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[MikeDundee]

Watching this thread with interest as I have exactly the same problem with fuel trim issues on both banks, and EML on, I changed the fuel filter a few weeks ago, interestingly I do appear to get the fuel reading from the MID eg range is giving me what is states around town. I have a GS 500 maxscan which I can reset and read the codes, but last time I reset the codes the engine does not like it at all, ad sounds like a pil of poo for a little while until it then eventually settles down, some folks may recall this from the Newent meet. May reset them again today and see what happens, and let you know.

[Albatross]

Watching this thread with interest as I have exactly the same problem with fuel trim issues on both banks, and EML on, I changed the fuel filter a few weeks ago, interestingly I do appear to get the fuel reading from the MID eg range is giving me what is states around town. I have a GS 500 maxscan which I can reset and read the codes, but last time I reset the codes the engine does not like it at all, ad sounds like a pil of poo for a little while until it then eventually settles down, some folks may recall this from the Newent meet. May reset them again today and see what happens, and let you know.

Hi Mike,

What engine size do you have?

When you say you're getting the same codes, do you mean that you get 0170 & 0173 together?

I don't fully understand some parts of your post there. When you say that "interestingly I do appear to get the fuel reading from the MID eg range is giving me what is states around town." I'm unsure.

Could you clarify this bit for me please?

I'll be changing my fuel filter today, assuming they have one on the shelf at the Vx stealers of course, and clearing the codes.

[Kevin Wood]

I reset the codes the engine does not like it at all, ad sounds like a pil of poo for a little while until it then eventually settles down, some folks may recall this from the Newent meet. May reset them again today and see what happens, and let you know.

Clearing the codes also appears to reset the fuel trim, so if the car needed a load of fuel trim for some reason, it will suddenly get a rich / lean mixture and run rough until it has established the correct fuel trim again.

Yours is a 2.6, IIRC? Does your scan tool let you see live data values? Can you see what the short term and long term fuel trims are doing when it's running, out of interest?

I'll be changing my fuel filter today, assuming they have one on the shelf at the Vx stealers of course, and clearing the codes.

Yep, give that a try first.  

Kevin

[feeutfo]

Received by PM...

Thanks as always Kevin.

Hi Nathan,
 
Hmm. Interesting thought. I guess you could. Only thing that might be an issue is that the single large cat might not get up to temperature as quick as the small pre-cat so if there is any monitoring of the warmup cycle it could raise a cat efficiency code. Given that the pre-cats are probably not working well if at all it might not be any different. There is always going to be a bit of "suck it and see" involved in this type of thing, but I'd say it might be worth a try. I'd certainly try a pair of 3.0 cats if my cats failed, put it that way.
 
Failing that, take out both cats and make up a pipe with a little sports cat each side. I wonder how much more restrictive the twin cat pipes are, if at all?
 
Kevin

Just a thought, but with the 3.0 litre cat in mind, is it worth moving the pre cat 02s into the old post cat holes on your current cat? Im thinking, in conjunction with the post cats moved behind big cats this would give as close as possible test as to weather the 3.0 cat would work? Might it even work better as that anyway? Or at least give the best location to add 02 bosses on the 3.0 cat?

[Kevin Wood]

Just a thought, but with the 3.0 litre cat in mind, is it worth moving the pre cat 02s into the old post cat holes on your current cat? Im thinking, in conjunction with the post cats moved behind big cats this would give as close as possible test as to weather the 3.0 cat would work? Might it even work better as that anyway? Or at least give the best location to add 02 bosses on the 3.0 cat?

The pre-cat sensors need to be seeing exhaust gas directly from the engine  as it's impossible to measure the actual fuel mixture burning in the engine once the mixture's been through a cat. I can't see any merit in moving the pre-cat sensors, TBH.

Kevin

[feeutfo]

Just a thought, but with the 3.0 litre cat in mind, is it worth moving the pre cat 02s into the old post cat holes on your current cat? Im thinking, in conjunction with the post cats moved behind big cats this would give as close as possible test as to weather the 3.0 cat would work? Might it even work better as that anyway? Or at least give the best location to add 02 bosses on the 3.0 cat?

The pre-cat sensors need to be seeing exhaust gas directly from the engine  as it's impossible to measure the actual fuel mixture burning in the engine once the mixture's been through a cat. I can't see any merit in moving the pre-cat sensors, TBH.

Kevin

Hmmm, am presumeing the pre cats are having little or no effect, thinking a little more seriously about the relevent codes have not returned so clearly must be doing something, fair enough.

[MikeDundee]

Watching this thread with interest as I have exactly the same problem with fuel trim issues on both banks, and EML on, I changed the fuel filter a few weeks ago, interestingly I do appear to get the fuel reading from the MID eg range is giving me what is states around town. I have a GS 500 maxscan which I can reset and read the codes, but last time I reset the codes the engine does not like it at all, ad sounds like a pil of poo for a little while until it then eventually settles down, some folks may recall this from the Newent meet. May reset them again today and see what happens, and let you know.

Hi Mike,

What engine size do you have?

When you say you're getting the same codes, do you mean that you get 0170 & 0173 together?

I don't fully understand some parts of your post there. When you say that "interestingly I do appear to get the fuel reading from the MID eg range is giving me what is states around town." I'm unsure.

Could you clarify this bit for me please?

I'll be changing my fuel filter today, assuming they have one on the shelf at the Vx stealers of course, and clearing the codes.

Exactly the same codes, read them off again tonight and reset them, restarted engine bit rough, but was OK after a minute or so, not as bad as at Newent, remember since then have done the coil packs, spark plugs and fuel filter.

Anyway, I have a 2.6, as I clock my mileage today (as I claim it back), turns out my MID reading was not giving me the same as the mileometer;
Range first thing this morning was 97 miles, done 2.1 miles and range was at 92 (bear in mind car not warmed up at that point), subsequently done a further 10 miles later today and MID went down to 72 from 92 (bear in mind I do not always drive normally). Then I reset the mpg etc., after doing less than 2 miles range at finish was 61 m/gal was showing 23.3.

I have just reset the EML will keep an eye on consumption etc tomorrow and dive normally.

[Albatross]

Ok, filter changed and codes cleared.

I drove it like a nutter for an extra long detour home of about 8 miles altogether. No codes recurring just yet, but I won't trust it until I've driven it a bit further.

I don't know if it's my imagination, but the car seemed about 20% more powerful today after the filter was changed. I booted it when I was driving at 30mph in the wet and the back wheels just kept spinning and jumping on and off the TC for about 200yds. It was great fun. The car seems to launch much more than it did.

As I said I have to drive to Gateshead this week so that is a good test. I fully suspect that I will get 0420 and 0430 again, but that doesn't bother me. If anything it is good because I am currently back where I started with regard to sensor positions etc. What I really want is not to get the 0170 and 0173 again.

I had a damn good look at all the various air pipes etc. and with the exception of the one which dissapears under the plenum, because I can't see it, and as far as I can make out all are confirmed as fine at the moment.

As for the suggestion to move the 1st sensors to behind the pre-cats, I agree with Kevin, there is very little point as it won't prove anything and won't reflect what a 3.0 cat section would be like anyway.

My intended sequence of next steps are:

• Carry on for now until I can confirm either way whether the 0170 and 0173 are fixed.
• Act further on 0170 and 0173 if necessary until fixed.
• Move secondary sensors to behind the main cats again and drive for a test period of 2 weeks or 500 miles whichever is sooner. This will test the 0420 and 0430.
• Then finally check out the resistance of the pre-cat to see if it is worth moving to a stainless steel set up with sports cats in the place of main cats only.

[Albatross]

I couldn't wait in all evening and not try, so I just went for a "pushing it" drive for 25 miles each way up the A1 and back.

No codes, not even an 0420 or 0430 as yet.

Considering that I got the 0173 and 0170 come up within 3 or 4 miles every time I had them cleared lately this is certainly an massive improvement so far.

I'll still stick to the plan.

[Kevin Wood]

Fingers crossed. Sounds like you need something that can look at the fuel trims live? That would be the best way to confirm it one way or the other although it doesn't take long for the fuel trims to settle. More power is an indication it was being starved of fuel before.

Kevin

[Albatross]

Bugger!  

0170 & 0173 on the way to work this morning. It's only a 4 mile journey and the EML light came on about half way there. After I pulled into the car park I switched the ignition off and then on again for the pedal trick...0170 and 0173 only.

I reckon this could be a combination of things. The fuel filter definitely made a difference.

What do you reckon next?  :-/

[MikeDundee]

Bugger!  

0170 & 0173 on the way to work this morning. It's only a 4 mile journey and the EML light came on about half way there. After I pulled into the car park I switched the ignition off and then on again for the pedal trick...0170 and 0173 only.

I reckon this could be a combination of things. The fuel filter definitely made a difference.

What do you reckon next?  :-/

Well I reset mine las nisght, done 12 miles today and EML still off, but normally will come back on between 40-70 miles, stays off when motorway driving untl hit town driving then would come on again, when I started the car this morning sounded like a pile of poo :-/....but did'nt take as long as before to sort itself out :-/ eg wanting to cut out.

[Albatross]

My car runs sweet as a nut even straight after resetting the codes. :-/

I wish I could find out the root cause of this. Someone said to me the other day that "MAF units are always going on Omegas", but I never see anyone complain about it on here, so I don't know whether to takke that with a pinch of salt or not.

[feeutfo]

My car runs sweet as a nut even straight after resetting the codes. :-/

I wish I could find out the root cause of this. Someone said to me the other day that "MAF units are always going on Omegas", but I never see anyone complain about it on here, so I don't know whether to takke that with a pinch of salt or not.

Genreal opinion on here,
Maf very rarely fails.
Im sure Jamie will agree when he sees this. And you have no Maf code?
Have the simple things been eliminated? have to say fuel filter would be one of them?(sorry, a bit of a low blow) air filter plugs usual service stuff. Just thinking if the fuel filter hash made a difference, have any other service items been over looked?

[Albatross]

My car runs sweet as a nut even straight after resetting the codes. :-/

I wish I could find out the root cause of this. Someone said to me the other day that "MAF units are always going on Omegas", but I never see anyone complain about it on here, so I don't know whether to takke that with a pinch of salt or not.

Genreal opinion on here,
Maf very rarely fails.
Im sure Jamie will agree when he sees this. And you have no Maf code?
Have the simple things been eliminated? have to say fuel filter would be one of them?(sorry, a bit of a low blow) air filter plugs usual service stuff. Just thinking if the fuel filter hash made a difference, have any other service items been over looked?

Fair question. I can't remember if I have missed something from this list:

• air filter
• plugs
• oil
• oil filter
• HT Leads
• plugs
• breathers cleaned thoroughly
• cam-cover gaskets
• plunum 'O' rings
• water pump
• timing belt
• coolant

All changed recently. Most of the big (timing belt related) stuff was done by JamesV6CDX.