cylinder 6 misfire

[harmankardon35]

for the past few weeks my car has had this jerk/stumble that felt like the TCC staying locked on after i came off the highway, and occasionally it would do it at low speeds as well. kept scanning for codes but got nothing, figured it must be an extended tranny code. Tonight it seemed a little worse, felt like it was slipping when i gave it gas but still no codes. So i went onto a back road and floored it from a stop, hitting 5-6k rpm and the MIL started blinking, i got cylinder 6 misfire. Turns out its not my tranny.. Plugs and wires were done last summer, any way i can check the coil pack? any other ideas?

[LittleHoov]

You should be able to check resistance with a multimeter on the terminals of the coil packs, the exact procedure and resistance numbers have of course escaped me. The procedure is usually described in a Chiltons or Haynes manual if you have one of those.

The other way would be to swap coil packs and see if your misfire moves. But if it took that long for your #6 to light up that might be a time consuming process. Also a potentially damaging one.

You might also pull the coil pack in question and check for corrosion on the underside of it and check to make sure that your #6 wire isnt coming into contact with anything that might cause it problems, I have heard of problems being created when the spark plug wire touches the O2 sensor wire, and I believe thats entirely possible on the #6 cylinder if im not mistaken.

You can also check resistance of spark plug wires with a multimeter, not sure what the specs are, I saw the procedure in the Chiltons for my Jeep, but its not here at the moment. Im also not entirely sure where the one is for my Intrigue haha.

[Make 'em Last]

As LittleHoov mentioned, the plug wire nearest the oxygen sensor (is it # 6?) can be damaged if it contacts the sensor housing - had a nice chunk melted out of mine. Just have to make sure it's routed correctly. Recommend you pull the plug and confirm it hasn't gotten fouled. The 3.8 plugs are a lot of fun on the firewall side. Maybe replace with new or one of the other plugs.

As intermittant as your misfire is, not sure if the coil pack resistance check will help you. As LittleHoov suggested, switching two coil packs may isolate the problem, especially if the symptom follows the coil pack. Autozone coil pack for my Intrique is $25 if you don't like the idea of switching your existing ones.

[harmankardon35]

just fired it up this morning and immediately noticed a miss when I reved it up. Yes #6 is the one right next to the oxygen sensor. Ill have to crawl back there and check the wire/pull the plug. This problem got bad rather quickly yesterday, and its still intermittent....(took it for a good hard test run, no misfire , started missing at idle before i turned it off.) Another thing i am remembering is when i did the plugs last summer one of the new ones cracked when i installed it, so i took it out and put the old one back in (wich was still in pretty good shape at the time) cant remember if that was #6 but it was at the firewall side.

[LittleHoov]

Keep in mind while working back toward the firewall that you can take loose your upper motor mounts (the ones that mount to the radiator support area, and rotate the engine forward.

Im not sure how the Intrigue with the 3.8 is set up in that department. I helped a friend do plugs/wires on his 3.8 Impala and the engine basically flopped forward and he pulled it a little farther and the was an additional hole milled into the mounting hardware to slip a bolt back in to hold it in that position.

I can testify that the 3.5 is entirely different from that setup, but can still be moved forward, though it takes a lot more than a big guy pullin on it.

[harmankardon35]

pulled the plug and wire, the plug seemed ok maybe a bit white (but not like coolant...just sorta ash/dry colour) the wire didnt have any bad spots in it. Replaced the plug anyway and still a bit of a miss. I also took out #3 and #5 plugs to make sure they were the same colour and they were identical. Im gonna switch the coil pack tomorrow and see what happens. If its still there than on to injectors...

[harmankardon35]

well I parked the truck and took the intrigue today, although it still has a bit of a miss/stumble/shake when i give it a good rev from 1k to the 4k limiter, driving seems to be entirely smooth even on full throttle downshifts on the road. Ill keep an eye on it, but the plug i pulled out of #6 was one of those Bosch platinum with the 'micro' pin tip electrode, and it seems to have possibly melted over that electrode slightly...anyway my next step if the problem re-occurs is to see weather heat is a factor (being an inclined small engine mechanic, i often see coils work fine when cold, but struggle and fail when hot due to thermal expansion etc...) ill post back and see what I find...

[Make 'em Last]

So after coaxing the # 6 cly misfire error, you've replaced the #6 plug wire, checked the plug, and swapped coil packs? Seems you either wait to coax another error, or replace more parts. Always tough to deal with intermittents. Good luck.