Quote:
Originally Posted by SkunkWorks
Thanks to Moozak for letting me borrow his gauges.
Issue: My US 1980 SC has a 2200 RPM stutter/buck at all operating temperatures. Generally seems to run rather lean when cold evidenced through occasional intake backfires and enhanced bucking from above. And has a low cold idle @6-700 RPM.
Been chasing the cause for the past few months, but I didn't want to take the car off the road and the issue was livable before. Would appreciate Pelican's insight and suggestions for things to check!
Things to note: Replaced all intake gaskets, performed a smoke test for vac leaks, adjusted timing to spec, CO adjusted to spec of 0.8, oil cap off results in lowered RPM and rough running.
Known possible issues:WUR (072) has resistance of 48 ohms but wouldn't this just affect how long it takes to warm up? and pulling the O2 relay with car running results in no change to running.
Performed the test with outside temps at 9C/48F
System: 62 psi/4.27 bar Slightly low, but close enough? Spec is 4.5-5.2 bar
Control: 10.5/0.7 Super low. Bentley calls for CP cold of 1.5-2 bar @ 10C
30 sec: 12
1 min: 16
2 min: 22
3 min: 27
4 min: 30
5 min: 32
7 min: 34
9 min: 35
12 min: 36/2.5 Also low, spec is 3.4-3.8 bar
Residual: 62 psi
10 min: 19 psi
Questions:
- Does my system pressure being off by 3 psi a major cause for concern? Will check the FP for leaks today
- Control pressure is very low. But wouldn't this result in very RICH condition? Currently car seems to run lean, not rich...
- The delta for my control pressure is 25.5 (36-10.5) while spec is 28 (50-22). Is this an indication that the WUR needs to be rebuilt and not just a case of readjusting the CP through the knocking of the plug?
I think that's it for now... Plan of attack? What to check first? Have Bentley, and have extra beer to go around. Thanks Pelican!
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Skunkworks,
If I were doing the troubleshooting of your
CIS, I would focus on the following:
1). You have the wrong
WUR internal parts. The
WUR housing is -072 as you stated. I would bet my money that someone installed the wrong bi-metalic heater either by you or someone before you. Don't expect it to work as well as the real WUR-072.
2). Cold control fuel pressure out of spec.
3). System fuel pressure out of spec.
4). Ideally, it would take between 3 to 4 mins. (or shorter) from
CP to
WCP depending on the ambient temperature.
With the engine fully warmed-up and running, place your fingers on the
FV located behind the engine. It should be vibrating or pulsating when in operation. You can't hear the
FP from the rear with the motor running unless you have super sensitive sense of hearing.
In case you need to borrow a calibrated
WUR-072 for your tests, I'll be more than happy to accommodate you, provided you have a
USA shipping address. You don't need to buy the WUR, just use try it on your car and return when you are done.
BTW, say hello to
Moozak (Jon). He called me a few times when he was having problem with his
CIS last year. And he's very capable doing systematic troubleshooting. He should lend a hand fixing your problem. Keep us posted.
Tony