Vectra C Throttle Body (Throttle Position Sensor)

Hey all. Looking for, well, anything. Advice, help, opinions, tips, etc.

Car went in for it's NCT today. Was expecting nothing but good things, BUT the guy comes back with a Fail/Refusal. I was stunned. Car flew it last year and it's done less driving and been better kept this year. Not to mention over €800 on new parts & tyres in the last couple of months.

The problem was the tester could not get an emissions reading, as such the car is classed as fail/refused. When I asked how he cannot get a reading he said there is an issue with the throttle. He explained that the car will not hold a constant rev at the required level to test. He said it starts to slowly rise in revs so he cannot get a constant and set reading.

I went home and tested it myself. Here is what I found.

It runs high when first started from cold (around 1,100 - 1,200 rpm) and quite quickly settles into an idle rev of 700 rpm. When I push the accelerator pedal there seems to be a "lag" but the revs climb. If I hold the pedal steady with the rev counter at 2,200 rpm or less it stays there without issue. As soon as I rev it above 2,300, lets say 2,500, it revs to that rpm, then without my pressing harder on pedal it climbs. Slowly, but surely. Eventually it comes to a rest at approx. 3,000 rpm. If I press the pedal again it'll climb higher and continue to rise a little bit more, when I've stopped pressing the pedal, until it again comes to rest at a higher rev than the pedal position should allow for.

Then an interesting thing caught my attention. When I release the pedal, at any rev, the revs stay where they are for about 1-2 second and slowly start to drop. At this point I have my foot off the pedal and the revs are dropping, but slowly. If I give the pedal a quick sharp push the rev counter almost doesn't move, whether from idle or alternating between various revs (although there is slightly more of a response when doing this from idle). If I floor the pedal, not stomping it just pushing it quickly, and then as quickly release it the rev counter and engine barely rev up past 1,100 - 1,200. IOW the delay between what I do with my foot and when the engine acts is a couple of seconds. So by the time it "knows" to rev up, my foot is off the pedal and it starts to wind down (before it's actually rev'ed up).

When the engine has settled on 3,000 rpm (example) regardless of my foot position and I begin to lift my foot of the pedal, the revs begin to slowly drop. However if I give a sharp press of the pedal as the revs are dropping, then take my foot off the pedal (not fully) as quick the revs never rise up at all, and simply continue to fall.

So I took off the air intake pipe, and there was some dirt/fouling/gunk around the butterfly valve and on the plate. I cleaned it thoroughly and inside and around the pipes. Then reconnected everything. I thought the throttle position sensor (TPS) would be external, but could not find it. I now know it's an integral part of the unit and as a sealed unit (only the jack plug extend out) cannot be removed, replaced on it's own.

So to the questions.

1. Would this be the cause of the "climbing" revs?
2. If not anything else that would cause this?
3. If it is the cause can these be repaired?
4. If so anyone any recommendations?
5. If not and a new unit is needed anyone any suggestions as to where to go for one as the prices I've found so far range from €450 upward.

I'm not one to skimp on parts, but after throwing over €800 into the car in the last 2 months, and not exactly being flush i'm trying to fix it right, but with costs as low as possible. Reason is simple, motor tax is due at the end of the month, so is the mortgage payment, and after Mother's day, 2 birthdays, and a loan to a family member so they can move house it's been a tight, tight month.

I see lots of second hand ones on Flea-bay, etc. but if i'm going to go second hand or refurbished i'll buy local so I have comeback and waiting for postage if there is an issue or return is a non runner. If this is not possible then so be it. I'll book the test as late as possible, then request a date as close to the end of the 30 day period to allow as much time as possible to get the few quid together. However I don't want to go through all that only to find the TPS is not the issue.

I never noticed the issue before the test, and what annoys me is it passed last year so the fault is/must be recent. The car drives well, and performance & economy are not effected. Well if they are it means it'll perform even better, when fixed, than it is now.


Picture of the unit in my car and a link to the one I need.

Link






Thanks in advance for any info.