Not F-body but GM electronic glitch
08-13-2010, 05:35 PM
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Car: 85 IROC / 69 Firebird convertible
Engine: 5.0 / 350
Transmission: t-5 / WC t-5
Axle/Gears: 3.27 / 3.08
Not F-body but GM electronic glitch
Having a strange problem with my work van, a '99 Chevy express van 2500 with a 5.0.
the speedo is reading two or three times the actual speed. At approx. 40 the needle is buried and the engine shuts down untill the speed drops a little. Tried a new cluster and the same thing happens. The trans wants to shift into over-drive way too early and lugs the motor. Driving in 3rd helps but cant get over 35 or 40 before the engine shuts down. Has anyone else had a problem like this? I've been pulling my hair out to no avail, and I don't have any to spare. Any ideas are welcome. Is there a way to check the speed sensor in the tranny?
the speedo is reading two or three times the actual speed. At approx. 40 the needle is buried and the engine shuts down untill the speed drops a little. Tried a new cluster and the same thing happens. The trans wants to shift into over-drive way too early and lugs the motor. Driving in 3rd helps but cant get over 35 or 40 before the engine shuts down. Has anyone else had a problem like this? I've been pulling my hair out to no avail, and I don't have any to spare. Any ideas are welcome. Is there a way to check the speed sensor in the tranny?
08-13-2010, 07:26 PM
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Car: 85 IROC / 69 Firebird convertible
Engine: 5.0 / 350
Transmission: t-5 / WC t-5
Axle/Gears: 3.27 / 3.08
Re: Not F-body but GM electronic glitch
Not the speed sensor. Put a new one in and no differance. I'm thinking it must be the computer. Any body have any thoughts on this.
08-13-2010, 08:45 PM
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Car: 1992 RS
Engine: Carbed 350
Transmission: 700R4
Axle/Gears: 3.42 posi
Re: Not F-body but GM electronic glitch
The ECM's have speed limiter's programmed in on the chips. Sounds like the VSS is translating speedo gear information incorrectly, and thus feeding the speedo and the ECM false speed readings, making the ECM shut down fuel output when that magic number is reached.
Have you tried checking/replacing the speed housing on the tranny or the VSS unit?
Have you tried checking/replacing the speed housing on the tranny or the VSS unit?
08-13-2010, 09:04 PM
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Car: 85 IROC / 69 Firebird convertible
Engine: 5.0 / 350
Transmission: t-5 / WC t-5
Axle/Gears: 3.27 / 3.08
Re: Not F-body but GM electronic glitch
I replaced the VSS on the transmission with a new one from NAPA. No change!
I realize that the engine is shutting down because the computer thinks the speed is too high, I just don't know why,
I realize that the engine is shutting down because the computer thinks the speed is too high, I just don't know why,
08-13-2010, 10:11 PM
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Car: 86 T/A, 83 Z/28
Engine: 5.0 TPI, 350 2 X 4 bbl
Transmission: 4 speed auto, 5 speed manual
Axle/Gears: 3.23 posi, 3.73 std
Re: Not F-body but GM electronic glitch
Not sure if this applies but on older cars they have a buffer box that conditions the output of the speed sensor for the ECM. Possibly your problem
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08-14-2010, 06:52 AM
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Car: 85 IROC / 69 Firebird convertible
Engine: 5.0 / 350
Transmission: t-5 / WC t-5
Axle/Gears: 3.27 / 3.08
Re: Not F-body but GM electronic glitch
Where in the system would I find the buffer box and is there a way to check it.
08-14-2010, 09:22 AM
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Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: Not F-body but GM electronic glitch
Its the inst cluster. There is a recall on those.
Go 2 dealer and ask if your van is on the recall list.
If its over so many miles or time they wont fix it 4 free tho.
Go 2 dealer and ask if your van is on the recall list.
If its over so many miles or time they wont fix it 4 free tho.
08-14-2010, 07:39 PM
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Car: 85 IROC / 69 Firebird convertible
Engine: 5.0 / 350
Transmission: t-5 / WC t-5
Axle/Gears: 3.27 / 3.08
Re: Not F-body but GM electronic glitch
Put a salvage yard cluster with 95k miles on it and no differance so I think I can rule out the cluster. That was the first thing I tried.
Thanks for the input.
Thanks for the input.
08-16-2010, 07:02 PM
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Car: 85 IROC / 69 Firebird convertible
Engine: 5.0 / 350
Transmission: t-5 / WC t-5
Axle/Gears: 3.27 / 3.08
Re: Not F-body but GM electronic glitch
OK, Got in the van yesterday a.m. just to move it so I could get my car out and noticed that the speedo seemed to be working. So I took it down the road a mile or so and guess what! Now it is working just fine. It has been very humid here for the last week or more. Could that have any effect on the electronics? At this point I don't have a whole lot of trust in the truck. Anybody want a real good deal on a '99 Chevy 2500 Express van.
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