Rover 100 idle speed - ECU again???

faulty throttle body sensor? sticking throttle body? the only other two things it could be....

I had a 111, 98(R) had that until last year, and the thing was not looked after very well at all, but never had that sort of problem.......

Common problem. They usually start idle at 1500RPM when warm and about 2500RPM when cold. The only thing that seems to cure if tor a short time is a new throttle switch. The other alternative is to have the ECU defaults loaded up but this will only work for a few months. It only happens on the 1.1 as well.

Thanks for the replies. Pretty sure the TB isn't sticking, so will probably have a go at the switch when I get a minute. Is this the thing the Rover Service Manual calls "Throttle Potentiometer"? What kind of money am I looking at for one of those? Looks handy enough to change... Suppose it's not worth bothering with a secondhand part?

Didn't know I could have default values loaded onto the ECU - might be an option to keep the thing drivable until I can fix it/get rid. I take it there isn't a sneaky reset button somewhere? Would it need Testbook or something?

Throttle Potentiometer is the throttle switch. Just out of interest is your 100 a SPI or MPI model.

my bet is on it being an spi

96 was bang on the change from SPI to MPI.

I have come across a company that can programme a 'free running' ecu for £200. They claim this should drop straight in without all the hassle of re-programming key fobs etc the web site is www.tunemycar.com. I haven't tried this but it might be worth looking at.

Adam D

Sejin26 said:

96 was bang on the change from SPI to MPI.

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I know but im guessing purely on the symptoms.

Yup, definitely an SPi. It was registered in January 1996 - I think the 111 GSi was only made for the 95 MY anyway. Didn't appear in brochures from 96 on...

If you change the throttle pot, be aware that it's positioning is critical as it tells the ECU when to start throwing fuel in and when to switch to the idle map.I don't think this will be your problem. Sounds more like a sticking idle valve or ECU problem as you suggest.
Have you checked the inlet manifold joints for air leaks? Spray some WD40 around them with the engine running and listen for the speed to change if it is getting sucked in.

1955diesel it does not matter once he takes the switch of as it will reset to the default position and the new one will only fit in the default position. I have a few things for you to check. You may have to goto a garage to get some done,

Check the mixture settings in the ECU and make sure that all the sensors are working via the ECU,

Is the air filter blocked more so on the SPI model,

Inlet manifold as previously posted could be leaking,

Is the timing belt correctly tensioned,

The HG could also be leaking as this causes increase in revs in the 8V to. To test that get it compression tested. My other suggestion is to disconnect the battery over night and plug it back on and see if the ECU may reset. The other thing you could try is reseting the stepper motor as that can cause them to rev a little high but I don't think the ECU will have had it.

make sure the throttle stop is correctly adjusted. Make sure there is a little slack in the cable. Reset the stepper motor. Check the throttle switch is ok.

The air filter's brand new and I've reset the stepper motor several times to no avail. Will have a go at disconnecting the battery though - I'm going home from Uni tomorrow for a week leaving the car here, so hopefully it'll reset itself in that time.

Will give the inlet manifold a look - hadn't thought of that. Hope it's not the HG... I've recently acquired a compression tester so will be able to do that when I come back next week. Oil and water both look okay though. Fingers crossed!!

Next term might be an expensive one

Sejin26 said:

My other suggestion is to disconnect the battery over night and plug it back on and see if the ECU may reset.

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Just to close this thread off in case someone else with the same problem finds it in future... I disconnected the ECU for a few days at the big plug (left the battery connected, to keep clock working), and lo and behold, the car is now behaving itself again! Must have reverted back to default values or something.

So if anyone else has this problem, it's definitely worth a try as a quick fix before spending big money on expensive bits. No idea how long it'll last, but fingers crossed it'll be okay for a while before realising it's got some sort of problem. I've only driven the car about 20 miles since plugging it back in, but in that time it has behaved impeccably, driving very smoothly

So thanks everyone for the suggestions!

Well if you take it to a dealer they can update the ecu with some new settings.

Sejin26 said:

Well if you take it to a dealer they can update the ecu with some new settings.

Click to expand...

I know they could, but they'd also update my bank balance with a much lower value!:banghead: As a poor student, I'll have to struggle on bodging for the time being...