Lumpy (cold) idle

[SamiS]

The idle on my 316i ('90) is starting to get on my nerves, so its time to just troubleshoot.

Firstly, I think its worth replacing the intake boot etc (as I've been told on here). So, I'm thinking I need the following 3 parts from the following image; do I need any more?

3. 13711709755
6. 13411247344 (may as well, cant be more than a tenner)
10. 11631714527


What else can I look at, preferably before spending any money!

[sihooker]

Before spending cash, clean out No.5 on the diagram (ICV), and check that your accelerator cable is adjusted correctly. Also check that your throttle position sensor is working properly and the air flow meter flap is moving freely.

[SamiS]

ICV has been cleaned (I also purchased an other and fitted; same issue), The accelerator cable is (very) slack, but it does this without me being in the car.

The AFM flap works fine and moves freely.

TPS is the only thing I've not done yet...Any guides?

I've also replaced the Blue sensor with a brand new one.

[sihooker]

Has the car been serviced recently? I'm thinking air filter, dizzy cap and rotor arm...

[SamiS]

Has the car been serviced recently? I'm thinking air filter, dizzy cap and rotor arm...

Inspection 2 and cam kit replacement all about 500 miles ago. The problem existed before and after.

Just to comfirm; TPS is part 2. What am I looking for when I test it?

[sihooker]

Yes, that's the TPS. There are three pins visible when you pull the connector off, though if it's an auto it might be different(?), and you are looking for continuity between the left and centre pins with the throttle closed. This continuity will stop as the throttle is opened slightly.

Next, you'll want continuity between the centre and right pin as the throttle approaches fully open. You will normally be able to hear it click, but some dont and still work ok...

[SamiS]

TPS seems fine.

I get high readings or nothing as the haynes describes. I can also hear a clicking noise when it closes...

[sihooker]

Have you done the air-leak test using WD40 or carb cleaner?

Another thing to consider is replacing the vacuum hose that goes to the fuel pressure regulator as this can fail internally whilst looking fine on the outside.

[SamiS]

To confirm: I get continuity on the pins. (As described in the haynes manual). It will read 0 when fully shut, then read 1 when open 0.5mm.

The haynes also says to test for 5v on the sensor, but I cannot see how this can be as it has no other input. I done it anyway, I get no reading from any pin to earth on the sensor or the connector. I tried this with the ignition at 'off' and 'stage 2'.

I picked up on an other topic about the solid pipe that has a rubber gromit on the end. This has a rather large crack. Could this cause such an issue?

I've not done the WD40 test, I'm assuming, cover the inlet boot in WD40 and rev engine to see if air is escaping. Would this be the issue if the car is only lumpy when cold for the first few minutes?

Can you point me in the direction of said vacuum hose?

[sihooker]

The 5volts will be found on the centre pin of the plug, not the socket.

The idea of the WD40 test is to spray it all over the inlet side of things whilst the car is running to see if the revs falter as it finds it's way into any leak-holes.

The vacuum hose comes off the left side of the throttle body and goes through the inlet manifold to the fuel pressure regulator. It is about 6mm in diameter and about 6-8 inches long. There is a similar pipe on the right hand side of the throttle body which goes nowhere and should be blocked off and airtight.

Where is the cracked pipe? Is it on one of the above diagrams you posted?

[SamiS]

There was no voltage from any of the pins, so maybe this is it?

I will do the other things tomorrow.

It's not a cracked pipe, but the rubber that goes over the end is cracked. I think this is the pipe you describe as to the right of the throttle body. Its solid and does 90degrees. The rubber is cracked.

I will check the vacuum hose tomorrow too.

[sihooker]

The 90 degree pipe could well be your problem, and it should show up with a squirt of WD40.

It's odd that there is no voltage at the TPS lead.

[SamiS]

The rubber gromit has had it. I've just put a latex glove over the hole and put the gromit back over to try and give it a good fix. It seemed better. I will give it an other go when its cold again.

I can ground the middle pin, so it must be completing a circuit.

The fuel vacuum hose seems fine, but if it can go without it showing, it sounds like it just needs replacing.

Just to confirm, the car bleeps the throttle from 700rpm to 1500rpm for a good few minutes, get lower every time. This is it keeping its self alive, but maybe more drastically due to the other problem.

The main problem is the jumping, like the mixture isnt right.

Both only happen when its cold, for the first bit of driving. No other issues. It pulls well etc.

[SamiS]

Seems better this morning. I drove it straight after turning the key, it was a little lumpy but much better.

At lunch, I'll leave it to idle and see if the rev peaks are so high.

I think its wise to order the gromit anyway, cant be more than a tenner!

EDIT: I cant see the gromit anywhere in RealOEM. Any ideas?

[sihooker]

The grommet will probably only available from the dealers. Try Cotswolds on here, giving them the part number....

http://www.e30zone.net/modules.php?name ... topic&f=39

[SamiS]

I cant find the part number, thats the problem :S

[sihooker]

Oh, i thought you meant the grommet (part no.6) in your first diagram.

If you mean the spare vacuum pipe on the right side of the throttle body, the easiest way to deal with that is to use a piece of vac hose and block the end of it with a plug or tight bolt...that's what i have done!

If you want to keep it OEM, maybe you could describe it to them...they're very helpful.

[SamiS]

Right...

I meant the spare vacuum pipe on the right. I done as you explained, and I'm sure its properly sealed now. But I've still got the issue!

Any other ideas?

[SamiS]

Bringing this back up, now its getting colder it seems to be as bad as ever.

Considering its the same issue and I've tested everything listed above, what do I do now?

To confirm, the car starts fine first time. For the first 1 or 2 minutes the revs will settle, which I assume is the auto-choke. But, when you try to pull away it jumps like crazy, the revs will dip (sometimes stalling the car). Once Its been going for a minute more its fine, pulling away etc.