1800ES Injection TPS issue? or not?

[Ozzy72]

Hi All - just joined up as I have a question. I'm in Australia and have recently bought a fantastic 1972 ES - love it! Thing is I did the usual and fell in love with the car before really doing my research. The seller who supposedly knows his stuff (been around volvo's for years but is also a dealer) insisted that the 'missing' experienced sometimes when just cruising along could easily be sorted with a minor adjustment to the TPS. He's about to hopefully sort it out, but today on the phone he insisted that this 'missing' or 'stuttering' whilst cruising was normal with the D-Jetronic?? I'm pretty sure it's not (have recently read about MAC's on line - 'missing at cruise'), but as I have never driven another 1800ES I don't know what it should be like. A couple of weeks back I did disconnect the TPS and the 'stutter' went away. It came back when I reconnected it. The other thing was, that when disconnected there was no loss of acceleration. From reading other forums/webpages I understood that the TPS aided with a bit of extra 'poke' when you planted the throttle. So if it makes no difference to the acceleration if the damn thing is connected or not, and it 'stutters' every now and then when cruising when it is connected, would I be right to assume the TPS is faulty? Seems logical, but the seller over here is trying to convince me otherwise and potentially not get it fixed (at his expense), which was our original deal. Anyway, other than that, the car runs like a dream, has no rust (lovely Aussie climate), and so I'm really looking forward to driving it more this summer. Any pointers appreciated - thanks.

[cassell]

Hi,

Welcome to the forum, have a read through this forum link regarding TPS:

https://www.volvoforums.org.uk/showt...osition+switch

Cleaning the circuit board gently with a pencil eraser is probably the first option, replacing the circuit board may be a more long-term option. As you've already established the TPS can be disconnected but remember that it also controls the provision of correct fuel for tickover as well as shutting off or reducing the supply when coasting or de-accelerating. None of these work if disconnected which may cause erratic running and high fuel consumption etc.

Let us all know how you get on, remember there is a wealth of knowledge from experienced D Jet owners on here, a particularly useful chap is Ron Kwas in America, he will probably also respond to your initial enquiry.

Paul

[Ron Kwas]

Ozzy;

Welcome to this forum!

This is not a simple issue...I have spent many (bordering on countless) hours researching it (there's a lot of info and also mis-info out there!), conducting first hand tests and electronic evaluations, so long as this posting is, this is still the shortest meaningful summary I can come up with...I direct any interested parties to the D-Jet page on the SW-EM site: https://www.sw-em.com/bosch_d-jetron...ection.htm#TPS

You have apparently already found your way to my information on the TPS and treatise on the MaC, as I believe I'm the only one who calls it that...yes this is a exceedingly tricky issue...complicated by the fact that it is not an unreasonable conclusion to reach that when one disconnects the TPS, and the symptoms go away, that the TPS is to blame and the problem exist within it...BUT, in my very careful investigation, I have found that the problem might very well not be within the TPS...its presence only allows them to occur!! Fact is also that almost ANY dirt or contamination issue with the D-Jet can and will result is a momentary fuel flow interruption which will result is a miss...and if this occurs at Cruise, the TPS is often and sometimes wrongly pointed to...

My extensive investigation (including with contact to D-Jet experts, among others Dr. D-jet in Germany, Brad Anders in the US, this issue plagues other D-Jet equipped vehicles also, and there are a lot!!), with electronic consideration of the circuit which connects to TPS within D-Jet Controller, is not yet concluded, and unfortunately, I (or the other experts) were not (yet) able to come to any final root cause determinations or conclusions.

What I will already say with very high confidence is that I have found wear the PCB NOT even possible to be the suspect(!!), because the circuit (withing D-Jet controller) it is connected to and works in conjunction with is highly and COMPLETELY forgiving of worn or resulting noisy slider comb-contacts! Furthermore, and as a supporting factor to my assertion, the slider contacts are COMPLETELY uninvolved during Cruise (slider contact only provides input to Controller from Comb-contacts during accel (NOT decel!)! I therefore recommend against abrading the extremely thin gold plating of the Comb-contacts of TPS, to try to address MaCs, but only recommend flushing them with Deoxit D5 Contact preserver and gently cleaning with a cotton swab only. Gold does not corrode needing abrasion of the corrosion to get back to a clean contact...but contamination which might/does collect on the surface can certainly benefit from flushing and a lubricating film Deoxit provides!

The other position and direction sensing contacts (of Drag Switch) within the TPS are not self-cleaning like a slider on the PCB...they are also the ones involved during steady state throttle position operation...I therefore believe these are the ones to be suspect! I do recommend very careful cleaning and anti-corrosion/lube treating these with Deoxit, see linked pages and info. (http://www.sw-em.com/Deoxit_D5_Addit...PS_Maintenance)

I also HIGHLY recommend against bending ANY of the TPS internal contacts, or springs, or ANYTHiNG in there for that matter, in an attempt to increase spring pressure on a contact! DON"T DO IT!

That's all for now.

Paul; Thanks for the reference!

Cheers from Connecticut!