Had no luck finding the air leak if that is indeed the cause of my problem. I made a hose clamp and experimented with clamping off various air pipes. Thought I'd found the cause but today the problem has returned. I tried disconnecting the IAC valve to eliminate it from the possible causes. It idled fine for 10mins then stalled. After reconnecting it, I found I had two new DTCs:
P0215 Engine shutoff solenoid malfunction P0515 Battery temperature sensor circuit
Both of these are puzzling to me, as I have no knowledge of the existence of a fuel cut-off solenoid on this vehicle, and I fail to see the significance of the second code at all. Can anyone shed any light on these, please?
I'm beginning to doubt if the problem is indeed due to an air leak, despite the fact that so far it only shows up when crawling or at idle. I've already replaced one pipe that had a definite split, yet it made no difference to the problem. OTOH, one would expect an ignition or fuel delivery problem to show up under other conditions. I'm starting to feel rather stumped :-(
The description is a generic EOBD description. The actual manufacturer's description may be worded slightly differently, so it's most likely related to you disconnecting the IAC valve.
Very few vehicles actually have battery temp sensors fitted, but some use a calculated temperature (ford certainly do), and playing around with things can cause weird apparently unrelated faults to be generated.
I didn't pay much attention to the original posts, but have you tried a different IAC valve? I have seen vehicles that do some weird things when the IAC valve is just starting to fail.
"Sandy Nuts" wrote in news:ePxjh.21078$ snipped-for-privacy@text.news.blueyonder.co.uk:
It's a turbo petrol. Please see my older post titled 'Paging Tim: T5 still misfiring'.
I'm also pretty sure it doesn't apply, but was wondering why this particular code would be triggered? As the car stalled when this code was logged, it suggests to me that the ECU is indicating a loss of fuel delivery, hence perhaps there is a problem with the fuel pump relay etc?
"moray" wrote in news:emmbtr$89v$1$ snipped-for-privacy@news.demon.co.uk:
Fairy nuff. I expected the IAC valve to come up with a code of it's own.
I'll ignore that one, then.
I honestly don't think the IAC valve is to blame, because I disconnected it and the engine idled fine (albeit slightly faster) for a full 10 minutes, then the problem started to show again.
What puzzles me is the intermitent nature of the fault. Although I have classic air leak symptons, I would expect a more regular fault pattern if that were the cause. Instead, I can leave it ticking over fine for several minutes and then it suddenly starts dying.
Crank sensors generally either work or don't work though, but I would of expected a cam/crank phase fault code to be stored if it was loosing one sensor intermittently.
I think it's going to need a live data plot during the rough running to check for any faulty sensors, and if that doesn't show anything up, then next steps will be even more involved (fuel pressure monitoring, manifold vacuum/pressure checking, exhaust back pressure....and so on).
But to me it sounds like a sensor issue. Just because there's no fault codes stored, does not mean the sensors are working as they should. If the ECU gets a dodgy signal in, then it'll give dodgy instructions out. And given it's a turbo, and the issue only appears during idle/light loads, it's most likely vacuum related. I'd be considering things like the MAP sensor, brake servo leakage, EVAP system (I know tim suggested blanking this in the previous thread, but did you try it), EGR valve, and anything else that would rely on a vacuum in the inlet manifold.
"mrcheerful ." wrote in news:NsEjh.21207$ snipped-for-privacy@text.news.blueyonder.co.uk:
I never doubted that they earn they're money. I just prefer to do things for myself. I've never used the services of a mechanic (apart from tyre fitters) for several years now, although that seems likely to change soon :-(
Thanks for the hint. At this stage, it looks like I'll have to take it to an auto electrician because I don't have a scope to be able to monitor the CAS output, a DVM and OBD scanner is all I'm equipped with. Out of interest, is there any particular reason why the CAS breaking down would produce a fault code for weak mixture rather than a code more specific to the sensor?
"Moray Cuthill" wrote in news:458f0c0f$0$15475$ snipped-for-privacy@free.teranews.com:
Could be the cam based sensor as Mr C has suggested. I doubt that it's the one on the crank as this measaures the rpm, which shows constant when I have the laptop hooked up.
I have a boost guage that I intend to hook up so I can keep any eye on the manifold vacuum level. Unfortunately, I don't have a fuel pressure guage or a scope, so if it gets to that stage I'll have to bite the bullet and take it to an auto electrician. I know a good one - not the kind that keeps charging for new parts until they stumble across the actual cause.
I checked out the EVAP system a few days ago and found no problem. There isn't (I think) a MAP sensor on this model or an EGR system. It just has a MAF, which looks OK on the laptop. It does have a barometric pressure sensor, perhaps this could cause problems, but I have no data to compare with so I can't test it. Good point about the brake servo, I haven't tried clamping that off yet. Needless to say, I wouldn't try any on the road testing with that particular hose clamped ;-)
A wild guess - are the battery and alternator ok? Checked earthing straps? I'm wondering if the battery and/or alternator are unable to sustain the electrical system load at low revs.
MAP sensor can also be known as the Barometric pressure sensor, aswell as another couple variations, but most petrols will have at least one in some shape or form, as it's used by the ECU to calculate the engine load and alter ignition timing. It may have two fitted, one of which sole job is to monitor the atmospheric pressure, but some cars rely on just the one and take a signal before the engine starts and stores it. But typically readings would be - With the engine switched off, it will either show 1bar or 0bar (it depends on if the ECU outputs the actual reading, or a corrected reading). At idle it should drop about 0.5bar or so below that static reading, and on overun it should be getting pretty near a full vacuum (ie getting close to 0 or -1bar). As revs increase, and the turbo spins up, the reading should start increasing into a positive figure, and if load is applied it should go up to full boost pressure. Off course, if you fit a boost gauge, you'll be able to compare figures.
And yes, the brake servo is an often overlooked part. I done a few on vectras, which could cause some weird running issues.
Same to you. Now that the rest of the family's up, I'm off to see what goodies I've got :-)
"moray" wrote in news:emo6a9$mp0$1$ snipped-for-privacy@news.demon.co.uk:
The barometric sensor on mine is for monitoring atmospheric pressure, to compensate for differing altitudes etc. I'm pretty sure now that it doesn't use a MAP sensor to monitor the manifold pressure, as only the Fenix and Motronic ME7 systems used one. Mine is a Motronic 4.4. However, the ECU must have some method of determining boost pressure, because it controls the wastegate feed via a solenoid and can cut the fuel supply if overboosting occurs.
I'll try that tomorrow or later in the week. I'm avoiding using it ATM, as I'm trying to preserve the CAT.
Mike Tomlinson wrote in news: snipped-for-privacy@jasper.org.uk:
Battery is only a couple of years old, but it's certainly worth a quick check on the alternator output at idle and the integrity of the ECU ground. I know that poor earthing can cause all kinds of gremlins with efi systems. Thanks for the suggestion.
because one fault can produce symptoms for another component, which is why you have take any code with a pinch of salt and try and interpret what it MIGHT mean, rather than just what it says.
some codes are generated completely spuriously if the car is not charging correctly, for instance.
I have seen codes generated because of a stiff throttle linkage !!!! they all were fine once that was fixed. other problem is that the ecu can't tell the difference between a dodgy connector and a failed sensor.
the cam/crank sensor issue can be masked by ambient temperature, try running it till it gives grief and spray the crank or cam sensor with something cold, if the fault changes there is a good chance it is one of those.
"mrcheerful ." wrote in news:rQNjh.21309$ snipped-for-privacy@text.news.blueyonder.co.uk:
OK. Just wondered what the logic sequence was that causes the ECU to link cutting out as a result of a failed CAS to an incorrect (weak) mixture. If it can happen for no particular reason, then that's fine by me. But, in that case, there must be a great deal of faults where DTCs are absolutely no help at all!
Should the ECU loose the cam sensor, it won't know what cylinder is doing what, so it can play havoc with fuelling / ignition. On a four cylinder engine, the ECU would just drop sequential injection, and depending on ignition system, just fire the sparkplugs in pairs (off course this happens on wasted spark anyway), and the engine would still run. But on a five cylinder, things get a bit more complicated, as the cylinders aren't in pairs, so cam sensor failure would most likely lead to the engine not running, so if it was giving out a spurious signal, it could cause erratic fuelling, but so could plenty other things. But regardless of this, the ECU should pick up and store a fault code for the two sensors not being in phase.
As for DTCs being absolutley no help at all, it's partly true. A DTC fault code reader is just another tool. It is not the be all and end all of diagnostics, but unfortunetly, there are a lot of people out there who think it is.
"moray" wrote in news:empch4$phs$1$ snipped-for-privacy@news.demon.co.uk:
Well, thanks very much to both yourself and Mr C for giving up your time on Xmas day to help out!
Although I've no equipment to monitor the cam sensor, I'll follow up those other suggestions re the brake servo and general electrical earthing and I'll let you know how I get on.
Stu wrote in news:1167088556 snipped-for-privacy@sp6iad.superfeed.net:
I've checked the charging system and electrical earths. No problem there. I eliminated the brake servo by removing it and plugging the inlet. Didn't help. I've now isolated every pipe that connects to the inlet manifold and have failed to eliminate the cause of the problem. The only thing I haven't checked is the PCV valve, though I doubt that it is the cause. I've checked the HT compontents and all I can report is that the plugs are sooty, but that doesn't surprise me with the amount of misfiring that has occurred recently.
It certainly seems to be heat related - today it has idled for over 30 minutes at normal temp without missing a beat, yet once I took it out and warmed it up properly, the problem reappeared. I'm now getting the occasional misfire on the road at lower speeds and the turbo performance seems to come and go, particularly at the lower end of it's operating range.
It's still very sporadic. For example, this afternoon I drove it hard for 30 minutes down a dual carrigeway bypass road. During this time it ran perfectly with no loss of performance. I then stopped for fuel and it idled for 5 minutes while I waited for a pump, again without any problem. After refuelling and returning to the car, it fired then died immediately. It would fire every time but refused to idle. I had to use lots of throttle to keep the engine going and build up the revs enough to allow be to move it, during which it coughed and spluttered terribly and I could smell the unburnt fuel from the exhaust (like the smell of an old carburettor car after a cold start). Once it had stood another 5 minutes or so, it was fine again!
Again, I'm very grateful for any more ideas I can follow up myself, but it looks like I'll have to get expert help with it. Problem is nobody is working till Tuesday, at which point I shall require transport to start my new job :-(
PS while checking the intercooler for leaks I noticed that it has a sort of breather hole, approx 3mm dia, in the plastic cap on the inlet side. This sucks or blows a small amount of air in proportion with the engine speed. Is this normal?
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