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

The cooling fans would never come on. Then you would overheat. Baddd!!!
Plus, then the fuel mixture will be really off when the air warms up. That would make it worse.
Read earlier in this post, and you can see that I did run a variable resistor (potentiometer) in the ECT sensor plug. I was able to gain knowledge from it, but interpreting that knowledge is now an issue.

warmonger

Hmm I have been told from many people that the stuttering is not the pump so I dumped the fuel pressure idea.

Well if I lean out my car enough then my engine light will come on right? I had it leaned out a few times and the car stutters the same lean or rich. There is no difference. When it runs lean for a few blocks the engine light freaks and starts to blink so I richen it up and the light is happy and doesn't come on again.

Any idea what that means when the check engine light actually flashes but doesn't stay on? It kind of freaked me out when I first saw that.

Other possibilities that I have been told is the TPS sensor is going bad. My neighbor said a TPS sensor going bad would cause problems at low RPMS and should be fine at high RPMS. Any thoughts?

Otherwise he suggested a vacuum leak. I sprayed engine starting fluid around the vacuum hoses but nothing happend so I am assuming thats not the problem.

It's most likely not the TPS.

The flashing CEL means that the engine is currently misfiring. I got that on my car as well when I was leaning out and playing with it.

What you may want to try is leaning it out just a little at 50% throttle and up. If that doesn't work then try richening it up just a bit in the same throttle range.
I think you will need to put it on a dyno with a wideband O2 sensor to see what the actual problem with the AF is going to be. My problem is greatly improved, but it is still there a little bit. I will be running on the dyno next week hopefully to see what is actually happening.

warmonger

Greetingz all, heres an update on my end:

In the time awaiting Joe from SP for the Pro-M(it seems very difficult to get ahold of him, it's like you get one chance then...), it seems I may have made some in-roads as to my 2000 svt stuttering issue. I tried removing the back-plate on the center post (per WarMongers experiments into this) and after extensive field testing through driving, I can say that "I" wouldnt recommend it for an unmodified svt. Its seems to have a nasty habit of stalling when thrown in neutral without the backplane. Also, my stuttering issue is still quite prevalent. My theory is that by getting rid of the long "tube" that is the center post, you reduce metering-air velocity. Now, heres to the interesting part -- I took out my MAF and placed another backplane on the center post, this time I extended it down a little, so the opening at the bottom is a bit smaller the stock (thus increasing metering-air velocity threotically indicating a little more load then real life [a little more rich?]). I just got back from driving around town at operating temp and I have noticed that my stuttering is not there. Did alot cruising around in 4rth and 5th gear too. I will update again after more field testing (need to make sure stuttering is gone or see where it still exists) but this looks very positive in my case. TtEl.

Pioneers...I love'em!

Anxiously waiting final verdict.

...Ed

This is very positive. I think that the reason I have seen good results with the back plate removed was because I had the 24# injectors in. My computer leaned out the fuel delivery because of that. When I cut the center post, the airflow signal went down and then the pcm didn't have to lean out the fuel system as much.
The problem with my car seems to be a non-linear increase in airflow that is too rich at idle but just right in the low rpm area is causing the computer to lean back the fuel trim. Then after it has the mixture adjusted right for its purposes, it no longer is adjusted right at the problem rpm.
THat goes along with the fact that I noticed the best overall driveability (without the GReddy) with just the backing plate removed. Once I removed the whole center post, I didn't get enough fuel delivery at high rpm.

warmonger
(you guys can refer to me as Tom if you want)

Well I am going to try blocking up more of the hole and see what happens. This is very strange though why would our car do this an none of the others? Is the MAF bad? Hmmm well I am still waiting to swap MAF's with another 2.5L which I am hoping will be next weekend. I will let you know.

BlackCoog -- Make sure to try the test situation where the bucking disappears. Leave your car all night, dont use it. Then start her up and let it idle for only 15 seconds then take off, dont wait any longer! You want to drive her when shes cold. Then try some accleration tests, esp in 3rd and 4rth where you would normally stutter -- you should see it not present. This works every time the engine is totally cold. I have tried this MANY times and just cant get over it, how does the car NOT stutter when in open loop/engine cold but then do it when starts to warm up and esp at close-loop/operating temp?? These MaF tricks are only band-aiding thr problem I think. Trust me, I am researching this extenesively and trying anything that might give me a clue. Good luck. More later.

- WarMonger - This is for you man. You and I both have confirmed the cold engine, no stutter situation. We know there are many 2000 svt's with this problem and it seems it can develop on on other v6's,years,and combo's. This is from personal research,searches on the forums,speaking with local CEG'rs,and your experience. I am working on every avenue trying to test out what it is exactly. In my on-going research, I have re-read all the prev. posts in here and it seems that when you tested with the variable resister, you confirmed that it was a function of measured coolant temp NOT actual engine temp; since you stated that when you turned the resistance so that the coolant temp read <80 deg F, the stutter was gone. This leads me to believe that ALL this stuttering is coming from the PCM and/or the chip calcs when coolant temp is read above a certain temp -- in this case around 80 degrees and hotter. I wanted to get your thoughts/confirmation on this so far and any comments on my theory - much appreciated. TtYs.

Well I tried the cold start thing and no stutter! Well the car still bogs down when I try and floor it in too high a gear but no stutter. It is like it wants to stutter but doesn't.

So if this is a ECU problem could I have my car professionally tuned and get rid of it?