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

Warmonger,

I wish you the best of luck on figuring out your engine stutter problems. I think any information you glean will help the rest of us. I have another link with a useful testing tip in it:

Link to a thread with an idea used to test stutter

Maybe that can give you some avenues of testing. In any case, good luck and if I find out anything on this end Ill let you know.

BlackCoog & svtavino,

The post I placed just before this contains the latest data so far on trying to TS this problem really. Alot of us, esp with 2000 v6's have had this low-mid rpm stutter with moderate-agressive throttle-positions. It seems changing plugs/wires/fuel filter/cleaning MAF/switching to stock paper filter-box/etc does nothing and the only wierd evidence (?) is the massive spark-retard (all way to -1; no knock showing at all either) when pressing throttle position (~36%+) in the rpms of ~~1900 to 3300 approx, in any gear (after about 3300 rpm to redline it doesnt seem stutter). It really sucks when your just cruising at about 42mph in 4rth gear and you want to gently speed up to 45 lets say (to move along with the solid traffic flow) and you stutter like a ***** when you get the throttle position around 36% or more. I can be going about 65mph on the freeway in 5th gear and it stutters when I do the same thing - gently press the accelerator trying to speed up to like 70 from 65. Any of this sound familiar? Well, like I said Ill shoot anything I find to the CEG and this post esp.

Panther and anyone with the issue.

I have been doing a little more Diagnosis and I have found something new.
When the car is very cold, 1st startup of the morning, I can take it out on the road and for maybe a mile I can accelerate without the stuttering. After that its all she wrote. I checked the coolant temp, and it was in the 120's degrees F that the car was running smooth. Above that it began to stutter and it got progressively worse as both the air and engine temps rose.

I think that any 'tricking' test should be done by controlling the resistance to the coolant temperature sensor going to the pcm. NOT the gauge. The coolant temp sensor is a two wire plug that you can pull off and stick a fixed value resistor in it to see what will happen.
The sensor is located on a crossover coolant pipe right below the throttle body.
I am going to try this soon. You can also use a poteniometer with two wires soldered on to it, and then you can use your OBD scanner to watch as you adjust it to the proper temperature.
Test several temperatures so that you can find the point that the stuttering goes away.

If enough of you can successfully use this approach to clarify the temperature that the stuttering goes away, then we can compile the data and you can go to Ford. This may get you a new calibration for your computer because there is a certain amount of fuel enrichment that the computer does when the engine temp is low. This evidence is surely a good way to indicate to Ford just how lean the engine runs below the IMRC opening point.

If ford doesn't want to do anything, then the best advice is to get the APEX SAFC, or a new MAF with an optimizer. If the test works on my car, then that is what I will do. There is no way in hell that my car will be warrantied now!

Apparently this is a lean-misfire condition that happens below the IMRC point because the IMRC point is a signal to the PCM to richen the fuel mixture.

Please past a link to this page to your buddies with the same problem so that they can test this theory also before they do any other circuit design.

All the symptoms you described are exactly what my car does. Right now I can't do any testing I have parked it for the winter. Has anyone put in an after market chip and seen the problem fixed? It seems that it must be a glitch in the 2000s program. I guess we will just have to drive above 3500rpm all the time.

I tested the theory, and I gained some good information.

I used a 50K potentiometer and plugged it into the coolant temp sensor.
The as the sensor's resistance climbs the OBD II shows the coolant temp dropping. If you unplug the sensor, the pcm reads -40 degrees.
If you have 0 resistance, the pcm shows over 300 degrees F.
It seems that 50,000 ohms will make the pcm see ~60 degrees F.

Anyway, to the results:
There are other factors such as intake air temperature, but the stuttering is greatly reduced for me when my temp is below 80 F.
When I dropped it to 60F and then accelerated in 2nd gear, the engine was fine with maybe one little hesistation or bump. When it hit about 3500 rpm, IMRC point it fell on its face because it was too rich.
So for me, the results tell me that I am way too lean below the IMRC point.
Bigger injectors don't help because the pcm scales everything based upon closed loop and part throttle readings. It just delivers the fuel that its fuel map tells it to based upon rpm, air and engine temp, and airflow. I guess this means I'm gonna need the SAFC or a custom chip.
I don't predict the new MAF I ordered to be able to compensate for this drastic difference in AF ratio above and below the IMRC point.
For those with the 2000 SVT's, check this out for verification. We may not have the same problem, but then we might.

warmonger

WarMonger,

I am going to test your theory and see if it applies. From the research you've done so far, it seems to fits right it. If this is really it, then it means that it is a "chip fix" to prevent lean/mis-fire below IRMC point with moderate throttle. Ill post here with my test results to confirm.

Great info I was just deciding not to get the S-AFC but if it has a chance of fixing this I will order it tomorrow. Let me know if this has a chance at fixing this. Good luck everyone on the testing. I have been tearing apart everything to figure out what it is. I am still conviced that piece of crap superchip has messed up my ecu right when I put it in. (I pulled it out a few months after I put it in because of major stalling issues and I even had the chip reburned when I sent my ecu to Florida with the chip but still no go)

...ahem... S-AFC ...ahem...

Oh yeah I told you that before...

I'm going to throw an observation I made last time I was tuning my AFC. I was cruising around after I was done with the laptop still hooked up, watching spark advance, RPM, and TPS. Seems that the stock spark curve was operating as folows for me (this is all 4th/5th gear highway cruising): Below RPM point, the higher the TPS the lower the SPKADV, and vice versa. Went as high as 20deg at low TPS and as low as 6deg at WOT. I don't know if this is normal or not, but if I get time I am going to drive my brother's 01 Duratech Cougar with the laptop tomorrow and see if his behaves in a similar way.

Just food for thought. Good luck with your problems.

Here's Stock, Chipped, and Chipped with pinned IMRC

[img]http://www.geocities.com/demonsvt/SPKADV.txt[/img]