Engine/Transmission (1998.5 - 2002) Trying to diagnose an engine miss / stumble...

[TORQUE THIS]

I have had an engine miss / stumble for about a year now. I have done the following things trying to diagnose the problem. (No codes set)



IAT

MAP

APPS

Stock ECM vs Marco ECM (no difference)

Swapped out injector pumps

Swapped out injectors / tubes

Checked and cleaned all grounds and electrical connections



The best way to describe it, Feels similiar to transmission shudder, but very faint. It is much worse when adding fuel, and when damp or raining out (feels like a gasser w/ a bad wire)



I am running with a DTT transmission, Marco ECM, TST3, and EDM 180 HP injectors... Fuel pressure is a solid 16 to 18 psi. No boost leaks.

Head has also been fire ringed and 12mm studs.



Anyone have any ideas?

 

[massdiesel]

Mark give me a call and can shoot some ideas at you.

 

[Walleye mike]

sound like the same thing we are going through. Let us know what you find.



https://www.turbodieselregister.com/forums/showthread.php?t=114086&page=2

 

[TORQUE THIS]

Scott, I'll talk to you on Saturday...



One thing I forgot to mention is that it happens all the time, light, mod and heavy accelerating.



Also, running at 60 to 65 it is really noticable, although it does happen at other speeds.

 

[gitchesum]

I had a similar issue with my 2002. Problem is, I did two things at the same time



I installed our high flow fuel system and also cleaned the connections from the PM3 comp to the MAP sensor.



Either way, the stumble went away after I did it.

 

[TORQUE THIS]

I have -8an lines from the tank to the VP, PE4200 pump supplying the fuel.



The miss occured with the drag comp I had and is the same with the TST.

 

[HBarlow]

A momentary "one beat" miss symptom like you describe can be caused by a failing lift/transfer pump. It can also be caused by the sensor on the differential housing that picks up ring gear rotation.



Harvey

 

[TORQUE THIS]

A momentary "one beat" miss symptom like you describe can be caused by a failing lift/transfer pump. It can also be caused by the sensor on the differential housing that picks up ring gear rotation.



Harvey

Speed Sensor... wouldn't it throw a code? Can it be cleaned and reinstalled?

 

[HBarlow]

I think my speed sensor did produce an error code if I remember correctly. No, I don't think it can be cleaned. Like many electromagnetic components, when they fail it is due to internal causes. It was a cheap part as I remember and easy to remove and install.



Harvey

 

[HBarlow]

I reread your symptoms. Sounds exactly like the symptoms I got when my lift pump failed. BTW, for all those who are mad at Dodge/Cummins over lift pump failure... . my pump failed at 68k and was replaced under warranty. My truck now shows 157k and the second pump still works fine. Of course, it could fail tomorrow. I carry a spare.



Harvey

 

[TORQUE THIS]

I've got steady fuel pressure... never falls below 16psi

 

[DavidC]

Speed Sensor... wouldn't it throw a code? Can it be cleaned and reinstalled?

My experience with the differential speed sensor when it failed on a 99 was a ABS and red brake light on constantly and no speedometer below 20mph. After 20 mph I had a speedometer which I assume is the speed sensor in the trans. Apparantly the trans, sensor picks up at 20mph and the differential anything less than 20. The differential sensor is about $45. 00. Don't know if this helps but if it would be a speed sensor I would look at the one in the trans. or the electrical connection to it.



Dave

 

[jhyatt]

hey what about fuel pick up in tank and may be recheck fuel press w/ mech gauge

 

[jhyatt]

one more thing u guys were right my vp44 in my old truck just went

 

[Marco]

More fuel = worse miss?



Hmmmmm.....



Then more fuel, then longer the fuel metering valve in the VP has to stay active. The longer the valve is active, then more electric energy it uses ( Ampere's). Could it possibly be that the circuits / wires that provide the VP with juice have a problem??? To check it out wouldn't be too difficult to do. .



The connector for the VP. Pin 7 = 12 Volt, Pin 6 = Ground.

You could hook a digital voltmeter to those wires and take it out for a spin.

How's the voltage acting when you get the miss?



Marco

On Edit. If you do this test, hook up both the + & - signal for the voltmeter as close to the VP as possible!

 

[jhyatt]

dam he's good that makes cense w/rain it's worse

 

[TORQUE THIS]

Marco, once I fix my oil leak and get the truck back on the road, I'll do that test. If there is a change in voltage, what would be the next thing to look for?

 

[GMills]

You might check your alternator. I had a similar problem for about a year. It wasn't until I replaced the alternator that it cleared up. I would recommend you have a charging specialist look at the alternator. I had mine to a dealership and they said it was fine, when I took it to the specialist, it was a goner.

 

[TORQUE THIS]

I got a noise filter to install... (haven't put it in yet)



Changed the cam position sensor... no difference.



If the noise filter dosen't work, the alternator will be the next thing I check.



If the alternator is good, I will try a pcm swap and see what happens.

 

[ToolManTimTaylor]

I think my speed sensor did produce an error code

Harvey

P0500 When it skips a beat at speed it will buck and complain like a bastad! I cleaned mine OUT (the connector) and it was swilled up with road crud thrown up from the front tires and road spray helped it into the connector.