Service Engine Light, Transmission bang shifting

Old 03-19-03, 07:21 AM
Ronald Lawhon
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Unhappy Service Engine Light, Transmission bang shifting

Problem: Engine overheating??? Service Engine Light
Vehicle: 1994 Chevrolet P30 Van
Engine: 350ci, 5.7L, V8
Transmission: Automatic
Air Conditioning: NO

Description: Originally the problem was indicated with a 'Service Engine' light followed by the transmission bang shifting. This was caused by overheating due to water loss. There was no indication of internal or external leakage (no steam in exhaust, no rust lines on block and no milky oil). Within the last month the milky oil appeared as well as an oil loss due to leaking oil cooler hoses. These problems were not addressed which resulted in engine failure (bearing seizure) when it was driven with no engine oil.

The engine has been replaced with a new Jasper engine. One of Jaspers warranty requirements for the new engine was that a new radiator had to be installed because of the possibility of oil cooler contamination when the engine failed (The radiator contains an engine oil cooler as well as a transmission oil cooler), the radiator was changed. New hoses were installed for the engine and transmission cooler ports of the radiator. New water pump (came on the new engine). New radiator hoses. No condensor to get clogged.

Even with all these changes the 'Service Engine' light and the transmission bang shifting still appear. The temperature gage now indicates 190 which is right.

I believe the problem occurs because the driving routine for this vehicle. This is used on a bread route where there are a lot of short trips, stop and shutoff engine and start up again. I think that heat soak after engine is shutoff is a big part of the problem because the 'Service Engine' light and the transmission bang shifting occur on start up after several short stops.

Beings the temperature gage reads OK, is there a separate temp sensor for the ECM.

I believe that this problem can be cured with an electric water pump and electric radiator cooling fans but this is getting expensive! I would rather replace a temp sensor than go this route.
Old 03-19-03, 10:44 AM
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I assume you have a scanner? If you don't, stop. You need one to diagnose why the engine light is on. That should help point to the problem at hand.

The coolant temp. sensor is separate from the temperature sending unit for the gauge.

Have Autozone pull the codes for you if you don't have a scanner. Tell us what they find.
Old 03-20-03, 04:42 AM
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Input speed sensor on tranny a possibility depending on your tranny; the 4L80E on my W-4 (w/Chevy 350 gas) goes out every couple of years and you get the neck-snapping upshifts. I wouldn't change it until you get some confirmation first or run out of other things - about a $60 part.

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