What this noise? (Video) & High Idle

[Eddie1990]

I've been getting this noise intermittently which does sound like its coming from the injectors. However I'm unsure if it is them and if it is what does the noise actually mean?



[youtube][/youtube]

This could be a separate issue but when turning the car on from cold, the revs are around 3/4k (4cyl taco) so probably about 2.5k.

This seems to very steady increase.

[Speedtouch]

Does indeed sound like it may be coming from the injectors. Use a long screwdriver or length of dowel, hosepipe, etc. as a stethoscope to pinpoint where it's coming from.

Check the blue temperature sensor re. the high idle:

http://www.e30zone.net/e30zonewiki/inde ... emp_Sensor

[Eddie1990]

Yeah to add to the comments above, the idle is very high, I'm not talking about 1500rpm or so. It's more like 3k+ and climbing.

We suspected an vacuum leak, but can't seem to find or even hear one. Would it matter that the brake boosters are E21 boosters, and not the E30 ones?

I've read that high idles could well be a fuelling issue, maybe that's related to the injectors buzzing?

I really want to get to the bottom of this ASAP.

[Speedtouch]

This link may provide some pointers:

http://www.e30zone.net/e30zonewiki/index.php/Intake

[Eddie1990]

It doesn't seem to, I went through that page today when working on the car.

It's got to be something else.

My main issue is I don't want to leave it idling at the moment as it's so high.

As a question, could it be either of the following?

1) I've not fitted the rest of the exhaust yet, so just the manifold and downpipes to the gearbox.
2) I don't have an O2 sensor fitted.

[Speedtouch]

Yes, if the exhaust hasn't got enough back-pressure, that could well cause a high idle.

The M20B25 should run fine without an O2 sensor.

Have you checked and cleaned the TPS and ICV?

[Eddie1990]

TPS is perfect, looked brand new inside and it clicks when it should.

ICV is an odd one, when I switch to ignition, it clicks and the little "door" opens inside it (we had it unplugged from the rubber boot to see inside it). Shouldn't the door open and close rapidly? We tried to free it up inside with some WD, didn't do much though. Might need a new ICV.

Hopefully when the new exhaust is on I'll be able to get a better idle.

The ECU has adaptive values right? How long will it take for those values to reset once the battery is unplugged, or is there a quick way to wipe these values, or are these values not likely to record a high idle and keep it?

[Speedtouch]

Disconnecting either the battery or ECU and leaving it for an hour or so will reset it. You can do it quicker if you disconnect both battery terminals and short them together with the ignition on.

Then leave it to idle for at least 10 minutes to enable base idle settings to be learnt, switch off, then take it for a drive throughout the rev range.

The ICV should normally 'hum' with the ignition switched on.

[Eddie1990]

Yeah, it was humming, but the little trap door wasn't moving. I understood the door should spin? Opening and closing rapidly and this controlling the idle speed of the engine.

The problem at the moment is the idle is so high that I can't leave it for 10 mins, it'll either hit the limiter or do lasting damage to the engine as it's stone cold of course.

Does anyone have any suggestions for the injector noise that's in the video in the OP?

[Speedtouch]

In that case, try a different ICV, or at least clean out your one with carb/brake cleaner.

You could try disconnecting it, and seeing what effect this has on the idle speed.

[Eddie1990]

Well we think it might be jammed open maybe, which would cause such a high idle, as it's as good as an air leak surely?

Cleaning it wise, I presume just spray brake cleaner in it and leave it to soak?

[Speedtouch]

Yes, and yes again. You could also soak it in petrol or paraffin, etc.

[Eddie1990]

After doing some digging and thinking, I'm swaying more and more to this being a fueling issue.

The injectors, early cars are high impedance, In was running a Motronic 1.0, and I believe the engine was completely standard. Later cars have low impedance injectors, I'm now running Motronic 1.3, so could it be that. If the injectors are running incorrectly, it could well cause a high idle, surely?

I got this information from the Wiki page on here.

[Speedtouch]

Yes, you need to have the correct injector impedance. The lower impedance ones would probably have blown the output transistors in the ECU by now though, in which case, the engine wouldn't run at all!

However, it's worth checking the impedance - you can use a multimeter on resistance range to check that.

[Eddie1990]

What should the low ones be showing?

[Speedtouch]

14.5-17.5 ohm high impedance range
2.5-3.0 ohm low impedance range