1988 3.2 CARRERA bad engine missfire!,HELP!!
09-07-2008, 05:01 PM
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1988 3.2 CARRERA bad engine missfire!,HELP!!
Recently just bought a new project with a bad engine missfire...
Its a 1988 3.2 carrera coupe and has a bad missfire which make it struggle to tick over..When the car is driven on full throttle however the missfire is much less evident ,although on cruise its there again!
Before i purchased the car the engine had been pulled from what i suspect was to cure this,,i have been informed the heads were taken off/checked and have receipts saying valve stems were replaced..
Also once back together the air flow was replaced with spare and found to be the same,no difference,ecu replaced with spare and no difference!
Since i have received car i have completed the below tasks and still the missfire is the same!! all the injectors cleaned/tested then re-fitted with new "o" rings
i then drained tank and put in fresh fuel.
When i disconnect the cylinder no 5 spark plug wire i am pretty sure i hear no engine sound difference compared when i disconnect the others 1 at a time so this made me point towards this no.5 cylinder........I then swapped the plug then plug wire from this cylinder to another and still No.5 cylinder seems to have no change in running noise when disconnected!!,so this proves plug and lead should be fine.
This still makes me think cylinder no.5 has a problem!!
Last task i performed there was to check the voltage into the fuel injector at no.5and i see 14volts which was the same result as Cylinder no.4!
I am unsure of the next step to take now in regards to testing,not 100% sure it may be a problem with cylinder no.5 although i do suspect it!!
Inlet manifold leak??
ANY help/suggestions would be much appreciated!!
Thanks in advance!
Its a 1988 3.2 carrera coupe and has a bad missfire which make it struggle to tick over..When the car is driven on full throttle however the missfire is much less evident ,although on cruise its there again!
Before i purchased the car the engine had been pulled from what i suspect was to cure this,,i have been informed the heads were taken off/checked and have receipts saying valve stems were replaced..
Also once back together the air flow was replaced with spare and found to be the same,no difference,ecu replaced with spare and no difference!
Since i have received car i have completed the below tasks and still the missfire is the same!! all the injectors cleaned/tested then re-fitted with new "o" rings
i then drained tank and put in fresh fuel.
When i disconnect the cylinder no 5 spark plug wire i am pretty sure i hear no engine sound difference compared when i disconnect the others 1 at a time so this made me point towards this no.5 cylinder........I then swapped the plug then plug wire from this cylinder to another and still No.5 cylinder seems to have no change in running noise when disconnected!!,so this proves plug and lead should be fine.
This still makes me think cylinder no.5 has a problem!!
Last task i performed there was to check the voltage into the fuel injector at no.5and i see 14volts which was the same result as Cylinder no.4!
I am unsure of the next step to take now in regards to testing,not 100% sure it may be a problem with cylinder no.5 although i do suspect it!!
Inlet manifold leak??
ANY help/suggestions would be much appreciated!!
Thanks in advance!
09-07-2008, 07:22 PM
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I agree with Bob; you first need to verify adequate compression in cyl #5. I would also look at the distributor cap. Look for corrosion under the cap on the #5 post and any other obvious damage. With the engine idling (ticking over) spray some carb cleaner around the #5 intake manifold gasket and see if the idle speed changes to check for vacuum leaks. How did the spark plug look on #5 when you pulled it out? Any different from the others? I once had a car (not a Porsche) that had an engine miss that drove me crazy trying to figure it out. It turned out the positive and negative wires to the coil were reversed so you might check that too..........
09-08-2008, 02:18 PM
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You said you checked the HT leads, so I presume you also checked the plug connector? I had one fail recently on my carrera.
Have you checked the CHT? I have the values if you would like them.
Have you checked the WOT switch is not stuck on?
The above advice was spot on.
Finally, try swapping an injector or pulling one and looking at the spray pattern.
Have you checked the CHT? I have the values if you would like them.
Have you checked the WOT switch is not stuck on?
The above advice was spot on.
Finally, try swapping an injector or pulling one and looking at the spray pattern.
Last edited by nathanUK '81 930 G50; 09-08-2008 at 02:39 PM.
09-20-2008, 03:10 PM
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Cheers for responses Guys!!
Car now running perfect,thread continued over on pelican!
http://forums.pelicanparts.com/showt...57#post4191857
Porsche inspector for Peter Morgan UK
http://www.petermorgan.org.uk/inspection.htm
"92" 964 turbo,recently rebuilt using all ARP hardware.Modified heads,SC cams 1 bar boost,headers,wastegate/ tial 0.8 spring to acheive 1 bar,cat bypass,own adj wur,rpm switch,powerflow air intake..bilstein hd with h&r springs,front carbon strut brace
Car now running perfect,thread continued over on pelican!
http://forums.pelicanparts.com/showt...57#post4191857
Porsche inspector for Peter Morgan UK
http://www.petermorgan.org.uk/inspection.htm
"92" 964 turbo,recently rebuilt using all ARP hardware.Modified heads,SC cams 1 bar boost,headers,wastegate/ tial 0.8 spring to acheive 1 bar,cat bypass,own adj wur,rpm switch,powerflow air intake..bilstein hd with h&r springs,front carbon strut brace
