M42 still overfuelling

[Touring Whore]

What reasons could there be for my M42 to overfuel? (blue temp sensor is fine)

[magpie]

your over fuelling symptoms are exactly?

[Touring Whore]

Stinks of petrol and uses too much of it. Definately not a leak.

Maybe running rich is a better description (I thought it was pretty much the same as overfuelling).

Temp is fine, temp sensor is fine, I reckon the AFM is fine as it runs well (no hesitating/stalling/flat spots when driving), all fuel lines are fine.

I've got some M42 injectors coming (they're not the same PN as listed on realOEM but I think they'll do the job), but if they don't sort it I don't know where to go with it.

[magpie]

split breathers will not help mpg.have you taken a couple of plugs out and had a look?

also the rubber pipes that go to the inlet manni perish on the seal.very hard to see without having a closer look.

removing and replacing every thing from the inlet fanny-mould isn't costly and worth while.

[Touring Whore]

I've done half of the rubbers, and the others looked ok(ish), but I'll put them on the list. I'll have a look at the plugs tomorrow (I checked after 100 miles or so and they seemed a little sooty).

I'll order the rubbers and such, and do a complete overhaul when the injectors come - I'm finding it a bit of a nightmare getting the manifold on and off (there's two pipes attatched to the throttle body that are a nighmare to get back on) so if I have to do it I want to get as much done as possible. The only thing that makes me think the rubbers aren't the problem is that they'd make it run lean if perished?

The other thing I've been thinking about is the fuel pressure regulator. Could this cause the overfuelling?

[mrLEE30]

your blue temp sensor may well work at the sensor, but does the signal get to the ECU.

you should check the resistance at the ECU plug not at the sendor unit itself, sorry to say i do not haqve info on what pins you must check for a 4 pot

[Touring Whore]

Many thanks for that will, it's given me a few things to check

MrLee - I've checked at the ECU and it's good there too, so I've ruled it out, cheers though

I gave it a quick look over today, after 1000 miles. The good news is the oil is still clean and at the right level, no coolant loss.

This is the spark plug (from 2, but one was the same, I didn't check 3&4). Rather sooty at the top, am I right in thinking that this is a sure sign of running rich, or is it fairly normal?





And my list of things to do is suck on FPR, gob full of fuel = U/S
Remove fuel rail and injectors, run fuel pump, check for leakage at fuel rail/injectors.
Test fire injectors and check spray pattern.
Fit new injectors anyway (they've been overhauled so will be better than what's on anyway).

One more question, is there a knack to getting the inlet manifold on and off - there's two pipes underneath (one to heater plate, one vacuum I think) and they're a bitch to get back on. Am I doing it wrong or is that the norm?

Many thanks,

Guy

[TheDutch]

One more question, is there a knack to getting the inlet manifold on and off - there's two pipes underneath (one to heater plate, one vacuum I think) and they're a bitch to get back on. Am I doing it wrong or is that the norm?

The vacuum one is necessary, however you can simply not bother refitting the throttle body heater plates and tidy up the hoses. It's not an uncommon modification and declutters the intake a bit. See the following link for details: http://www.m42club.com/forums/showthread.php?t=2742

[Touring Whore]

Thanks for the replies. I'll do the heater plate at a later date, unless I can be arsed to get a new TB gasket.

Apologies for the out of focus pics, but it's a sooty black, so overfuelling is confirmed at least

[Touring Whore]

Right, time for an update...

I've changed the AFM, changed the injectors for clean ones, sucked on the FPR (not to completion though - so that must be OK) and I even checked the ECU to make sure it was the correct chip and not aftermarket. Then I took the spark plug out of #1 (which looked like the plug pictured above i.e. sooty), cleaned all of the soot off, refitted and drove for ~ 100 miles.

The resulting plug...



So it's still running rich (or would you expect the plug to be like that after 100 miles?). I have to admit there were a few sub 3 mile journeys in that, but even after the long runs it smells like it's running rich.

So the things done so far are...

AFM replaced.
FPR checked (and OK)
Temp sensor checked (at ECU - OK)
Thermostat changed.
Injectors swapped (for a clean set).
No leaks detected.
Most rubbers OK (though vac leaks would cause lean running so not suspecting that yet).

What else is there to do?

[Touring Whore]

Anyone? Is that plug OK or showing signs of overfuelling?

[HJG-E30]

looks like it's running lean and getting hot to me !!

[JWaller360]

What sort of miles are you getting to a tankful? Motorway driving/Town/mixed?

[Touring Whore]

What sort of miles are you getting to a tankful? Motorway driving/Town/mixed?

Working it out reserve light to reserve light, I get around 28mpg regardless of how I drive, most journeys ~8 miles, steady 50mph stuff (I thought I would be able to achieve mid 30's comfortably with sensible driving). I'm more basing my overfuelling theory on the smell of unburnt fuel and the state of the plugs, however...

looks like it's running lean and getting hot to me !!

Really? Black sooty deposits?

[JWaller360]

Mine smells of fuel, I reckon I probably get about 28mpg, this doesn't really help but I wonder if mine is overfuelling too!

[HJG-E30]

I was going more by the tips of the electrode...look pretty white to me. Didn't pick up on the sooty deposits.

Should get an emissions check to see the level of hydrocarbons

[alync205]

Your oxygen sensor is something else that could be faulty. Not easy to test though.

Most don't have an oxygen sensor,I have not seen one with an oxygen sensor yet.

[HairyScreech]

plug looks beautiful to me, id say give that another couple of hundred miles and it will have a dusty light brown powder on it.

perhaps your petrol smell is more down to incorrect enrichment on acceleration or idle, have you got an ebay wonder chip on it?

although dont take just one plug as an indication, take all of them out as you may have a weeping injector or another issue.

also you may be over fueling but the plug is staying hot enough to burn the carbon away as normal.

gas analyser is the way foreward.