Idle adjustments in the hunt for a better idle? (Fixed)

[x-works]

Hello folks, just wondering if anybody can offer any information on a few things I have to adjust on an 88 320
to get it to idle correctly. Brief history on whats I've done up till now. Originally bought car with engine
running crap and investigation found poor compression on cylinder one so, engine rebuilt top and bottom
to cure dud valve seats and siezed rings. Started engine yesterday and engine is better but not yet cured,
hunting up and down about 150 rpm from 700 to 850ish. Checked IAC valve and electric side of it pin's
out ok on the resistance check not so sure about the mechanical operation of it though so going
to try and track one down tomorrow. Checked the loom out coming down to the IAC valve and according
to the Haynes manual I should have 12V domn the middle wire and the outer two should earth 10v,
I've got the 12v down the middle and one of the outer earths 10v but the other only earths 4v. The Haynes
manual doesn't give any further advice on this and I'm not sure how much of a fault I should read
into this, not having access to another car to make comparrison checks on. Pined out the 3 wires back
up to the ECU plug and there ok. I should probably mention at this stage that removing the plug on the
IAC valve while the engine is running makes no difference to engine what so ever.
I'm as sure as can be that I have no vacume leaks on the engine side of the throttle butterfly as every gasket
has been replaced in the rebuild and I was carefull to make sure everything sealed well going back together.
What I don't know how to set and is probably having an effect on the running is the idle adjustment screw
on the throttle buterfly. Does anybody know how far this needs to be screwed in? I was of the opinion that
at idle the butterfly is fully closed allowing no air to pass and that the IAC valve controls all the air needed,
but am now starting to think that maybe the butterfly needs to be open a small amount and that the IAC
valve only controls enough air to maintain a smooth idle. Anybody any advice on how exactly the system
is meant to work.
The final thing which needs to be set is the air by-pass screw on the air flow meter. I think I remember reading
somewhere that a base setting for this was to screw it fully down and then unscrew it 2 turns.
I realise that a CO meter is needed for the fine tuneing of this screw but I just want to get this engine idleing
right first before I get it put on a gas meter.
Unfortunatly the reason all these things need setting up is the previous owner seems to have adjusted
everything from the windscreen wipers to the plug leads in a vain attempt to fix the problem despite having no
knowledge of cars. God loves an optimist, fortunately he didn't have a problem with the brakes!
The only other things I can think of is there appears to be no air leaks in the servo system or the pipe from
the airflow meter and the throttle position switch is working as it should.
If anybody can offer any advice on any of the above i'd greatly appreciate it.
Cheers.

[Dan318-is]

sometimes air flow metres just need replacing, i changed mine an my idle is now like a dream

failing that, temperature sender, (the blue plug going into the block) may also need replacing

re: idle vlave, have u jus given it a clean with carb cleaner? mine had the wrong readings coming out the plugs but i cleaned the valve changed the AFM an its fine now sits at 800 pretty

hth

[x-works]

Thanks for the reply,
Second hand parts in scrap yards are hard to find this side of the pond so all parts have to be bought new which tends to make you a little cautious when
diagnosing faulty parts. The IAC valve shouldn't cost to much I hope so I hope to buy one tomorrow but the airflow meter costs a wee chunk of cash more which I seem to have difficulty finding after the engine rebuild. If I can get everything else set up right and it's the only suspect thing left then the cash will be found somewhere. Need to find out how to set up those two screws first though so I can start narrowing down the list of things which could be gone t*ts up.

[Andy_magic]

Clean out the ICV, AFM and TB with carb cleaner and set up the TPS, I'm sure theres a guide somewhere telling you all about it

Here it is!!

http://www.e30zone.co.uk/modules.php?na ... ning+guide

Don't forget to vote!

[Dan318-is]

what engine is in your motor dude

replace the sender also it maeks the world of difference

[MONSPORT42]

Have you run the engine long enough for the ecu to relearn it's settings? Wouldn't adjust or replace anything 'til that's done. It can take a good few miles too.

[tourer-dan]

sorry to hijack your post, but how much did the bottom end rebuild cost? Did you do it yourself? what exactly did you replace?

regarding your problem: After I did my top end rebuild my car didn't idle nicely. Now there is a difference between an uneven idle (which mine had) and the type of dodgy idle characterised by a fauly ICV.
(If you've got an ICV fault, your idle speed will likely 'oscillate' with a kind of regularity)
I readjusted the valve clearances which had all myseriously closed up a bit. Being a dab hand at the valve clearances now, my advice is set on the slack side as opposed to the tight side. With my dodgy idle, my engine was described as being 'too quiet' for an M20 and now it is a touch more tappety, but idles nice and smoothly (and the clearances is the only thing I changed)

[Andy_magic]

Valve clearances do make quite a bit of difference, I set mine the other day and it now idles cleaner, but if your TPS is incorrectly set and the TB/AFM is gunked up with carbonised oil it will run like a bag 'o' shite.

Doing whats in the guide will sweeten things up and rule out one more thing.

[x-works]

Thanks one and all for the replys,
The tps is set and working correctly the only reason I'm sure of this is I stripped it apart during the rebuild and adjusted the tiny micro-switch for throttle opening. It's adjusted now to give the tiny click when the butterfly just starts to open and the multi-meter restistance test confirms it's doing it's job both at throttle opening and full throttle. The airflow meter was also stripped during rebuild and the tracks found to be spotless and all contacts in good condition. The resistance check didn't make a lot of sence though with the values riseing and then falling off as the flap was moved from fully closed to fully open, however with the ignition switched on and the volts being returned to the ECU measured there is a smooth increase in voltage which I took as an indication of good health, still can't figure out the resistance check though.
The throttle body was cleaned spotless also during the rebuild and appears to be in good condition, I even vacume tested it incase any of the seals on the spindle were leaking air. Both servo tee-offs are sealed tight in the housing and system was checked and found to hold vacume.
I'm starting to think the problem might be with the IAC valve and tried priceing one today and the cheapest I can find is 154euro from a spurious parts supplier near by called OTTO. German Sweedish and French informed me they don't do an IAC valve for the 1988 m20 engined320.
I'm trying to get my hands on a 325 to service in the next few days so I can swap over the valve to see if it makes any difference, but the owner is getting suspicious why i'm now tracking him down to service his car when it's usually him that has to pester me in to doing it
The valve clearances have been reset after the engine was run up to operating temperature for the first time. The idle is oscillating as you have mentioned (glad you were able to spell that as I had to copy) rather than a lumpy or misfireing idle which is what is leading me to suspect an electrical fault rather than a mechanical one.
If anybody knows I'd still like to get some info on the set up proceedure for the throttle butterfly screw.
I've rebuilt the engine myself apart from the machine work but I don't know how relevant the prices will be for the rebuild, being as there all in euro's but here's what it cost me for parts.
Headset including inlet and exhaust manifold gaskets and a 0.3mm oversized headgasket (to make up for the 0.5mm to be skimed of a warped head) 63e.
Water pump 31e.
5 sets of piston rings @ 6euro each 30e.
1 std size piston complete with rings 80e.
Set of std size big end bearings 30e.
Set of std main bearings 48e.
Gates timing belt and tensioner 58e.
6 injectors reconditioned 120e.
Oil pump 104e.
Sump gasket 6e.
Head skimmed, pressure tested, valve seats recut and valves reground and stem seals fitted 180e.

And an engine that idles smooth "priceless".

[Andy_magic]

Whats the CO like, sounds like you have covered pretty much everything.

The only other things I can think of are oil dip stick o rings and oil filler cap seal.

[x-works]

Don't know what the co reading is yet as I haven't got me own co meter, the plan was to get her running reasonably smooth after the rebuild and then bring her to a mates garage to fine tune the CO for the NCT/DOE. Don't think she's running over rich though as the exhaust is reasonably clear and smells ok'ish, can't tell if she's running lean though. Dipstick was refitted to the block with lock and seal and there was new O rings for the dipstick in the headset which suprised me. The breather pipe from cam cover to tb was also replaced as it had perished.

[tourer-dan]

where did you source the parts from? they seem like good prices - although I'm only going by euro car parts.
Is your idle valve a T or L shaped one? thay come up on ebay quite often, and I bet half the guys on here have spares to sell, so pop a thread in the wanted section.
I know what you mean about wanting to try first. It's a shame you don't know someone who would *willingly* let you try bits
Hope it works out for you -I really agree the next step is substituting parts. When it's all going you're gonna have a nice smooth runner though.

Ps: I'm sure the preferred method of valve clearances is cold. There is a published hot setting, but I think still 90% swear by a cold setting for accuracy.

[x-works]

Thanks for the reply,
Will give the valves another check tonight when cold, (if I keep going at this rate i'm going to wear the metal off the blades ) The parts I got from a local engine remanufacturer supplier and cut out the motor factors from the price chain which helped keep the price down.
Just talking to a mate who run a tyre fitting shop and says he has a 320 coming in for new tyres tomorrow, can see that car having problems which require it to be kept for a little longer than usual

[tourer-dan]

Just a thought:
I never got dipstick 'o' rings in my headset (elring) Theres a straight metal breather pipe from the inlet manifold to the block which has an o ring at either end, did you replace these?
If you didn't, check for air leaks by spraying carb cleaner around the joints with the engine running (just start with a little puff, mind!!)

[x-works]

Well, another 2 evenings work and still no closer to an even idle and enthuasism is starts to get hard to find. Actually managed to find a breakers 80mile away which had an IAC valve and airflow meter today so made the 160 miles round trip and shelled out the 100euro's for the parts only for them to make no difference what so ever. That was fairly hard to swallow. Rechecked the tappet clearance and everythings still as it should be. The breather pipe from sump to manifold has 2 new O rings and would appear to be sealing ok. I'm convinced this has to be an airleak somewhere. While workin on it earlier we decided to loosen the fuel rail and and give it a wiggle to see if any of the injector bottom O rings weren't seating properly in the manifold and the engine came right for about 2 minutes during this time I pulled the plug on the IAC valve to see if it was now using this air supply only and hey presto the engine cut out. Then restarted it and she won't idle right again. So off with the rail and injectors, changed all the bottom O rings again, cleaned the hole's in the manifold where the injectors sit and refitted everything. No difference, crap idle.
I've two questions which maybe someone could answer please.
I've now ammased a collection of 3 airflow meters and none of these conform to the test which the Haynes manual suggest, which is when the flap is opened from till its fully opened there should be a steady increase in resistance. The 3 I have start at about 550 ohms rise to about 1200ohms at one third open and then smoothly fall in resistance for the rest of the opening till reaching 330ohms at fully open. I'm finding it hard to belive that all 3 I have are identically shagged and am much more inclined to belive the info in the Haynes manual is incorrect. Has anybody on here tested an airflow meter and if so what sort of readings did you get?
The second question is does the 88 320's ecu store fault codes. It's the more modern Motronic ecu with 3 row's of pins. If they do store faults I might try track someone down with the gear to read it and see if it throws up anything usefull.
Cheers.

[tourer-dan]

I can't answer your questions I'm afraid mate.
A couple of other suggestions: (clutching at straws now)
have you changed the fuel filter?
dist cap and rotor in good condition?
Having said that, If it idled well for a short while after you wiggled the injector rail it could be a problem there. Was it ok until you pulled the ICV plug, and then wonky again when you restarted - could be a problem there too?
Sounds like a bummer mate, I hate it when things like this happen to me, so I'm feeling for you!
When mine was bad I drove it to a BMW specialist who gave me some advice which sorted it all out (valve clearances) Is there someone you could take it to for an expert listen?

[x-works]

Another evenings work playing with the engine and have managed to rule a few more things out which i suppose brings us a little closer to finding the fault Done a few tests this evening which I'm pretty sure won't be found in the haynes manual. The first step was to rig up a vacume gauge to the inlet system to see what sort of vacume the engine runs at tick over and then the next step (no laughing at the back now) was to hook up the vacume cleaner to the engine. Basically we couldn't be sure if there was an air leak because we couldn't hear it with the engine running and the easy start sprayed around the manifold wasn't showing any noticable change in rev's. So we hooked up an industrial strength vacume cleaner to the tail pipe and removed the airflow meter and blocked the pipe off so the system should be fairly airtight. The speed was set on the vacume cleaner so that it gave the same amount of vacume as the engine had while ticking over and all we found was a very slight weep from one of the rubber blocks that slide into the top of the head under the rocker cover gasket. Removed it and sealed it with sealer and the whole system seems air tight. So we're fairly sure we've no air leaks now.
In answer to your post Dan the fuel filter, cap, rotor arm and leads are all new, no joy there i'm afraid. Not a lot else I can think of doing now, just waiting till monday when I hope to get her rigged up to a gas meter and find out if she's running rich or lean which hopefully should point us in the right direction.

[E30-OBSESSION]

I wish you good luck, I have a very similar problem, after much work my '88 320i touring currently runs like a bag of Sh#t! I managed to limp to the MOT centre and it registered over 4000ppm on the HC scale, CO was way down so it is just everywhere.

My dizzy cap and arm are new, that's as far as i've got, now also struggling for motivation to look at vacuum's and Ohms etc.
Hope a quick fix is out there, again good luck and keep us all posted

[Andy_magic]

Another check I had completley forgotten about is the engine temp sensor.

I had a similar problem with my E30 when I got it, it was also the reson the owner sold it as he couldn't get the CO/HC right

The signal lead that runs from the engine temp sensor to the ECU was corroded in the multi plug under the inlet manifold, a continuity test between the sensor and the ECU showed an OPEN circuit so the engine always thought it was stone cold and overfulled like a bitch.

I repaired the loom on the car and everything is as it should be. An easy test is to get the car running and up to operating temperature and remove the multiplug from the engine temp sensor, if there is no audible change in the engine note you have found the problem.

It took me 4 days to find that one when I was doing it and sorry for not mentioning it sooner.

I wrote a motronic setup guide and sent it to someone on the zone for inclusion in the tech articles but never heard anything back....

Here it is, it's not pretty but should be of some help.

http://mysite.wanadoo-members.co.uk/e30/motronic.pdf

[x-works]

Thanks very much for the info and encouragment lads, both needed at this stage. Andy thanks a million for the PM'd info has helped a lot. Will pin out the few remaining wires today hopefully and failing anything showing up she's going to the gas tester tomorrow which should hopefully point us in the right direction.
Theres a BW mechanic down the road from me who says the throttle butterfly was only to be screwed out enough to stop the butterfly getting jamed when it snaps shut, ie you just screw it out till the stickyness goes out of the lever when opening the throttle the first tiny bit, which basically leaves the throttle closed at idle and this is what I had it set at. So I will try your suggestion of the 0.75mm gap and see if it makes any difference.
Cheers.

[TouringMatt]

This had kinda crossed into the problem/thread

http://www.e30zone.co.uk/modules.php?na ... ic&t=19750

I set my butterfly to 0.75mm with the feeler gauges/stop screw but could not get the TPS to click, so i turned the TPS as far as i could and then backed the stop screw off until it clicked ( gap was around 0.4mm )
Re-assembled it all, fired it up and the car idled at 1500rpm

Backing the screw off had no effect, in a drastic measure ( cos u cant get the TPS screws once its all in place ) i put an extension bar against the base of the of the TPS and tapped it round with a hammer until the revs dropped below 1000rpm ( strange how the TPS can do this, as its just an on/off switch AFAIK )
By luck it ended up set kinda right, open the throttle and the TPS clicks as you do, revs sit at 900rpm which is a bit high but i'd run out of daylight and it does pull out of junctions easier!

I really cant see how you can set the gap at 0.75mm tho, not knocking Andy's guide because i used it in the past and its a great help but it just didn't work for me

Matt

[x-works]

I don't want to jump the gun on this but I think we might have found the fault. Managed to get the car down to the mates garage today and get it hooked up to the 4 gas meter and sure enough it was running fairly rich, so a few turns of the air bypass screw brought it back down to normal again but the crap idle still remained. Next up was to plug in the diagnostics leads and "see" what the ecu was seeing. No fault codes storded and TPS and airflow meter showing to be working correctly. Was starting to get a little worried at this stage as this was basically my last chance saloon if we didn't find anything I'd run out of things to change. So the last peice of test equipment was rolled out, the Sun machine, 15 years old and looking none the better for it, hooked up the various clamps to the battery, HT leads and coil wires and switched it on. Straight away it showed that the dwell angel was all over the place and the current at the coil was dropping badly , sometimes alltogether under load at higher revs. This seems to tie in with the crap idle and the jerkiness under acceleration. With this version of motronic the ignition module is an integral part of the ECU so it's next up on the replacement list. Going to give the local breakers a try in the morning and if no joy i'll be back on here to see if anybody can help me out.

[x-works]

Managed to find an ECU in a breakers today and when fitted it has transformed the car, idle's smoothly, accelerates perfectly and catches the idle when you snap open and close the throttle without cutting out. Thanks to one and all for the advice and the words of encouragment. Just gotta sort the rest of her out now and then get her up for sale

[hogweed]

Anything to help a fellow Irishman (though I live n England now).

(1) If you've taken the battery off the ECU for more than a couple of seconds, your idle will be SHITE for up to several hours till it draws itself a new map. ThatÔš's just the way it is.
(2) Throw the Haynes Joke Book in the bin IMMEDIATELY Ԛ—a itÔš's full of crap. You canÔš't measure the resistance of the AFM Ԛ—a itÔš'll do exactly as you say. If IÔš'm really energetic some night IÔš'll explain it to you! Measure the voltage across it, and should be smooth.
(3) IÔš'm NEARLY certain the butterfly is near as dammit closed Ԛ—a the ICV should do all the idle.

If you want to put together a cheap collection of parts, I have them all on e-bay Ԛ—a but they might not do a 320, mineÔš's a 325. Have a look at:

http://search.ebay.co.uk/_W0QQsassZheynumberoneQQhtZ-1

Bosch code on my AFM is 0 280 202 082; ICV is 0 280 140 509.

Hope that helps!

Roger
pqvx@hotmail.com