98 Grand Carvan Misfire code

My Van started to run just slightly rough last week then the service engine soon light came on. I then proceeded to take it to my mechanic, Two codes were found - missfire and cylinder 6 missfire. He changed the plugs, wires, PCV valve, rotor, distributor cap and fuel filter.
When I picked up the van it started nice as usual and ran nice and smooth.
I got about 100yards away and all of a sudden the service engine soon light came on and it started running slighlty rough again.... I turned around and had him check the codes, they now say missfire and cylinder #1 missfire..

My mechanic wants me to bring it back to him next week, anyone have some suggestion??

Since he changed the dist cap you must have the 3.0 ltr engine. Make sure you include your engine size in any performance type problem.

I'm not somebody who likes to shotgun parts but, I have plenty of time to pick problems apart. Mechanics usually don't have that luxury. The parts he changed make sense. The fuel filter is a bit of a stretch. He probably had injectors in mind but opted for the first easy step in the fuel system as a CYA thing. You need to change it periodically anyway so no harm done there. You may be wondering why the PCV valve. If it's stuck it can overpressurise the oil system and make the oil seep into the cylinders and cause plug fowling...and a missfire.

From my cushy chair in front of this one eyed monster I'm looking at two possibilities. When the mechanic installed the plug/plug wire on #1 he didn't get the connection tight either at the plug or the cap...or...your fuel injectors are starting to get clogged.

Either you or the mechanic need to check the connections at the spark plugs and the distributor. The back row of plugs are hard to get at but doable. You can pour a can of fuel injector cleaner in the tank at the next fill. Usually a professional cleaning is needed to clean them completely. You've got a 50/50 chance of fixing this kind of problem the first time. I'd give him another chance. If somebody works on my cars I usually give them two strikes. His first mistake was not test driving the car to see if what he did fixed it. Keep in touch.

Thanks for the comments!


Yesterday we checked all connections and Last tuesday I put a additive called techtonics for the fuel ingectors, I was told that stuff was the best. We still have the same problem.

It's wierd all I have to do is slightly touch the gas pedal and the engine smooths right out and runs beatiful. My major problem is I need the inspection sticker and I can't get it if the missfire codes don't go away.

Myself or somebody else could suggest you change this or change that and maybe fix it or just empty your wallet. I recommend you have the guy look at it again and see what he finds. A several hundred mile disconnect from your van does not help. There is nothing better than having your hands and eyes on the problem. Come back here after he looks at it again.

Throttle position sensor or again injectors are candidates. BTW - my 96GC 3.8ltr hesitates ever so slightly when it's cold. 3-4 minutes later it runs fine. No check engine light though. Been doing it for 10 years. A slight tap on the pedal gets it going. Hmm............

[quote=ken288]Thanks for the comments!


Yesterday we checked all connections and Last tuesday I put a additive called techtonics for the fuel ingectors, I was told that stuff was the best. We still have the same problem.

It's wierd all I have to do is slightly touch the gas pedal and the engine smooths right out and runs beatiful. My major problem is I need the inspection sticker and I can't get it if the missfire codes don't go away.[/quote


i had the very same problem 2 months ago on a rebuilt motor, 5000km 2yrs.
turned out to be valves. 2 burnt exhaust 6 worn guides. i discovered by performing leak-down test, after changing a lot of unnesscessry parts. hope this information help you, but i hope its not your problem because its queit expensive,