E30 M52 running idling issues - video - please help

Post Sun Sep 25, 2011 11:45 pm

Just got my conversion going but it runs like a pig. Idling is slow and lumpy and it doesn't 'clear it's throat' until revving harder. Also sounds like it's backfiring through the air intake.
I've taken a video to aid diagnosis - any ideas please? I want to drive the thing!

[youtube][/youtube]

Post Mon Sep 26, 2011 10:51 am

Check all the grounds, try running another ground to the ECU separately. Also check there's no intake leaks before the MAF. Does it improve at all when it's hot?

Post Mon Sep 26, 2011 3:56 pm

I feared it could be something electrical - my absolute weak point on cars.
I have no idea how to run another ground to the ECU - it's electronics and I don't want to fry them!
It gets no better when warm/hot. It idles so badly I don't really get the chance without continually restarting it!
Any other ideas?

Post Mon Sep 26, 2011 4:05 pm

I would say you have a big air leak.

(I have not been able to view your video as i can't do this at work)

So I would be checking all vacum hoses under the inlet manifold are not split and are all connected well with jubilee clips.

have a look in here for info about how everything is connected up.

http://www.e30zone.net/modules.php?name ... c&t=181824

Another thing to double check is that you actually have a 2.5 inlet manifold. Some sneaky types have been selling M50 2.0 inlet manifolds and the upshot is that the inlet ports on the side of the head are bigger than the inlet tracts/ rubber gaskets on the manifold.

Dezzy had this problem and his car was coughing and backfiring out the MAF sensor/ inlet when starting it, it would not tick over and would only behave with a boot full of throttle.

Post Mon Sep 26, 2011 4:45 pm

Lambdas connected the correct way around?

Post Mon Sep 26, 2011 5:36 pm

^^^^^^^^^^
Thanks for the info E30BeemerLad - will check it out.

The engine ran very well in the donor (was in a E30 before mine) with the 2.5 inlet manifold, so should all be fine. It's quite possible that something has become disconnected or split during the installation. I'll give it a thorough going over at the weekend. I may need to take the inlet off anyway as I don't know if this engine has the brown M20 temperature sensor. I don't get a reading on the gauge - the needle moves slightly when the ignition is switched on, but then stays put. With all the pipe work and throttle body etc. in the way it's impossible to see what's connected to the block.

Post Mon Sep 26, 2011 7:17 pm

dani_d wrote:I feared it could be something electrical - my absolute weak point on cars.
I have no idea how to run another ground to the ECU - it's electronics and I don't want to fry them!
It gets no better when warm/hot. It idles so badly I don't really get the chance without continually restarting it!
Any other ideas?

Make sure the big earth lead is connected from somewhere on the block or head to the chassis. An extra earth to the ECU would just be a bit of wire from the chassis to the ECU box, on mine I've just backed one of the four star screws off a touch and trapped it there. The brown sensor not working would tie in with no earth to the block. Assuming it's plugged in lol... that's the problem in this situation nothing's taken for granted!

Post Mon Sep 26, 2011 8:57 pm

Earth strap for the engine should go from the driver side engine mount arm to the side of the front chassis rail. You could put another one on the other side, but not absolutely necessary.

As EKO said, the lambda sensors need to be plugged in the right way around. The sensor for the rear exhaust branch connects to the front plug on top of the fuel rail area and the front branch sensor plugs to the connector nearest the rear on top of the fuel rail.

Can you post a pic of the wiring going to your battery terminals and the driver side front strut top housing area?

Post Mon Sep 26, 2011 10:48 pm

Thanks all. I may not get a chance to look at this before the weekend. Will report back & post pictures as soon as I can.

Again, many thanks for the prompt responses and ideas of what it may be. Fingers crossed it's straight forward!

Post Sun Oct 02, 2011 8:16 pm

I managed to find a couple of hours this afternoon to try to sort the running problems.

First thing was to check the earth lead from the engine mount to chassis - all good. I made another one for the other side - made absolutely no difference.

Decided to check all the hoses systematically and also wanted to get to the bottom of having no temperature signal. As I started to remove the M50 inlet manifold I found that the air temp sensor plug had come adrift - could this be the issue? I was too far into disassembly to plug it straight back in & check.

I discovered that the M20 temp sensor is not installed. My cylinder head only has 2 outlets as opposed to the 3 I've seen on others, so I have disconnected the throttle body water heater hose and will have my M20 temperature sensor tuned down to fit. What I don't know is how to fit it - WOULD SOMEBODY PLEASE ADVISE - I assume I need to cut the plug & a length of wiring off my old M20? Clear instructions would be great as I have no idea about electrics

Once I've done all this I can connect everything back up and check it all fits well.
One more question - can anyone identify the plug/sensor shown in the pic below? It's been connected to the loom with the lovely connector you can see in the pic. I can't work out where it goes or if I need it:

Finally I need a M50 MAF boot - does anyone have one on here? Mine only has the 1 exit and I need the correct one with 2.

Thanks all.

Post Sun Oct 02, 2011 8:36 pm

E30BeemerLad wrote:I would say you have a big air leak.

This^^

260MAF wrote:

Finally I need a M50 MAF boot - does anyone have one on here? Mine only has the 1 exit and I need the correct one with 2.

Thanks all.

That goes into the inlet manifold, on the underside, it's the air temp sensor, and if it's not plugged in..
well...
there's just a hole sucking in air.....

Post Sun Oct 02, 2011 8:50 pm

^^^^^^^^^^^^^^
Thanks - strange thing is that there is already an air temp sensor on the inlet manifold, although the plug had become disconnected. There was no hole in the manifold, but also no reading from the sensor - could this have caused the running issues?
This 'secondary' sensor is connected to the loom, although it disappears somewhere into depths I can't follow. Why would there be 2???

EDIT - thinking about this - are you sure that's an air temp sensor for the manifold? The one that's fitted already to the manifold screws in - this looks like a push fit.

Post Mon Oct 03, 2011 10:31 pm

Anyone?

Post Wed Oct 05, 2011 10:30 am

Suspect that would have gone into the airbox if you had one?

Post Wed Oct 05, 2011 11:02 am

#13 on there is the air temp sensor, it's underneath where the line guides it in. Not sure what that sensor you have there is exactly, if you can get a pic of the plug shape I could have a look to see which it matches on mine.

Just get a new MAF boot from BMW mine only cost £11.50 part number 13 54 1 738 757

Perrrrfect

Post Wed Oct 05, 2011 4:41 pm

Thanks, I've been ordering a few parts including a new boot - how cheap?!

I already have an air temp sensor attached to the inlet manifold - this appears to be another one, but I have no idea where it goes. If it's surplus to requirements can I just bin it?