Yet another misfire prob HELP!

[DarksideGA]

I have a 99 se 3.4 and it seems when the engine bay is fully saturated with heat and im cruising along between 1200 and 1900 rpm the engine will have slight random misfires, and it also does it when there are grade changes in the road, i.e. when the road is sloping upwards, it will only misfire once when i start climbing the hills and thats when the load is placed on the engine at the bottom of the hill. wtf is going on?? i checked the plugs replaced the wires and its sitll doing it. has anyone else had a problem like this with their 3400? if so and u found the problem let me know, or if you have any other knowledge about this problem. thanks in advance!!!

[Factory_freak2k]

check your gaps, and your compression ... and check and make sure your wires aren't mixed up... and check your air filter and funnel for blockage or buildup... and switch gas stations... or get higher octance fuel... see if that changes anything ... and it never hurts a little fuel injection cleaner thorugh the engine when some power is lost... dirty injectors are causes of nasty problems... Good Luck !

[rixGAphx]

Dark-

To the best of my knowledge, there is no 'endemic' problem of this sort with 3.4's.

Have you had the codes read? That would be step 1.

Step 2 is the things Factory spoke of, since they are free and simple.
Except raising fuel octane: you should NEVER have a problem with a stock 3.4 using 87 octane from a name-brand gas company.
However, none of them leap to mind as a cause of random mis-fire.

Please describe the 'misfire':
Is it a jolting thing, or just a slight hesitation?
Is there a noise, either ping ('knocking') or a 'pop' (slight backfire)?

I'm thinking a minor vacuum leak, so check all the vac hoses and connections.
There's a 'vacuum accumulator' bottle (under the battery on the earlier 3.1's, and I think on your 3.4 also), with a plastic T-fitting about 4 inches out into the engine bay. This T is easily disconnected by accident, so look at that.

The other possibility is a slightly-loose, or failing, coil pack.
If the stored codes indicate that the 'random miss' is on a particular pair of cylinders, then try replacing that single coil.

To the best of my knowledge, there is no 'endemic' problem os this sort with 3.4's.

Good luck.
-Rick