Misfire now..

[350rs]

Unbelievable..

Finally have idle problem solved and all was FINALLY running well with the car. First time since shortly after i bought it. And now i throw code P0300. Using search i found that the NGK Iridium plugs have been known to mess with these cars. But ive had them in there 15k miles or more.. I guess all i can do is pull them and check them out, replace maybe. Ill check the boots. One coil pack is brand new but i still have the old one. Maybe it went bad somehow?

Was fine on the way to work. On the way home however.. I had to hammer it to get past a super slow lady on the highway. Only went from 55 or so to 70 or 75 but i think thats what did me in. Ran fine the rest of the way on the highway. As soon as i got off and to a complete stop though heavy shaking from the misfire. Had to get home though and i was still 15 mins away. I made it home and messed with it a few seconds before shutting it off. It runs better but not great in neutral or park ( no load ).

What is MOST COMMONLY the issue here? Ill check what can be checked shortly. How often do these cars jump a tooth on the timing chain? With the RPM's and whatnot i about half expect that issue. But i dont at the same time since it runs fine at speed.

[350rs]

checked all plugs and wires. two looked fishy ( from the same coil that i just replaced) so i replaced them. Now i have it down to ONE cylinder at least. Cylinder three. But this scares me. The two i replaced looked to have a lot of rust of them. All of them seemed to have some. And two of the cylinders are right beside each other.. AND i noticed im loosing coolant. But not externally and its not mixing with oil. I dont notice any white smoke. but that dont mean its not a small enough leak that i dont notice the smoke. So, possible head gasket job comming up.

[350rs]

well due to all problems im having.. im pulling the motor. Ive got several leaks anyway. Worth my time to take pics and make a walk through? IMO if you need one you shouldnt do it.. but some people are just bound and determined.

[AaronGTR]

just fyi, I've never had any problems with NGK iridium plugs or heard of them causing misfires. They wouldn't be fine for 15k miles then just suddenly cause a misfire problem to pop up that is severe enough to set a code in the PCM. There has got to be some other issue.

[350rs]

there is. head gaskets causeing them to foul. but none the less i found a few threads stating that they had trouble with them.

[stewartfn18]

how would a hg cause a spark plug to foul. please explain. since ive:
a. never heard of this happening, and
b. never heard of the iridium plugs causing problems on the 3400.

i have them and have had no problems with them.

[GrandAmGT-2008]

a head gasket pumping too much oil/antifreeze would be enough to foul a plug.. i would think the head gasket would be a bigger issue than a fouled plug though.. imo

[stewartfn18]

Originally Posted by GrandAmGT-2008

a head gasket pumping too much oil/antifreeze would be enough to foul a plug.. i would think the head gasket would be a bigger issue than a fouled plug though.. imo

ok ummm, unless the hg failed coolant and oil should NOT be in the combustion chamber AT ALL. ignorance is bliss. good god. fouled plugs are usually caused by the car running too"rich", do i need to explain to u what running rich is??

[GrandAmGT-2008]

then where is his coolant going genius? and yeah what is rich? do you mean there is too much fuel and not enough air? crazy..

[stewartfn18]

Originally Posted by GrandAmGT-2008

then where is his coolant going genius? and yeah what is rich? do you mean there is too much fuel and not enough air? crazy..

coolant does not go into the cc. it circulates through passages in the block. good lord do i need to school u again or are u going to drop this e thug thing u got going, and y do u need to resort to name calling. are you 12?

[GrandAmGT-2008]

you basically called me ignorant.. Your also telling me that there is no way that a head gasket could be blown out between the combustion chamber and a coolant passage.. or that it runs in the lower intake.. could be leaking from a coolant passage to an intake runner too. either way... a head gasket is a possibility... maybe he should do a leak down test on the coolant system, and/or the cylinders.

[stewartfn18]

Originally Posted by stewartfn18

ok ummm, unless the hg failed coolant and oil should NOT be in the combustion chamber AT ALL. ignorance is bliss. good god. fouled plugs are usually caused by the car running too"rich", do i need to explain to u what running rich is??

as you can see, i DID say that if the hg failed coolant could "possibly" enter the cc. OP never stated that that was the problem though

[stewartfn18]

OP do a compression test and youll get ur answer, we cant diagnose your problem, thats up to u. all we can do is point u in the right direction

[avro206]

Had the same thing on wifes 3400 powered Olds minivan. Had the code cleared, never came back. Maybe it's bad gas?

Guess I was lucky. Read this

http://www.obd-codes.com/p0300

[350rs]

a head gasket failure can cause coolant to enter my combustion chamber. causing the small amounts of rust im seeing. Which would also explain my nearly empty tank.

Planned on doing a compression test before ripping motor out. I have a small puddle under the TB again which could be the LIM again OR the head gaskets. But this isnt nearly enough mess to cause all of that to leak out in less than a week. Its been starting rough also.

The thing with the plugs was found on this site using the search function. Look or dont look, i found it in several older posts two or three pages back.

Im not here to start the apparent pissing match that has occurred.

edit: its not just any iridium. its the NGK IX or something like that ( which im using ) that have been the problem.

[AaronGTR]

A head gasket failure could cause you to be burning coolant and could foul a plug. That would be the result of the head gasket failure though of course and would not be a sign that there is anything wrong with iridium plugs or NGK's.... any plug will foul under those conditions no matter what type or brand.

If you had a blown head gasket, you'd know it for sure. If you are getting coolant under the Tb, it most likely is not the head gasket but rather the LIM gasket or something else in that area. There are a lot of coolant connections there.


For your previous question about the timing chain, they usually don't jump a tooth... if they jump they come right off the sprocket and you are gonna bend some valves at the least. It is common for the stock chains to stretch out a bit, and they might jump or break if you push them. That is why most performance builds people go to the beefier early timing set. The stock chain is only really likely to jump off if you are doing something stupid though. Like that guy from california with the built engine and turbo who was revving his motor to 7,000 rpm, after we told him not to.

[stewartfn18]

Originally Posted by AaronGTR

For your previous question about the timing chain, they usually don't jump a tooth... if they jump they come right off the sprocket and you are gonna bend some valves at the least. It is common for the stock chains to stretch out a bit, and they might jump or break if you push them. That is why most performance builds people go to the beefier early timing set.

i wish i wouldve known this when i built my motor

[350rs]

Originally Posted by AaronGTR

For your previous question about the timing chain, they usually don't jump a tooth... if they jump they come right off the sprocket and you are gonna bend some valves at the least. It is common for the stock chains to stretch out a bit, and they might jump or break if you push them. That is why most performance builds people go to the beefier early timing set. The stock chain is only really likely to jump off if you are doing something stupid though. Like that guy from california with the built engine and turbo who was revving his motor to 7,000 rpm, after we told him not to.

which set is that? Im about a hour or so away from having the motor out and i planned on replacing the chain at least if its getting close to the stretch limit.

When i pulled the radiator hosed ( couldnt get the pet**** lose) i had a strange thing happen. The lower hose was pretty normal. However the upper had the milky oil looking stuff. But when i drained my oil it was clean even for almost 3000 miles. So there is some kind of leaking somewhere. Maybe even in a few places. Ill be getting the radiator cleaned and flushed while im at this stage. Im hoping i can find one of those little comb like things to straighten the fins out on the radiator. Its pretty messed up on the bottom.

Considering replacing the torque converter as well. I have the also typical 2 or 300 RPM jump in overdrive. Has anybody come up with a deffinate fix? Ive heard of a seal on some main shaft leaking, ive heard the TC, the TCC.. anything that is solidly it?

[stewartfn18]

alot of times people use the 99 3400 timing set

[350rs]

can i use just the chain? or do i need the whole setup?