Thread: Inconsistant engine miss

I have a a misfire for a few months that has gradually gotton worse. I have replaced plugs and wires, cam sensor and crank sensor. I dont think its a mechanical miss because there is nothing consistant about it. Looking for more ideas. Thanks

2000 gt

yes. the silver heat shields are in place

Could you explain why? Im not against trying it but I would like to understand it.

I would NOT get rid of the heat sleeves. They are there to keep the wires from burning up from exhaust heat. If your wires are good they will not arc through the sleeves. When does it misfire? Did a set a DTC for a misfire? You need to determine which cylinder is misfiring to fix it. It could still be a coil, module, injector, wiring, vacuum leak, or mechanical. If the plugs and wires are good the next most likely causes are a coil or injector/injector wiring. I am assuming you did gap the plugs correctly.

its strange. seems to miss mostly at low RPM and it can be idling and missing then suddenly smooth out......
Gapped plugs at .60

What kind of plugs did you install?

I have recently discovered that my map sensor was wiggling. i separated the the things that hold it in place and half the sensor lifted up...... kinda like opening a chest..... anyway..... i ordered one off ebay. will put that on and see how it runs in a few days.

Ok map sensor didnt fix the miss.... im gonna try swapping out a coil pack with a used one a friend has.....

ok it looks like it was a coil. Got a set of used coil packs from a friend and so far no misfiring. Thanks for the advice

Intermittent Misfire While Driving

An intermittent misfire that occurs while driving may be caused by a weak coil or worn spark plugs. The distributorless ignition system on the 3800 V6 is a waste spark system with three ignition coils. Each pair of cylinders shares a common ignition coil. Cylinders that are opposite one another in the engine's firing order are paired so their spark plugs share the same coil. This reduces the total number of coils needed. When each coil discharges its high voltage output, it fires two spark plugs simultaneously: one when cylinder is on its compression stroke, and the other when the cylinder is on its exhaust stroke.
They call it a "waste spark" system because the plug that fires on the exhaust stroke does nothing. Only the plug that fires during its compression stroke produces power. Even so, both spark plugs experience roughly twice the electrode wear that spark plugs in other types of ignition systems undergo (because the fire every engine revolution rather than every other engine revolution).
Remove and inspect the spark plugs. Replace the spark plugs if any are found to be fouled or worn. The spark plugs should be gapped to .060 inches. If the spark plugs appear to be okay, inspect the ignition wires. High mileage wires (those with over 100,000 miles on them) can develop increased resistance that may cause the engine to misfire. Replace any wires that are cracked, fit loosely or are damaged.
If the plugs and wires are okay (or you've replaced them), and the engine still experiences misfires, use a scan tool to check for misfire codes. The Check Engine light should be on, and there should be one or more misfire codes for the cylinders that are misfiring.
The last digit on a misfire code indicates the cylinder number. A code P0302, for example, would tell you cylinder #2 is misfiring. Chances are the misfire is due to a weak ignition coil.
Buick 3800 ignition coils
The three ignition coils on the 3800 engine fire cylinders 6 and 3, 2 and 5, and 1 and 4. If you find misfire codes for any of these paired cylinders, you can be sure the problem is a bad ignition coil and not something else such as lean misfire caused by a bad fuel injector, vacuum leak or EGR leak, or compression misfire due to leaky or sticky valves.
Ignition coils can be replaced separately on the ignition module. But if one coil is bad, it may be a good idea to replace all three on a high mileage engine to prevent similar problems down the road.

I found it on Google, who da thunk it.