AFRs in slow motion

[Ian C]

If it's going lean when you accelerate and rich when you lift off, I'd say the ECU isn't getting a useful throttle position sensor signal. It never knows the TPS position is changing so it doesn't drop out of closed loop - no extra fuel on acceleration, no injector cut on the overrun. Does it burble and pop when you lift off and engine brake?

 

Check error codes then get a multimeter on the TPS wire.

 

-Ian

[Golfpro]

If it's going lean when you accelerate and rich when you lift off, I'd say the ECU isn't getting a useful throttle position sensor signal. It never knows the TPS position is changing so it doesn't drop out of closed loop - no extra fuel on acceleration, no injector cut on the overrun. Does it burble and pop when you lift off and engine brake?

 

Check error codes then get a multimeter on the TPS wire.

 

-Ian

 

When I lift off it goes very lean (18) for a couple of seconds then it moves quickly to rich (11) for about 10 seconds.

[Tricky-Ricky]

As i said earlier in this thread, and as IanC said, check for error codes, and check that the TPS is showing an increasing/decreasing signal/resistance(can't remember which off hand) and reset the point at which it opens by the manual specs.

Will have a look and see if i can find them.

[Golfpro]

As i said earlier in this thread, and as IanC said, check for error codes, and check that the TPS is showing an increasing/decreasing signal/resistance(can't remember which off hand) and reset the point at which it opens by the manual specs.

Will have a look and see if i can find them.

 

Does an error code not bring up the triangle light on the dash?

[Ian C]

Does an error code not bring up the triangle light on the dash?

 

Not all of them, not under all circumstances

 

Reset your ECU first so you don't read off any dating back to 2003 or something That usually causes a panic.

 

-Ian

[Golfpro]

If it's going lean when you accelerate and rich when you lift off, I'd say the ECU isn't getting a useful throttle position sensor signal. It never knows the TPS position is changing so it doesn't drop out of closed loop - no extra fuel on acceleration, no injector cut on the overrun. Does it burble and pop when you lift off and engine brake?

 

Check error codes then get a multimeter on the TPS wire.

 

-Ian

 

I dont have a multimeter so the best thing is probably to bring it back to the mapper to check it out. I have been in touch and he is happy to give it the once over.

 

Just thought that I would do a bit of research to see if it was something simple I could fix myself. Probably better to leave it to the experts this time.

[Golfpro]

Hopefully sorted now.

 

Took the car to the mapper this afternoon and he could find no obvious mechanical or electrical faults.

 

He hooked up the laptop to the MAP ECU and did a bit of tweeking. He basically reduced the fuelling as he suspected that the cold weather was causing it to run really rich. I guess that the car was originally mapped in the spring when it was a good bit warmer than it is now. Also we recently built a cold air box with ram air ducts so the cold air is now coming straight in without getting warmed at all passing through the hot engine bay.

 

We will do a propper winter map in the next few months and run this until it warms up again when we can switch back to the original.

[Tricky-Ricky]

Thats good! but odd, as even if the map was originally done in warm weather, it still wouldn't account for the AFRs you described, glad its sorted though.