yamlover

1998 Sable with the DOHC engine. 98000 miles. I noticed a slightly rough engine idle and hesitation on acceleration. I replaced fuel filter, all spark plugs with no effect. Upon pulling the #6 cylinder plug wire cap off the spark plug, I realized this cylinder was dead. I slipped a spark tester in the #6 plug wire while running and the gap would easly jump 5/16 of an inch and consistant with engine rpm. Compression for this cylinder reads just under 120 psi cold. I replaced the #6 cylinder fuel injector and spark plug with no effect. No engine codes stored either. Any clues?

R.S.LOGAN

If you are getting fuel and ignition it's got to be compression ? Have you done a compression test on adjoining cyl / other cyls ?

yamlover

I've only checked cylinders 4,5, and 6. They are reading between 115 and 125 psi according to my gauge. I touched the fuel injectors with my stethescope and they all were "clicking". Wondering if the no. 6 cylinder injector isn't getting a signal to open or/and the spark isn't happening at the proper time of the crank rotation.

RickMN

Let me get this straight. You're getting spark on #6. The injector is clicking. Right?

Well, if I remember correctly, back in '98 they used a DIS ignition system. That means it's a waste spark system--one coil covers two cylinders. So if you pulled a plug wire off of #6, that should have killed two cylinders. #6 and it's partner. Did you check compression on the partner cylinder?

Let me just talk out loud for a second......The computer gets it's timing from the crankshaft sensor. That's how it knows to switch ground on and off to the injectors. So, if your check engine light goes off when the engine fires up, your crankshaft position sensor is good. It can't be on target for some cylinders and not others. It either works or it doesn't . And, you're hearing clicking at the injector--so it's getting ground switched on and off. Yet, you think the cylinder is dead. That leaves no fuel or bad compression as the culprits. But the compression looks within range. Which makes me wonder if you've got a clogged injector at #6---or a huge vacuum leak.

If you're thinking of running out and buying a new injector, don't. Remove all the injectors and send them to Linder Tech for testing and rebuilding. They charge about $150 for a set of six. They'll test them and let you know how they worked. Then they rebuild them--better than new.

Hope that "thinking out loud" helped.

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I'm a retired ASE Master/L-1 Technician. I still keep current with the latest automotive technology. Visit my blog for cool articles and TSB's: http://www.ricksfreeautorepairadvice.com/