65 replies to this topic

[nicksuth]

Help!!!!

You may have read my previous threads about my MPi and it's constant poor running?

I recently changed the head gasket having identified an oil leak (with the help of John Guess) as coming from the corner of the head. This indeed turned out to be the case (back right hand side corner) and also into No.3 cylinder (from n/s end) which was a bit wet/oily/sooty (although the plugs never really indicated that) I also took the opportunity to change the Lambda sensor having had the car to Icklemini for plugging into his reader and identifying it as a possible problem (readings at tickover jumped about between 1 and 4 mV and on a run dropped an maintained 0mV, we also ran it disconnected which seemed to make the engine run better?).
Well after all this along with new plugs and leads (new set of iridium BKR7EIX's and today BPR6E's), new Air Temperature sensor and Camshaft sensor it still has the spluttering under steady acceleration!!! When I say "steady", it runs okay if very light and very heavy throttle used but anything in between casues it to hesitate/splutter as if it's getting starved of fuel?
It becomes worse once the engine is up to running temperature but ticks over no problem at around 850/900 rpm, saying that when ever you rev the engine it drops to around 1500 for about 2 or 3 seconds before it returns to normal 850/900.
Within the last 1500 miles (most of which was before I had it) it's had a new coil pack, wiring from ECU to coil pack, ECU removed and checked over, direct feed from battery through extra relay fitted to fuel pump (due to low volts identified [11.2v]) and injectors cleaned and new o rings.

Looking at a previous service (Dyno-Tune) report sypmtom is as follows..............."As engine warmns up, fueling leans off until hesitation occurs at all engine speeds, emmission measurements variable" The previous owner then spent over £850 on having it fixed from which the only change that improved things was the fuel pump direct feed through relay!!!

I am fast running out of money to replace anything else........HEEEELLLLLPPPP

PS - Southam Mini & Metro Centre had a quick look at it on their diagnostics machine and thought it was a fuel/air problem and to check for leaks - been all over it to no avail. They also suggested fitting a variable fuel regulator thinking it may be fuel pressure related? (is it 2 bar they run at?)

PPS - It has a Race Icon Chip fitted but have tried it with this linked out (thanks to Icklemini) and it made no difference at all?

Edited by nicksuth, 22 November 2008 - 11:14 PM.

[KLAS]

what about the manifold pressure sensor? sometimes they give wrong data resulting in strange behavior. maybe you can borrow one from a known good running engine for testing

[Purple Tom]

I'm not an MPi expert by any stretch, but I've done quite a bit of work on other cars with EFi. Does the MPi have a throttle position sensor? I'm sure it does, and if so it sounds like it could be something to do with that being faulty?

[_dougie_]

...also always a good hint in case of rought running MPI (and no other reason can be found):

The Rover Bulletin re. MPI Engine Loom Failiure

You will find the mentioned Ground Point in the Engine Loom, left of the Intake Manifold (if you stand in front of the Engine).
A bunch of 5 thin pink cables with a black stripe are connected together and covered by some isolating tape.

Those cables are sensor ground. They're providing ground for water temp sensor, intake air temp sensor, lambda sensor, throttle position senor and manifold absolute pressure (MAP) sensor. If this becomes faulty, you see a number of weird effects, but all of them related to those sensors.

BR
Ralf

Edited by _dougie_, 23 November 2008 - 10:05 AM.

[nicksuth]

Sod It, bought a MAP sensor as they have come down in price (Minispares) from £153.73 to 64.63.

http://www.minispare...earch.aspx?au=1

Still thinking about the Throttle Potentiometr at £105.59????

PS - if it was a sensor earth fault, would it not run rough all the time (tickover, medium revs and high revs)?

[nicksuth]

Now bought the Throttle Potentiometer as I found 2 new ones for sale on eBay and bought both for £25.00 total (posted), now that is a bargain!!!

http://cgi.ebay.co.u...em=190267352352

[iansmini]

If this doesn't help your problem I would be looking into the coil pack, to see if this is your problem.

[nicksuth]

If this doesn't help your problem I would be looking into the coil pack, to see if this is your problem.

Coil Pack has already been replaced (there's not going to be a lot left that hasn't been replaced!!!)

Thinks???? I wish I'd bought my son a Corsa now (no, not really)

[Southy]

If the Throttle Potentiometer doesnt solve your problem then a new throttle body could well done it, as we had a very similar problem with my mates Mpi, and we were suggested to change over the throttle body as with the standard throttle body being plastic over the years it becomes worn and when the pedal is slightly pressed it lets far to much air in. We swapped it for one off a Rover 200 and it was ok for a while but this was also worn (mate had to save up money) and we have now replaced it for the uprated 54mm throttle body which is metal so wear shouldnt be a problem.

[iansmini]

If this doesn't help your problem I would be looking into the coil pack, to see if this is your problem.

Coil Pack has already been replaced (there's not going to be a lot left that hasn't been replaced!!!)

Thinks???? I wish I'd bought my son a Corsa now (no, not really)

I do apologise didn't notice it in your first post.

Yes there won't be much more left to replace, like idle air control valve and inlet air temp sensor.

[nicksuth]

Throttle Body is Alloy Type and IAT sensor has been changed. Not changed the IACV as no problem with idling (or have I missed the point?).

It's all pointing tyoward the fuel regulator I think? Might take Southam Mini & Metro Centre's advice and replace the standard unit with an adjustable regulator?

PS - just checked fuel consumption which is 33mpg, this having driven it with a lot of booting the throttle to get a reasonable acceleration and running response. What should you expect from a mildly tuned MPi (Icon chip, mild cam [assumed not confirmed yet], K&N, 5 speed Tran-X, 1.5 Roller Rockers)?

[wombat_mini]

Hi Nick

I've also got the problem of when I rev the engine and take my foot off the gas, the revs stick at about 1,500 for 2-3 secs before returning to idle.

It did this the other week when the revs stuck at whatever you were at so when you took your foot off the gas it took a while for the revs to drop. ie a totally sticky throttle cable. However, my cable isn't kinked or anything and after a bit of WD40 on the throttle body cable join it now reverts to the sticking at 1500, so I've deduced this rules out a sticky throttle cable.

The only thing I've done is remove the air filter case as well as remove the crank case breather (to try and replace the upper engine stabiliser).

I'm not sure If i've destroyed the crank case breather gasket, which I'll replace this afternoon, other than that I'm gonna have a look at the throttle body (I've got the standard (plastic I'm guessing) throttle body) if this is the problem.

If you solve the problem, let me know how!

Ta

[nicksuth]

Just photo'd my plugs that came out yesterday (nearly new Iridium BKR7EIX's), they look about the right colour to me with no evidence of lean/rich or sooty/oil deposits - anyone care to comment?

[attachment=75349:DSC00313.JPG]

[Southy]

All them plugs look the right colour to me,as you say no signs of it running rich/lean or burning any oil.

[nicksuth]

You just know it's going to be something dead simple in the end - after all this expense and discussion???