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[feeutfo]

Sensors now moved back and codes cleared.


Let's see where we go from here...

 

Any bets? Ill have a pound on...
 No fuel codes, back to cat codes.

[Albatross]

Sensors now moved back and codes cleared.


Let's see where we go from here...

 

Any bets? Ill have a pound on...
 No fuel codes, back to cat codes.

No bet from my end I'm afraid as I'm pretty damn sure that's what'll happen too. I know this is resolvable though and I will come up with the final solution.

[Albatross]

Now here's what I was not expecting.

Sensors in the standard postition and all codes cleared. I take the car out for a good thrash and keep the foot down and ...

wahey the EML light re-appears...

0420, 0430 you're thinking?

Nope :-/

Bloody 0170 and 0173 again.

Now that points me back to low fuel pressure, dirty filter, lazy fuel pump or air leak.

On the other hand, that still leaves the distinct prossibility (probability) that moving the sensors did work, because I haven't had a single 0420 or 0430 whilst they were back there.

So I need to solve these 0170 & 0173 fuel trim issues on both sides 1^st then once I have that settled then I need to start looking at moving the O2 sensors back again.

Or is there some possibility that after having the codes cleared (Cheapo TechII) that there was some residual effect of the "long term fuel trim" readings left in the system that has caused the recurrence of the fault code? All he did was "CLEAR ALL DTS CODES".

Any ideas on where to start? I suppose it is the same answer(s) of "change the fuel filter" and then "get the fuel pressure checked" isn't it?

[Kevin Wood]

I would say change the fuel filter if it's not been done recently.

Oh, and I reckon the cat codes will be back in a day or two.

At least it looks like the fix will work. Just got to find out why the fuel trim problems now. I would say fuel pressure won't be a problem at idle because it was winding up the fuel trim under load. Measuring the flow rate from the return from the rail would be a useful diagnostic step if the filter doesn't help.

Kevin

[Albatross]

I would say change the fuel filter if it's not been done recently.

Oh, and I reckon the cat codes will be back in a day or two.

At least it looks like the fix will work. Just got to find out why the fuel trim problems now. I would say fuel pressure won't be a problem at idle because it was winding up the fuel trim under load. Measuring the flow rate from the return from the rail would be a useful diagnostic step if the filter doesn't help.

Kevin

Is this what you were talking about when you were here (i.e. a garage can check the pressure) or is this something different?

How can I measure this accurately?

EDIT: Kevin, would a damaged secondary 02 sensor on ONE side possibly cause a fuel trim error on both sides simulataneously? I ask becasue when I was moving the sensors back to the original position yesterday I noticed that the sensor on the near-side bank was a bit scratched just inside the thread (slight flaw in the o2 sensor boss on the new SS exhaust which is now fixed with a round file). The end point where the actual sensor hole is was fine, but I am just checking. I suspect that it is unlikely and we should be looking or something that is common to both sides, and "pre-combustion", due to the symetry of the errors.

[Kevin Wood]

The problem is, the fuel pressure can only be measured when it's idling.

Looking at the datalog I took, when the engine is idling the fuel trim is OK. It is when we were driving it that it struggled, thus I expect, if it's a fuel system problem the pressure will be OK at idle but will drop off as the demand for fuel increases.

What I was proposing is to remove the return line from the tank or the fuel rail, running the pump and measuring the volume of fuel returned per minte. This is a measure of how much fuel the pump is shifting at rated pressure, rather then whether it can maintain that pressure with very little demand.

Simple things first, though. Try changing the filter.

I'd ve very surprised if you've damaged the Lambda sensor with a burr on the boss thread. You'd get other codes if the sensor was misbehaving anyway.

Kevin

[Albatross]

OK fuel filter will be changed on Monday and codes cleared again.

I just checked the top panel of the fuel pump, cleaned it off, cleaned all the contacts with cleaner and checked that there were no leaks at the junction between the flat plate and the metal 90^o elbow bends. There was a little surface rust, but I cleaned that off and all looks good.

I'll post again with reports after another thrashing with a new fuel filter. What I need to try to achive now is a code 0420 and/or 0430, but no 0170 or 0173 over a period of a few days.

Once I can do that then I can start thinking about moving the secondary O2 sensors back to behind the main cats and clearing the codes.

Then it is another re-test.

Is there anywhere under the bonnet that I should be looking for fuel / air leaks?

JamesV6CDX and I had the plenum off and he re-sealed my cam-covers for me and replaced the cam-belt, water pump and rollers, whilst I cleaned out the plenum and breather pipes. All rubber seals were replaced and were checked for quality before use. The MAF/Plenum gasket was replaced as were both the big (arms thickness) rubber hose elbows which are jubilee clipped to the front of the throttle body /  plenum.
We also changed the plugs (the dealer gave me those 4 point plugs). We changed the HT leads too.

Air filter is less than 500 miles old and the box is perectly sealed. Oil and oil filter less than 1000 miles.

[Albatross]

Kevin,

I've just PM'd you with this same question, but it seems to make sense to post it here as it is somewhat related:


First two assumptions:

Assumption 1:

• I get to the bottom of this fuel trim issue of the codes 0170 and 0173.

Assumption 2:

• Once I have done the above I have reverted to having the secondary 02 sensors behind the main cats and that this solves the original problem of 0420 and 0430 pre-cat deficiency issues.

Question:

• Would I be mad for thinking that I could actually fit 3.0 standard cat sections into my 3.2 exhaust system?

The reason I ask is three-fold:

The first two are Economy & Availability as the single cat sections are both cheaper and more readily available second hand.

The third is increased air-flow out through the exhaust system as I would only have a single cat on each side to contend with.

[Albatross]

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

[Kevin Wood]

Regarding air leaks, etc:

I think you're looking for something upstream of the throttle since fuel trim is positive and gets worse under load (not under vacuum).

I'd check the pipe from the bottom of the throttle body to the fuel pressure regulator. Very difficult with the plenum on but check that the front end is Ok where it turns 90 degrees and in to the bottom of the throttle body (I had a feel under here last weekend and it seemed ok) and also see if you can see / feel it under the back of the plenum as it goes into the FPR.

Then we're left with the TB to multiram pipes which looked OK, multiram to MAF which also looked OK and we're at the MAF now so nothing further upstream matters.

Kevin

[Albatross]

Thanks Kevin,

Not sure I understand all that, but I'll have a go. I'm not sure what the throttle looks like for starters. :-/

What does the fuel pressure regulator look like and where will I find it?

After consideraton, do you still think that it can't be the increased flow (reduced restriction) of the new stainless cat-back exhaust?

[Kevin Wood]

Thanks Kevin,

Not sure I understand all that, but I'll have a go. I'm not sure what the throttle looks like for starters. :-/

The throttle body is the cast aluminium block that sits between the plenum and the two elbows. You should find a small breathe out of the bottom of this which runs under the plenum to the fuel pressure regulator. TBH, i doubt it's big enough to greate a significant air leak anyway.

After consideraton, do you still think that it can't be the increased flow (reduced restriction) of the new stainless cat-back exhaust?

I would expect any extra flow would be matched by additional air, which would be measured by the MAF, so at the moment my money is on poor fuel delivery for some reason.

One thing might be interesting: Is average fuel consumption being accurately calculated by the display in the car or does it differ from what you're putting into the tank?

Kevin

[Albatross]

Thanks for all of that, I'll have a look in daylight tomorrow.

One thing might be interesting: Is average fuel consumption being accurately calculated by the display in the car or does it differ from what you're putting into the tank?

Kevin

Christ on a bike, now you're asking. I never take note of that; I can do now though.

I'll start soon. I'll run her nearly dry and then fill up with Super Unleaded, it should be in the next couple of days. I'll take note of the amount of litres put in, reset all the clocks etc. and then run her for a while, what say 3 or 4 days? I have to nip up to Gateshead this week, so that will give me the opportunity to fill up at least once or twice. :-/.

Then I'll take note of how many litres it is to fill her up again each time and a reading from the odometer and all the clock readings on the CID.

[Kevin Wood]

Thanks for all of that, I'll have a look in daylight tomorrow.

One thing might be interesting: Is average fuel consumption being accurately calculated by the display in the car or does it differ from what you're putting into the tank?

Kevin

Christ on a bike, now you're asking. I never take note of that; I can do now though.

I'll start soon. I'll run her nearly dry and then fill up with Super Unleaded, it should be in the next couple of days. I'll take note of the amount of litres put in, reset all the clocks etc. and then run her for a while, what say 3 or 4 days? I have to nip up to Gateshead this week, so that will give me the opportunity to fill up at least once or twice. :-/.

Then I'll take note of how many litres it is to fill her up again each time and a reading from the odometer and all the clock readings on the CID.

Yep, reset the avg consumption and odo when you fill up, give it a tank or two, keeping note of what you've put in and see if it is accurate. See if it is injecting as much fuel as it thinks it is.

Kevin

[Albatross]

Will it matter if I have the fuel filter changed during this measuring/reconciliation process?

I think I might try to get the fuel filter done first, codes cleared and then go down to the petrol station.

Would that be the best approach?