 2.
In my experience, a rolling Idle usually indicates a lean condition. Engines require more fuel to idle when cold. You should include more information from instrumentation.
 

Gene Van Horn

Active Member
Bob,make a video. No way it should be pinging at 1to 2000 idle, if your hearing metal noises there is prob more in depth prob. How does it actually run down the road, any knock happening when driving?
 

bob brady

3 black cars
Bob,make a video. No way it should be pinging at 1to 2000 idle, if your hearing metal noises there is prob more in depth prob. How does it actually run down the road, any knock happening when driving?
once it's been running 2 minutes, the idle is normal, and the noise is gone! runs perfectly!
 

bob brady

3 black cars
Bob,make a video. No way it should be pinging at 1to 2000 idle, if your hearing metal noises there is prob more in depth prob. How does it actually run down the road, any knock happening when driving?
Bob,make a video. No way it should be pinging at 1to 2000 idle, if your hearing metal noises there is prob more in depth prob. How does it actually run down the road, any knock happening when driving?
Bob,make a video. No way it should be pinging at 1to 2000 idle, if your hearing metal noises there is prob more in depth prob. How does it actually run down the road, any knock happening when driving?
after getting closer to engine, it is not a ping! sounds deeper.
 

Butchman

Member
I had that issue years ago with my T-Type. It would race around on its own for a minute and then idle and run fine. I had a few vacuum leaks and my IAT was cracked. When I replaced that it stopped.
 

bob brady

3 black cars
i disconnected the cam sensor while car was running erratically, and it straightened right out! found a cracked cam sensor cap!
 

NY Twin Turbo

All the good stuff.....Times 2.
Still say it’s lean. Try increasing the fuel pressure before the motor goes into closed loop. Easy to do a quick check. If it doesn’t work put it back where it was and no harm no foul. Then move on to something else.
 

dank GN

BlackArts Automotive (661)993-8277
Have you set your IAC correctly? Your TPS? What kinda vacuum are you pulling at idle? Have you check that your crank and cam sensor are set correctly ? If you don’t know how to set them go to What are your scanmaster readings ? Post them up so we can possibly help you if not we are all just guessing right along with you . If you don’t know how to set it correctly then I would suggest you spend some time reading all this great material http://www.vortexbuicks-etc.com/
 
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