Rallye 350 abnormal rough idle
#1
Rallye 350 abnormal rough idle
RE: '70 Rallye 350
Hi everyone,
Before I list everything that I've done to try to get the idle less rough, let me describe the situation as specifically as possible.
*Abnormally-rough warm idle to where the entire car shakes (rather violently) in gear, less rough out of gear, and smoothes-out beautifully when idle is slightly raised. Outside of the idle issue, the throttle response is phenomenal, and it runs like a top. It just acts like a milkshake machine at idle.*
I've done the following:
I'm going to do a compression test next, but my only other thought is whether a leaky exhaust system would cause this rough idle? Almost half the exhaust is escaping before the muffler, and the mufflers themselves have holes in them. I tried the dollar-bill trick at the tailpipe, but I don't think enough exhaust is coming out to determine if I have a burnt valve; if that would be a contributor to such a violent idle.
Also, maybe it's fickle crack in the intake or near a vacuum source?
I look forward to whatever any of you can suggest; as this car is an 86k survivor, and a blast to drive, I just can't keep a topless can of pop in the car...
-Christian
Hi everyone,
Before I list everything that I've done to try to get the idle less rough, let me describe the situation as specifically as possible.
*Abnormally-rough warm idle to where the entire car shakes (rather violently) in gear, less rough out of gear, and smoothes-out beautifully when idle is slightly raised. Outside of the idle issue, the throttle response is phenomenal, and it runs like a top. It just acts like a milkshake machine at idle.*
I've done the following:
- Replaced points, condenser, plugs, wires, cap, rotor, air/fuel filters, set initial timing @ 7, & set dwell @ 32.
- Carb. rebuilt.
- Intake gasket replaced.
- All vacuum hoses replaced.
I'm going to do a compression test next, but my only other thought is whether a leaky exhaust system would cause this rough idle? Almost half the exhaust is escaping before the muffler, and the mufflers themselves have holes in them. I tried the dollar-bill trick at the tailpipe, but I don't think enough exhaust is coming out to determine if I have a burnt valve; if that would be a contributor to such a violent idle.
Also, maybe it's fickle crack in the intake or near a vacuum source?
I look forward to whatever any of you can suggest; as this car is an 86k survivor, and a blast to drive, I just can't keep a topless can of pop in the car...
-Christian
#4
DoubleV: Yes. Actually, it ran rougher before I did these things. I've already adjusted the mixture screws as well as identified all vacuum leaks (the biggest ones were around the intake, shich I replaced). I'll throw the vacuum gauge back on it tomorrow as post what I'm pulling.
boese1978: I did not check that. But that does raise a question; I thought that split motor mounts would only cause the motor itself to abnormally shake, and not the entire car...
boese1978: I did not check that. But that does raise a question; I thought that split motor mounts would only cause the motor itself to abnormally shake, and not the entire car...
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August 22nd, 2019 08:45 AM