1999 Buick Regal LS Random Cylinder Misfire - Page 2

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Thread: 1999 Buick Regal LS Random Cylinder Misfire

  1. #16
    5.3 Liter Vortec V8 boston boy's Avatar
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    Re: 1999 Buick Regal LS Random Cylinder Misfire

    my buddy 1997 olds 88 was throwing a misfiring code & it was his coil pack working sometimes. He got one from the junk yard & started to change them & the middle one was the problem.
    If you have a spare coil pack I would try this. Get one at the junk yard

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  3. #17
    Tex is offline
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    Re: 1999 Buick Regal LS Random Cylinder Misfire

    Ok, here's an update. I replaced the coil packs with new- no change. After some advice from a friend, I was introduced to the apparently common LIM gasket failures.

    I tore the car apart, found that the LIM gaskets were beyond shot (4 out of 5 ports ruptured on each bank), put the new Fel-pro LIM and UIM gaskets on, and put it all back together. The re-assembly went great. It was long but very smooth. During the process, I drained the radiator via the valve on the driver's side and removed the upper radiator hose and thermostat housing. After everything was back together, I drained the remainder of the coolant by removing the knock sensor. I reinstalled the petcock and knock sensor, and filled the radiator to the lip, as prescribed, and filled the overflow tank slightly above the MIN line, also as prescribed.

    After a ton of cranking, as expected, the car started and ran rough-ish, but far better than before. I had forgot to clear the P0300- Multiple/Random cylinder misfire code from earlier. I cleared it and it continued to run. It was definitely running better, idling fairly smoothly on its own at ~1000 RPM, compared to before when it would idle at around 400 and generally die if you didn't give it some gas. I figured that a slight misfire now might be due to a weak coil pack (I put the old ones back one when the new ones didn't solve the problem), masked before by downright mayhem from the LIM gasket failure. It idled for about 20 minutes while I was waiting for the thermostat to open to be able to add the rest of the coolant. As soon as the thermostat opened, it coughed and shut off.

    It was very hard to restart, just like before, but it DID eventually restart. But once it restarted, it was back to the same exact poor running condition condition from before I replaced the gaskets- P0300, barely idle, had to give it gas. The upper radiator hose was warm, indicating that the thermostat had opened (I guess), but I turned the heat on, and only got cold air (not good).

    I don't know where to go from here. I don't have anymore time to work on this car, but I don't want to leave my mother hanging with it either, and she has put a lot of money into it just in parts in the last few months, to still not even be able to drive it.

    I KNOW the gaskets all went on right, I mean they had locating pins and all the bolts went in fine. I followed the instructions and put globs of the included RTV in the corners where each head met the center ends. I didn't put RTV on the whole gaskets around the ports like my buddy told me to, because the instructions said not to and it was so cold in the garage that I was afraid it wouldn't set. I gently used a heat gun on the 4 blobs in the corners. The mating surfaces on the heads, LIM, and UIM were all clean. All the bolts and nuts were accounted for and I know I put them all back in the right place and torqued them properly.

    It seems like the issue begins as soon as the coolant is present in the block, which honestly scares the hell out of me. The only other thing is that the front head smokes when it's running. I attributed it to the oil and junk that had been there from earlier, as I did have to replace the front valve cover gasket earlier this summer and it was smoking then. Head gaskets don't seem to be a common problem in these motors, but I guess it COULD happen. It doesn't knock or whine like it has any valve or bearing issues.

    At this point, I'm looking for ANY ideas. I'm at a loss. Part of me wants to tear it all back apart to check the LIM gasket, but I just simply physically do not have the time left at this point, as I am leaving to go back to the other side of the country on the 28th, and won't be able to come back for at least six months.
    Last edited by Tex; 12-24-2009 at 12:28 AM.
    2009 Pontiac G8 GT | 346WHP/376WTQ
    1966 Shelby Cobra | 351 Cleveland | Midstates Classics kit

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