Misfire?


90gmcmoneypit
05-16-2005, 07:49 AM
Ok, my scenario is that I recently purchased a 1990 GMC Jimmy 4.3 4wd with a little over 140k miles. I notice at speeds of 60mph or more when accelerating, I hear a slight knock. As of last night, when accelerating, I notice a "sputter" where the engine stalls briefly (leading me to believe that it's one cylinder that is acting up), accompanied by a knocking. The fuel mixture is obviously rich, as my tail pipe is carbonized at the tip. The plugs are old, as are the wires (all things that I just haven't gotten to yet) and the air filter is dirty, but not dirty enough to cause a major issue. No check engine light (so I'm assuming no codes). Any suggestions?

rlith
05-16-2005, 08:39 AM
Do a tune up, replace your ignition module (use lots of dialectric grease) If that doesn't help, I would start looking to the cat. You say you have a lot of soot at the tail pipe, well, it has to go through the car first and it may be clogged. Also check your injector flow. They should be firing an nice cone. If they are dripping what so ever, replace them.

90gmcmoneypit
05-16-2005, 08:48 AM
Forgot to mention fuel smell on the dipstick.

BlazerLT
05-18-2005, 06:12 PM
Forgot to mention fuel smell on the dipstick.

Change the oil ASAP.

Get the engine timed with a timing gun and the timing wire disconnected.

Change the plugs, wires, cap and rotor, PCV valve, air filter, fuel filter.

Schrade
05-21-2005, 09:14 PM
A leaking injector could be allowing fuel to drip into the cylinder, and into the crankcase after shutdown (overnight).
Does the check engine light 'light up' when you turn the key to the 'start' position? If it doesn't, fix this FIRST!!!

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