96SE - PCM or Injector issue - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 05-16-2006, 04:18 PM   #1
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Default 96SE - PCM or Injector issue

Hello All,

I have a 96SE that has been going south for a while now. Basically about a year and a half ago after my Bonny sat for 4 days I noticed it stumbling/missing a little when I first drove it after that period that it sat. After driving it for a day it would run great and no futher problems. No SES light or codes. If I let the car set for an extended period the senairio would happen again. About 6 months ago it started to get worse. I actually would get it on the highway and it would cut out/miss while driving 75mph . Again No ses light or codes. This condition would come and go. I could drive it for a week and no problems then one day it would act up. I would run injector cleaner through it and it would SEEM to clear things up. I stress the word seems because at this point I'm not sure wether it'* an injector problem or PCM. Finally Saturday 5/6 I got in it, started it and it missed bad - worse than it had before, and turned on the check engine light. I gave it to the local mechanic and he pulled the codes.....misfire on #1 and #5. He hooked up OTC canister to it to clean the injectors and drove it 10 miles and proclaimed it fixed. I drove it to Indy this weekend (120 miles) and it did great, until I got off the highway and it started missing. - no ses light or codes. it acted up till we got back on the highway and it ran great all the way home. Today it started to miss again and it gave another check engine light. I went over to local Autozone , they scanned it and this time it was a misfire on #6. He cleared the light. I have replaced the Fuel filter about 70,000 miles ago. I would say around 4 years ago. Also It has newer plugs and wires on it. (I did try the ol' spray bottle deal on the coil packs) I think about 40,000 on the plugs and wires.

I have browsed your wonderful forum about the PCM/injector troubles. I guess what I would like to do is try to figure this out here if possible. I don't feel like spending a bunch of $ at the dealer to replace 6 injectors if it'* the PCM. My questions to you folks are ....

1. Do you think it is PCM or Injectors ?
2. Where would you start ? Get a PCM at the junkyard then go from there?
3. what additional troubleshooting can I do to help me determine which way to go ?
4. If I get a PCM from the junkyard, what steps do I need to do to it so it will work on my car. I think I understand about the KS (knock sensor).

My guess would be that the PCM is going bad. I want to make sure I understand COMPLETLY what I need to do to make sure a PCM swap would work. As long as I get one exaclty like mine I should be ok right ? I wont have to change out the KS ? right ? Any other PCM I need to change out the KS right ? I don't want to pay the dealer 70.00 to program. Thanks for your input !
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Old 05-16-2006, 04:23 PM   #2
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I'm wondering more along the lines of an ignition control module or bad connections.

If you will...let'* start off with the free and fairly easy things.

Pull your battery cables and clean them at both ends. Look for any corrosion any place that you can. Clean the block where the negative cable hooks up. The starter and alternator for the positive cable. Then both ends at the battery.

From there pull the 3 coils off and check the connection of the ICM (Ignition control module), then clean the mounting plate it sits on and the ground under that mounting plate.

There is a good chance you have a poor connection. Our cars are known to be tempermental when they have dirty connections.
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Old 05-16-2006, 04:28 PM   #3
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Will do Boost37. thanks. Anyone else ?
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Old 05-16-2006, 04:31 PM   #4
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The battery ends should be good. I keep an eye on them regularly, but I will clean them as well I'll check it all out and get back to ya. Thanks again.
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Old 05-16-2006, 04:41 PM   #5
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I'm going to have to agree with Bill on this one (dammit! :P ).

IMO, it'* always best to start with the free and known possibilities, before starting on the swapping and expensive ones.

Additionally, I would recommend you change that fuel filter and review any other regular Preventive Maintenance items that might need doing. Not that they are specific to this issue, but just because it'* always easier to diagnose a problem if you're sure the basics are covered adequately.
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Old 05-16-2006, 04:42 PM   #6
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BMW...pull them anyway and check under the red and black plastic cable covers. People have looked and found tons of corrosion before..and sometimes..nothing...worth a look though.
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Old 05-16-2006, 04:50 PM   #7
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Boost37 & Lash,

Thanks. Ya I was already going to replace the fuel filter again. This car has been such a good car. I forgot how many miles I had put on Bufford. Boost, I WILL check ALL of the connections. One minor piece of info, shorlty after I got the car, back in 01' I noticed how bad the + battery connector was and I replaced it with after market connector. It hasn't corroded on me at all. I will check it though. thanks again guy'*. Looks like I better pick up some Goop on the way home tonight.....along with the Fuel filter. Time to get dirty.
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Old 05-16-2006, 04:58 PM   #8
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Sounds good! Let us know how it goes.
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Old 05-16-2006, 05:02 PM   #9
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Dielectric goop never resided in my toolbox until I bought a bonneville. Now..I feel like a salesperson.
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Old 05-16-2006, 06:33 PM   #10
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One other little piece of info.....when it misfires, the oil pressure drops, and the voltmeter drops to 8 vdc. I guess you chalk that up to the fact that the RPMS are dropping because of the misfires. Of course I notice this when it misfires at idle in gear.
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