longhaul

Anyone have a problem with continuing "misfires" (breaking up-rough running) around 4500 rpm+? I've been in and out of the dealer 4 times now...
Doesn't always do it, but many times at a hard pull, it misfires badly (actually has small backfires through the exhaust). I have deprogrammed it and returned it to stock. I though a bad coil pack, but I replaced them with new Accels and still there. Not throwing any codes at all.
Also has a noisy valve tapping at idle when cold. I know there is aTSB on this, but the dealer claims this is normal (yea, right!) Maybe for my 1960 pickup-but an overhead cam(actually cams)?
Anyone had simular problems? I can't even run the car hard, have to baby it to avoid the problems. I have the new factory upgraded fuel pump, and a new filter. Has been doing this for many tanks of fuel, so I don't think it's just a bad batch of gas.
Car has only about 22k on it, and I am getting tired of this . Before it had misfires, and finally, after my demanding they retest, they found a bad coil pack. But after replaceing all with aftermarket-I don't think this is it, this time.
Open to suggestions, anyone?

moosestang

Ummm, have you looked at your spark plugs? Do a compression test to see if all cylinders are within 10% of each other. The only other possible cause is the fuel injectors. Try a can of seafoam and see if that helps.

I have not had that problem by the way. Mine pulls hard all the way up to redline.

Wally39

I had a misfire problem twice before. Once was because I didn't have the spark plugs tight enough when I put them back in and one of them worked it's way loose. The other time was the gap on one of the spark plugs was too big.

moosestang

That reminds me, I need to get one of those special gap tools for our special spark plugs. I feel so special.

hammeron

longhaul, i'm not sure why your getting the misfires....i
like what moose recommended




me too, i've been meaning to get a small vise



[IMG]local://upfiles/37808/62FDD5351CFE4DA1A0BA0DB65BB0F908.jpg[/IMG]

22kart22

yea, check the plugs, and disconnect your battery terminal for a few minutes to reset the computer.

Maybe your computer was screwing up the timing.


Oh and valve-tap occurs when your valve springs wear out and become soft, or usually when your engine has lots of mileage on it.

For example: my dad's 97 expedition has 200,000 miles and half of those were pulling a racing trailer, and the valvetapping just started. Its normal if you have lots of mileage.

Hope this helps alittle!

coji5gt

22kart22, you can recommend clearing the KAM and even if that were to have an effect on the timing, which it most likely will not,you have to think of what caused the car to jump time in the first place. Food for thought.

jrm1900

I'd check the MAF voltage, it should read up to 5v at full throttle, but since your problem happens erratically it might be hard to pinpoint, now if you have a tuner with data logging capabilities you can use it while trying to replicate the problem and read the data in your PC to see if it reveals any problem.
Other possible sources as mentioned before could be fuel filter, fuel injectors, fuel pressure regulator, damaged or bent fuel lines under the car, sparks plugs, a bad contact, fried wires etc etc.
I am sorry you are facing one of those not so straight forward problems, it happens every now and then, I wish you good luck.

22kart22

just an idea......

It may be the problem.

It sometimes works when other cars have problems...

coji5gt

An easier way to check the MAF is toto take a look atthe barometric frequency, it should be between about 152-158 mhz.