Think Ive Sorted Idle Problems

Andy, sounds like your car isn't a heavy oil burner then, you can't mistake the whiff when there's smog plus you said that your pipes were quite clean anyway. Sounds like your car was just running a bit lean (maybe Lambda probe feedback not perfect?) and cutting off the extra air from the high RPM breather restored the mixture.

You never answered if your engine noises sounded like pinking. If you uncap the hole or fit a K&N it will take the mixture back towards lean and it's pot luck whether the ECU can adjust the map far enough to cope without re-programming. You'll probably get a turbo like whistling or induction roar with that hole uncapped and a small K&N on an extra bit of pipe so you're not sucking in unfiltered air.

Having spent another few hours going through the schematics there are a few possible problems caused by that idle breather valve that I can work out. Smaky or someone who does tuning re-chipping may well be able to work out or know of more.

1) Clogged or stuck shut valve, as the ECU relies on the air through that valve the engine will run rich at tickover.
2) The spring becomes weak and doesn't shut the valve when negative pressure from the high RPM breather pipe builds up behind the valve. This would cause marginally weak running at higher RPM
3) O ring perishes or unseats if body clip worn allowing air to be drawn in causing weaker running at all RPM.

With the bores wearing with age and oil consumption increasing there would be less useable oxygen but this would be compensated by the throttle body wearing where the butterfly shuts allowing a little more air to leak in.

So Ransoman replacing that valve might help if your exhaust smells rich at idle and sputters a bit?
But if have you replaced either the ISM/TPS or throttle body recently, either of these would upset the balance of having all components aged the same so may require some basic mixture parameters resetting in the ECU.

I can see how a few "bodges" might help if (like me) you want to sort the problem, can't get a dealer to acknowledge the valve exists and order it and haven't a bottomless budget compared to the cars value for an immediate recon/new everything to correct oil burning problems and an ECU re-tune afterwards.
1) Tweak the spring longer in small steps to compensate for weakening with age.
2) Fit a new O ring inside the valve, use some silicon adhesive and glue another O ring (cut to allow for the clip flange) where the valve seats on the intake manifold then push the valve down onto that and hold it in place with a stainless tie-wrap or pipe clip.
3) If you have replaced the valve and ISM/TPS and your throttle bore isn't worn so the problem didn't go away mark the original position with nail varnish or similar then try tweaking the idle stop screw in eigth turns clockwise to allow a little more air in at idle. The idle RPM might go up 100 or so but restoring the mixture should help stop the sputtering and stalling/surging symptoms.

Think ill leave it as it is then, Cheers Guys

Originally Posted by Andy146ti

Think ill leave it as it is then, Cheers Guys

after reading everything that everyone wrote, including all the technical stuff, that was exactly my thought

Originally Posted by rafe005

after reading everything that everyone wrote, including all the technical stuff, that was exactly my thought

LMAO, I think we lost him there in the jungle of technical WTF?

Infact, i was just speaking to my mechanic and he was going through all the bits i should also check, clean etc...incase that is the problem...........and now i'm at the stage where he can bloody sort it out So booked in for major service (its about time anyway)

Sorry it takes me longer to figure out how things work these days and I'm terrible at explaining things. This is the most straight-forward way I have come up with to explain the cause of symptoms common to many cars here at low RPM.

Basically the Bosch 1,5,5 system on the plastic topped cars is designed fairly well that as things wear they mostly compensate each other and the ECU learns to look in different places on it's map over time according to what the sensors are telling it.

Obviously there are some faults where it can't find the right combination of settings to cope with so the engine runs rough or the ECU searches the map adjusting settings so the revs might rise and fall "on their own" while it does this.

Similarly if a critical component fails and you replace it the ECU needs to learn to look in a different part of the map where it isn't used to looking so might need a reset.

Most cases on this thread the problems are during the phasing of the hand over of control of the throttle under 1800RPM from the main injection system to the idle stepper motor.

On the plastic topped engines this is in one unit with the throttle position sensor so if this assembly gets changed after it has got really knackered you might just swap the old problem for a less serious new one:

If your old TPS pot went high resistance then with the new one the ECU might think the throttle is open a slightly different amount to what it actually is until other sensors complete the picture (slow RPM drop to tickover or almost stalling RPM drop around tickover).
If the gears were badly worn in the old ISM then the ECU might be running the new stepper motor slightly longer than necessary (higher tickover, jerky decelerating, surging on part throttle)
My best guess is that this is because the ECU is looking in places on the map at combinations of "worn" settings it has got used to and even if you do a basic reset the ECU might not have the right combination of settings in it's map for worn everything else and a brand new ISM/TPS.

So if after fitting a new one there is still a problem you either need to be able to reprogramme the ECU to look in a different part of the map for the new ISM/TPS settings or visit a specialist who can re-calibrate it for you.

It would be great if anyone on the forum who actually did re-chipping / re-programming on these could confirm whether in their experience sometimes re-calibration within the ECU is required after fitting a new ISM/TPS.

I must admit that whenever i fit a new part or change/clean something I always take my car down to the garage to have everything reset.

Ransoman if you are still suffering from the RPM/Idle glitch I have found a few other things worth checking. There is an air intake valve which can become clogged which is No4 here (mine was covered in sticky dust)

There is a valve in the fuel vapour system under the throttle body also worth checking and a purge valve on the canister inside the offside inner wing which can become corroded-this is listed as a known cause of idle problems on another website.
Hope this helps
Bren

Thanks Bren.

your first post of those 2 show the vacum valve that changes the inlet manifold between long and short, not sure if you know that already but thought i would just mention.

I will check all those out at the weekend but tbh i might not bother, there is a 90% chance i will be trading it in this weekend.

Think i have solved the starting problems, it is the battery. i have come to the conclusion that the new battery is not powerfull enough since they only started when i replaced the battery. needless to say, old one will be going back in and new one will be cashed in for refund.

As for the idle problems, still at a total blank, but both these posts help.

oh yes, one more thing, my throttle body had a fair bit of oil spray over it (cleaned and polished 3k miles ago) so obviously my cam breather lets out a lot of oil (which is probably killing my lambda) so in theory, a catch tank and a new lambda should sort it??

Have i just hit the nail on the proverbial?

Yes, I was trying to avoid heavy theory and just give a pointer but if that air intake gets blocked the actuator will have an incorrect comparison level between vacuum and atmospheric pressures.
I haven't had time to clean mine because I want to carry out tests and observe what it affects at the same time but obviously my initial suspicions are it delaying or at worst case stopping the manifold length change.
Also I can't find the main engine air intake which normally comes via a pipe after the air filter on most cars, according to the manual the engine also draws some air down into the rocker cover through that valve on the actuator.
If the engine needs that air for purging smog so instead trys to draw it through the breathers it would result in oil not returning freely to the sump and also mess up the expected pressures at the intake mainfold and affect running especially once warm at low RPM. (Hence Andy's magic cure?)

The canister purge valve is listed on an Alfa Romeo website for dealers to locate common idle faults. Apparantly screen wash or rain water run-off from the grill under the windscreen can get through a gap at the top of the inner wing and contaminate or corrode the valve, they recommend sorting the valve out then blocking the gap off by cutting a rubber block to mastic in place.
I asked in a previous thread on here but no-one could tell me where to find the canister and I hadn't found it by following the pipes. I didn't know it was inside the wing until I found the manual I pinched the picture from. Before that I had also assumed the 2 fuel pipes were flow and return rather than both flow, with the second one coming into use only after petrol fume pressure exceeds a certain limit, that's why I thought to check the valve under the throttle body as if it doesn't tell the ECU it's open the engine will run rich when it is. Presumably this problem would be worse on hot days when petrol evaporates more or if you fill up and run on a whole tank for a while rather than puttting in smaller amounts of petrol more regularly thus venting the system by taking out the filler cap.
So if you're idle problem goes away when it's cold and wet or by running with the filler cap loose there's the probable answer.

The short answer is yes, I'll try to explain it in plainer English this time lol.

As an engine wears, especially the bores & rings, crankcase pressure builds forcing more power robbing smog into the intake system and wet oil residues that coat lambda probes. My trade meant I have averaged 80,000 miles a year upwards and I have had Subarus and Volvos do 200,000+ miles without wet oil residues but the Alfa twin sparks seem to start getting them around 100,000 miles.

So taking it away results in cleaner running and more power as Andy has found, plus you should stop killing lambdas.

There are 2 big "BUTs" if you do this though:

1) On a high mileage car around 50% of it's carbon emmissions are from this smog which is why just venting it to atmosphere means an MOT fail and is not even allowed through scrutineering on track days.

2) Regardless of whether you don't want the smog in the combustion process the whole system is designed so that by connecting it to the intake vacuum it actively sucks out the smog from the crankcase thus keeping crankcase pressure down. (on drag strip cars they often use an electric vacuum pump to do this)
So if you unbalance the whole system sooner or later the excess crank case pressure will result in blown gaskets or seals. If you google you can find umpteen people that have tried what Andy has done that this has happened to which is why I was concerned about his engine and trying to warn him.

This is why I was recommending using an external oil separator like they fit as standard to very high RPM engines, turbo charged ones or track cars. It is a good compromise until you can't get away without a rebore any longer as you avoid the worst parts of the smog going into the injection system, still get your engine actively vented and can still get an MOT without putting all the breathers back to standard before going.

There is a very basic oil separator inside that black plastic box where the pipes connect to the rocker cover, you can try to improve it's efficiency (packing it with more steel wool is a common DIY trick) to delay buying an external separator or having a rebore. The idea is to stop the heavy wet crankcase fumes but not impede the exit of the pressure causing gasses.

I think people who looked at the previous post were put off by the theory link showing the need to drill and tap a return oil flow line from the external separator into the sump. You don't need to do this, if you prefer just run the output of the separator to a catch tank and empty it when the sight level shows it's full.

Glad you've sorted the starting problem, that makes sense, if the battery wasn't rated for enough cranking amps (People often just check the main amp hours rating and forget the cranking one) then the ECU and sensors wouldn't be getting a full 12 volts + to work with while it was turning over on the starter.

Hope the above was some help and not just gobbledegook, Im more used to showing what's going on than explaining it and often been told I'd never have made a good teacher.

Regards
Bren

Forgot to say that if you go to a supplier that fabricates the oil separators and catch tanks on site then for a few extra quid you can get them to make you a twin input and output tank with baffling inside and pack it with steel wool so that you can do the job with one tank and a few metres of 15mm fuel pipe.

And I don't know why Alfa call that valve the Idle Breather Valve and not just the PCV valve like everyone else does, then their dealers might have a clue what part I'm trying to order.

I had time to look at mine this morning and found that once warm and idling the engine is sucking IN air through the high RPM breather like an industrial hoover. So much that it is robbing the injection system of enough air to cause the high idle and low RPM throttle glitches. It is obviously venting at high RPM because yet again there is wet oil residue in there.

I checked the operation of the PCV valve by pulling the pipe off the rocker cover to see if there was suction at idle, then taking the guts out the valve, running a long length of pipe then squeezing the end of the pipe open and shut and it does run better doing that than manually than letting the valve do it. Apparently the spring has been re-specified in new valves as the earlier verions could become coil-bound stopping full operation of the valve so I'm going to try again with Smaky's part number at the dealers.

I haven't had any luck yet web-searching to find out where the engine should draw clean air in from at high RPM or what might be causing it to suck so hard on the high RPM breather at low revs just other people with the same problem asking how to cure it.

I did find a really helpful site though which also answers my earlier question with a definite yes that after fitting a new ISM/TPS it does need setting up with diagnostics so thanks Rafe you were right.

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The names of the links haven't appeared but they still work.

The first one is a good guide to the PCV valve and Idle Stepper Motor with clear pictures.

The second one deals with just how much the guy had to do with diagnostics to get his tickover down and stop intermittent stalls after trying with old and new ISMs to cure his problems.

thanks for the posts. my brain really hurts

I have fixed it now, by deciding to throw in the towl and replace the old girl with a new girl, ergo no more problems.

I put the old battery in because it does start better. the idle issue i am still none the wiser on but i don't want to spend any more time dismantling things, finding out it is in perfect condition, cleaning it anyway then putting it back together with no results,

Hey i too have this annoying 'revs itself' problem at idle speeds.Glad to see you sorted it, just wanted to ask if you have stuck with this mod (the small breather and the black tape!) and if its kept the dodgy idle at bay? Also whats it like when the engine warms up, as i wouldnt imagine that much colder air getting to the breather then?
Im ready to do this fix on mine if its good! also, did that pipe u seperated have a bit of oil in it? mine did! Cheers