Our Discovery runs on LPG most of time, we tend to do a few miles on petrol when we run out. But now on petrol it runs really rough, feels like its going to stall when on tick over (its fine on gas). I was wondering if the injectors get clogged if they arent used much? If so, is it worth putting injector cleaner in the tank or taking them out and getting them checked/cleaned? Or does anyone have any other ideas? Thanks Richard
On or around Sun, 07 Nov 2004 16:40:29 GMT, "Richard" enlightened us thusly:
sounds a bit like mine. I think it's a good idea to run it a bit on petrol every now and then.
mind, there's a funny problem on mine, which means it doesn't run that well on petrol anyway, also the ignition is advanced on account of the gas, so I wouldn't expect the petrol to be perfect.
thassa point, any hotwire experts care to inform if there's a temperature-sensitive enrichment or any such thing on it? 'cos mine seems to go better when it's cold.
In message , Richard writes
It's a possibility - which is why some installers don't use emulators but stop the petrol pump. If you don't normally use petrol for starting then it is quite likely that the injectors are clogged. Also you may have an emulator problem. Is it consistently the same cylinders which are misfiring - might indicate an emulator problem Your idle speed control valve would probably show up on gas too. Have you checked your coolant level in the radiator (not the header tank)?
The injectors can get blocked or rust/oxidise when running full time LPG which is a good reason to start on petrol even if your system (like mine) will start quite happily on LPG. You may also find that your timing has been set to suit LPG more than petrol which can also make a difference, especially at tick over.
Getting the injectors cleaned is a major PITA. I got two sets cleaned at Billing on the stand - I took a set out of my Disco (the Disco stayed at home) and used my competition motor to go to the show with the caravan on the back. The competition motor took an hour to strip and about 2 hours to put back together again with the cleaned injectors. The Disco took an hour to take apart and 6 hours to put back together when I struggled to get the fuel system fuel tight again and ended up doing the whole job twice with a trip to Thirsk and back to get some fresh sealing rings in between.
The results in the competition motor (3.9 auto Defender) were good with a definite improvement in response and torque. The results in the Disco weren't noticeable, it still runs rough on petrol :-( I'd certainly give some injector cleaner in the tank a go. With any hotwire system it's always worth changing the EFi coolant temperature sender just to see... they are cheap and easy enough to replace and have a huge bearing on the fuelling under all conditions. It's located at the front left of the engine, just behind the distributor (if you have one).
cheers
Dave W.
There is a thermistor located at the front left of the engine (just behind the distributor) that the ECU uses for the engine coolant temperature. This temperature input is used to shift the fuelling map up or down to compensate for the engine's temperature. It is so simple to replace (a couple of minutes) and so cheap to buy from Land Rover that it's hardly worth trying to test it. Note that this is not the same temperature sender that the temperature gauge in the dash uses. It has a connector on to the top of it that is the same as the injector connectors.
There is also a fuel rail temperature sender but I've not known one of these to cause a problem. It's also worth checking/adjusting the MAF meter as, when not running in closed loop with lambda sensors, the primary fuelling information comes from the MAF meter (measuring the quantity and mass/density of the air going into the engine) and the engine and fuel temperature which allows it to compensate for cool running/starting and high or low fuel temperature which effects the density and hence the quantity of fuel. The only other important input is the throttle position from the throttle potentiometer but that is used more for transitions than constant revs.
Don't know if that makes any sense but in summary, change the temperature sender and see if that helps :-)
cheers
Dave W.
On or around Sun, 7 Nov 2004 22:34:54 +0000 (UTC), Dave White enlightened us thusly:
OK. I'll have a look.
the MAF was adjusted, sometime after I got it. Basically, it runs nicely at whatever speed it's doing but it's not so good at small variations of speed mid-throttle, and mid-revs. get the revs over 3000 at high throttle opening and it goes pretty well - applying a bit more throttle at say 1800 revs makes not much difference, or not as much as I'd expect.
might just be a tired cam, at that, I've not looked, and it has done about
97K miles now.
I have changed the coolant temp sensor (not the one for the gauge, the other one), it has been on a diagnostic computer and it was all ok. I have checked the coolant level in the header tank and it was down about an inch, I havent checked the rad level yet, would this be any differant ? If so, how does it make it run rough ? Richard
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