Hello, greetings and MPI Idle intermitant/loss of power problem!
Turbo Mini Forums

Hello, nev_payne (same one from TMF) seeking help. I'm "that stupidly tall guy with the Knightsbridge". Over the last 4 years it's undergone a nut and bolt restoration, and as of mid-December is now back on the road. Not without teething problems, but that's breaking in for you.

While the Knighty hasn't even hit 200 miles, I've become increasingly aware of a lack of engine power in the idle and 2000-2500rpm range. While the idler gear / clutch release bearing is rattling and this/these will be replaced in the Spring, I'm sure is related to electrimagicals/sensors. To keep things clean:

- Idle is very throaty, needle sitting at 900rpm but sounds like there's a lumpy cam especially when cold, persists when the engine is warm. Feel like I have to keep constant attention on the revs in case they drop. With the clutch pedal depressed, while the idler gear does shut up, the revs continue to sound like there's a race cam in there (the cam wasn't replaced, original as far as I'm aware).

- Especially notable in 2nd and 4th gear (driving through town, cruising on the main road at 40-45MPH respectfully).

- In the RPM range it feels like the battery (brand new, pulling 14v from alternator) is running flat or possibly a lack of fuel.

- Above the range is perfect and more than happy to accelerate on with no hesitation.

Suggestions welcome and thanks in advance, more than happy to post a video if that would help :)

Regards,
Nev_Payne

Hello and welcome

Anyone got an idea?

Welcome to TM.

Not knowledgable about MPIs at all, but I have heard incorrect working coolant sensor can do weird things to engine controlls.

Dazed and Confused....

Hi,
Is the engine standard? or are you running anything non standard?
Could be a number of things from knackered plugs or lambda to poor fueling from messing with the exhaust or filter.

The engine specs:

Re-honed and completely rebuilt 1275 MPI
Standard filter box with K&N insert filter.
Burlen 48mm replacement t-body
Standard rockers
Standard cam and crank
Standard head
Metro Turbo 3.2 FD gearbox with 'Spares X-pin diff, Central pickup - stripped and rebuilt.

Engine is into 200-miles breaking in. Plugs, Lamda, were all brand new when fitted.

Video for some clarity:

http://www.youtube.com/watch?v=vnIpCiBcLF0

Edited by nev_payne on 31st Jan, 2012.

I guess this is also on the standard ECU then?

Have you checked/cleaned out the Idle air control valve, its not uncommon for them to become 'gummed' up which can cause them to stick and/or slow i there response. It can be whipped off the inlet manifold by the 2 torx which secure it and then stripped and cleaned...certainly worth a try as its a relativley quick and easy job to do.

Do you have any diagnostic equipment?

Did you re fill the tank with fresh fuel?

Sensor wise the MPI's have the same (fitting) plugs for several senors. Some that will fit with in reach of the wrong sensor. From memory they are down the front of the engine on the clutch side. Could some thing be connected up wrong?

Sticky air valve as already commented or could be fuel pressure issue

Edited by shellspeed on 31st Jan, 2012.

Yup all standard on the electro-magicals.

I haven't checked the IACV, will deffinately have a look over that this evening. What would you recommend for cleaning, brake cleaner and kitchen towel kinda thing?

No diagnostic equipment but a good handful of sub-30 mile away Rover garages.

Edited by nev_payne on 31st Jan, 2012.

Yes just a bit of brake cleaner or petrol and a rag.

Let us know how you get on, and il have a think about this as well. Fuel pressure as above could be an issue or even timing but I doubt it. Is it down on power or does it drive ok?

Cheers
Andy

Sorry just re read the post and im starting to lean toward the idea that this is an air leak on the inlet manifold gasket. even a tiny oner on the MPI plays buggery with the whole thing.

have you checked the plugs? Are the normal colouring
Thanks
Andy

usualy stuff like this points to an air leak on the intake manifold but with the mods on the inlet side i would guess the bigger tb and the k&n are the reason to it being lean, have you got a wideband or access to something to measure its fueling?
it really is THE most valuable tool i have ever bought

Yes i moved to the darkside

Instagram @jdm_brett

You need to get that on a diagnostic and look at the stepper motor function when it is doing this.

Without live data to look at you'll be chacing your own heels.

As orhers have said, an air leak. This will cause the stepper motor to close off at idle, and if it is severe enough the ignition advance will retard to bring the idle speed down. so, idling with the stepper full closed and a retarded ignition advance will give a ropey idle, and likey the stumble too.

I had a similar problem twice, when setting up the programable ECU. exactly the same symptom, but a slightly different issue. On over run, the ECU shut the stepper all the way and when you dipped the clutch, it stalled the engine. There was no air! This was a firmware bug. The second time was down to poor mapping of the bottom line low RPm transition from overrun fuel cut to idle

On 15th Dec, 2010 Mini_the_minx said:

Burlen 48mm replacement t-body

replace the old one and get back to us

The Burlen throttle body is a dirrect replacement alloy body for the standard plastic Rover one. It shouldn't cause any issues, unless it leaks

Indeed 48mm is standard, but they do do a 52mm as well.

Wow, thanks for all the replies :) The IACV was loaded with carbon for starters. After a clean and a check of the breather hose:

http://www.youtube.com/watch?v=82drtiEP4Ls Much smoother, and a cold start idle is now ~1050-1100rpm by the tacho' (900rpm and struggling beforehand).

Yes, to clarify I've got the direct replacement 48mm - the old throttle body lost most of it's sprung return and had warped badly from heat exposure. @Brett - could you clarify for me on that one - Wideband fuel measuring?

I'll have a check for leaks tomorrow.

Edited by nev_payne on 1st Feb, 2012.

Great stuff, glad your making progress!

nev have a look here http://www.ebay.co.uk/sch/i.html?_nkw=aem+...6.c0.m270.l1313