Modified URS6 running rich

[twoqu]

There used to be two different catagories for emissions where one was a lot more generous! The cut off was Aug 95 I sem to recall. It's possible that its changed. However if your vehicle is earlier than Aug 95 then it should be tested under the less stringent version.
Not sure if you leave it at the MOT centre or arrive with it 1 min before having spent the previous 1/2 an hour blasting it around to get the oil temp up. The letter is better as I doubt they can get the oil temp up from cold to do the test from cold.
Is it actually failing the idle test (high CO) or is it when they hold it at half engine speed?

[twoqu]

On a stock AAN the fuel pressure should be 4.0-4.2 bar at idle. As Des has said it should drop by 0.5 bar when vac connected. However as the car is not stock we don't know whether this increase in base fuel pressure is intentional or a bad fpr! There were 5 bar fpr available but they were expensive so the alternative was to modify a stock one by crushing it a bit to increase the fuel pressure to what was required.
It does seem to be nearly 1 bar out of whack from that guage so it might be worth double checking if you have access to another more accurate one as a check.
Don't forget the fpr sets the base fuel pressure througout the range so swapping it out will effect fueling under all the operating conditions not just idle. It would be less rich with a 4 bar fpr than a 5 bar fpr but not at the proportional difference between the two.
Also the lambda is not closed loop on these so after some threshold above idle it goes open loop.

[diesel des]

You can hot wire the fuel pump to stay on constant and check pressure that way. 5 bar sounds too high. What is the map expecting. 034 did sell a 5 bar kit at one time, so maybe your regulator is from that.

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[S4Marc]

At idle assuming you have 0.5 bar vacume a 4 bar regulator should show 4-0.5=3.5 bar.

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Should I get a more accurate gauge and put 0.5bar of vacuum on the FPR and see what happens?

This FPR when disconnected from vacuum sits at 5bar........I'm going to obtain a more accurate gauge with a larger scale from work tomorrow. I found this gauge in the back of the garage

[S4Marc]

At natural idle the car is very close to passing emissions

[S4Marc]

Have you measured the lambda output. If it's always rich it will show a voltage higher than 0.45 volts constantly with respect to ground on the signal wire. I would expect it full saturated at 0.8v.

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I purchased a cheap narrowband guage from that well known auction site

At idle the gauge fluctuates between lean and rich as I would expect it to

Any level of throttle the gauge instantly goes to rich

During the MOT emission test (2.5-3krpm) the lambda was telling the ECU "I'm rich" 0.82v

[diesel des]

Have you measured the lambda output. If it's always rich it will show a voltage higher than 0.45 volts constantly with respect to ground on the signal wire. I would expect it full saturated at 0.8v.

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[diesel des]

At idle assuming you have 0.5 bar vacume a 4 bar regulator should show 4-0.5=3.5 bar.

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[S4Marc]

Writing things as they come into my head in the hope I might get there in the end

The car has an 034 Motorsport upgraded Bosch fuel pump but a standard FPR would this cause rich running due to a mismatched fuel pump and regulator?

What should the fuel rail pressure be at idle

Alas I was barking up the wrong tree.......my "A" version of the 4bar pressure regulator does an admirable job of maintaining pressure. Well whilst revving on my driveway anyway

[S4Marc]

Writing things as they come into my head in the hope I might get there in the end

The car has an 034 Motorsport upgraded Bosch fuel pump but a standard FPR would this cause rich running due to a mismatched fuel pump and regulator?

What should the fuel rail pressure be at idle

[S4Marc]

Here's a picture of the cars initial Dyno which shows a good AFR so does this mean it must be component failure over the years??

[Tractor Dave]

No problem. I will send you a PM

[S4Marc]

Where are you based? I have a gunston gas tester i can lend you so you can play around at home and know what it's doing.

I'm based in Dorset

That's a very kind offer I'd happily pay for postage and a deposit if needed

Really want to save the car as underneath isn't bad at all just some corroded brake pipes and rear Flexi hoses

[Tractor Dave]

Where are you based? I have a gunston gas tester i can lend you so you can play around at home and know what it's doing.

[S4Marc]

Is getting the car remapped the next port of call or a £350 MAF sensor?

It runs well and pulls hard with no obvious black/brown exhaust smoke