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944 missfire

N

NeilBplymouth

PCGB Member
Member
Hi

I have an 83 944 that has no spark to cylinders 2 and 3. The ECU has been checked by 2 independent engineers who do this sort of thing and both pronounced it OK. Have changed distributor cap and rotor arm; and HT leads all check out. Am coming back to the idea it must be the ECU and its failing under load some how, even when testing OK. Any one got any suggestions? Been off the road for 10 weeks now and getting a bit desperate.
 
Hi

Crank sensors checked and OK.

Found info saying there are 2 capacitors in ECU one does cylinders 1 and 4 the other 2 and 3. Which is why I keep coming back to ECU even though it tests OK. If only I could get a replacement on a trial basis!

Neil
 
If you can obtain a timing light with inductive pick up, you could check each plug lead in turn both with the plug in & with it removed-it would only take a few secs to do each plug & prove that under cranking the ECU was breaking down-you could also disconnect the appropriate injector to avoid fuel spraying in unburnt.

I admit I have never actually needed to do this but have used mine to generally prove similar problems.
 
Hi

What you describe is pretty much what's been done. The puzzle is that the ECU tests OK, so I'm now questioning the reliability of the tests (both of them). Thinking I'll just have to bite the bullet and get a new ECU and hope there isn't something else I've missed.

Neil
 
One thing I forgot to mention the rev counter is only showing half revs too, so something isn't registering right

Neil
 
Do you know anybody with similar car you could swap your ECU into before you buy another?

 
Could it be a wiring issue between the ecu and the coil? (assuming that is where the outputs end up!) one of the outputs from the ecu grounded? Its a while since I looked at it but I think the workshop manual details the colours and outputs from the ecu multiplug
Tony
 
Been trying to trace the harness but nothing obvious to date; may have to revisit that before trying the new ecvu route
 

ORIGINAL: Frenchy

Might sound daft but have you tried swapping the plugs ?
Click to expand...
Always check the silly things first. My car sucked a bit of oil through the breather ( long story ). Cleaned it out and it would not run at all ,sounded like a bag of spanners, put the old plugs in it and hey presto car running spot on. purring like a kitten
 
Hi

Had it "running" with each plug out in turn and no spark at the lead. But I kniw what you mean its always the siple tings that .... up up

Neil
 
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