[jasper6bears]

Hello Listers

Just got hold of a RR 1995 4.6 V8 - working our way through it problems.

Runs like a bag of nails and pops through exhausts - heres the work done so far!!

New Exhaust and Cats
New Coils and HT leads
New plugs
New Fuel Filter
New o2 Sensor

It has a Prins LPG conversion on it, but runs in the same rough fashion on both fuels

There was a possiblity that the new O2 sensor means the ECU fuel mapping needs resetting? Is that true?

MAF seems ok - Spark on all plugs.

I would guess also that the previous owner played with this fuel mapping whilst cats were shot.

Anybody local with hardware to check and reset for us would be great - Or any advice would be great.

We are willing to pay for any physical help given - It is getting a bit annoying NOW!!!

Thanks Epsom Surrey

 

[lrscott]

Have you tried unplugging the maf sensor to see if it runs better? Have you tested the the coil pack, is it throwing any codes etc. Could also be the cam shaft or push rod. Valves could also be sticking.

 

[jasper6bears]

Hello

Unplugging MAF makes no difference.

Coil pack is new and fitted by me. Sparks on all plugs.

Have not go tester myself - but local garage found no stored codes.

1 O2 sensor was down according to another garage - so I changed it - no different - although I am told the ECU will need resetting after this change ? Is this correct?

I am doing a compression test today - but plug colours look ok and no signs in oil or water etc so no sign
s of head gaskets failing!!!

Any help appreciated?

A local member with the reset tool for ECU would be ideal BUT!!!! finding them?

I am in Surrey UK

 

[luvs2getmuddy]

My Range Classic did all that once upon a time, after doing all the things you've mentioned, it turned out to be weak compression in 2 cylinders=rebuilt. Hopefully it is not your faith too.

 

[jasper6bears]

Hello All

Today I have Tested compression cold all in 140's 150's .

Any More clues out there - my money is still on Fuel set up in ECUt

Thanks

 

[Rowant]

I am under the impression that it is not possible to re-map the fuel system - unless you are a specialist programmer. So I would discount that for now.

How does it idle? Reasonable smoothly? Or does it run like a ´bodily function´ right across the rev range? If something is not tight or connected then you might have a slight ait leak somewhere - just 2c from my experoence of non-efi engines.
Did the garages you consulted have the correct diagnostic tools - Rovacom/testbook etc? I don´t know if other types of general/generiic tools are as effective.

Just some things to consider.

 

[stu1]

Can you give a few more details about the problem - is it back-firing? At all rev ranges? Is there un-burnt fuel out of the exhaust? When cold, when hot?

Anyway, the things I'd check in this order are (in the absence of diagnostics) :
1. The correct HT lead is going to each cylinder.
2. Vacuum leaks.
3. Fuel pressure.
4. Crank sensor output (you'll need a scope or something else capable of displaying the output waveform)
5. Valve timing.
6. Coolant temperature sensor (depending on the symptoms)

Stu.

 

[jasper6bears]

Hello

Heres some details as requested ;

Backfires - more pops really in exhausts. (runs badly on tickover and all rev ranges)

HT leads correcly routed.

Has petrol and gas - runs bad on both so I discounted fuel pressure?

Has new cats,Maf seems ok,New o2 sensor,new coil pack,new plugs,new ht leads

I have not got any diagnostic kit for this car.

Thanks

 

[Rewmer]

If you have changed the O2 sensor(s) You need to get the adaptions re-set before you do anything else. If the long term trims are out after trying to fight with a duff sensor, you wont have any luck untill they are put back to base line.

 

[jsp]

my 2 cents - its a gems - check all the hoses.

Mine went through 2 "specialists" who couldnt find the rough idle and lack of power at RPM's and all it turned out to be was a vacuum hose between the RH rocker cover and the plenum chamber, it has a flame trap in the rocker cover which had blocked, and then the hose had collapsed over time under vacuum, it was replaced but took me a bit more time to work out the flame trap was full of gunk as well.

I had to put cable ties around this hose as it blows off if the LPG front fires, which it does about once a month, but its a single point vaporised system.

 

[HSE]

Check your IAC valve, amazing the difference a cleaned one will do. But remember that it will need to be diagnostically re-set after cleaning/replacement.
Russell.

 

[paul.adshead]

Sounds like vacuum leaks in the 'valley gasket' (- gasket between intake-manifold and each cyl-head) to me. Early engines had a plain 'tin' gasket, that decays over time and bits fall out, leaving gaps that leak air. These vaccum leaks allow additinonal (un-meterred) air into the engine, which affects engine fueling/AFR. You hear the effects of this in the tailpipe as 'popping'. The later engines have a revised gasket impregnated with a sticky glue type substance, that is far more resilient. You need to get one of these later style gaskets fitted (I had exactly the same symptoms s**t running on petrol and LPG), that was fixed by changing this gasket.

Is your LPG system analogue or digital? Do you know if it interrogates the MAF signal, or does it 'piggy back' off the 'petrol injector signals' to fire the 'LPG injectors'?