Rover V8 assistance required ! 1993 Range Rover Classic running rich

[FrankXK8]

Hi folks

Having real trouble with idle on my 1993 RRC, are there any experts in the Rover V8 in NI ? Thinking perhaps TVR people would know...

The car is a 1993 Range Rover with the 3.9 V8, catalyst-equipped and 14CUX “hotwire” electronics.

The problem is that the emissions are poor (high CO (1.5%) and extremely high HC (3240) readings.

The idle is lumpy, very up and down. The car accelerates and cruises very well, but idles badly and will stall when coming to a stop in Drive or Reverse. Always restarts with no issue.

1. New AIR Filter, spark plugs,
2. New coil, plug leads, distributor cap, distributor rotor, Denso spark plugs
3. New Lucas idle control valve, MAF and O2 sensors
4. New coolant temperature sensor (CTS)
5. Oil change, coolant change
6. Checked all vacuum tubes, and flex tube between MAF and plenum, replaced the T-piece in the breather assembly
7. Cleaned flame-trap and the breather.
8. Clamped off the idle control valve pipe – idle unaffected, is still up and down.
9. Disconnected the MAF connector – idle unaffected, is still up and down.
10. New fuel-pressure-regulator
11. Even put new/reconditioned injectors in, thinking the old ones might have been drippy
12. Tried a new MAF (ebay cheapie) - no difference, so refitted the old original
12. Sprayed carb cleaner around the plenum, injectors, vacuum hoses, joins – no effect.

There are no fault codes showing up in Rovergauge diagnostics. All of the sensors old and new are showing up okay in Rovergauge (Transmission PNPS, road speed sensor, fuel temperature sensor). It is not catalyst-related as there are no sensors after the cars, only before.

A log was gathered during a test drive, the stall event can be seen around lines 937 in the log.

But I think the key fact is that the car is running rich, and the short-term-fuel-trim is like -90% (therefore the ECU sees that it is rich, so is decreasing the injector time)

Running out of skills and ideas now, so will have to find someone with the brains and experience ! The car failed its MOT due to emissions. Based in Downpatrick.

Cheers
Frank

 

[NI_Volvo_Nut]

I have heard of these things giving problems with air flow meters which would cause idle issues?

 

[FrankXK8]

Yeah man, that was my first go-to and the second was the coolant-temperature sensor, they both can cause the car to run rich. But unless my cheap ebay airflow sensor is crap, we can rule it out. I put the old sensor back in anyway since the new one made no difference.

To be honest, I am looking for help now from someone that knows these engines - this is my first Rover V8 so it's a steep learning curve. Eg. the camshaft is regarded to be a wear item, but I don't know how to check for that other than stripping the engine and looking, and I don't know even if something like that would cause rich-mixture.

The diagnostic logs still indicate that it is overfuelling and that the ECU is trying hard to de-fuel - that's why I replaced the injectors (in case one or more were dripping) and the fuel pressure regulator (if it wasn't working it would cause overpressure of the fuel rail).

I don't want to keep throwing parts at the problem, but my final one will be the fuel-pump (in case the old one was over-pressurising the fuel rail, or was not providing a consistent flow). Waiting for that to arrive. I don't have a gauge to test fuel pressure and TBH wanted to stay away from anything petrol related what with my garage being underneath the house !

So looking mainly for recommendations on someone with LR/Rover-V8 experience to look at it for me

 

[Coog]

What fuel map is it referencing? Is it on a stock tune & ECU?

 

[FrankXK8]

Fuel map 5, which I believe is for a UK 3.9 with catalytic convertors. I checked that the tune-resistor is in place in the loom, and it is. Rovergauge reports map 5. No idea what it means by "Tune: R2925" though, whether that is standard or not.

The ECU has a chip with a faded label on it, so it is likely to be the original programming if the label is that old.

The car came to me in January with no real history, and it had been laid up for 7 years (perhaps due to engine issues, who knows...)

 

[adzy]

Checked the ignition timing?

 

[stevieturbo]

Those hydrocarbons are massively high.....that plain and simple is unburnt fuel going out the exhaust.

If the CO reading of 1.5% is accurate, the engine is not running excessively rich by any means..

Find out why fuel is going straight out the exhaust and stop throwing parts at it. It's probably destroyed the cats too.

Simple first steps, O2 readings on each bank, and a proper 4 gas reading from each bank. Compression test. And ensure ignition system is working properly.

It is highly unlikely to be an injector issue unless one or more is stuck wide open, but with a claimed CO reading of 1.5% that would seem impossible unless the reading is incorrect.

 

[FrankXK8]

Is there someone you would recommend to do those tests and more ?

This is my problem, I don't have the tools, etc, to do the O2 readings you are talking about - they make sense but it's beyond me. I am able to remove things and install them, but do not have troubleshooting knowledge/experience/tools.

This was from the MOT, CO near 1.5% but HC very high.

 

[Mark_C]

As above, that sounds more like a misfire,so need to work out where and why.

A lot of people will smell petrolly fumes at the exhaust and cast the 'running rich' diagnosis when in fact its a misfire.

 

[NI_Volvo_Nut]

Hi HC is unburnt fuel, so it's not running rich, it's not burning fuel, running rich would result in high CO.

 

[FrankXK8]

Cool, so a misfire as Mark_C also said

The car has new sparkplugs, distributor cap, rotor arm, coil and sparkplug leads. No improvement over the old items. All of the old sparkplugs had pretty much even colouring when removed.

 

[gary1365]

Have you done a compression test yet would be worth buying a gauge as they’re not very expensive just to rule it out.

 

[FrankXK8]

Have you done a compression test yet would be worth buying a gauge as they’re not very expensive just to rule it out.

Yeah, compression was 170psi on 6 cylinders and 160psi on 2 (different banks). So nothing of note there.

I read about camshaft wear, slipped liners and so on with these motors but wouldn't know where to start with that level of check.

 

[vw1500]

There is a guy I've heard of up near Ballymena, JimRobinson I think? He's well known for Rover V8s, had built the engine in a mates Vitesse before he got it.
EDIT: Googled it, worth a try

https://www.v8register.net/subpages/news110811JRV8.htm

JRV8

Rover & Chevy V8 Parts and Engines

www.jrv8.co.uk

 

[stevieturbo]

The fuel trims at -70 to 80% make little sense.

For whatever reason, your lambda sensors ( if correct ) think things are too rich, and it's pulling fuel like a MF. However the CO reading kinda says otherwise because it is not rich.. Odd they didn't give a lambda reading too.

Without a gas analyser, you're not really going to get too far here. I would want to unplug the o2 sensors and see what impact that has on mixtures. Ideally I'd want to get a proper reading via gas analyser on each bank during this test, or at a minimum a reading from a wideband lambda.

Your screenshot of the ecu also show throttle at 3% ? Is this deemed normal for an at idle reading ? Or should be it be 0% ? ie, someone has adjusted or messed with the sensor position, or the blade is being held open for some reason ?
I presume whoever makes that software you are using can advise on that.

It also shows idle target rpm is 792....yet you're up in the 900 range ? So this is potentially another issue ( or related to the partially open throttle )

Although despite all this, HC should be nowhere near where they are.

Again with a gas analyser, you could run it and unpug each injector in turn to see if this reading changes massively....although a lot of gas analysers wont be happy running for long periods getting that amount of fuel chucked into them.

 

[FrankXK8]

Mother f****r

I pulled the crankcase ventilation system to clean it, and notice that the vent from one bank of the V8 is clean and with no pressure to speak of; the other is quite high in pressure with a bit of smoke... makes me think rings, head gasket or valves on that bank might be bad.

Got hold of a boroscope at last (thanks Amazon Prime) and looked into one of the two cylinders that had returned 160psi in the compression test (6 of the other 7 had returned 170psi). I see a gouge in the top of the piston. So it looks like this engine is junk ?

With that in mind, who's good for rebuilds ?
Or even to put something more interesting in there (LS1) ?

 

[stevieturbo]

Such cameras are often hard to get good images, and benign features can appear like something else.

Jim Robinson could no doubt rebuild yours, and this would be the cheapest course of action. If indeed it needs rebuilt. I'd rather a proper diagnosis first.

You would have to ask yourself how could a gouge like that even be possible, with no other markings ? I would question the image unless there was some other evidence.

And even your basic compression test indicates there is some decent sealing