m30 gurus needed.!

[mcbonio]

Need some help from you m30 brains, Ok so I've got my m30 project car, pleased with it but it has running issues.

When cold it starts up fine then idle seeks for a second but stabilizes, but when you touch the throttle the thing chokes up horribly, to the point it sometimes misses a beat for a second then continues to run. It also sounds like a harley davidson at low revs all choked up and stuttering, really not running well.!

Once its warmed up its a little better, but still horrible and difficult to drive, practically stalling the thing as I take off.

Any ideas what I can begin to check?

[mcbonio]

Been reading the entire m30 thread and have a list of potential suspects...

throttle position sensor
idle control valve
blue temp sensor and wiring
crank sensor wiring
air flow meter

Anyone like to share any thoughts?

[MJJ_ZX6RR]

My M30 suffered the same symptoms.

My donor engine came from a catalyst equipped E32 so had a lambda sensor fitted. Unplugging this worked wonders as the car works happily on a default fuel map.

I also had an air leak in the small elbow pipe that runs from the rocker cover to the inlet tract, just before the MAF IIRC. Replacing that elbow helped.

Martin.

[mcbonio]

Ah good point, I'm not sure which car my M30B35 is from, but I'm pretty sure it doesn't have a lambda sensor fitted. Will double check.

I'm also suspecting low fuel pressure, travelling on the motorway at 70mpg the car was stuttering back like the gas pedal was being blipped. Also it stutters/splutters when you open the throttle hot or cold....

[Bristol_Jer]

70 mpg with an m30!

+1 for checking airleaks, mine was an absolute pig to get running properly. An inlet manifold gasket (replaced the lot), a couple of breather hoses and the big AFM pipe on mine all were causing airleaks amongst other things.

Also my fuel filter was ancient, 10 years old I think, so that wasn't helping matters and would be something to check.

If you are ok with a multimeter then you can check crank position sensor, plug leads, blue temp sensor etc for resistance, I found the values by searching on here but can't remember where I found them sorry.

[mcbonio]

I mean 70mph.! Doh.! Although you should see my fuel gauge it gets further to the full mark as you go..!

[Rav335uk]

Check you rotor arm and plugs first, these are the easy ones.
If it's still out, then the crank sensor, leaks in the rubber hoses etc....

DO NOT TOUCH THE AFM yet, if that's origional factory setup, you want to leave it as is.!

[mcbonio]

I've checked everything, my m30 is still jerking and spluttering about upon throttle opening...

How can I test the M30 AFM?

[Rav335uk]

Have you checked the TPS yet??

[mcbonio]

Yeah TPS is working fine and calibrated.!

I've checked ICV, working fine. Cleaned out all the air intake system. Idle is good.

Still chokes up bad when you touch the throttle, hot or cold.

[zaust]

Sounds like an air leak or faulty cap if all else has been checked.

[sag]

Have you checked the fuel pipes are the right way around?

[mcbonio]

Will check dizzy cap tomorrow, I didn't do this m30 build I purchased it as a running project.

Which 2 fuel lines could get mixed up?

[Rav335uk]

Check under the inlet manifold, you'll see 2 feul pipes there.

[mcbonio]

And during an m30 build these get mixed up? I've suspected fuel delivery as the ride is pretty jerky as if there wasn't a steady supply of fuel. I'll try swapping them around see how it runs.

[mcbonio]

Heres a video of it, you really have to rev it to get it stable enough to clutch out and move.

[Rav335uk]

For a start, get rid of the shi77y K&N filter, all your doing is sucking in hot air that side of the engine.
Get the OEM airbox back on, then try.

[mcbonio]

Yeah it came with that on.! Not a fan of Ken and Norman myself but it still runs like cr@p with the normal airbox on.

[mcbonio]

Ok checked dizzy and rotor arm, plugs and leads. All look pretty new.

Tested AFM too, reads 2.5 - 3.5 ohms from closed to open.

Also double checked for air leaks, all is good.

ICV is working, buzzes when ignition is on, valve is free to move.

Replaced blue temp sensor with known working one.

Only thing I can think now is fuel pressure.? What other reason would it choke up when I open the throttle?

[Rav335uk]

What is the car listed as on the V5?

[mcbonio]

Its not been declared yet, still 325i, its also SORN. Why?

[Rav335uk]

Wondering if it was a 4 pot and not enough fuel coming through via the pump

[mcbonio]

Good call, was a 325i though. Thing is it seems fine at mid to high revs, pulls like a train too.


Where is the best place to test fuel pressure? At the fuel rail?

Oh, would a badly leaking centre exhaust box create these running problems? Loss of back pressure perhaps?

[Rav335uk]

A loss of back pressure wouldn't cause that much of an issue.

Have you have the pot out of the tank???
Maybe some blockage or crap in the bottom of the pot.?

[mcbonio]

Yeah thats my next port of call, have a look at the fuel delivery system. When travelling in 4th or 5th gear at around 50-7mph, I can feel it shuddering back slightly, as if the fuel supply was being interrupted...

Where is the best place to test fuel pressure? At the fuel rail?

[zaust]

No chance of exhaust problem. What year is the engine and what are the last 3 numbers on the ecu ? 179 ? 153 ?

Is the engine earthed correctly? Tps set correctl. There is not much to getting these Lumps running.

[Rav335uk]

Yes.
Have you changed the FPR on the rail??

I had a problem with mine years ago, changed the FPR and it's been ok after that.

[mcbonio]

Good questions guys, its running Zaust just chokes up bad when I open the throttle.

- How can I tell the year of the engine? Where is the serial?

- How can I test the FPR?

[Rav335uk]

The date of manufacture is on the head, can remeber exactly where though, inlet or exhaust side.
It's large enough to see though enclosed in a circle.

[mcbonio]

Ok will have a look, see if it matches up with ECU.

And the FPR, how can I test that?

[mcbonio]

Ok the engine has '89 stamped on it and the ECU has 173 on it. Isn't the 173 from the M20 engine?

[Bristol_Jer]

Yea, I thought the m30 has a 179 ECU?

[Rav335uk]

There's 2, 150 and 179 iirc.

[Bristol_Jer]

Am I right in saying the 173 ecu can be used if the m30 chip from a 179 is fitted? Maybe the wrong ECU could be the cause of the running problems?

[Rav335uk]

I have an M20 ECU running my M30 in the Cab, but it has one of Speedtouch's chip in it, and no running issues.