Following up on this: Are my fuel pressure numbers good? Bad? Indicative of anything?


The Cat on Bank 1 might be out of commission - the downstream 02 sensor is fluctuating in voltage when apparently it should be constant. The Cat on Bank 2 downstream 02 sensor stays up at 1.005 without fluctuating. I still need to temp test them to see but looks like it may be bad.


Bank 1 STFT is fluctuating in the negative numbers.
Bank 2 STFT is fluctuating in the positive numbers.


LTFT is still 6.3 and hasn't changed for four days.

 

Fuel pressure leak down says the FPR is moderately leaking. Shouldn't leak down, should remain at pressure indefinitely. Not a tell all really other than it may have some rust/fuel crust. When your running on highway it's going to be closed, less vacuum releases diaphragm spring.

If in fact the cat is whacked that may explain the higher LFTF number with the ECM adding more fuel to achieve power.

 

Thanks. I've got a heat gun and a vacuum gauge coming so I should be able to do more engine diagnosis.

You think the gradual loss of pressure is the regulator and not a bad injector? I know a bad injector should cause an immediate drop in fuel pressure, but gradual is something else?


One of the cats seems whacked but will have to wait for the heat laser to tell - the 02 sensor for one stays static, the 02 sensor for the other seems to correlate with the upstream one....I read somewhere it should stay static.

Of course they're both welded in so if one's bad it's a trip to the exhaust shop...

 

Actually it could be an injector now that you mention it. I did have one fail open but the motor ran like crap, had no power, coincidentally happened while I was on the highway....

 

I may have bad cats. I threw a vacuum gauge on the motor and it's within spec, operates as it should, doesn't fluctuate, indicating good engine ops and no intake leaks.

Bank 1
Downstream 02 voltage stays at 1.005. Generally that should show a good cat but the temperature difference between front and rear of the Cat doesn't change much, so that shows a cat that is likely bad.

Bank 2
Downstream 02 voltage fluctuates all over the place. Generally that should show a bad Cat, but the temperature shows a 90 degree difference between the front and rear, which shows a cat that is likely bad.

So maybe both cats went south on me? I don't know if that is affecting mpg but its clearly something needing correction

 

All City driving. No idle in the morning. 46 miles. 7 gallons. 6.5 MPG.

Ludicrous.

LTFT 3.3

I did pull a trailer with 1000lbs load (trailer about 750lbs) about 7 miles...

 

No one has any ideas? Folks just given up on helping? I'm super frustrated here, sorry.


6.5 miles per gallon isn't even comprehensible in my mind. I can't even fathom how a fuel injected semi-modern vehicle with a computer can even produce something that atrocious.

I've checked everything. Any ideas?

 

pull and test all the fuel injectors. new front O2 sensors. replace catalytic converters.

but i think that you were already looking at all those items.

the rear O2 sensors have nothing to do with how the ECU fuels the engine.

 

Front sensors are new.


I am looking at new Cats now...I still haven't understood how they would so drastically screw up miles per gallon, but everything else is new.


The injectors pass the leak down test, but they could be spraying like crap or poorly, so will look at those, too. I just need a plenum gasket, right? No other gaskets are necessary when pulling injectors?

 

There isn't one beneath the trumpets, machined. I don't think there's one for the plenum either since it's machined, most including me use RTV.

Do you know if the "Y" pipe has been replaced?

Realistically the cats might make 120k, the OEM's did have a way of "chunking" which would clatter in the can. Aftermarket cats are @ $50 a piece but as it's a Rover it's not a straight through it's offset so modifications are needed to line up the rest of the "Y" to the bung. Shorty headers are one way to skin that but if you're not a welder it's moot.

Injectors - early Ford 5.0 19ohm guys replaced the Rover fire hose pattern with.

I am out of ideas, it was running fine on your weekend trip and then its like a gate was dropped. I'm just a shade tree with a brain but I'm stretching because I'm better at hunches while the motor is running in front of me.

Something happened because the bottom fell out and now it's worse than before. Your making me happy I got rid of my Disco.......