Stutter at around 2K RPM/40MPH

[N40GL]

Okay - I need the technical experts here to help me out.

I'm getting a little stutter at around 2K RPM, and around 40 MPH. What its similar to is a blocked fuel filter, or when air bubbles hit an injector - kind of a 'thunk'.

Thinking it actually was a blocked fuel filter, I bought a new one from Kinsler that's quite a bit larger than the one I originally got from Dennis (and which straightened out the ninety-degree bend in the line). I also cleaned the air filter (an AirRaid, not a K&N; same principle however). Reduced the stutter quite a bit, but its still there.

I'm going to do some data logging this weekend, but before I do I wanted to put this question up for the experts around here to see what you thought. What I'm most interested in is what to look for in the logging. Eventually I'll send this info down to Dennis so he can adjust my tune (if that's where the problem lies) and correct the issue.

I'd sure appreciate any insight anyone can share about this. Thanks,

Mark


NOTE: Help me solve my technical problem. If so inclined, please leave snide comments about Dennis aside. He's always treated me well, and besides that I'm proud to call him a friend. You are free to put your comments elsewhere -- don't hijack my thread.

[fastblackmerc]

Check the plugs and coil connectors.

[Marauderjack]

What gear are you in and are you at a constant speed or accelerating??:confused:

Is the TC locked or unlocked when this happens??:cool:

[LeoVampire]

If the problem got a bit better by changing or cleaning the air filter then you should consider the fact that the MAF and or the IAC is also effecting it and might need to be cleaned as well.

[Paul T. Casey]

Stutter or flat spot? I've been living with the "flat spot" since day one. Managed to move it around some, and shrink it some (through tuning and mods), but it's always there. Trying to move 2 tons with only 281 cubes I figure.

[Paul T. Casey]

It was there again this morning, nearly let that silver G8 slip by.

[babbage]

Water in the DPFE - take it out. Pass side firewall, remove it slap it in your hand. Notice the water come out. Replace - then notice the buck at float is gone.

[Blackened300a]

I would think a coil is starting to act up under a load. Trying to locate it is going to be a mission.

[N40GL]

What gear are you in and are you at a constant speed or accelerating??

Is the TC locked or unlocked when this happens??

Steady Speed (or very slightly accelerating); TC unlocked.


If the problem got a bit better by changing or cleaning the air filter then you should consider the fact that the MAF and or the IAC is also effecting it and might need to be cleaned as well.

This might be a dumb question, but on the premise that "there are no dumb questions" I'll ask: clean it with what?


Water in the DPFE - take it out. Pass side firewall, remove it slap it in your hand. Notice the water come out. Replace - then notice the buck at float is gone.

Another dumb question: What in the world is a DPFE, and what does it look like?


Check the plugs and coil connectors.

The plugs've been in there for maybe 35K, so its worth replacing them anyway - good thought.

[LeoVampire]

MAF specific cleaner that comes in an arisol can.

[4play]

Did you use ford plugs?

[ntd]

My suggestion would be to load test the coils(needs to be done by the dealership or competent shop) as on light acceleration and high load a failing coil is more noticeable. If Dennis is your tuner contact him about your problems and ask him what he would like to see data logged to make sure it's not a tuning problem

[babbage]

Another dumb question: What in the world is a DPFE, and what does it look like?


Differential Pressure Feedback EGR, it's actually ontop of the EGR valve. This could be causing it. Very common problem on the 4.6 2v they would get moisture in them and would act as you have described.

[marvin]

have u pressure washed your motor before this...? I have had the same problem with my mm, and the problem was the water got down into the coil connectors. my #4 coil was already going bad. once i washed the engine , it basically zapped it. i had to replace all 8 boots to the coil packs and replaced the#4 coil. of coarse this called for another tune up. i went on and replaced the fuel filter as well. And that fixed my shutter problem.

[N40GL]

Over the weekend, I removed, cleaned and reinstalled the MAF sensor. I removed the Motorcraft AWSFA22C plugs (some of which were gapped wrong - interesting!) and replaced them with NGK TR6 plugs, gapped to 0.035". I recleaned (again!) the air filter, and then oiled it with as little oil as I could put there (basically, I held up the oil near the filter and whispered "oil" at the filter). And I had a new braided line made for the large fuel filter that took out the curlique that was in the prior line, so it's a straight through feed.

With that, the problem went almost completely away. I tried all sorts of things to try to induce the problem, and nothing worked. So, I think I'm done with this for now.

As I worked on the car, I noticed how greasy the engine had gotten, and went over and pressure washed it. So now I have a situation where the electrical will completely cut out and then come back on. It happened three times on the way back from the mall after dinner - each 'session' lasted no more than about one second.

I'm hoping that this means water got somewhere it shouldn't (and, yes, I kept the washer away from the fuse box), and eventually will evaporate back out. Since I don't drive this during the week (or, in bad weather, not during the weekend), hopefully that'll give it a week in the garage to dry out. Then I'll try it again. It doesn't seem to have developed marvin's problem with the coil packs, so for now no issues there.

I really have to learn to leave well-enough alone (i.e. greasy engines). *>sigh<* :depress:

Mark

[merc]

You could barrow my backup set of coils and EGR if needed.

[N40GL]

You could barrow my backup set of coils and EGR if needed.


Thanks for the offer - I'll let you know after a week of drying out.