1998 945 2.3LPT lambda woes

[Dave Munro]

Exactly - back to basics is the key.

You probably have multiple problems. The apparant rich running almost certainly has nothing to do with the misfire.

Firstly, establish which cylinder is misbehaving and fix that.

The hole in your down pipe will not affect the misfire, but will not help the system overall, so get it fixed. I had exactly the same thing happen on my 2.0 HPT - we welded a plate over the hole.

The mystery connector on the nearside looks like it comes from the cruise control system.

Disconnect the battery for half an hour, reset the codes, then either read them yourself or have them read.

This should give some indication of the source of the rich running. Likely candidates are engine temperature sensor, lambda sensor, MAF, or air leaks in any of the inlet air piping.

What fuel consumption are you getting?
Should be around 25/26 in town and up to 30 on a run.

[Steve940estate]

Originally Posted by Dave Munro

Exactly - back to basics is the key.

You probably have multiple problems. The apparant rich running almost certainly has nothing to do with the misfire.

I agree with the multiple problems bit but if the plugs are fouled enough by the engine running rich they will cause a misfire. The slightly wet looking one is where I would start looking. It's either sooted up badly enough it cant fire, it's stopped working or there is something up with the lead or cap.

[mylittletony]

Originally Posted by Dave Munro

Exactly - back to basics is the key.

You probably have multiple problems. The apparant rich running almost certainly has nothing to do with the misfire.

Firstly, establish which cylinder is misbehaving and fix that.

The hole in your down pipe will not affect the misfire, but will not help the system overall, so get it fixed. I had exactly the same thing happen on my 2.0 HPT - we welded a plate over the hole.

The mystery connector on the nearside looks like it comes from the cruise control system.

Disconnect the battery for half an hour, reset the codes, then either read them yourself or have them read.

This should give some indication of the source of the rich running. Likely candidates are engine temperature sensor, lambda sensor, MAF, or air leaks in any of the inlet air piping.

What fuel consumption are you getting?
Should be around 25/26 in town and up to 30 on a run.

thanks for all the advice. I'm going to replace the cap, rotor arm and leads as a matter of course as they are old and I should have done them a while back. Hopefully it'll cure the misfire, if not then I have new ignition bits anyway.

I'll also plug/cover the hole, tried with an exhaust bandage but soon blew through it. Was planning to weld it up at a friend's barn but now immobile!!

I'll also reset the fault codes, hopefully without losing the radio code though!

regards the mileage, This is where it gets interesting: I've twice now got 450 miles from a 70 litre fill up. This equates to 29mpg and was varied driving, some town, some 70mph and some a bit more than that, both short and long journeys... I certainly wouldn't say I was driving economically and by all accounts this economy is pretty good!!!

[bobf192]

That plug blew out on us at 70 on the M4, car ran like a dog till we got off at the Bath jcn and got recovered, the lambda light came on almost immediately, firstly weld up the hole, secondly get the lambda reset, that done we were running perfectly, if not then start looking for other problems I reckon.

[Dave Munro]

450 miles on a fill - can't be too much wrong with the car!
(Temp sensor, MAF and Lambda must all be working correctly.)
I have seen 500+, but that was all motorway - at around 70mph.

Plug the hole, sort out the misfire, reset everything and you probably end up with a nice, smooth motor.

Good Luck.

[Dave Munro]

Another thing to consider - when you sort the misfire:
What happens when you first start the car, from cold?
It should (immediately) settle into a steady idle at around 750 rpm.
If it does not do this - idles high/low/not at all, or hunts/surges - then you have another problem.

[mylittletony]

Hi all,

long overdue update on this. Bought new rotor arm, dizzy cap, leads and plugs suspecting an ignition fault. They finally arrived yesterday, so I set about fitting them this evening:

distributor cap was well worn, lots of wear to the brass posts. Same for the rotor arm - lots of evidence of arcing and burning. So I was hopeful this would cure the problem...

Fitted the new leads while I was at it, then fired it up... no joy, still running rough, although running at least. Thought I'd whip out the plugs and fit the new ones for completeness. Now running badly again, on 3 maybe 2 cylinders.

So I thought I'd remove the leads one by one as volvoz2000 suggested. This didn't appear to change anything for the three front cylinders, although removing the one closest to the bulkhead killed it. I can't believe it would run on one cylinder??

I'm borrowing a compression tester from a colleague tomorrow, otherwise I'm sh*t out of ideas. Anyone?

[barkster1971]

Turning the boost back down to 4PSI from 10 would be my first advice. I presume you have an mbc and calibrated boost gauge fitted? Take the plug of the AMM and see if that makes it run like a dog. It should do. You menetioned that the coolant was low which could be a nick in the HG. Have you done a sniff test/ compression test yet? A blocked PCV system will give you problems also and could be the source of the black plugs.
Clean the contacts on the coil too.
Cheers, Carl.

[mylittletony]

Time for another update!

Carl, thanks for the ideas, unfortunately it runs like a dog already!!

Finally did the compression test this evening, reading from bulkhead forwards:
130psi
140
125
120

Having no experience I would say that's ok, but this now leaves me even more in the dark!!

Have borrowed a multimeter to read my fault codes tomorrow eve, my next guess is injectors/sensors if I've got new ignition bits and good compression...

I checked the coil terminals and they seem fine, no corrosion to speak of...

Thanks again

Tony

[mylittletony]

Me again!!!

Read the fault codes just now (first attempt, so took a while...)

From pin 1 I got 1-1-1, so all good it appears...

From pin 3 I got 2-2-1 (I thought it might have been 2-2-2, but turns out that's not an option)

The page I'm referring to says this is lean under part load. Unrelated, I had a chat with some colleagues who thought it might be due to low fuel pressure... Thinking I might change the fuel filter, but is the AMM a likely candidate?? What should I be checking?

All comments greatly appreciated!

Thanks,

Tony