PO171 too lean

[960kg]

Have you checked for any air leaks in the exhaust system ?......it has to be leak free!

[Wella Fella]

I've checked all the hoses that are upstream of the intake from the air box etc. I've had just about every pipe off and checked it, cleaned it and put it back. I'll check all the exhaust as well then. Thanks.

[Wella Fella]

OK, so I spend £84 on a terraclean - WOW !!!!

Engine lights come back on after 100 miles or so, but - WOW !!!! What a difference the terraclean has made. Car runs smoother and the emission print tells quite a story. I would really recommend it for the money - especially if the car either fails or is struggling on the MOT emission test.

Anyway, back to the old PO171.

I'll keep looking. I've noticed some oil or other goo around the turbo. Not massess of it, but if oil is getting out, presumeably, air can get in. Does anyone know if air getting in around the turbo could or would give a lean reading???

Your expertise, knowledge and help is most appreciated.

[Wella Fella]

HELP HELP HELP !!!

The car is running real rough now at idle (but only when not up to temp) and it's throwing P0300 random misfire all cylinders each time it's started from cold.

As soon as it warms up it runs fine without issue and no performance loss. Before it's warm, it's just awful.

Couple of other things I've done in my spare time (time that I'll never get back) (

1) I ran the engine and removed the wiring to the idle control valve thinking that as this was only at idle, it must be this that is knackered. My logic was that if this was disconnected (if knackered) then the car would perform the same. The engine immediately stalled and threw a code relating to the ICV
(P0505 I think) and this has never returned so am thinking that this is working OK. It's clean as a whistle having had me clean it a number of times. Replaced the gasket and sprayed with carb cleaner whilst running, no leaks.

2) I've had the inlet manifold off and cleared through the PCV system. Was dirty but no where near clogged up but it had a good clean none the less. Sprayed what I can with carb cleaner with engine running, no leaks.
Also, I replaced the injector O rings in case there was a leak from them. They had flattened off a bit, but replacement has made no difference. Sprayed with carb cleaner whilst running, no leaks. Sprayed inlet manifold where it meets the block and no leaks around the gasket.

3) Exhaust manifold inspection left hand outer nut = nearly backed off, right hand outer nut and washer = missing. Torqued up the one thats still there and no change. I'll replace the other one in the next few days.

4) Checked all hoses again thinking I've missed something but can't find anything obvious.

5) Had a brain fart and decided to conducted an air pressure test (very low tech) whereby I took the large hose from the MAF and sealed this with a rubber glove, and pushed air (from relatively low pressure air compressor) into the intake manifold. The glove inflated and it all seemed to be holding pressure.

Few questions on this little experiment :

Would I be right in thinking that:

a) this is what is supposed to happen (i.e. pressure is maintained) therefore being pretty indicative of the fact that there is no air leak
b) With the large hose to the MAF still connected and pushing air through, would / should I hear the turbo impellor spin (or am I just hearing the air leaking into the air filter box?)
c) the turbo is the only thing I haven't really paid any attention to - could this be the source of an air leak that would give a too lean reading that would get so bad it would cause misfire???

Really appreciate any help, knowledge, expertise or other miracle cures !!!

[Dazza007]

if it was a dirty maf sensor or vacuum leak goin to the turbo then all cylinders would be lean, the fact that its always the same bank would have me focus on bank 1. Try and swap the injectors round, if it moves to a different bank then its the injector.

[Wella Fella]

Cheers for the advice, I'll give it a go. So when it says bank 1, is that literally cylinder 1 or a combo of 1 & 2, 1 & 3 etc???

[960kg]

Originally Posted by Wella Fella

Cheers for the advice, I'll give it a go. So when it says bank 1, is that literally cylinder 1 or a combo of 1 & 2, 1 & 3 etc???

Because the OBD11 codes cover more that a 4 cylinder engine as i believe it the bank refers to bank of cylinders.

Just to keep you looking here is the page for your error code in Volvo codes:

PO171 = ECM-262A Long Term Fuel Trim Upper Limit

PO172 = ECM-262A Long Term Fuel Trim Lower Limit

So have a look at the pic. and check what you have done or replaced.

Good Luck.

[Wella Fella]

OK, so I take it to Volvo and speak with the mechanic who was really helpful and we had a chat over all that I'd done already. At the weekend, I checked the spark plugs and noticed that 3 out of 4 had oil on them. Straight away he commented that it could be valve seats or piston rings. 1 compression test later my worst fears confirmed. The head needs to come off to look at the valve seats and establish whether its these or the piston rings. Given the fact that I've just had the terraclean done and that it's oil on the plugs, my guess is with the piston rings. I'm £190 lighter for the diagnosis and absolutely gutted.

Some work ahead.

[Dazza007]

i had to get my rings replaced 30k ago. Birkenhead engines done it for £850, when I got it back it was a completely different engine, the car is awesome now. Sounds like your oil separater rings.

[960kg]

Originally Posted by Wella Fella

OK, so I take it to Volvo and speak with the mechanic who was really helpful and we had a chat over all that I'd done already. At the weekend, I checked the spark plugs and noticed that 3 out of 4 had oil on them. Straight away he commented that it could be valve seats or piston rings. 1 compression test later my worst fears confirmed. The head needs to come off to look at the valve seats and establish whether its these or the piston rings. Given the fact that I've just had the terraclean done and that it's oil on the plugs, my guess is with the piston rings. I'm £190 lighter for the diagnosis and absolutely gutted.

Some work ahead.

Don`t give up!

If you did the compression test yourself do it again but pour one teaspoon of oil in each cylinder and leave it for 20 mins before you test it again, doing this the oil goes around the rings and it should give a better compression telling you it is the valves leaking. The smoke may be due to knackered valves seals which may of been cooked by the Terracleans high running temperatures needed to burn off the carbon.

If it`s your rings worn as the engine is only a pump it will put oil or smoke out the dipstick hole when running, if not it is the valves again.

You said from Terraclean it ran superbly so an engine doesn`t deteriorate that quickly in two or three weeks!!

Good Luck