2002 Dodge Ram Poor Towing performance

Tiny
WBELL1263
  • MEMBER
  • 2002 DODGE RAM
  • V8
  • 4WD
  • AUTOMATIC
  • 110,000 MILES
Hi, I am experiencing major towing issues with my truck. Seems to run ok not towing an gets about 14.5 mpg on the highway at 75 mph. When towing my camper around 7000 lbs, it really struggles to get it done. MPG drops to 6 on the highway and the engine just doesn't want to do it. I had a tune up done and things didn't improve. The computer at my mechanic shows 1 cylynder misfiring only when idiling and not in gear. Won't to it in gear. My mechanics has determined the value is not performing under load and we should do a complete value job to improve performance and mpg. What do you think? Thanks in advance for your help at correcting this issue!
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Wednesday, June 2nd, 2010 AT 9:58 PM

4 Replies

Tiny
CARADIODOC
  • EXPERT
Hi wbell1263. Welcome to the forum. This doesn't sound like a valve problem at all. A cylinder leak test would confirm if valves are leaking. It sounds typical of a partially plugged catalytic converter. A special tool is made for measuring exhaust back pressure. It involves drilling a 1/8" hole in front of the converter, then sticking the tool's probe in there to measure the pressure while the engine is running. Also, if there's an exhaust restriction, the sound out of the tail pipe will be more of a hiss instead of the normal "putt putt".

Caradiodoc
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Thursday, June 3rd, 2010 AT 6:19 AM
Tiny
WBELL1263
  • MEMBER
Thank you for your quick response. The misfire that occurs is always on cyclinder #2. They have swapped out the plug, cable and injector and no matter what the combo, the same one misfires, #2. If the catalytic converter was causing my problem, wouldn't several cyclinders misfire or different ones? They also told me that doing the value job my improve engine performance some, but would not improve mpg. Any other thoughts? Thanks for your help! William Bell
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Monday, June 7th, 2010 AT 7:49 AM
Tiny
CARADIODOC
  • EXPERT
The only way I can see a valve job helping is if the timing chain is stretched and they replace that at the same time. A sloppy chain will retard valve timing resulting in increased torque at low rpm and decreased torque at high rpm. The ability to pull a load will be reduced. One way to check for a stretched chain is to watch the rotor in the distributor, (if you still have one), to see how far you can turn the crankshaft before it starts to turn. I don't know what normal looks like because I just pull the cover off and look at the chain. Another way to measure the wear is to remove the fuel pump block-off plate on the right front of the engine and use a stiff piece of wire to pull the chain in and out. Older carbureted engines had a mechanical fuel pump bolted there that could be removed. Newer engines that were never available with a mechanical fuel pump won't have that plate.

Before I would commit to a valve job, I would insist on seeing the results of a cylinder leakage test. This involves bringing each piston, one at a time, to top dead center, then forcing compressed air in through the spark plug hole. A gauge on the tester will indicate the precent of air leaking out. If the engine is cold, ten percent is not uncommon. You can listen at four places for the results of the leakage. Hissing at the tail pipe indicates a leaking exhaust valve, at the intake system means a leaking intake valve, at the oil fill cap or dipstick tube is due to leakage past the piston rings, and air bubbles in the radiator indicates a leaking head gasket or cracked head.

Caradiodoc
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Tuesday, June 8th, 2010 AT 6:34 AM
Tiny
WBELL1263
  • MEMBER
Thank You for the additional info! I'll insist on the test. In talking to other people, I'm starting to wonder if I can even get more than 6 mpg when pulling the same weight as the truck and having overdrive off. Thanks again!

William Bell
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Tuesday, June 8th, 2010 AT 8:27 AM

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