My Marauder will not upshift from 1st or 2nd gear when at full throtttle; Help

J

johnjamis

Member
2003 Marauder will not upshift from 1st or 2nd gear when at full throtttle. It just maintains 5500rpm in 1st or 5000rpm if in 2nd gear. In order to get it to upshift I must reduce throttle position to about 1/2 throttle or a little less.

I replaced the MAF and have tested with the air cleaner on and off with no difference. I also replaced the coil packs last year, thinking it might help. It did not help.

The car and engine operate normally except at full throttle. The transmission downshifts normally. Only the full throttle upshift is abnormal. The check engine light is not illuminated.

I also had the transmission fluid changed just to see if it would fix the problem; it did not. I just checked the trans fluid level and it is a bit high at the top of the hash marked area on the dipstick.

Has anybody had this problem or have a suggestion as to where to investigate next?

Thanks
 
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maybe you have a vacuum leak, would explain why it shifts at light throttle ok.

take it to a transmission shop have them drive it. How many miles are on it?
 
Do you have a spare throttle position sensor you can try? Does the up shift issue occur in the 2 - 3 shift at full throttle as well?
 
I will look for any vacuum leaks.

I will also look at the throttle position sensor. An OEM TPS sensor is only $30, so I will just replace it and hope for a fix. I will report back.

The up shift issue does also occur on the 2 - 3 shift at full throttle. The engine power/rpm goes flat at 5000rpm and does not upshift to 3rd gear until I reduce throttle to about 1/2.
 
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I replaced the MAF sensor and the Throttle position sensor, with no change to the problem.

It runs totally normal other than the full throttle no shift issue.

Thanks for the suggestions.
 
Drop the pan, inspect the filter. Maybe broken oring on a tv valve.. might be pieces in the pan to help identify what the main issue is
 
I wonder if I could have an obstruction in the exhaust that is causing the high rpm power loss that does not allow the transmission to reach "shift conditions". Maybe a blocked up CAT?

Thanks for the suggestion.
 
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The tune is on a chip, not tuned that way today, it was the way back then. Rheinshart is gone, pissed alot of folks along the way.
 
It won't hurt to try this since you've had the PCM out before!!:cool:

Disconnect the negative battery terminal then unplug all electrical connections on the PCM looking for corrosion.....if you find some corrosion clean it up and re-lubricate the connector(s) and hook 'em back up!!:)

Reconnect the negative battery terminal and see what happens!!:beer::burnout:

Good Luck!!:beer:
 
I can’t stress enough how important the contacts where the chip plugs onto is CLEAN. And also the chip is taped up really tight so it can’t wiggle around.

This many years gone by I would assume both need attention.


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We just had an 06 impala in the shop doing the same thing. Not saying it is your problem but the catalytic converter was partially plugged / fouled. It drove well under part throttle but could not Rev past 4800 rpm at wide open throttle and it would not shift at wot either.

Now the mm has 4 cats but is there a chance one or more have become plugged? Do you have an infrared thermometer to check their temps individually?
 
JimP said:
We just had an 06 impala in the shop doing the same thing. Not saying it is your problem but the catalytic converter was partially plugged / fouled. It drove well under part throttle but could not Rev past 4800 rpm at wide open throttle and it would not shift at wot either.

Now the mm has 4 cats but is there a chance one or more have become plugged? Do you have an infrared thermometer to check their temps individually?
Click to expand...

I suspected it could be an obstruction in one of the cats. The infrared thermometer check of the cats is an excellent idea. Thanks, John
 
if its been fine for 15 years the tune is not the problem

if you want to put the stock tune back on it the cheapest method is to buy a moates quarterhorse and load a stock tune on it to verify, not the problem though

most likely your trans is on its way out
 
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