[68FB]

I have the problem with jerky 1-2 shift, a slight bog under harder acceleration from idle, and what I think is a lack of power at lower rpm, so while I am waiting for my Peake reader, I checked the TPS with an AutoTap scanner. Below is the trace I got while depressing the gas pedal slowly and as steadily as I could to the floor (engine off, of course).
It looks strange to me. It got to 50% very quickly, in about 1/8-1/4" of pedal travel, then increased to ~95% in about 1/3rd of the pedal travel, and then flat-lined the remaining 2/3rds of travel to the floor.
The graph also shows where I floored it 3 times. For those cases it went up to close to 100%.
Then I started the engine and raised the rpm but the scanner just read zero as I depressed the pedal, like it had lost the signal, unless I blipped the throttle, when it quickly flashed up a number, then instantly dropped back to zero.
The response to the gas pedal feels fairly normal while driving.
Any one any ideas what is happening here? Does the fly-by-wire throttle act like this with the engine off?
Thanks.

 

[technician117]

Interested to see what others think. I have pretty much the same symptoms as you. The only difference is that although I do occasionally get the typical jerking I do not relate it to a problem with the car. I can usually clutch/throttle those gears without a problem. Its when I'm sloppy or not paying attention that will allow it to get jerky. Another observation on that topic: When I was running snowtires I almost never had the jerkiness. The snow tires were 245/40r18's so I think the tire would slip instead of jerking the car..

As far as the other symptoms, I could describe mine the same way... I was thinking TPS and/or CPS. I will try to get my car scanned today and we can compare codes. Hopefully with two of us with the same/similar problem we will get better responses, not trying to hijack your post!

Thanks,

Tim

 

[nightkrawler]

normal, even dis/gt1 will only show the voltage values for the tps with the engine off. the graph looks normal as well, if you had the plenum off you can see this first hand as you depress the pedal.

 

[Sailor24]

I am assuming you have codes? Engine was off and no other things got bumped? It does not look like what I would expect, but god knows what BMW engineers come up with to test the system. Would not want to guess if this is right or wrong. It does look rather consistent however. You say TPS of which there are two or was this the pedal output?

 

[ard]

How does your VANOS look at low RPM?

 

[68FB]

Thanks, nightkrawler, I'll cross TPS's off my list of suspects for now.

I have no CEL, and no DTC's on the generic scanner. When I get my Peake reader, I should be able to figure our what is happening with all the info available on this board.

Sailor24, the scanner is picking up a parameter it calls Throttle Position Angle. I assume that is one of the TPS's rather that the pedal position potentiometer. I wonder which TPS it picks up?

Tim, no problem with you chiming in. From the reading I have done, CPS's are a likely candidate for my problems, or at least being down on power. The Peake codes should help me confirm this. Let us know what you get from the dealer.

ard, I have no way of looking at the Vanos behaviour. If the Peake codes don't get me going in the right direction, I will get the GT1 tests done. That includes a Vanos functional test, doesn't it?

 

[cab]

I have autotap too and find that value on our cars to be somewhat worthless. I just logged a 10 minute drive and it showed to be zero for most of that drive. See my post regarding my O2 sensors here: http://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/173850-jerky-throttle-response-solved-new-fuel-pump-6.html

 

[ard]

Thanks, nightkrawler, I'll cross TPS's off my list of suspects for now.

I have no CEL, and no DTC's on the generic scanner. When I get my Peake reader, I should be able to figure our what is happening with all the info available on this board.

Sailor24, the scanner is picking up a parameter it calls Throttle Position Angle. I assume that is one of the TPS's rather that the pedal position potentiometer. I wonder which TPS it picks up?

Tim, no problem with you chiming in. From the reading I have done, CPS's are a likely candidate for my problems, or at least being down on power. The Peake codes should help me confirm this. Let us know what you get from the dealer.

ard, I have no way of looking at the Vanos behaviour. If the Peake codes don't get me going in the right direction, I will get the GT1 tests done. That includes a Vanos functional test, doesn't it?

1. If you have no codes and no CEL, then the Peake will do no better than a generic reader

2. Yes, GT1 and other full-function computers can run a vanos test. Maybe someone can comment on any special TPS-type test they can run.

GL

A

 

[68FB]

As nightkrawler says above, it works with engine off but not running. Go figure.
See my response to slow poll times in the other thread. Your right, the M5 ALDL is pretty sluggish with AutoTap.