D-jet TPS

[oscar]

For ages now I've been putting up with a bucking part throttle response which was due to the Throttle Position Sensor having worn contacts and poor movement of the internals.  Wont go into too much detail except to say I got a replacement 2nd hand one that is working perfectly and acceleration and deceleration is smoooooth as.

An interesting fact; although the 350 TPS has 4 electrical pins and the 450 has 5 pins with the 5th pin being for a full throttle switch, a 450 TPS will work on a 350 and the 4pin female 350 plug fits perfectly on the 450's 5pin male socket.  That's what I'm running on the 350 now. 

Since a new TPS costs approx 115euro as per the Classic Centre's parts availability page, I thought I'd take a chance on a secondhand 450 TPS.  At the very least I would've been able to use its parts to rebuild the 350's old TPS.  But didn't have to, the 450 TPS works perfectly wihtout any modding or rewiring.

Photo - Old and newer, 350 on the left, 450 right.  Tiny differences, the obviousl one being the fifth pin on the 450.

To test yours if you think you might have a faulty TPS I've put a couple of vids up for comparison of what should and shouldn't happen.
- Remove air filter housing.
- Turn your igintion on to (II) but don't start the engine.
- Operate the acclerator linkages from closed trottle to full throttle and back again
- There should be 20 only audible clicks on the way to full throttle.
- No clicks should be heard as the throttle returns to a closed position.
Faulty TPS video.
Good TPS video

[WGB]

The D-jet remains a complete mystery to me I'm pleased it is in your capable hands Oscar.

Bill

[oscar]

I think my dream w116 would be a d-jet 6.9.

[koan]

I think my dream w116 would be a d-jet 6.9.

So you would replace a beautiful system of bi-metal strips, springs, a big airflow flap and a piston uncovering slits to meter fuel with a monstrosity of pressure sensor, throttle position switch (the purpose of which is to make clicking sounds from what I read) and an electronic control unit?

No way! It will never catch on

It is a bit odd that Bosch went electronic route with D-Jet that I think they bought the rights to from Bendix, then went to the non electronic K-Jet and then after a few years reintroduced electronics on the KE-Jetronic system. After that, electronics all the way.

koan

[oscar]

Positively Yes

I think d-jet is a beautiful thing.  Just a shame the three or four commonly failing items cost a small fortune but if replaced with new, they're good for another 20+years like the original items.

[13B]

Oscar did you buy that TPS on evil-bay seller describing it as "Unknown Bosch part for Mercedes" ?  If so very lucky, I recognised the part in the picture and was this close to bidding, but forgot to...

Ian.

[oscar]

Yeah that was the one. 

A tad under $20 all up so yes, very lucky that it works and lucky that the price didn't blow out at the end.  I might point out too that I should be very thankful to koan who spotted it for me and convinced me to try it.  Thanks koan   I didn't see it during my searches and I've been doing worldwide searches for one for a while now.  Plus I also had reservations that an M117 tps would be a simple drop in replacement on an m116 but it was.   

I'd like to know why a 450 has a full throttle switch though.  There's a circuit there my 350's lacking.

[Big_Richard]

.

[oscar]

That sounds logical.   The pressure sensor also has a full throttle setting which does something similar so far as it means max enrichment when the vac drops below a certain mmHg.  I read somewhere about vac lag which is more pronounced during spirited driving and is overcome by the TPS giving immediate input to the ECU.  It sounds as though the 450 can get max enrichment in an instant compared to a 350.

[13B]

It sounds as though the 450 can get max enrichment in an instant compared to a 350.

Mine would want to!

I've also observed on other manufacturers cars fitted with the afterburner emissions control system some of them need a switch to tell the emissions system to cut air feed to the manifolds at WOT, the idea being that at WOT its already so hot in there that the addition of more oxygen will turn the manifolds white hot. 

I.