Quoting misterfixit:
Paul,
The only things I can suggest are the little things.
Its nearly stock, has the previous owner paid attention to it closely, does the wiring around the t/stat housing feel soft and malleable or is it hard and brittle? Just trying to get a feel here.
If its seem to be temperature dependent then try cleaning up the temp sensor contacts, Where the end of the spade connector looks like [_] try crushing it a bit with pliers and reinstalling it back to the plastic plug so its got a nice tight bond on the tab.
Check the earth between the inlet manifold and the firewall, if that's shitty clean out the threads and reinstall, also under the air box to the inner wing is the battery tie down, give that a damn good clean and reinstall it. That should ballast the electrics properly.
The bov question is valid, but it's more likely to be a breaking down type thing. Have you checked out the injector resistors to see if the pack is still ok.
THe last one is what is the breather system like, is the breather pipe clean or filmed with sludge? Check and clean out the PCV, if thats cakky get into the throttle body. The other one that could be causing issue is a sticky/leaky butterfly bar on the cyclone is there any witness of weepage near the end of that.
The last favourite is leaky crusty vacuum hoses, Check these around the pressure control solenoid, the boost solenoid and the cyclone canister, make sure they are not perished.
I didn't suggest the ignition leads as you've already changed them, but check their resistances (I have posted these before for the JDM motor) as an indicator of their condition.
one last thing is the wax operated thermo valve in the throttle body, was a favourite to get clogged up and cause rough running in all my brothers German obsession cars, and have decoked/declogged these on many cars here. Look for oil sludge/carbon build up on the needle and the valve seat.
Pull the throttle body and drop the servo block off the bottom, You'll be able to see it clearly then. It should be nice and clean and open an close smoothly with the application of warm water through the throttle body. Same mechanism as the thermostat, so could stuck, or those coolant passages blocked, or disconnected.
Let us know how these things check out. It's most likely to be an age/heat/crud thing you are looking for.
Should keep you going a bit!
Rich
Rich,
The VIN is E39A-0021298. It is in very good condition in general but I will check the wiring you have suggested. Is there more than one temp sensor, what is the sensor on the left hand side of the block near the intake pipe?
Checking injector resistors to find out if the pack is okay. Is this the same thing Red was asking me to check above or different. If so how do I check. I am really bad with electrics!
I'll check out the intake, throttle body and intake manifold. Vacuum hoses look fine but I'll check again. Same with the tie down and earth. Looks fine but I will check.
Like you said that will keep me going for a few days /ubbthreads/images/graemlins/grin.gif
Thanks,
Paul