Wow D- jet runs better no TPS
 

I was getting pretty frustrated with the d-jet fuel cut-off deal. So i just unpluged the damn throttle switch. Car runs better, before I had a slight surging deal at coasting just with foot barely on the pedal. I assumed that maybe the fuel cut off adjustments were not quite right. So I just unplugged the damn thing. runs better. No tps going right now. Someone tell me why I should get this tps back how it should be, if you know. Otherwise I'm leaving it out for now.
PS . I can't stand the damn fuel cut off switch, that the car would just drop out all the sudden coming up to a stop sign or whatever. Then buck back up when the car hit 900 rpms all the sudden get fuel again. Very annoying. Like it better now. If this is OK should I just bypass the Idle switch wires (12 and 17?) and leave the tps as it is. any info appreciated.

One wiping contact is used to inform the ECU that the throttle is closed.Another makes contact only when the throttle is wide open and a third makes and breaks contact twenty times as the throttle opens.The electrical pulses created by the making and breaking of the contacts signals the ECU to open the injectors more frequently,thereby enriching the mixture for acceleration.

Hi Marcades, Nutzforbenz is spot on with the benefits of the TPS. And those 20 wipers acting as an 'electronic' accelerator pump add a fair bit of get up and go when you push the foot down. My 3.5 sagged badly when I left it off once. That may have been more noticeable due to the 3.5 having no full throttle position switch.

I reckon you're correct with the idle switch adjustment being the problem. Its not too hard to set up, and there's some good posts on the forum on how to do it. When it is set correctly and your on the idle circuit, check the ECU enrichment setting screw. Mine sits in the middle of the 18 clicks (or whatever it is) and I was surprised how sensitive it is to the position. By going full rich (cw) or full lean (ccw), I could make the engine run very poorly...almost stall full lean...and run like the 'choke' is stuck on at the other extreme.

Cheers.

I agree that the idle speed is not set correctly. The "Bucking" or "Surging" occurs usually when your idle mix is so far off the ECU can't tell if you're idling or coasting. It sounds like your idle mixture is rich, or your aux air screw is too far unscrewed, or both.

Also, keep in mind these cars have no overdrive, so there is no "Coasting" really in them. Taking your foot off the gas going downhill should result in the car slowing down (on a fairly steep hill, it might sustain speed).

I have plugged the tps back in for the throttle movement contacts, but I did leave wire 17 off because I do not like the fuel cut off. The surging was very slight. But I could feel it in the pedal. It runs better and Idles better without it. I will attemt to adjust it when I can figure out how to get to the bottom bolt. I guess my idle is being run by MAP now rather than ecu. Need to find someone around north GA that can set it up with a co analyzer and all.

Ah yes, can remember that.... The only way I got to it was by removing the whole throttle plate housing...4 nuts and linkage. As it turned out, I think this made the setting easier to do having it on the bench...then just reinstall. This and the whole job is well referred to in Graham's guide here.

http://www.peachparts.com/shopforum/attachments/vintage-mercedes-forum/73989d1257435944-73-450se-should-i-replace-intake-manifold-seals-adjusting-cleaning-tps-r107-mercedes.pdf

thanks stumps

As a follow up I removed the entire throttle body to clean, and adjust it tps. With no luck surging/ bucking continued at very light throttle. I figured out it waas not the fuel cut off or idle switch wires 12 and 17, but instead was the track of switches to let the ecu see accelaration. wires 12 and 9. I removed wire 9 and problem went away. I really see very little to no difference in accelaration so will be leaving it disconnected for now. I need to get a rebuilt circuit board if anyone knows of such thing, or possibly a dealer item. thx