Help with idle/random acceleration

[KoN_mkII]

I'm running MSnS-E (latest I think) and MT 2.25 on a VW 16v motor (using hall sensor/distributer).

I'm having a few problems, but one might be due to the fact that I am NOT running an idle device of any kind.

If the motor is idling, and I rev the motor up, the RPM's dive way down below cranking speed before bouncing back up to idle speed. Often time, the motor just dies, and I must restart. If I don't give it any throttle when cranking, the motor will start, rev up, and die immediatly.

My other problem, which is more pressing of an issue, is that the car will randomly start accelerating on its own.

I'll be driving, then let off the gas, push in the clutch (idling essentially) and MT will be showing a MAP of around 27 (normally idles around 36-40kpA), and the ignition advance will be around 26 or 27. This essentially means the car is accelerating on its own. If I push the clutch in during one of these periods, the car will idle at around 3200 RPM's. If I let off the gas while moving when its doing this, the car will NOT go into deccel, but will instead continue accelerating (which means I have to really use my brakes to slow the car.

I'm still new to MS tuning, and I know my desciption is kinda dull. Unfortunatly, I went out today, it started doing this again, and I pulled over to get gas and to start the datalogger so I could record it when it happens. But it went away, and the car did not do it a single time the whole drive. Nothing seems to cause it, it just seems to be random at this point, and nothing seems to make it go away (also seems random). I'm pretty sure the throttle is NOT getting stuck. A possible problem I see is that my MAP sensor for MS is on a shared vacuum port on the intake manifold. But Its been like this the entire time, and hasn't done this yet until fairly recently.

This is a very annoying problem. I will try my best to grab a datalog of it, but its very difficult not knowing what is going to cause it, and what doesn't.

[PSIG]

Please post your msq and a short datalog of 'normal' running even if it's not acting up. Also verify which version of Extra you're running.
Is there a PCV valve installed and is your vacuum cannister system still original?

[KoN_mkII]

Okay, here is my current MSQ file, and a datalog of just relativly normal driving. I did NOT experience the described problem during this log however.

[KoN_mkII]

Alright, I got a log of it doing it.

Looks like the TPS has a way high reading for idle?

[KariM]

I'm having a few problems, but one might be due to the fact that I am NOT running an idle device of any kind.

That does not affect, most engines idle happily without any active control when warm.

If the motor is idling, and I rev the motor up, the RPM's dive way down below cranking speed before bouncing back up to idle speed. Often time, the motor just dies, and I must restart.

To me this seems a problem with acceleration enrichments. If your msq opened correctly in my Megatune, you don't have any AE at all, is this correct?

I'll be driving, then let off the gas, push in the clutch (idling essentially) and MT will be showing a MAP of around 27 (normally idles around 36-40kpA), and the ignition advance will be around 26 or 27. This essentially means the car is accelerating on its own.

I guess you don't hit the lowest kPA rows on your spark table on normal drive? There is the 10°BTDC region between 800-1500rpm, try to extend that to higher rpms on low MAP. I mean, fill the 20kPa row with 10° and put somewhat lower values in the 30kPa row too.

[KoN_mkII]

Yes, I was not running any AE while I was tuning the upper half of my VE table. I hadn't gotten a chance to put them back.


I checked the throttle body, cable, and for the life of me cannot get it to stick.

I checked the throttle itself while it was doing this during that log, and it was resting on the idle stop, like expected. I'm going to try removing the stop screw from the TB. Perhaps that is vibrating itself open and closed (the only thing I can think of throttle related to check).

Could a vacuume leak be to blame? I would think that the TPS wouldn't be registering that high if it was just a vacuum leak. Unleess there is noise on that line, but I've gone this whole time tuning without a single problem like this until recently.

Thanks for the help guys.

[KoN_mkII]

My AE's are totally off right now. I'm going to try resetting them to what I had them before, and see if that helps my rough running/idle issue, but I'm really more concerned about getting my other issue solved. I also noticed that in the realtime display, hitting the throttle didn't change the TPS reading at all. But that might just be because I have the AE's all set to 0.

[KoN_mkII]

Okay, well I think I solved my more pressing issue with the high idle. With the car idling in the garage, I pressed the throttle body, and literally watched the screw on the throttle stop spin several threads with the vibrations. This, I'm sure would be enough to hold the throttle open just enough to keep the RPM's that high at idle. I locked it down the lock nut that was previously loose, and I'm hoping thats all there is to that issue.


Now for the AE's. I did put in my old settings, and noticed that the car ran MUCH smoother. The motor didn't stall once, and didn't really dive in RPM's when I pushed in the cltuch. Starts from a standstill also went much smoother. However, all is not perfect yet. Now it seems that my Decelerations are wrong. Its smooth on decel, but the AFR is sweeping from 13.6 or so to high 14's, whereas before, the engine received almost no fuel while Deccelerating. Could this be caused by this "constant enrichment" you are talking about? What could be the cause of this?

I've noticed that with the throttle pedal competly out, the value in realtime display shows a reading of 30. When I floor the pedal, it only sweeps to around 75 or so. I have tried calibrating it several times. Any ideas there?

WOuld this be caused by the incorrect trigger? What kind of numbers should I be looking at for that value? Am I just supposed to play around with it till I get it smooth? Where would I go to change this trigger? Is it the same value as the "TPSdot Threshold"?

[mops]

i had the same problem with tps when it was wired incorrectly.
not my tps is single most accurate sensor in the car. it showes every time from 0 to 100%, no noises there.

I suggest check tps wiring and then recalibrate to be consistent.