Archived Intermittent low power/loss of tach

[jgallentine]

1999 3500 5-speed 4-wheel drive. Issue started with low power and tons of black smoke out the tailpipe. On flat ground I maxed at 2200 in third gear. Cleaned itslef up and ran okay the next 15 miles home.



Changed the fuel filter seemed to run good. The old one was black, no signs of water. Added some Powere Services cleaner and cetane booster.



Next morning started the truck and left it for about five minutes to warm up. When I got in the check engine light was on and is still on.



Now I intermittently loose the tach and experience low power at the same time. No excessive smoke noticed though. The truck cruises fine but has a hard time accelerating empty. The tach has come back during acceleration and you can feel a real kick to power when that happens. The truck also will not start at times. Every time the truck starts the tach works at least for a moment.



I am assuming all of these problems are connected but am lost from there.



Any ideas?



Thanks

 

[Jhillmann]

Loss of tach

I had the same problem a couple of months ago. The cam position sensor was bad. The dealer replaced the sensor and I have had no problems since.

 

[Dave Fritz]

jgallentine,



The crankshaft position sensor output is used to determine injection timing, the fuel delivery rate, and the engine speed for the tachometer. If the crank sensor fails, the cam position sensor is used as a backup, but the engine will exhibit the problems you have observed.



Some 1999 models can display the PCM fault codes in the odometer by cycling the key on/off/on/off/on/off/on. Try this and see if any of these code are stored:



P0219 crank position sensor overspeed signal

P0320 No crank position sensor signal to PCM

P0336 Crank position sensor voltage/signal problem

P0387 Crank position sensor supply voltage too low

P0388 Crank position sensor supply voltage too high

P1391 Intermittent loss of crank or cam position sensor

P1690 Fuel inj pump CKP sensor does not agree with ECM crank postion sensor





Good luck, Dave

 

[jgallentine]

Thanks for the info. Due to the starting problem I could not drive it today but I will check for the codes again when I get home. I have tried a method similar to yours for codes which was holding the trip reset and cycling on/off/on/off/on. That did not give me any codes but it did put the guages through a nice test pattern.



Sounds like it must be in one of the two sensors. I'd like to see the codes before I take it in but it must go tonight as I have to tow on Friday.



Thanks for the help.



Jeff

 

[jgallentine]

Well, it was the crank position sensor. I got the truck back from the dealer today and $225 later it seems to be fine. Time will tell. I have a hard time trusting dealers to set tire air pressure let alone work on the best of the best.



Thanks for the advice, you guys were right on.



Jeff

 

[DC101]

I am having similar problems with a Dodge Dakota V6. Not sure which sensor to replace, Crank of Cam?