CIS help?

Roa, Greg Greg.Roa at Cinergy.COM
Mon Dec 8 13:58:52 EST 2003

Having trouble with my semi-newly aquired 87' 5ktq (MC-1, mac 11).

I've been chasing down a missing at idle and at low speeds.  So far I've found and corrected a few vacuum leaks, and broken wires at the idle/wot connector.

I can get the engine to run pretty well now, with the missing almost completely gone, if I set the duty cycle for the CO% at about 70%.

If I try to set the mixture at the recommended 48%, the engine runs poorly, the idle speed drops, and the missing is very pronounced.  When doing this, the % seems to vary a lot, and getting a good reading is not very easy.  If I disconnect the oxs (new BTW), the mixture does not seem to sit at a steady 50% as I would expect.

I also have found that when I set the mixture to where it should be (48%ish), the frequency valve starts intermittently buzzing, with the misses corresponding directly with the buzzes.

Am I to be looking for a vacuum leak, incorrect fuel pressure, burnt valves, bad injectors, different meter?  Something is definitely not right, but I can't seem to identify the problem.

Thanks in advance!
Greg Roa
Cincinnati, OH
86' 4kcsq x2
87' 5kcstq
93' 90CS
83' 944

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