Suburban misfire again.

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gn69z28
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Suburban misfire again.

Post by gn69z28 »

2005 5.3 random misfire on cylinders 1and 8. Everything new. Switched coils and injectors with other cylinders and no change. I believe it's an ignition issue. At speed with converter locked up going up hill it will start missing. Also random miss at idle. Other than that runs fine. Also noticed that at idle when it misses,the PRND21 and trip odometer light will flicker in unison with the miss. Is there a specific ground wire for the ignition system and where is it located. There is a small black wire attached to the drivers side of the block where the main ground wire from the battery is but it's connected. All sensors are new and all coils,plugs and wires are new. 60lbs fuel pressure at idle and steady 19 on vacuum gauge at idle. I'm wondering if it's a ground problem.
dannobee
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Re: Suburban misfire again.

Post by dannobee »

There's actually a bulletin on misfires caused by a rusted/corroded G103 ground. Bulletin is 06-06-04-046, Doc ID 1861549.

G103 is shown as a ground on the RH cylinder head. On an 05 Suburban it should be at the back. By the cheesy diagram GM has, it looks like it's near the back of the intake/cylinder head area.

And looking at the wiring diagram, it grounds the ECM, so who knows what gremlins it could cause. One of which shows to be the Class 2 serial data line, which could explain the cluster problems.
gn69z28
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Re: Suburban misfire again.

Post by gn69z28 »

Thanks for that info. I will check the ground wires at the back of the engine. I remember there are a couple attached to the block at the back..Thanks.
1980RS
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Re: Suburban misfire again.

Post by 1980RS »

We had a 99 Trans Am years ago that was a buy back form GM with a mis-fire problem that had been to 15 dealers out in comifornia. When our dealer git it my biddy and I started to look at the car and 1 and 8 were having misfires, the guy at TIS (GM's trouble center) asked how we got that car as it was supposed to be scrapped. We told him there was no car we could not fix, it turned out to be a bad ground on the back of the pass side head. The local Zone rep a week later said all those other dealers were getting charge backs and several techs were fired.
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