System too rich

[deathrider311271]

Originally Posted by WSparrow

Thanks, I will try and get my hands on a replacement.

my only advice is if its bosch get genuine bosch, just another thought have you had your injectors cleaned as that code indicates its running lean not rich

[WSparrow]

I cleaned the injectors a couple months ago, so I don't think that's the problem but I guess it wouldn't hurt to look into it. But are you sure about it being lean? Every code book I've seen says 0172 is too rich. Or does Volvo not follow the generic codes?

[deathrider311271]

Originally Posted by WSparrow

I cleaned the injectors a couple months ago, so I don't think that's the problem but I guess it wouldn't hurt to look into it. But are you sure about it being lean? Every code book I've seen says 0172 is too rich. Or does Volvo not follow the generic codes?

Volvo have there own definitions for the generic codes,
here is a link to all the generic codes and what they mean for the 850/P1V70: http://forums.t5d5.org/topic/12265-dtc-codes/

[WSparrow]

Thanks, that explains a lot. I'm printing that off for safe keeping.

[Chris_Rogers]

Originally Posted by deathrider311271

my only advice is if its bosch get genuine bosch, just another thought have you had your injectors cleaned as that code indicates its running lean not rich

Sorry I don't agree, The definition is:

P0172 Long-term fuel trim Lower limit
or
P0172 System too Rich (Bank 1)

Which amounts to the same thing.

This is saying the ECU can't lower the injection time any further to get the fuel trim back to Lambda = 1. i.e. the mixture is still too rich.

From the symptoms it also seems the mixture is too weak at idle, probably because the LTFT has adapted to a low value trying to correct over fueling at high engine loads, or there is an induction air leak.

Causes of this could be:
Induction air leak
Fuel pressure too high at higher throttle openings.
Lambda sensor failing to measure properly.
MAF sensor over reading.

Have you just got a code reader or can you log live data?

This may help as well:

http://www.volvoforums.org.uk/showth...ighlight=P0172

[WSparrow]

Okay, I replaced the MAF last week, and replaced the lambda this morning. That's made the idle SLIGHTLY smoother, but other than that there is no change. I am fairly confident that it's not a vacuum leak, I spent a couple solid days checking and replacing air lines. But I can't be completely sure about that. There's quite a few areas where I just can't get at the line/elbow/connector well enough.

As for the codes, I have an OBD to com port cable which I plug into my laptop. I can read and clear codes with it, but haven't been able to get my hands on any software that will give me more data. Can't afford the full-fledged DICE system. But if you have any alternative software suggestions, I'm all ears.

I've added a bottle of injector kleen to the fuel, but I haven't driven it enough yet for that to do any good.

Regarding "Fuel pressure too high at higher throttle openings.", what can I do about that?

Thanks

[Merc85]

i had the same code, turn out my Dump valve a dv26 was faling to open and close properly, causing a intake leak top of the intercooler.

Also if the top hose to intercooler is split the car will struggle to run under acceleration.

[WSparrow]

Funny you should mention that actually. I was just poking around and found that one of the hoses on the IAC was a bit stretched. It looked good but wiggled around quite a bit. I know somebody will give me a hard time for this, but I was in a rush so I glued the bugger. Now the engine hesitates a bit but it doesn't bog down and try to stall/flood when I accelerate hard. The hose in question is the one that branches out and goes to the throttle valve assembly (among other things). I'm going to order a new one and replace the whole hose just to be safe.

I have a feeling that's only half the problem, but here's hoping.

[misa]

P0172 can also mean a bad fuel pressure regulator.

With your symptoms....i vote for bad fuel pressure regulator.

[Chris_Rogers]

Originally Posted by WSparrow

Funny you should mention that actually. I was just poking around and found that one of the hoses on the IAC was a bit stretched. It looked good but wiggled around quite a bit. I know somebody will give me a hard time for this, but I was in a rush so I glued the bugger. Now the engine hesitates a bit but it doesn't bog down and try to stall/flood when I accelerate hard. The hose in question is the one that branches out and goes to the throttle valve assembly (among other things). I'm going to order a new one and replace the whole hose just to be safe.

I have a feeling that's only half the problem, but here's hoping.

This makes sense, if there is a split pipe, it will let air in at idle causing the weak mixture and it will let air out under boost causing the MAF to read more air than is actually going into the engine hence rich mixture. This will be compounded by the LTFT being at minimum to try and correct the overfueling under booost and consequently even weaker at idle.