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Q: Keep getting multiple misfire codes, normally different cylinders except on cylinder (0307), can this one be throwing off the rest

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It started with what I thought was lack of fuel, tapped on the gas tank and boom fired up. That to me said fuel pump was going, had it replaced by a certified garage. Got it back it kept having misfire codes so did a almost full tune up, almost because the wiring for this truck is no longer made. The misfire happens some times and at different times. Like sometimes on rough start sometime on accelerating, and sometimes at idle. I have a regular scanning tool and i keep getting multiple misfire codes, sometimes 2 sometimes 5 more so with 6 but always with 7 (sometimes just the 7 cylinder). Now can this number 7 be throwing them off to where they give multiple misfires?

My car has 145500 miles.
My car has an automatic transmission.

A: This may be a problem with the exhaust cata...

This may be a problem with the exhaust catalyst partly clogged causing excessive back pressure. There is a test where the O2 sensor is removed and the back pressure tester is put in the hole to see if the catalyst is clogged.

The computer should be scanned to see if you are running lean from bad O2 sensors or for some other reason. The coil may also be weak and not putting out enough spark energy. Have the system checked by a mechanic since this truck engine may have exhaust problems, engine carbon build up, cracked valve seats, O2 sensor problems, coil problems, camshaft and distributor cam gear worn problems. The list goes on and will require a qualified mechanic time to diagnose this complaint for you. If a shop or mechanic cannot figure it out then it may take a factory trained mechanic to be able to diagnose the problem down to one of the listed issues. The best thing to recommend is to replace all the tune up items first so these can be eliminated. This means coils, plugs, wires, fuel filter and air filter, and PCV valve.

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