Do a compression check.

 

don't get me wrong here; I appreciate the help. Just explain to me how would a mechanical engine problem cause an intermitant problem?

 

What have you physically replaced/changed/inspected so far? (meaning NOT checking it on the scan tool)

The scan tool is only going to take you so far, and if an EGR valve is not functioning properly, it is still possible for the voltage reading to change if you try to adjust it via the computer/scan tool.

You aren't getting a check engine light so there aren't any read trouble codes appearing, so we can't even verify that there is in fact a real problem.

I can't help you much more without actually getting my hands on the truck and looking at it.

I am suggesting that you do a compression check b/c you've looked at almost everything else.

I am going to narrow it down a little bit.

1) EGR (still possibly the problem, and I would replace it with brand new one to check)

2) Bad Coil(s) - if you isolate the misfire you should be able to swap that coil with another known good one and see if the problem carries with the coil.

Your Fancy scan tool should have a misfire counter for each cylinder, unless our engines aren't able to monitor individual misfires. (I'm not 100% sure on the misfire counts as I haven't used that scan tool on a Ram)

3) Bad Fuel Pump - Simply check pressure at the fuel rails.

4) Bad Injector - again if you can isolate misfire and the problem didn't carry with the coil that you swapped then swap injectors and see if the problem carries now.

5) Bad Compression - Do a compression test and find out. Post results.

Might as well do a leak down test if compression test comes back bad as well that will help narrow the problem even further.

 

Unlike gm products which show misfire history and current misfire data this dodge does not...at least not on a generic scan tool. I was trying to find misfire information using mode 6 of the scan tool but it is not there either.

without the misfire data its hard to isolate this concern to a single cylinder. I'm gonna put the ignition scope on it...each coil, one at a time. I think this will rule out ignition system.


if the fuel pump was bad the fuel trim would be adding at wot and its not

I agree on a possible bad coil but with this 2 spark plugs per cylinder... wouldn't it take 2 bad coils to the same cylinder to cause a misfire? I could see leaking/old/mis-routed spark plug wires causing this.

I'm tempted to buy a generic injector puse tester to do an injector balance test...$200

I am a gm tech but we have different methods to diagnose this...like current missfire counters and an active fuel injector testor that will perform a injector balance test in a matter of minutes. This is my first dodge product.

Thanks for the suggestions. I will report my findings after the weekend.

 

Yeah I figured Dodge wouldn't have the misfire counts, mainly b/c they use a MAP sensor instead of MAF....

Even if the fuel trim is "normal" if the pump itself is not giving you enough pressure, it might cause "intermittent" misfires without affecting the fuel trims.

It's hard for me to diagnose the problem without seeing all of the different engine variables... were you able to get a datalog of it happening? If so, would you be able to post anything up? I'm looking for MAP, IAT, Throttle Position, Feedback Knock (or similar), Timing, A/F, and w/e else you can get... then I can throw it up on a graph and see what it looks like.

 

dodge is still using speed density calculations for fuel metering??

i spoke to the shop foreman at a nearby dodge dealership. After a short discussion, he told me that they don't see much ignition or injector problems. He suggested it may be the torque convertor clutch and that I should graph the tcc signal and see if it pulse width modulating when the jerking/shudder (what i perceived to be a misfire) is occuring. I will graph it tomorrow.

I did try using the tow haul switch to see if it would lock out the tcc. It locked out 5th gear but I think the tcc is still locking up in tow/haul mode in 4th. Is that normal operation for this trans?

 

Yes. in Tow/Haul mode you will lock out 5th gear and the torque converter will lockup to give you better towing performance, it will also extend the shift points to a higher RPM to eliminate stalling out when shifting into higher gear.

In later years we also got the O/D Off option as well which locks out 4th and 5th gear as well as the same as above.

It is possible that what you are experiencing is a trans problem but the engine would bog down and you would feel a little resistance to accelerating while driving.

I thought you said it did the same thing if you just rev'ed it up while in Park or Neutral is that not correct?

 

I was gonna say MDS, but I reread the post and you have an 05, so that rules that out.

 

Izero- the problem only happens driving down the road. There is no engine bogg or resistance to accell.

The trans has no slipping. Shift timing and feel are great. accell's fantastic.

do the 2005's have MDS?

This shudder is big. I can feel it through the floor. if you were holding a full cup of coffee with arm extended, you would spill it when the shudder is active.

The scan tool showed the tcc in full lock...then i created a light load condition...it shuddered untill the truck downshifted. I could not see the tcc solenoid voltage, just the on and off signal.

If I step on it hard when the tcc is fully locked, the shudder is not there?
If it is the tcc; it is smooth locking up but harsh releasing.

Would be nice if it just needed a pcm reprogram rather than R&R the torque convertor...

the genysis did show a code for the trans but could not define it...code 79...yep not a p-code, a 2 digit code that i haven't found any information on.

 

did a complete trans fluid exchange and replaced both trans filters yesterday hoping the shudder was from incorrect trans fluid. After 17 liters of mopar brand atf+4...no change.

Anyone know if there are any pcm programming updates governing tcc apply and release for a 2005?