E30 Zone

The other day when leaving work, the car started fine, but when idling the engine would rev between 500-1200 rpm, and sounding like it was about to stall. It did it again this morning twice when I tried to start it. Any ideas? My only guess is either head gasket, or fuel injectors are blocked?
Many thanks.[/youtube]

Check for air leaks in the big rubber air pipe between the airflow meter and throttle body - if its split this will cause the idle symptoms you mention.

Still available brand new from the dealer for about £15 if you need a new one.

same thing happen to me, took off the airflow meter and give it a good service, and the problem are gone

Thanks for the advice, will try those today. what does an AFM service involve? Would it be easier to buy a good secondhand one?
Many thanks

Help!
Just taken off the airbox and AFM. The inlet pipe to the throttle body has perished slightly but there are no cracks as far as I can see. Also, the engine was still idling in the same way when I started it with the pipe off. The AFM appears to work fine, I checked it with the airbox off. I checked the spoark plugs and they are slightly black and smell of petrol, also the exhaust fumes smell of petrol.

I took the inlet manifold off this morning, and found one of the breather pipes was cracked (the one going from the bottom of the inlet hose) could this be the problem?
Thanks.

yes could be, replace the breather hose, as far as i know if those leak, its the same thing if u start the engine with the head cover loose,

i mean head cover cap

You have the car running and spray some WD40 around it the car should rev up and will confirm the hose is perished... but seeing as you've taken it off already and it has started to wear you're better off replacing it now anyways.

Where can I get the three hoses in the centre of the photo from?Or would lots of electrical tape work just as well?

The short hose on the right is a fuel hose so any motor factors should have them to the right size.

The other two pipes are actually connected in the middle inbetween the two hose clamps on the left hand pipe. The left is a coolant pipe to help warm the air intakes for cold starts and the one in the middle is the intake for the ICV.

You could probably just replace them with standard hoses but you may have trouble getting the right size hoses so the dealers might be your best option.

Oh ok I think i'll replace all three as they are all perished. Yes the two on the left seem to be stuck together...

just go to bm, there not too dear

Hi, just replaced the hoses and the problem is still there... any more ideas as I am running out of ideas myself...The engine still starts, then surges to about 1200 rpm then stalls again, unless you open up the throttle in which case it seems fine.

throttle positioning sensor possibly? im not entirely sure.. i have a known working one here if you want?

Where is the TPS located on a M40 1.8?

Under the throttle body

sorry just realised yours is an m40, the m42 tps may be different

You mentioned that the plugs were black. As a temporary fix you could try scraping them with a wire brush or simply replacing them. Black spark plugs is also a sign that the engine is running rich.

Yes wil try that although they were replaced only a few hundred miles ago, and I think they are black because the engine isn't getting run properly...

Has anyone got any more suggestions as to why it's trying to stall as soon as the engine is started??
Thanks in advance...

Replace the coolant temp sensor, don't know if it has one for the gauge and one for the ecu or a combined one. I know you have replaced some hoses but you didn't say if you tried spraying with wd40 or carb cleaner, you might have missed where the air leak is. do that first and see if the revs increase.

OK, will try that... Any idea where it is on an M40? what should I spray, the main air inlet pipe?
Thanks for your help.

Don't just go replacing parts until the problem is fixed. That's a very expensive way of solving things.

It does still sound like an airleak, and possibly from the blanking plug on the back of the throttle body (a hard cap that falls off and lets air straight into the TB.)

Next step is the TPS getting oily from the return breather hose; this can be tested with a multimeter to ensure that it's switching as soon as the accelerator is pressed.

The blue coolant temp sensor is the next culprit; it should be measured with an ohmeter at hot and cold. I can't remember standard readings off the top of my head, but a search on here for "blue temp sensor" will tell you what to look for.

I'm pretty sure that the blanking plug on the TB is still there, but I'll check...
Is the TPS located underneath the throttle body, and if so, can it be checked without removing the inlet manifold? When I took the main air inlet pipe out, there seemed to be an oily residue on the inside, at the TB end, is this a sign of anything wrong??
Many thanks for your help...

You have to take off the TB to access the TPS, but you don't have to remove the manifold. Before removing anything, operate the throttle by hand (engine off) and listen for a "click". It should happen as soon as the throttle is moved off the rest position.

If you don't hear it, take the plug off the TPS (it's a tight squeeze, but you can see it by removing the big air hose) and connect an ohmeter (multimeter, set to resistance) to the centre pin and one of the side pins. Again, operate the throttle by hand, and you should see 0 resistance at closed throttle, becoming infinite resistance when the throttle is opened. It might be the other way round, but it doesn't matter; it just shows that the TPS is switching (it's a switch, not a sensor.)

If it's NOT switching, take off the TB, unscrew the TPS and spray it with carb cleaner. It does get oiled up over the years, and BrianMooore recommends drilling a small drain hole in the middle of it to let that oil seep out. If you're worried about it, just fill it with carb cleaner for the night, drain it out in the morning and retest it. If it's still not switching, replace it.

If it IS switching when removed, but not when fitted to the TB, then someone has messed around with the throttle stop screw, which needs to be adjusted correctly.

Have just cleaned the TB and ICV thoroughly and the engine is still stalling...
I held the throttle open at about 1800-2000rpm for about 5 mins and then gradually closed the throttle and it idled ok for a bit but then stalled again. Think I'll replace the TPS next unless anyone's got any ideas?