THE ROVER SD1 FORUM

Mattv8 · SD1 User Joined: 20 Sep 2007 Posts: 28

Im having Issues with my car over fueling. It will not Idel just cut out and race to 4500 rpm when the throttle is touched.

With the ignition on and the engine off I can slowly open the throttle and hear the injectors fire ( sometime 2 or 3 times before full throttle) but if I open the throttle fast I get no clicks..

Is this correct??

Chris P · Posted: Tue Oct 09, 2007 11:02 am Post subject:

No, that's not correct. Opening the throttle slowly, you should not hear the injectors
fire. A fast open, you should hear them fire - this is the acceleration enrichment part
of the ECU working. Of course it depends what you mean by 'slowly' Smile

Sounds like you have a noisy throttle pot, this is covered in Ramon's guides. As others
have said, you can run the car without the pot, but will get poor performance under
heavy throttle.

New throttle pots are made from pure unobtainium. However, there are some alternatives.
One recent posting (I think it was on the SD1 Club forum) was looking into obtaining
Jaguar parts to use a later Lucas pot - I don't know what came of this unfortunately.

tommosredone · Posted: Tue Oct 09, 2007 12:56 pm Post subject:

Hi Matt, you can use a standard RS part (see Ramon's definitive guide), and make an adaptor plate to fit the plenum chamber. I've done it, but i'm not totally happy with the plate or the pot. When I get some time, i'll have another plate made with some variations, and try again.
Any solution will be a compromise, but to reiterate what Chris says, you can drive fine without a pot connected,it just feels lumpy and a bit 'flat'.
I don''t think it would cause such a drastic condition as you still have.
Cheers

_________________
I wish I could make my own petrol.

Mattv8 · SD1 User Joined: 20 Sep 2007 Posts: 28

Can you please tell me what you mean by "Niosy"

And should my car run if I disconnect the TP

Lehto · Posted: Tue Oct 09, 2007 6:15 pm Post subject:

Noisy must mean theres a lot of eletrical interference so the signal is disturbed for some reason or another.

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Owner of 3 Rovers and 1 MG.

Chris P · Posted: Tue Oct 09, 2007 7:53 pm Post subject:

Lehto wrote:

Noisy must mean theres a lot of eletrical interference so the signal is disturbed for some reason or another.

It's caused by a worn track inside the pot, so rather than giving a clean
sweep of voltage it makes and breaks circuit as it's swept. A worn (or
cheap) stereo volume control would do the same thing, you'd get noise
as you control the volume.

Noise from the throttle pot would trick the ECU into thinking enrichment
is required - as the ECU uses rate of change of voltage (dV/dt) from the
pot to enrich the mixture for acceleration.

Lehto · Posted: Tue Oct 09, 2007 8:03 pm Post subject:

Yea I kind of imagined it like that inside my head.

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Owner of 3 Rovers and 1 MG.

Mattv8 · SD1 User Joined: 20 Sep 2007 Posts: 28

And should the car still run if the TP is disconnected from the wireing loom at its plug?

Also how can I test if I have a leaking injector?

Chris P · Posted: Tue Oct 09, 2007 10:34 pm Post subject:

Mattv8 wrote:

And should the car still run if the TP is disconnected from the wireing loom at its plug?

I believe the engine will start and run withouth the throttle pot connected.
The car may stutter or stall (?) under heavy throttle usage as there will
be no enrichment, but I can't see why it wouldn't run.

ramon alban · Posted: Tue Oct 09, 2007 10:37 pm Post subject:

Mattv8 wrote:

And should the car still run if the TP is disconnected from the wireing loom at its plug?

Also how can I test if I have a leaking injector?

Matt, this is probably a bit contrary, but none of my three decent Efi's ever ran at all well with the Throt Pot disconnected and one car refused to run at all. Now that could be because there were other problems going on, but I never cracked it until I repaired the fault.

I'm not surprised because the input to the ECU that expects a set-up reading of 330 millivolts is, in fact, floating, so the ECU cannot know the state of the throttle plate (electronically speaking). Then when one tries to accelerate there is no enrichment signal, the car runs weak and if its cold it will most likely stall.

If you can get it to run at all I would only use it as a "get U home" because the longer you run and the faster you go, richer mixtures are generally required, but with no enrichment and running weak at high speed would cause overheating and burn out exhaust valves. Woe, Woe, and Thrice Woe!

I'd be interested to know just how many owners can get their cars to run with the TP disconnected.

A leaking injector will cause fuel pressure to fall quickly when the engine is switched off, see page 5 of the PDF here:

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If you detect a problem with that test, then for a full injector test program:

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Ramon

Mattv8 · SD1 User Joined: 20 Sep 2007 Posts: 28

I think I have exhausted all the tests in the PDF, which has been very helpfull, but unfortunately I can not find any faults Except for the fuel pressure dropping imidiatly by 4psi when the fuel was tested with ignision on but engine off. This could bu due to the fuel pump return valve or the pressure regulator or a dodge fuel pressure guage.

I am at a loss and do not know which way to turn.

What should I do next. I dont really want to give a blank cheque to a V8 specialist but will I have to and it so Which one? Confused

ramon alban · Posted: Wed Oct 10, 2007 12:51 pm Post subject:

Mattv8 wrote:

I think I have exhausted all the tests in the PDF, which has been very helpfull, but unfortunately I can not find any faults

Matt, you told us that the throttle pot does not behave as recommended. What happened when you replaced or mended it? Does the throt pot test now come out OK?

What did you decide after you were advised by Chris that is was Faulty?

Except for the fuel pressure dropping imidiatly by 4psi when the fuel was tested with ignision on but engine off. This could bu due to the fuel pump return valve or the pressure regulator or a dodge fuel pressure guage.

The possibility of pressure regulator or return valve faults etc was diagnosed on another thread. Are the symptoms still there?

I am at a loss and do not know which way to turn. What should I do next.

We share your frustration and even non-rookies get stuck for ages on these systems. All you can do is keep testing and when the result is NOT as specified, replace or adjust as appropriate.

I dont really want to give a blank cheque to a V8 specialist but will I have to and it so Which one?

And nor should you! If this is really getting beyond you, the big problem is that even V8 specialists may not be Rover Efi savvy so my advice would be to trawl thro your yellow pages for small garages, engine tuners or auto electricians and go talk to a couple of them to see if they have any experience on your system before you commit to let them have a go.

Another possibility is to spend a modest amount on a set of spare Efi component from Ebay or forum members so you have some components to swap over.

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Ramon

tommosredone · Posted: Thu Oct 11, 2007 12:08 am Post subject:

Matt, mine runs almost as well with the pot disconnected.
You can tell it's not right, but I could quiet happily drive it around without it.
It starts, and drive well enough in traffic, it just hasn't the 'umph' that it usually has.
Hope you get it sorted.

_________________
I wish I could make my own petrol.

Mattv8 · SD1 User Joined: 20 Sep 2007 Posts: 28

Ok thanks All.

I have tryed disconecting the TP from the loom and tryed leaving it conected but detatched from the throttle spindle and set at the correct voltage but neither way made any difference to the running of the engine.

The engine still starts first time races to 5000rpm 'ish' the drops and cuts out.

Some thing I did notice that is different this time is..... The injectors were only fireing when the TP was de-celerated and not excelerated. This is a new problem not one I have missed but new.

Also could the engine not be getting enough air as apposed to too much fuel??

Does the over run valve on the plenum chamber let air in or out??

tommosredone · Posted: Mon Oct 15, 2007 9:20 pm Post subject:

Hi Matt,
Are you saying that you start the car, and with no throttle pedal movement, the engine races up to 5000 rpm on it's own?
That would indicate to me throttle cable/spindle/disc problems...
If you are not touching the throttle, there could be no way the engine could get enough air to reach 5000rpm on it's own.
Lets have some more info on this!
Good luck!

_________________
I wish I could make my own petrol.