RomRaider

Dear Rom Raider MS41 community, Zhora here again with a seriously nagging problem. I have had the pleasure of dealing with Todd from Riot Racing here in California. The problem is that there is a persistent Check Engine Light that comes on when using his 68 mm big bore throttle body. The light itself turns on about 5 minutes into a drive session but the pending code is constantly on. Even when clearing the code it is still right back on as pending. This is a serious problem as a pending code will not allow the Emissions Readiness Monitors start. I found this out as my car needed to go in for a smog and just barely passed with the stock throttle body fitted.

My question is, with a completely thorough and fine tuned adjustment on the Throttle Position Sensor and the Idle Stop Screw how could it be possible to have a pending code? I have the pin out check for the TPS and I have diagnosed the problem with a heavy duty Snap On Verus Pro. Everything is within range. There does not seem to be a reason for the code set.

Some believe that the bigger throttle body needs a tune for this error. I do not doubt it needs a tune for MAF Scaling but as for the error, how could the ECU throw a code and on what grounds? There is a post saying that the ECU checks between the TPS value and the MAF value and if something is off then there will be a code. I find all of this somewhat difficult to understand.

Any thoughts as to what the problem might be and a possible fix? Thank you all for your time. This is a big topic on bimmerforums but I have not seen it on any tuning forums just yet.

The car is a 1999 BMW (e36) 328iS, M52 engine with an M50 Manifold, 68 mm Throttle Body, ASC Delete Boot, Custom Conical Intake, Turner Under Drive Pulleys and Mishimoto Electric Fan. My tune is a MAF Scaling and Injector Scaling to set Wide Open Throttle to .90-.88 Lambda.

You may need to play with dashpot.

Thank you for the reply my friend. I was actually thinking the same thing. It still does not quiet make sense to me though but I will keep looking into it.

The throttle body is just probaply made poorly and the throttle flap is in different angle than as stock when closed. Thus causing the dtc. There is thresold for closed tps adc value in current ms41 definitions. You could try playing around with that.

Dashpot affects iacv. Not tps.

That was another map I was curious about. There is an Idle Stop Screw that I have adjusted and played with to get to stock values. There is also a trick with the TPS to get it to adjust to get it into stock values. I have played around with both parameters. Nothing works. I would love to block the DTC but don’t know how. Currently, it was mentioned somewhere that the ECU references the TPS value with the current MAF values. My adjustment is in stock range and I still have a DTC. It is very confusing and I still can’t see how the ECU will know if something is wrong with the throttle when all values are within stock values. I have verified the values with a scanner.

DTC 12 can be disabled in the Diagnostic Trouble Codes folder...

Did you solve this issue ?