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4.9 Runnin' Rough


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Afternoon.

My 93 DeVille is doing something strange, and I wonder if you can help me figure it out. When cold, it runs fine. After driving a while, you lose all power in the top end (70 at best-down hill), and the longer you drive (and the hotter it is), the shorter is the distance that you can push the accellerator before it starts to buck, fart, surge, and use a BOATLOAD of fuel, until eventually, you lose all power, and it plain won't run any more.

I was driving from Orlando to Tampa on a 100 degree day last week, and by the time I got three quarters of the way to Tampa, I had to coast off the road, as there WAS no more power, and the car would barely idle. After 15 minutes, it started right back up and away I drove. Not great, but drivable, and enough power to get where I was going. Twenty minutes later, it started to REALLY run like crap again. Parked the car for 6 hours, then got in it, and proceeded to drive home (60 miles), and didn't have any problem at all until after about 40 miles. Bear in mind that it was night, much cooler, and raining, just to give you all of the circumstances.

As I said, this only seems to happen after at least 30 minutes of "hot" driving. When at it's worst, it's as if the fuel supply is intermittently being interrupted and restored (Like when you take it to 108 and the PROM shuts it down), but time seems to temporarily "heal" or at least improve the problem.

Not getting a check engine light, so I imagine that there are no codes to scan. Is there a way to check the codes thru the climate control like some of the older ones? Does this sound like a restricted converter?

As I can't really take my car into the shop, and tell the guy to drive it till it won't run anymore, I would greatly appreciate any help or suggestions that anyone might have.

Regards,

Tim

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Sounds like either the fuel pump, ignition module or a coil pack, probably the ignition module given that it runs so badly, I think the coil packs effects pairs of cylinders, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Did you run diagnostics?

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Just a shot in the dark here but a fuel pressure guage on it when it starts acting up might explain a lot. I'm leaning toward a fuel pump here if you couldn't tell. I had a pump go on my '92 Deville. When it was cold (the engine) I could give it WOT and it would run fine but after about :15-:20 of running it would fall flat on it's face when give WOT. I know the symptoms are a bit different but the common denomonator is getting worse with time. Bottom line is fuel pressure will either comfirm of rule out a pump.

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Just a shot in the dark here but a fuel pressure guage on it when it starts acting up might explain a lot. I'm leaning toward a fuel pump here if you couldn't tell. I had a pump go on my '92 Deville. When it was cold (the engine) I could give it WOT and it would run fine but after about :15-:20 of running it would fall flat on it's face when give WOT. I know the symptoms are a bit different but the common denomonator is getting worse with time. Bottom line is fuel pressure will either comfirm of rule out a pump.

Larry, I remember when that happened I think, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Just a shot in the dark here but a fuel pressure guage on it when it starts acting up might explain a lot. I'm leaning toward a fuel pump here if you couldn't tell. I had a pump go on my '92 Deville. When it was cold (the engine) I could give it WOT and it would run fine but after about :15-:20 of running it would fall flat on it's face when give WOT. I know the  symptoms are a bit different but the common denomonator is getting worse with time.  Bottom line is fuel pressure will either comfirm of rule out a pump.

Larry, I remember when that happened I think, Mike

Mike,

You probably remember me relating the story as I had not found this wonderful site yet when that happened.

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Can the codes be checked thru the climate control like the older models?

Any possibility this is a restricted converter?

Tim

Yes Tim, you can. Hold the OFF and HIGH fan buttons together, all lights will light up as a check, and then it will start giving you codes. Have pencil and write down the codes and post them here. Turn the ignition off then back on again and run it again if you have to, the codes come fast and you may not be able to write them down fast enough. Report them here and we will let you know what they mean, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Can the codes be checked thru the climate control like the older models?

Any possibility this is a restricted converter?

Tim

My guess is that it is unlikely your cat, its related to heat. I would go with Larry's suggestion or a bad ignition module. Codes may tell us something, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Do you mean no codes or the system will not enter diagnostics?

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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If you held the OFF and WARMER buttons for 3-5 seconds and the system would not enter diagnostics, further troubleshooting is required. There is a specific trouble chart for that failure.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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I was holding the OFF and HI buttons, as previously instructed in this thread. If I hold the OFF and WARMER buttons, I get the following displays on the FUEL CENTER panel:

-L100

-KM888

-.E

-.31.

-.F

-.F48

-.7

-.0

And on the Climate Control Display:

Farenheit

Hi Fan

Thanks,

Tim :ph34r:

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I am sorry a mess up on my part, yes it is OFF and WARMER, turn the key off and try it again, what you posted does not look right, Mike

post-3-1087310761.jpg

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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If code E31 is displayed, that is a shorted MAP sensor. This would explain the drivability problems.

The F48 code is Low A/C refrigerant

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Thanks so much to all. That makes perfect sense, as the A/C compressor sprung a leak, so I had to order another one, and after reading about the effects of a bad MAP sensor, I am convinced that's where the problem lies.

Is this a tough part to get to? I'm an old Ford Truck gearhead, and know very little about the Caddy 4.9

Cheers,

Tim

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I just e-mailed you a diagram from my service manual of the MAP location, and details for R&R. However, run the diagnostics again and post the codes. Kevin is probably right with the MAP however the way you posted the code, its not what is usually the way it is indicated is should say E031 for shorted MAP or E032 for open MAP. Good Luck, Mike

If you are unable to receive email let me know where to send it by emailing me.

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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  • 2 weeks later...
Just wanted to give everyone an update, for anyone who is interested. Despite the fact that the computer was throwing off a bad MAP sensor code (Changing the MAP sensor had absolutely no effect), the culprit was the TPS.

Great day to all.

Cheers,

Tim

Tim were you getting a code for the TPS? WHen mine when I got a code for an 'intermittant TPS signal" . Glad you got it straightened out, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Nope, no TPS code. Just shorted MAP Sensor.

Cheers,

Tim

Hmmm, very odd but I am glad its fixed, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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