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

[johnjamis]

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

[Agent2006]

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?

[johnjamis]

The car has 122,000 miles.

[JimP]

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?

[johnjamis]

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.

[Agent2006]

Any chance your tune is acting up? ---go back to stock tune and see if it shifts OK

[johnjamis]

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.

[Turbov6Bryan]

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

[Turbov6Bryan]

Does the car just bounce off the rev limiter?
What rpm does it go up to and your saying it doesn't shift?

[johnjamis]

It revs up to 5500 in 1st gear and seems to go flat on power there and will not upshift.

[decipha]

Any chance your tune is acting up? ---go back to stock tune and see if it shifts OK


x2, take out as many variables as you can

[johnjamis]

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.

[RubberCtyRauder]

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.

[johnjamis]

Until this issue, the marauder has been working perfect for 15 years.

[Marauderjack]

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:

[johnjamis]

Thanks for the suggestion. I will give it a try.

[justbob]

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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[JimP]

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?

[johnjamis]

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?

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

[decipha]

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

[johnjamis]

I am hoping it is a CAT blockage; thanks for your ideas.

[johnjamis]

I am replacing the left cat. I will post the results after I change it out.

Thanks for all the help.

[Granddaddy Marq]

Check the presser at the O2 sensors between the cats. Anything over 3 or 4 psi then suspect the cats. It cost me $108 at the dealer to learn that.

[johnjamis]

Check the presser at the O2 sensors between the cats. Anything over 3 or 4 psi then suspect the cats. It cost me $108 at the dealer to learn that.

Thanks. I will do that depending on the cost to get a new cat assembly from KOOKS.

[justbob]

Higher temps equal blockage.


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[johnjamis]

Higher temps equal blockage.


Sent from my iPhone using Tapatalk ProI just looked online and copied this info about how to determine the bad cat using an IR temperature sensor.

[justbob]

You don’t even have to check temps when a cat that is fully blocked. Just look for the glowing one or determine which side of the car is more crispy after the fire is put out from parking on the grass. [emoji6]


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[decipha]

lol

if the cat is bad you should feel the car bog down up top, would be a noticeable power loss not just a lack of trans shifting

[johnjamis]

[QUOTE=decipha;1573647]lol




UPDATE: Right CAT replaced; did not fix the problem. I will investigate further using the suggestions made in this thread.

[Agent2006]

Would a broken 2-3 accumulator piston spring cause this? You might see spring pieces in the bottom of the pan.

[johnjamis]

I am taking it to a local tuner who has a dyno to have him do some diagnostics on the problem. Thanks for the input.

[decipha]

you can do an even better job diagnosing it than he could with a simple $250 moates quarterhorse

[johnjamis]

The obd data port is not been powered. I made a patch cable and plug into the accessory receptacle now to power it.

[johnjamis]

I took it in for a dyno diagnostic session.

The problem was a weak fuel pump. I changed the fuel pump and the car is back to normal.

It would not shift because the weak fuel pump would not allow the rpm to reach the 6000rpm shift point at full throttle.

It also has a bad left front oxygen sensor. I will change it tomorrow.

Also, the power lead to the OBD port is open. Had to jump power to the obd port to do the diagnostics.

Thanks to all for your suggestions.

The part I used is; Delphi HP10233 Fuel Pump Hanger Assembly; Sold by: Amazon.com Services, Inc. It works fine.