850: 850 T-5R misfire

[PSJVTHEBEST]

I have a 1995 850 T5r saloon which I have owned for nearly 25 years and for the first time ever I can’t get it to start let alone run smoothly.
I have to admit that I think my problem is at least in part down to the fact that I don’t use it nearly enough and although under a breathable cover she hadn’t seen light of day for nearly a year when it started playing up.
I know I need shooting!
So, the build up to the ‘not-starting’ – the symptoms were a drop in performance and very poor mpg (down from c. 26 to sub 20 on a long run. But it started and ran. I read the fault codes and variously read 121 (MAF) and 231 (Long term fuel mixture too lean or rich in part load stage). All cleared and haven’t recurred.
I then experienced significant hesitation on acceleration and loss of power generally but still ran. Then I struggled to get home – lumpy running, cutting out etc.
So into my garage for some Stage 0 tuning stuff (although missed a couple of things-later).

What I have done:
- New MAF sensor (not Bosch! But really, would this stop the car from running at all?)
- Tried starting with MAF unplugged (default mode?) and would not start
- All new vacuum hoses
- New distributor cap and rotor arm
- Cleaned plugs and leads
- New O2 sensor (Bosch) – there’s only one pre-cat
- New fuel pump
- Checked fuel pressure and c. 40 psi – ok
- Cleaned and serviced injectors (new seals and filters)
- Changed oil, filter and air filter

What I haven’t done (yet):
- Changed plugs and leads (leads are a pain to source and the plugs looked ok)
- Changed TCV (turbo control valve) or FPR (fuel pressure regulator), both cited on line as potential issues but not for an inability to start the car!

So just tried to start it and it fires for about a couple of seconds, really rough and dies. Also strange squeak – never had before!
I opened up the oil filler to check for obvious signs of head gasket failure i.e. milky oil and nothing but it did look like there was a lot of misty vapour in there!

Sorry for the lengthy post but if anyone has any ideas I would love to hear them.
Thanks.
Pete

Forgot to mention - PCV done too.

[duke1]

Originally Posted by PSJVTHEBEST

I have a 1995 850 T5r saloon which I have owned for nearly 25 years and for the first time ever I can’t get it to start let alone run smoothly.
I have to admit that I think my problem is at least in part down to the fact that I don’t use it nearly enough and although under a breathable cover she hadn’t seen light of day for nearly a year when it started playing up.
I know I need shooting!
So, the build up to the ‘not-starting’ – the symptoms were a drop in performance and very poor mpg (down from c. 26 to sub 20 on a long run. But it started and ran. I read the fault codes and variously read 121 (MAF) and 231 (Long term fuel mixture too lean or rich in part load stage). All cleared and haven’t recurred.
I then experienced significant hesitation on acceleration and loss of power generally but still ran. Then I struggled to get home – lumpy running, cutting out etc.
So into my garage for some Stage 0 tuning stuff (although missed a couple of things-later).

What I have done:
- New MAF sensor (not Bosch! But really, would this stop the car from running at all?)
- Tried starting with MAF unplugged (default mode?) and would not start
- All new vacuum hoses
- New distributor cap and rotor arm
- Cleaned plugs and leads
- New O2 sensor (Bosch) – there’s only one pre-cat
- New fuel pump
- Checked fuel pressure and c. 40 psi – ok
- Cleaned and serviced injectors (new seals and filters)
- Changed oil, filter and air filter

What I haven’t done (yet):
- Changed plugs and leads (leads are a pain to source and the plugs looked ok)
- Changed TCV (turbo control valve) or FPR (fuel pressure regulator), both cited on line as potential issues but not for an inability to start the car!

So just tried to start it and it fires for about a couple of seconds, really rough and dies. Also strange squeak – never had before!
I opened up the oil filler to check for obvious signs of head gasket failure i.e. milky oil and nothing but it did look like there was a lot of misty vapour in there!

Sorry for the lengthy post but if anyone has any ideas I would love to hear them.
Thanks.
Pete

Forgot to mention - PCV done too.

stale fuel?if its got any ethanol in fuel stored long term can get moisture, would check at the schrader valve on the end of the fuel injector rail you need a good amount of pressure there around 40/50 psi ,mouse nest in the air filter housing. look for evidence of gnawing and chewed cables etc thats where id start,good luck

[PSJVTHEBEST]

Really appreciate you taking the time
Fuel was a concern but now have a full tank of new petrol and having cleaned the injectors and getting 40 psi which is around the right pressure I eliminated that possibility.
I've had all the hoses, housings pre and post turbo off and checked.
But thanks for the suggestions.

[Luxobarge]

Originally Posted by PSJVTHEBEST

So just tried to start it and it fires for about a couple of seconds, really rough and dies.

That is the classic symptom of poor contacts to the antenna ring that sits around the ignition barrel, the antenna detects the chip in the key and turns the immobiliser off. Try a *thorough* clean of the antenna ring contacts, in rare cases the antenna ring will need replacing, but having stood for ages is consistent with the contacts going bad. You can also try a different key, if you have one.

OK, I know it wouldn't explain the poor running that you were experiencing previously, but that may have been another fault and given the amount of work you've done on it you may well have fixed that now, but it still won't run if the immo is not turning off as it should. It's an easy thing to do, and pretty much free, so that's where I'd be going next.

[PSJVTHEBEST]

Thanks for the suggestion but I don't think I have a chip in my key. It's an old ignition system as far as I can tell with a separate remote. That said, it still could be to do with the immobiliser as I have had intermittent problems with that. I will try the second one I have in the morning. Thanks again.

[stevepcar]

Originally Posted by PSJVTHEBEST

Thanks for the suggestion but I don't think I have a chip in my key. It's an old ignition system as far as I can tell with a separate remote. That said, it still could be to do with the immobiliser as I have had intermittent problems with that. I will try the second one I have in the morning. Thanks again.

Looks like you have changed or checked most of the things that could be causing the problem. I recently had a similar problem & it turned out to be a faulty fuel pump relay. It is located under the fuses & is number 103. Pretty easy to take the relay out, put a lead in between pins 15 & 87 to bypass it. It worked with mine. Shouldn't run it for too long like that though. Good luck

[cyclogenesis]

I realise you mentioned you have changed all the vacuum hoses but whenever my 850 has played up like you describe it is because of an induction leak. Check for good seal everywhere from the airbox, down to the turbo, up and over the engine and then back to the throttle body. In my worst case, the seal between the throttle body and the hose was not secure and under pressure (post turbo) was allowing air to leak, thereby sending the ECU into fits. This was particularly problematic when I swapped to silicon pipes and I know there are advocates on here but they are difficult to seal without the right fittings and by their very nature, are slippy!

Fully check for vacuum leaks first, then plugs and points before spending any more money.

Fuel, Air, Spark

I know the antenna ring is often mentioned but your symptoms and codes lead me to believe it is air related.

Good luck on getting it running again

[PSJVTHEBEST]

Originally Posted by stevepcar

Looks like you have changed or checked most of the things that could be causing the problem. I recently had a similar problem & it turned out to be a faulty fuel pump relay. It is located under the fuses & is number 103. Pretty easy to take the relay out, put a lead in between pins 15 & 87 to bypass it. It worked with mine. Shouldn't run it for too long like that though. Good luck

Thanks and I have checked that with a jumper - all good. When I started i checked the fuel pressure and I was down some 10 psi (to under 30) and thought hurrah, I've found the problem so changed the fuel pump and filter but that's obviously not the issue although at that time it still ran.

[PSJVTHEBEST]

Originally Posted by cyclogenesis

I realise you mentioned you have changed all the vacuum hoses but whenever my 850 has played up like you describe it is because of an induction leak. Check for good seal everywhere from the airbox, down to the turbo, up and over the engine and then back to the throttle body. In my worst case, the seal between the throttle body and the hose was not secure and under pressure (post turbo) was allowing air to leak, thereby sending the ECU into fits. This was particularly problematic when I swapped to silicon pipes and I know there are advocates on here but they are difficult to seal without the right fittings and by their very nature, are slippy!

Fully check for vacuum leaks first, then plugs and points before spending any more money.

Fuel, Air, Spark

I know the antenna ring is often mentioned but your symptoms and codes lead me to believe it is air related.

Good luck on getting it running again

Thanks for the good wishes! Like you said, a lot of the symptoms shout a vacuum issue so I made sure I replaced pretty much all the hoses and when re-assembling checked and double checked the hoses were tight, renewing clips where necessary. I'm pretty sure I'm getting fuel - I have good pressure at the rail. Whether or not the injectors are opening is another matter and I may have to look at the fuel injector relay (above the fan housing) next. I'm getting a spark from the coil to the lead to the distributor and need to check from distributor to spark plugs. Plugs looked good and aren't that old.

[PSJVTHEBEST]

Thanks for all the suggestions, friends, in the meantime I have done some more research and it's leading me down the path to a possible problem with the camshaft position sensor - seemingly a common thread running through a lot of people's issues. So I have taken it off and apart and uploaded some photos. There is some oil seepage around the seal but inside looks reasonably clean. Tried to get a photo of the 'contact's but I would have to drill out rivets for that and although I have ordered another (Bosch), I don't really want to trash it just yet! Any thoughts on the possibility this might be the cause? Thanks again to all.