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Re: Very odd idle.... Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 27 Jun 2001 11:28:01
In Reply to: Very odd idle...., David Szyszka, Wed, 27 Jun 2001 09:14:33 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Well, never going beyond mid-yellow means that your car is stuck at the base (turbo) boost level. It should got to the end of the yellow/just touch the red.
Without more information, I'd guess that the car is running lean, and that it's knocking. The APC will dial back boost to the base level when it detects knock. That gives you the mid-yellow. Lean running gives you the great fuel mileage (for now).
Of course, that doesn't explain everything. The hunting needle on the tach could be a bad crankshaft sensor, or worse, a slipped tooth on the intake cam. If the intake timing were off, that would increase gas mileage (at the detriment of performance), and make some interesting rattling noises that could fool the knock sensor into dialing back boost.
The comments about damage to cylinder #3 are worrysome, also. What happened? If there is some damage to the head or pistons, that could be causing a hot spot or high compression, either of which can cause knock.
First off, get back to the shop and ask for more details. Next, pull the spark plugs and look - are they a harsh white (indication of running lean?). Look around for leaky vacuum hoses. If you aren't already running premium fuel, run a tank or two and see if that quiets things down.
It may be necessary to pull the valve cover (no big deal) and check the alignment of the cams. Pretty easy - just turn the engine to TDC for cylinder #1, and check the alignment of the marks on the cams versus the marks on the cam blocks. If the mechanic had the head off (to see the cylinder #3 damage), perhaps the cams weren't aligned properly, or the chain wasn't (or isn't) properly tensioned.
Sorry for providing more questions than answers.
, Wed, 27 Jun 2001 11:28:01 <-- Viewing This Message
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