Idle-Studder fixes

SuperXRAY · 01-28-2009, 11:20 AM

This question is in regards to our 1983 944 with the DME 1.1. It has the idle studder when the throttle is released and I'm really not in the mood to down the girlfriend's daily driver by ordering the software fix and updating the DME. I also don't have a spare DME, so as not to accidentally destroy the original, and see no need to buy one. Please note, I am NOT trying to disregard or damage anyone's ideas.

It has been suggested to 'fix' the problem by turning the throttle plate stop screw until the TPS clicks off of idle. Then, readjust the idle screw to compensate. While I have performed this fix, I don't like it much...let me explain.

Performing this fix modifies what the engineers designed into the air intake system. It affects idle simply because it allows more than the designed air flow into the engine, by bypassing the Idle Air Valve to some extent. This also has an effect on the vacuum port directly behind the throttle plate.

Would it not work if I were to rotate the TPS to achieve the same goal? This is the method used on every other car I've worked on to achieve the correct 'idle switch point'. Most throttle bodies are set by very precise flow metering equipment, so I am more leaning towards putting the plate back in its original position and rotating the TPS.

Looking for feedback...

carsontc · 01-28-2009, 12:29 PM

this used to be the answer:

944 shudder fix

maybe you can find an early DME already chipped with FR Wilk's power prom

HondaDustR · 01-28-2009, 12:29 PM

That can do it as well, but the problem with that solution is you'll also lose a lot of engine braking effect, since the idle switch also shuts off fuel flow above something like 1500 rpms. It's kind of weird feeling driving it that way when you're used to how it usually decelerates.

SuperXRAY · 01-28-2009, 12:58 PM

Thanks guys,

I was aware of the consequences before performing the procedure, but in effort to get the car driving for her after sitting for a couple years due to other influences, I took this route just to alleviate the complaints. I suppose it's really up to her if she wants to spend the money. I've put enough into the car for it not being mine.

Was more looking for feedback on which one is the preferred method; moving the TPS or the stop screw.

I hate to say this, but our '89 Supra had a much simpler design for this problem. Then again, it's not a Porsche and is six years newer.

I will look into finding a DME and modifying it. I hate ordering parts, though.

SuperXRAY · 01-28-2009, 07:48 PM

Didn't realize the BMW ECU's were so cheap. I'll be ordering one tomorrow.

Dunno yet about the money on the chip, might just order a stock replacement.

Thanks.

Rasta Monsta · Rasta Monsta's Garage

Couldn't this be from cracked/leaking vacuum lines as well?

SuperXRAY · 01-30-2009, 10:38 AM

Rasta,

Thanks for replying. I have checked most all the vacuum lines one by one with a vacuum pump. It actually seems to be getting better now that some Seafoam is in the tank and we've ran a few miles through it. It also got better cleaning the throttle body. I've since repaired the AFM and just finished putting it back together. I haven't started it yet as I have other real work going on.

Taking it to the car wash in a bit and there is still one vacuum line that could possibly be leaking...I'll let you know how it all goes.