10 replies to this topic

[se7enmvu]

Can anyone help me with a problem i'm having with my mpi.

I started it for the first time after 18 months a couple of weeks ago and when it was running the hotter it got the higher the idle speed increased. I was also getting intermittent boiling water in the expansion tank.

So at the weekend I replaced head and manifold gaskets, thermostat and expansion cap. When I had the head off I noticed the lambada sensor was damaged so that was replaced.

I also cleaned the air flow sensor.

Now when I start it, it idles at around 1200 and as it warms up drops down to 900rpm.

But after 10 minutes or so the idle speed starts increasing to 4000rpm.

If i try and restart when hot it idles at 4000rpm but if I wait til its cold its fine until it gets hot again.

Anyone any ideas? Was hoping to get it mot'd before month end but im running out of ideas.

[Fast Ivan]

Most high idles are associated with an air leak of some kind. Check in and around the inlet manifold, includin the throttle body area. Check the hoses, there's one that goes from the idle air control valve to the throttle body. Also remove the idle air control valve and clean it

[minidaves]

Air leak something aint pluged in or a faulty sensor

[orcadian]

When you first start from cold it idles at 1200 then slowly drops to 900, which is normal and what yours used to do before the lay up, is that right? At that point the idle air control valve must have been put in that good position by the ecu. Have you tried disconnecting the IACV at that point which should leave it in that position. I can't say I've ever done this so the ecu might have a hissy fit with no connection but I doubt it as that bit is open loop with only connections to the stepper coils.
This might get you an MOT if it behaves, then you can sort it later. If it works Ok then something is telling the IACV to open further later on to give you the very high idle. Can't think what though unless maf or temp. Crank or cam shouldn't give your symptoms. If there was an air leak then surely the revs should always be high.
Ian

[Fast Ivan]

Some parts, such as the throttle body and hoses deform when hot, which can cause a high idle, so not always high as you suggest

[jamesquintin]

I had a similar problem years ago, it was caused by the temp sender. I replaced that and the cable with this special rover cable made specifically for this problem:

 

http://www.minispare.../YMQ105690.aspx

 

 

Q

[se7enmvu]

Thanks for your replies everyone.

I'll try unplugging the stepper tomorrow and see if it behaves.

Yesterday I swapped the stepper, and throttle body from my other mpi that's been off the road since 2010 and it's made no difference.

If I unplug the coolant temp sensor the fan comes on so that's OK? So could it be the other temp sensor on the manifold?

I might just buy a new stepper although why would it be opening once the engine is up to temp?

[Fast Ivan]

By unplugging the temp sensor you are confirming that the sensor, loom and ecu are working for that part of the system, yes.
The sender in the manifold is the inlet air sensor, could it be this? Maybe, same as it could be the a number of things.
If you've ruled out an air leak then the next step would be to plug it in to a code reader and start looking at the data stream to check if the sensors are operating within spec.
Do you have access to a code reader?

[se7enmvu]

Again thanks for the replies.

I'll try swapping the other temp sensor tomorrow.

Regarding air leaks, theres the two hoses from the throttle body which are fine and then the manifold gasket and throttle body o ring which are ok. The push fitting for the servo and pipe are also good.

Is there anywhere I'm missing?

I don't have a code reader so i'll have to get it to a garage.

[se7enmvu]

I think the problem may have been the accelerator cable being to tight. As since I backed it off a bit it's been OK.
And it passed it's mot first time on Friday so just a few finishing touches left to do.

[tugman]

I had the same problem in my 1999 mpi and it turned out to be the lamda sensor