Skipping

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Skipping

Postby gdaddy » Wed Jul 01, 2015 2:29 pm

OK. I have in my shop a 1988 Ford ranger with a V6 2.9 engine. It came in with a misfire on cylinders 1 and 4. The customer had replaced the plugs and wires. He took it to another shop and they replaced the fuel pressure regulator and the distributor cap. I replaced the distributor and the ECM. No help. I did a flow test on the injectors are they passed. I raised the fuel rail and did a pattern test and that led to replacing the two injectors on cylinders 1 and 4. The static compression is 180 on 2356. 1 and 4 are about 10 pounds less. I installed the cylinder pressure tester from Pico and the pattern looks god. Running compression is about 10 pounds less than the other cylinders. Vacuum gauge reads steady. Spark is good, injector pattern looks normal. Cylinders 1,4,and 2 are on the same control wire to the ECM. This is a hard dead skip. I have tried everything I know to do and nothing helps. Any advice would be appreciated. This system has the TFI module mounted to the distributor. Adding small amount of propane makes things worse. Thanks in advance, Mie
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Re: Skipping

Postby roadserpent » Sat Jul 04, 2015 4:09 am

After reading your post, I took a peak at alldata to look at engine configuration. Firing order, intake manifold layouts ( upper and lower ), cylinder numbering and so on. #1 and #4 cylinders are both front cylinders left and right banks , they share a common intake runner and fire one right after another. with the info posted here without you posting some wave forms to look at, my best three guesses would be - big vacuum leak at front of manifold, tight valve adjustments ( this is a solid lifter cam ), burnt or leaking valves caused by different reasons, and possibly worn cam lobe or lobes. If you have a WPS500 pressure transducer you should post running and cranking cylinder pressure waveforms of both dead cylinders and ones of a good running cylinder to compare them to. Posting one of the WPS500 hooked up to the intake vacuum at cranking might be helpful also.

Jim just south of ya in Florida.
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Re: Skipping

Postby gdaddy » Tue Jul 07, 2015 3:52 pm

Thank you for the reply. I will do that,Mike
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