Thread: Rough idling Disco

If you have already tried cleaning and re-sealing the Idle Air Control valve, maybe try swapping it for a known working one.

LukeV

I'll give it a go this weekend. In the meantime the engine is running better with the new MAF but it still revs up to 1700 rpm at times but settles down to 750MAF eventually. Today it was surging up and down so there's something going on with the IACV or the Throttle position sensor. Any ideas welcome.
Also, is it a big job to change the timing chain on a Series I?

Regards
Viv

You have not replied to the person who suggested that the temperature sensor is crook.
Have you tested it and checked the contacts? It should read 300-400 Ohms across the contacts at 82C+. Ie operating temperature.

Really you should undertake a full injection troubleshoot which is in the manual, to identify the area of problem.
This testing involves backprobing the ECU plug, and will see the voltage input values that the computer sees. Maybe you have a bad connection somewhere between the MAF and ECU, or temp sensor and ECU.
It may seem tedious but to be systematic is really the only way to find these elusive problems.
Have you cleaned the throttle body and oil ventilation ports thoroughly and set the base idle? Are you sure there are no leaks in the hose between the MAF and throttle body? Have you checked the earths for the injectors at the rear of the LH head?( This may be the wild card)
Regards Philip A

Thanks for the reply. I have limited access to tools, and workshops that really know what they are looking for so have to make do here in the Middle East.
I am not sure what you mean by back probing? I am guessing using a meter on the ECU plug contacts? and where would I check the results against, is it in the manual?
I will try the easier tasks first, i.e. cleaning and checking for leaks then have a go at the output task. Tedious but passes the time!

Regards
Viv

I'll have a look at the Temp sensor and get back to you. I have to find a decent meter which easier said than done here as there's all this junk counterfeit gear from China here so hard to find a meter that will give a true reading!

Originally Posted by procrastination inc

any chance you've got a faulty temp sensor and it isn't coming of cold start enrichment?

Is this the Fuel Temp sensor or the Coolant tempe sensor? that I should be checking.

thanks

Viv

Originally Posted by vrdw

Also, is it a big job to change the timing chain on a Series I?

Regards
Viv

No hard to do but time consuming, I've done it 2 times.
You need to disconnect the oil cooler hoses from the timing case. remove Visco fan, water pump the front 2 sump nuts. ( I used another sump nut to lock the existing nut to allow me to remove the front sump studs..... you'll see why, as it'll allow you to slide the timing case cover forward instead of trying to lift it off the studs when you try to move it forward)
You need to remove the harmonic balancer, this can be a pain if your puller doesn't have long enough puller bolts.I used a std 3 armed puller kit and went to a bolt place and bought 3 longer hardened bolts to suit, did it easy. to undo the harmonic balance pulley bolt you do need to stop engine rotating.
I diff locked the disco put her in low range and chocked the wheels and managed to crack it easy, or you can jam a socket on it and crank the engine a revolution to loosen it. disconnect the coil 1st though.
If you are replacing the timing chain with something like a roll master or similar , you get a new chain, cam gear and crankshaft gear in the kit, you might have to grind off the lug on the inside of your timing cover at the dizzy entrance, the chain will rub here if not done. Also I had to machine a groove on the oil pump cover plate to allow clearance as it rubs there also. These chains are wider than the OEM ones.
PS. (I think from Memory the power steering pump bracket might have to be removed also. check)

I am not sure what you mean by back probing? I am guessing using a meter on the ECU plug contacts? and where would I check the results against, is it in the manual?
I will try the easier tasks first, i.e. cleaning and checking for leaks then have a go at the output task. Tedious but passes the time!

Yes, back probing is to stick the terminal of the multimeter in the back of the ECU plug, after you pull the cover off. It is held together by 2 screws which are under the gasket.

The full procedure is in the manual. I have a PDF copy of the injection section for a Range Rover Classic which I could attach to an email . Can your ISP account accept 6 megs? The zip file is long gone.
If you want this PM me with your email address.

Regards Philip A