1998 106 1.1 Zest 3 Idling Issues

[Robc76]

Good afternoon,
I have a 1998 106 1.1 Zest 3 which, I believe, has the TU1M(HDZ) engine with the Bosch fuel injection. A couple of months ago two issues manifested:

1) The engine misfired when accelerating
2) The idle speed would drop to 500rpm or the engine would stall completely.

Issue #1 was fixed with new spark plugs and HT leads.

Issue #2 is intermittent. Sometimes the engine will idle fine, sometimes idle at 500rpm and sometimes cut out entirely. Often, mostly when the engine is cold, the check engine light illuminates for a few seconds. Often the engine will idle fine when warming up then the revs will drop, or the engine will cut out entirely when at full operating temperature. As the car is pre-ODB-II I cannot read the codes myself so I took it to my local garage. They saw codes for coils, throttle position sensor and idle control valve which they subsequently cleared. They also spotted a damaged pin on the throttle position sensor connector plug which they repaired. After this they took the car on a test drive then let it idle for some time. Once again, the low idle returned and they found error codes for coils, throttle position sensor and idle control valve. They suspect an ECU or wiring loom fault.

So that's the summary. My questions to this forum are:

1) Is it likely the ECU or wiring loom has a fault somewhere?
2) The car has had a new coil pack in the last year or so, before my ownership.
3) The Bosch throttle body does not appear to have a throttle position sensor that looks anything like those for sale online. Is this throttle body one that needs to be replaced in its entirety just to replace that sensor?
4) Am I even looking in the right place for the throttle position sensor (right had side of the throttle body as you look down on it)?
5) The idle control valve also does not look like anything available online although it does look like it can be removed easily. Can someone point me toward a suitable replacement?

What else can I do to trace this issue? I bought this car for my son to learn to drive in and this issue is making it difficult for him. Once the car is moving it normally runs perfectly. I say normally because yesterday it would cough and kangaroo when accelerating in 1st, 2nd &3rd between 2,500 - 3,000 rpm. This is a new behaviour and I am unsure of this is a symptom of the existing issue or something entirely new.

Any help or advice would be very welcome. If I can provide more information please just ask.

Regards

RobC

[Oldpug]

https://uk.vicedeal.com/products/idle-c ... bAEALw_wcB
Does your idle control valve look like this?

[CitroJim]

Does your car have the Bosch single-point injection?

If so, the symptoms point to a defective throttle position sensor pot. I've had this issue twice and both times successfully resolved it by very carefully dismantling the throttle pot, gently cleaning it with a solvens such as IPA and reassembling it.

The throttle pot is very much part of the throttle body is not available as a separate replacement part.

I cannot emphasise how delicate the cleaning job is. It is all too easy to damage it beyond repair. Also, the assembly is held together with Security Torx screws and heavily Loctited. So much so, it's possible to shear off the screws. Bosch really don't want you going into the pot!

[Robc76]

@Oldpug, my idle control valve looks much different. It appears to be a threaded rod that is actuated by a sprocket inside the valve housing. I have seen it move in an out from time to time.

@CitroJim, I do have the Bosch fuel injection and, I believe, it is the single point version. Do you have, or can you point me toward, a diagram, or photos, of the throttle pot and it's relative location on the throttle body? I'm not familiar with the term so I'm not 100% sure to what you are referring. I guess it is on the right side of the throttle body as you look down on it (with the air intake removed) which appears to have the throttle butterfly spindle connected. Is that right?

Regards

RobC

[CitroJim]

Rob, this is the best I can do with a photo of the throttle pot and it's location on the throttle body...

Have a look and it'll be found on the right-hand side as you look at the engine from the front. It has a big electrical connector plugged into it...

The job can be done in-situ with care but do lay plenty of clean rags around just in case any screws try to make a bid for freedom.

Hope that helps a bit. I no longer have a car with an injected TU engine else I'd go and take more photos.

[Oldpug]

If you have mono injection forget my post, its for multi injection.

I would follow citrojim`s advice, mind you as jim has admitted, stripping the unit right down can be precarious. Why not first try a "basic" clean with special intake cleaner, all multi plugs checked and cleaned, that sort of thing.
If you could find an old school Peugeot Tech` with the old Peugeot Diag 2000 tool, who could clear the codes and reset the ECU that may help as well.

[Robc76]

Thank you.

For now, I think I will get some carb cleaner to see if a gentle clean of the throttle body and ancillaries will make any difference.

Thinking further ahead, I wonder if anyone has a Bosch throttle body complete with idle control valve and throttle position sensor for sale?

Regards

RobC

[Oldpug]

The best guy to try is Dean Hunter, www.peugeotparts.co.uk. I’ve used him many times, good service, can mail it.
He is also a Peugeot boffin and could give you some tips.

[Robc76]

Quick update: 10 minutes work with a toothbrush and half a tin of carb cleaner seems to have improved matters somewhat. The car is still not idling 100% but it has been much better these last couple of days. I thought the inside of the throttle body was painted black but it is just covered in old petrol residue. I may clean it some more to get it as clean as it can be (without completely dismantling it).

Regards

RobC

[CitroJim]

That's good to hear Rob