Bad fuel injector... what should I do? UPDATE! - Page 3 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 11-24-2004, 06:17 PM   #21
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I picked up a PCM from the junkyard, and the thing makes the car misfire like crazy! I called the yard and the guy says he gave me a PCM with the same numbers and everything. I compared stickers from the old and new PCMs, and the SERV. # and HDW #* are the same. However, the original PCM has a CALM designation on it, whereas the new one has a BXUF (or maybe BUXF?) designation on it. Does this mean he sold me the wrong computer? I even switched the PROM or KS or whatever it'* called from the old to the new, but still the same result. The car barely starts, and when I get it going it runs like crap and smells insanely rich. What'* going on? I don't want to pay to have it reprogrammed!
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Old 11-24-2004, 07:35 PM   #22
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Okay, I figured out what my problem is. I tried the new PCM before putting the old KS (knock sensor) module into it. This is a no-no. I found this on grandprix.net, it explains everything.

Quote:
Disconnect the existing PCM and note the blue and clear connectors and their positions. (For 1997 vehicles only: open the small cover on the PCM using a torx bit and remove the knock sensor module and install into the new PCM)
.
..
...
....
IMPORTANT: If you are installing a reprogrammed PCM, make sure to take the car to the dealer to get the crank sensor position (or CASE) learned. This is not required for 1997 GP PCMs because the data is already stored in the knock sensor you switched above. You may get a "Service Engine Soon" lamp after the installation - this is due to the CASE learn not having been performed. Whether you get the SES light or not, you should still get the CASE learn procedure performed.
Boy, do I feel like a dummy! The Chiltons even said to switch the module, but it said to do it if the PCM was equipped with an EEPROM. I figured a KS is different from an EEPROM, so I threw in the whole new PCM just as I bought it. So the new unit was clueless as to the position of the crank, and now since I ran the motor the original KS doesn't know where the crank is either! Off to the dealership on Friday!
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Old 11-24-2004, 07:48 PM   #23
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If you take it to the dealership they can probably reflash the PCM for you, a Crankshaft Position Variance or CASE learn will probably cost you whatever the dealership charges for labor/hour. Since you now have 2 PCM'* why not send one to INTENSE?
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Old 11-26-2004, 06:16 PM   #24
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Bad news guys... the new PCM does NOT resolve the misfire issue. I had the car towed to the dealership and reprogrammed, only to find that the misfire in cylinder 1 still exists :( . I guess the only thing I can do is recheck all the electrical wiring and spark plugs and wires; hopefully something turns up. What a bummer.

One question though: the PCM in the car is the new one, but it has the old KS module transplanted into it. Is the old KS module the root of the problem? I'm not gonna start shotgunning parts into this thing, because (correct me if I'm wrong) every PCM swap is going to require a reflash. But if someone can show me that I need to swap the new KS module in and get it flashed again I'll do it. Please give me anything and everything you guys can come up with. This one is baffling me!
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Old 11-26-2004, 07:56 PM   #25
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Okay guys, got another update...

We tested the plug wire to the bad cylinder multiple times, and it checked out okay. We then put the wire back on its coil and put a plug in the boot to test for spark. We get absolutely NOTHING from the #1 side of the 1-4 ignition coil. Using the same wire and plug we get spark from all the other coil terminals, but terminal #1 is dead. We're waiting to swap a coil from our Olds 88 and see if it solves the problem.

I don't get it! Not only are they new MSD 8224s (only two months old), but last Friday I pulled the #1 plug wire and watched the terminal arc a spark to the nearest piece of metal! It was definitely working a week ago, at least intermittently. If I find it'* the coil, I'll throw my old stockers back on (and send the junk coil back to MSD). But if it'* not the coil, what could it be? ICM? Bad wiring between the coils and ICM? And wouldn't you think the shop that diagnosed a bad injector would have first checked for spark at the plug? We've narrowed things down, but none of this makes sense. Why would the coil have worked a week ago, but now be totally dead? I'll still take anything you guys can come up with. Thanks.

EDIT: The coil in question tests within the acceptable range of values specified in the TechInfo article. We tested both the primaries and secondaries.
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Old 11-26-2004, 09:18 PM   #26
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It'* the coil. Switched positions with one of the other coils (duh), and sure enough it'* still not sparking. We're looking into the possibility that I burned it out when I had it sparking without a wire on it. Hopefully we don't fix this problem only to find we still have a fuel delivery issue. But one step at a time. I'll keep this posted with what we find.
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Old 11-26-2004, 09:22 PM   #27
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Oh man, I feel your pain! Problems like this can drive you crazy. Hang in there and keep us updated.
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Old 11-26-2004, 10:42 PM   #28
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First of all, I know I'll catch a lot of **** for this but, IMHO I would stick with A/C Delco parts. I have heard many stories of guys trying to re-engineer what the factory did and have nothing but problems. Been there, done that.

Secondly, and don't quote me on this but I don't think a coil will go bad on one side. I think if it fails, it will do so to both cylinders so I think that would rule out a coil if I am correct.

Last but not least. don't rule out the obvious. I just went through this same problem on a Northstar a couple of weeks ago. The engine idled smooth as glass. I put a spark tester on each wire and they all carried the current. Changed plugs and swapped all 4 coils with a known good one from my wifes Bonneville. All checked out ok yet I still had a miss under light loads but would run great at idle & WOT. I finally decided that one or more wires were breaking down under load and put on a new set of A/C Delco wires. Problem solved.

Just my $0.02
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Old 11-27-2004, 06:56 PM   #29
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I appreciate the input, but a coil can go bad on just one side. I asked a mechanic friend about it and he confirmed this. So after more swapping around I finally got a good coil off our Olds 88 and threw it on there. Problem solved! It was the coil the whole time. This one was totally mystifying me, since a week ago I saw that coil sparking with my own two eyes. I'm actually wondering if I had two separate issues here, maybe the injector driver in the old PCM was bad, but then taking the resistance off the coil while it was firing may have burned it up. So maybe I fixed the fuel problem but then had a totally separate ignition issue? I might send my old PCM to Intense one of these days and see what they can do with it. But like I said, she ran like butter with a good coil. Case closed!
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Old 11-27-2004, 09:54 PM   #30
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Quote:
Originally Posted by big_news_1
I appreciate the input, but a coil can go bad on just one side. I asked a mechanic friend about it and he confirmed this.
Live and learn. Thanks for setting me straight.
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