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

BlackCoog - you seem to be having the exact same problem as the rest of us. You mentioned today that your car stutterd all the way up the rpm range now, not just below IRMC point? Is that with the S-AFC turned off/normalized? Perhaps your car has finally failed to a point that we can locate the source of the stuttering through an extreme elevation in the symptoms. Please let us know =-\ TtEl.

Blackcoog,

I notice that you have a really opened up exhaust system. Did you have this stuttering problem before you did any exhaust modifications?
warmonger

Blackcoog, and Blackpanther!

Do you guys notice how you both have gutted pre-cats?
So do I.

Do you think this might be a clue?

The guy DavidZ has not indicated any stuttering issue, and he has MSDS headers on with a Bassani exhaust.

We need to look into this issue soon. With gutted pre-cats on the stock exhaust, I didn't have any issues. With the exhaust unrestricted, now I have issues. What if the pre-cats are allowing an expansion chamber which is causing the low-rpm driveability issue?

warmonger

Warmonger,
I had this problem since brand new - no mods whatsoever. I mean, 32 miles on the odometer at the dealer and me not touching a thing. All these mods were done after the fact. Hell I didnt even throw a K&N drop in untill almost a year later - first mod. I dont think its the exhaust. There is enough exhaust restriction to allow the egr DPFE sensor to work and the less exhaust restriction only serves to allow the gases to escape sooner and to prevent cylinder intake charge dilution. The Maf compensates for the extra flow ability in anycase, at least that which might be provided by the less restricted exhaust.

..and my last post further reminds me of the service rep at Jerome Duncan who said to me that the stuttering was normal and that there is nothing they can do. He said, yeah I owned one and it didnt bother me.... Im like WTF. Fugging dealers fuggs.

I did another test tonight. Drove the car around for about 20 miles round-trip - ended back at my house. I then proceded to disconnect the upstream O2 sensors - the ones used to calculate lean or rich. I then reset the PCM. I then took her out for a test drive. Aside from the idle being unstable and she was stalling in neutral (waiting at lights), I had no stutter. It was just like driving when the engine was cold but instead she was at operating temp. I had no stutter until the CEL came on, then it came back. Of course I immediately hooked them back up when I got home. This kind of test is difficult to do more extensively because of the unstable idle - up and down then stall in neutral. For what its worth...

Just wondering if everyone that is having this problem is a returnless fuel system? I work at a place that builds fuel systems. We have been recetly working on a new fuel system using a pressure sensor and pump speed control. If our cars are using a system like this it could be causing the problem. When the system needs fuel the speed of the motor speeds up. Now if you stomp on the gas it may cause a pressure dip then a spike then it dips and spikes again like a sin wave until the controller can catch up and make it even again. I have seen it done on the bench it would probably cause our problem. Now I noticed this weekend our system does have a some sort of pressure sensor at the fuel rail so it is possible that this type of system is on our car and causing the problem.
If that isn't the problem I was considering developing a controller that makes the maf have a greater signal in the area we are having the problem so that it would make it richer. I would do this by tieing it in to the throttle positioning sensor so that it would only go on at certian times so the PCM can't tune it back out. If it is actually the fuel system then hopefully my company will develop a better controller and maybe we can use it.

Svtavino - hello. Yes, all 2000 svt's have the returnless fuel system. Some late model year 99's also had the returnless system as well. So would this problem be in the sensor or the electronics in the fuel pump itself? Thanks for the great information! TtEl.

Svtavino - Hey again. One thing to keep in mind too is that this problem is not present when the engine is pure cold, just 15 second warmup and go. After 2 minutes or so/gets to operating temp and goes into closed loop it starts. Warmonger tried this with engine hot but tricking the PCM with a resister inline with the Coolant temp sensor - making the PCM think it was only 60 deg Far. That was done as one test. Any thoughts on that? Thanks!

Hey guys, wanted to post this:

2000 svt pcm Ford part number:
XS2Z-12A650-AAB

Casting number:
XS2A-AAB

All 2000's should also be tear tag:
XGT1

That is not what is interesting. I looked on the label on the inside of my door opening, not the door, and I found my PCM flash rev number. It is 9LCMA. I called up Ford parts and they said they only had one rev number for 2000 svt's BUT it is 9LCMAXE. It appears I dont have the latest, or only for that matter, flash rev for my PCM. Can any of you guys confirm on your tours? Going to check and see if this means anything but at first glance means the code in my PCM is not the official latest... Ill see. Thanks!