Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec ?Help tracking down the stuttering problem....Long...

MastaMoon - No worries man. As stated before, noone is driving their car around town with it tricked into thinking its cold all the time - one blatent problem would be that the PCM wouldnt turn on the fans. Those tests with the variable resister were only done to confirm the theory not for day-to-day operation. To get a perm fix to this, one must either use the Greddy to adjust injector pulse width or, I think, to get the chip adjusted so it uses a quicker and larger pump-shot during acceleration and make it so it runs "a little" richer through the injector tables. This whole thing has something to do with closed-loop operation - ie. using sensors and esp. the 02s instead of predefined tables), like you said. ....something with what I just mentioned - the fuel acceleration tables since its happening during acceleration but disappears when the secndaries open, ie. fuel enrichment. My actual personal opinion is that the closed-loop part throttle cruising is being held to stoic but dangerously close to lean, for fuel economy, but the prom doesnt have the adequate fuel advance plugged in for the different throttle positions and it lean mis-fires because of it. I believe this is exactly what you were saying MastaMoon. Trying to get WarMongers ideas on this as well (and anyone's opinion - there are alot of us watching this thread). I noticed in your sig. that you have a 2000 v6 manual. Your post doesnt seem to indicate you have any stuttering problems..? Might I ask you to post your PCM number and tear tag number? I can send that info to Diablo sports to cross-reference against my pcm and tear tags. The calcs will be different based on sport vs svt needs but we can see if there is any huge difference or odd changes in basic things like acceleration tables, etc etc. Thanks for the post in any case.

OMG - where did MastaMoons post go? I thought he posted right after mine. Hmm I must be on crack, or its an old post in this thread or BOTH. Heh. BlackCoog, check out my latest post man. I see you are the same way - cold=no stutter. What you described IS exactly what my car does! This is awesome because this is proving we all have the same problem. If others with this problem could test this out and post they exeperienced it to, it will be all the help. I do believe it is a problem you must address in the prom chip but I am awaiting other opinions and that of Diablo sport too. All the evidence says to me 98% chip/or pcm; just my opinion. TtEs.

Well this summer no matter what it is getting fixed. I have the car paid off so I will have cash and I know a really good shop that has an in-house dyno that should be able to fix it and squeeze everything else out of the engine.

Hi all,
I'm still here, and still stuttering! I tried tuning the stutter away with the GReddy unit, but it didn't work. The AF correction device can 'change' its characteristics, but not get rid of it. I have started playing with injector pulsewidth, but I am limited to tuning because of the cost and availability of a dyno, and a fast laptop computer.
The software supports data logging and realtime tracing, but the laptop I'm using is so slow that it misses most of the data, so it's like a half-azzed delayed trace. I am able to make small improvements to the stuttering issue, but I'm to the point that I just want to put a gun to the damn pcm and fire it!

To answer the earlier post, I tricked the pcm with the adjustible resistor by setting the coolant temp to about 60 F.
It reduced most of the stutter, but there was an occasional jump from the motor.
It is Definitely a computer related issue.

**I confirmed on the DYNO yesterday that the car is running lean when the stuttering occurs.***
I can also say that the computer will not allow much adjustment with the airflow. Everytime you make adjustments it tunes them back out.

I have to go now, but I have more information to give.

Later,

warmonger

Hi Tom, Chris, and all,

Hope you don't think this silly...this is the way we "solve" problems at work...just throw out ideas till something "clicks" with somebody. Most often nonsense comes from the group till one little thing strikes a chord with someone...

Do you think it possible,

1. The way our coil pack fires positive/negative or whatever, could it contribute to the problem. Constantly switching grounds? (I don't have a clue how it actually works). Is the voltage supplied to it uninterrupted/consistent?
Does the MSD DIS-4 fire differently?
2. The way the O2 sensors switch...is the fuel program written too precisely and in need of a bit "fuzzier" logic? Can you put in a bit of "resistance" to slow down the switching? Smaller gauge wire?
3. I think I remember a while back changing my air filter and immediately noticing the "stutter"...apparently it had either reduced with a dirty/restrictive filter OR I had gotten used to it, (although not likely). Has anyone tried to restrict the intake to see if it makes a difference one way or another?
4. What would a faulty cam or crank position sensor result in?
5. Spark plug gaps too large?
6. Winter grade oxygenated fuel?

??????????????????????????

Also, my car does run BETTER when COLD, however it certainly isn't totally gone while cold.

...Ed

Hi,

One more thing...would K&N oil on a stock Fram filter "restrict" it? I have ordered a new K&N dropin and would be willing to "trash" the old one to experiment.

...Ed

EderFox,

When we reference cold, we mean literally and before 2 minutes passes for the testing. Def below 60 degrees on the PCM CTS or coolant temp sensor.. This problem occurs when the PCM goes into closed loop mode. In my case, it is 99% gone when absolutely cold and before 2 minutes or so passes. I can be very aggressive on it in 4rth gear from 39 mph and it doesnt stutter. 3rd gear is all the way cool too - I can stomp that sucker too going 29mph in 3rd and no stutter when cold. I try that same thing after it starts to get warm or at operating temp and boom, nasty stuttering the whole way up. These are just extreme examples to show that even under very hard acceleration the condition is almost non-existant when cold. The spark plug gaps and wires and coil are static, they would cause a problem regarless, cold or warm - open or closed loop. The plugs should all be gapped correctly and inspected, along with the wires, to make sure they arnt contributing to the problem. Myself, I replaced the grounds from my tranny/fuel rail/coil with 4 gauge wire directly to frame points just yesterday. My opinion is that the PCM is maitaining a very lean a/f ratio when under IRMC open point and that it def. does not give adequate/quick fuel enrichment when accelerating in any form - until you hit IRMC open point. Warmonger confirmed it was running lean when the stuttering happens and that is what it is, lean-misfires - from what we have seen so far. K&N oil on the stock paper filter would only clog up the spaces inbetween the paper fibers I would think and also be absorbed into the fibers, expanding them closing off more space to breath - just personal conjecture here nothing concrete on that. TtYs.

Here is something I picked up from this web site: SmogSite

It says:

EGR Problems: Either it doesn't work when it should, or it does work when it shouldn't. Or it doesn't work the right amount.
The EGR may not work because vacuum lines crack, fall off, or are misrouted. Or the big EGR diaphragms leak away the vacuum, or the transducer won't close off it's vacuum leak so the vacuum signal doesn't get to the EGR valve. The EGR valve may be corroded shut, or maybe even the EGR passage is plugged up so exhaust gas can't flow to the valve. Or maybe the computer solenoid goes bad and won't turn on the EGR vacuum or valve anymore. All these will stop the EGR from working.
Maybe the EGR sensor on top of the EGR gets a glitch in it, so the computer doesn't know exactly how open the valve is. It gets all confused and either turns the valve on too much or not enough erratically. The customer experiences some hesitation or real bucking. Part of this is because the computer is advancing the ignition timing more with the EGR flowing, to try to give us more fuel mileage and power with the EGR on. Then when it doesn't know the EGR position exactly, this computerized timing advance jumps all around.

The EGR only starts being used when in closed loop and at part-throttle operation - not WOT or open loop, if my memory serves me correctly...? This may be an avenue or not but I thought I would post it to spur thought. Any thoughts on this at all? Thanks.

Here is another site with very useful info on the 5 gases present in exhaust. The amount of each present indicates what kind of problem exists. Perhaps take a look.

5 gases present in exhaust, what they mean.

Yet another site with info. These things might be avenues. This one points out some more ideas.

tech tips

When manning data stream, check the PRNDL section. Shift from park to reverse to neutral to drive. Does the data stream indicate the movement? Some problems that may occur if the PRNDL is not working include no timing advance, set fuel delivery and pinging. If the PCM thinks the car is not driving, it will not advance timing, keep fuel delivery to a minimum and not turn the EGR valve on. Bad PRNDL has also set VSS codes, because the PCM does not believe the car should be moving -- obviously a bad VSS signal!

EGR Problems
..... If a car has an over-active, or non-controllable EGR valve it may develop extremely lean misfire. The EGR reduces oxygen content in the exhaust, and if too much EGR is sensed by the 02 sensor, it thinks the car is running rich (not enough free 02), sends the PCM the message to lean the mixture. Leaning the mixture, on top of too much EGR, and the misfire causes more oxygen to go downstream -- well, you can see what happens to the AF mixture. This type of misfire will actually get worse when propane is added, leading you to the EGR problem.