Throttle Shenanigans?

[SCGT]

Wondering if anyone here has issues with their throttle misbehaving. I'm not talking about throttle closures, I'm speaking of throttle not fully opening (tune related) or, more importantly, throttle not closing after certain WOT conditions.

If I bang first, slam second and near the top of the RPM's in second go off throttle/put in clutch, I've found that my throttle actually doesn't close... it drifts shut. Thus boost bleeds off slowly as it's consumed by the engine because there isn't enough of a pressure differential between pre/post throttle to open BOV (tial; light spring, also did this with stock & forge DV's).

My mechanical boost gauge shows it, and I finally caught it on my cobb as well... TPS actual will just slowly drift down. I'd suggest that maybe the throttle was sticking at the top, but drifting down doesn't make sense, hanging then slamming shut would make sense. I have NOT captured this in a log.

Car is an '07, nearly 100k on it. The throttle not closing after some WOT conditions has occured both on my Brentune as well as the OTS Cobb E30 map, tweaked for E60.

Anyone see this? Tried all the normal re-sets/adaptation/etc. Car throws a fit when I try to reset throttle adaptation through BT, but I'm not 100% sure I've done it correctly.

Any input besides burn it to the ground and buy an M4?

[djpaulie]

Did this condition develop along with a recent change in AP map or hardware? It sounds like it's been a problem for a while just curious if you may have a hardware problem as opposed to a MAP/tune issue. Also while cruising around town does it have any weird symptoms or only on and off of WOT?

[SCGT]

Thanks for your response.

The one issue with throttle not opening all the way (~60% TPS Actual) came about after switching from a Cobb V2 to Cobb V3, only on my protuned map. Last night I switched to the OTS E30 map, tweaked for E60 and on full accellerator position nails 81* immediately. So that's something in the protuned map.

The other issue with the throttle plate slowly drifting shut on sudden off-throttle conditions is not anything I can attribute to a particular hardware or software change. It doesn't do it every time, which means to me it's either software and I'm not always meeting the conditions required for it to happen, or it's merely an off/on thing with a failing throttle body.

Cruising around town it mostly behaves, I've seen some hesitation that I've linked with throttle body closures when part throttle. To be clear, say you press the accellerator pedal 30% and hold it steady, I've seen on multiple maps where the throttle plate will initially open some large amount, hold for a second or so, suddenly close about 20*, then re-open and slowly close as the car accellerates and the load demand decreases. Like a throttle closure at WOT, except no timing issues, no misfires, and certainly not at WOT. Subjectively, it makes the car feel like it hesitates while going through the spot where the throttle plate is wonky. FWIW I had no WOT throttle closures on the same map. Well behaved.

I'm hesitant to replace the throttle body as I'm not sure throwing new parts at it without really understanding what's going on is the best method, especially since it's not throwing any codes. Posted here to see if anyone else has experienced similar things or has some useful experience.

[djpaulie]

I would recommend that if you have some diagnostic time to spare on it that you shouold uninstall the cobb so software is out of the equasion and take it for a drive in stock setting and see how the throttle reacts under the same conditions. If it is harware related you should see similar symptoms as long as they are not power related of course. I know you have an ethanol mix wich may make this have to wait till the tank is empty and place a couple gallons of 91/93 in to remove fuel from the equasion as well as stock the vehicle isn't exactly calibrated for high ethanol fuel. Have you tried logging everything such as AFR, Trims, and your HPFP and LPFP or to make sure the closure of throttle doesn't have anything to do with fuel pump related issues on an aggressive map.

[SCGT]

Thanks, but it's not related to fueling or lack thereof; it's not a throttle closure, it's a throttle staying OPEN when it ought to close issue.

[BuraQ]

@SCGT

If I recall correctly, if the Threshold (Major Throttle Closures) table value is set too low it behaves similar to what you have described

Stock value is 0.985
Cobb's OTS map value is 0.960

"Depending on the car and tuner" anything below 0.960 wills start to result in what your are experiencing

I myself have experienced something similar as you have when I reduced the value too much especially when the car is cold

[SCGT]

Super useful. Thanks!

[lulz_m3]

@SCGT a bit anecdotal, but i have *heard* reference made that the DME attempts to hold the throttle plate open during certain conditions - ie, WOT + shift after xxxx rpm's it wont snap the throttle plate closed in what i assume is an attempt to reduce lag between shifts. Whenever i did the vent to atmosphere mod to the stock DV's (I'm a ricer at heart) and the car was completed stock i still noticed delayed venting when at higher RPM's. Its very inconsistent sometimes, so hard to methodically determine when the DME is attempting to keep the plate open, but i believe this is normal behavior nonetheless.

[SCGT]

I wondered about that as a possibility. Helping hold boost between shifts. Worth noting is that I cannot reproduce it when short shifting. Hmmm. Thanks for your input!