14 CUX Injection Problem?

landrovernuts · Post by **landrovernuts** » Sat Jul 11, 2009 4:32 pm

Hello All

Wander if anyone has any ideas about a problem with the injection on my 4.2 which has run faultlessly until now and I am convinced its an injection fault and not an ignition, but happy to be proved wrong if anyone thinks different.

The engine runs normally an well and while driving you suddenly get a small dip in power and all of a sudden it starts running so rich its black smoking, it then starts surging and sounds like the choke is out on a carburettor motor. During this time the rev counter gives no indications of an ignition fault and neither does it miss fire. It will then suddenly start running normally again and there does not seem to be a pattern of when it does it or for how long. I have run like this with a pressure gauge (calibrated) on the fuel line and fuel pressure is between 32 and 38 psi depending on manifold vacuum, this is a tad low, but OK. So the apparent over fueling is not fuel pressure/regulator. I have done a leak test on the fuel rail, Landrover say 7psi in 10 mins is just acceptable, my leak test dropped nothing in half an hour. The last time it was in the fault condition I unplugged each injector in turn and it still gave visible black smoke when reved up. All spark plugs checked and were all very slightly sooty as one would expect, but no individual discolouring between plugs, indicating the fault is on all cylinders.

I have taken the stepper motor out and replaced it with a dummy one and proved that it is working (I could watch it moving ) I cleaned it and lubricated it while it was out. I then plugged the stepper motor air pipe and set the idle on the throttle bypass air screw to about 600 RPM while I was doing this, as I knew this adjustment has been well out and it would just die before. When all connected up it idles about 850 RPM, which is what it was set up to do when Mark Adams had it on the rollers about 10 years ago.

I have changed the coolant temperature sensor and the fuel temperature sensor for known good items and have done the voltage test on the airflow meter (ECU pin 35 to ground) LR say between 0.3 and 0.6 volts my one is reading 0.47 volts, but I have not managed to test this when it is in fault condition.

I have changed the ECU for another known good one that I have (this one is set up for a 3.5, but still gave the fault when plugged into this engine)

Could I be looking at at fault with the air flow meter and is there any more tests I can do to eliminate this when it is in fault condition again, or has anyone got any other ideas. The only other thing I have noticed is the revs fall like a stone when you take your foot off the throttle and not slowly in the series of stages like it normally does when it is in the fault condition. I have tried taking the cap of the fuel tank to make sure its not pressurised and its not. I am open to any suggestions at the moment if anyone has any!

Toby

Robrover · Post by **Robrover** » Sun Jul 12, 2009 3:02 am

Lambda sensors or TPS switch sound like they could be the culprits.

landrovernuts · Post by **landrovernuts** » Sun Jul 12, 2009 6:29 am

Thanks for the reply, throttle pot set to 0.34 volts and appears smooth in operation, however open to opinions at the moment and the next time it plays up will look at the TPS. Its an early hotwire (1990) with no lambda sensors fitted.

Toby

Post by **katanaman** » Sun Jul 12, 2009 12:46 pm

Could be a sticky injector?

landrovernuts · Post by **landrovernuts** » Sun Jul 12, 2009 1:42 pm

Thanks for replies, I have found the little gremlin. Its the airflow meter, when it goes into fault condition the pin 35 to ground voltage drops to zero (actually 0.07 volts) and am just wandering if its failed due to how its mounted. Currently on rubber isolators, but on its side ie plastic cover with 3AM Hitachi etc on is at 90 deg, would this have any effect? It of course could just have died due to age! It does breath through a snorkel, but I would have thought cool air from outside engine bay would help it.

Anyone got a good 3AM or 5AM air flow meter they don't want or know where I can get one, as I do not want a cheap copy version from ebay?

Toby

r2d2hp · Post by **r2d2hp** » Sun Jul 12, 2009 1:58 pm

I have a 5AM that I upgraded to the 20am when fitting Tornado chip

landrovernuts · Post by **landrovernuts** » Sun Jul 12, 2009 4:17 pm

PM sent

Toby