Thread: V8 Question

Sean, did you remove the stepper motor from the back of the plenum to clean it? if so did you replace the gasket on the valve body, check there are no air leaks (vacuum) from hoses on stepper valve. I clean the MAF electrical connection pins by gently grasping then with needle nose pliers and pulling gently to remove any buildup, then I give them a slight twist, spray with contact cleaner, the plug as well, refit and remove the plug a few times, spray again with contact cleaner, refit and put 2 large plastic ties around MAF and plug.
I would also clean (or replace) the whole of the crankcase ventilation system, esp. the metal parts (T-pieces and so on) including the part on the rocker cover, drivers side.
If none of that helps it is time to check the electrical bits, go to an Auto Leccy and get them to test the coil and the Module on the dissy, you can check that the module has Heat Dissipating grease between the module and the dissy body, they get hot and need to dissipate the heat, you can get the thermo grease from any computer shop.
It doesn't sound like fuel as the problem seems to be at or near idle, so it could be temp. sender or even Throttle Pos. sensor, do you have a Thermostat fitted, if not it may not be reaching operating temp.
I would also clean all of the under bonnet electrical connectors with contact cleaner, incl. injector harness plugs.
It is extremely hard to diagnose a problem from afar, so I hope one of my suggestions works, call me if you wish, Regards Frank.

Check throttle position sensor is working properly and inlet manifold bolts are not loose. Also may be worth cleaning around the throttle butterfly.

H guys, thanks for that Frank. I'd done most of those things, perhaps the gasket and vacuum hoses are worth a look. My sensor has not yet arrived. LV spares are usually quicker than this. Oh well, monday I guess. Anyway, it seems to be deteriorating, now I'm noticing rough running under gentle acceleration. (not that I do that too often)
It doesn't seem to want to accelerate at low revs, perhaps the worsening idle issue???
I'll play around and check and re-check a few things this weekend.
regards,
Sean.

Sean, if all the above check out it only leaves Fuel, maybe dirty/faulty injectors, try some good quality injector cleaner (suggestions anyone), next is fuel pressure regulator, take the small vacuum hose off the IAC valve(back of plenum), suck on hose if you get no vacuum or petrol in your gob, then that's the problem, from there it is the fuel filter and then the pump, good luck, Regards Frank.

My Rossi did this twice,,
first was the stepper,
second was a split crankcase vent hose.

Me (and my mechanic) tried Frank's suggestions from earlier threads also. Worked OK for a while - but eventually it was easier to just replace the damn MAF with a reco unit. I notice they are a lot cheaper on EBay these days...I paid $600 for a reco swap out.
Good luck with it.

Hey Sean,
I recently had a similar prob to what you're describing.
After much "diagnosis" I had been informed to replace the MAF, leads, plugs, and both CATS (after each item had been replaced seperately and the problem still existing after each), and it turned out to be the O2 sensors.

Just thought I'd mention it as no-one else has yet hinted at these.
My Disco runs much better.....for now!

Good look. Its as frustrating as hell, innit!

Cheers,

..:: KIEREN ::..
2000 Disco II Auto V8 (lemon edition)
AussieAubs Disco Page

Originally Posted by Pedro_The_Swift

My Rossi did this twice,,
first was the stepper,
second was a split crankcase vent hose.

When the MAF died it would only run properly on FULL go-pedal,,,



you can imagine how the fuel guage reacted to that
luckily the tank was full--
and it was only 200 kays to home---