Am pleased of some help Steptoe.
SPARK PLUGS - just taken them out, they are twin electrode, look okay, but I note that the gap between each electrode to the centre is narrower than what the Vectra handbook says (0.9mm to 1.1mm), it's a gap of about 0.6mm on there at the moment.
Do twin electrodes need gapping?
Found this at NGK website USA www.ngksparkplugs.com/tech_support/spark_plugs/ins...g
3. Gapping
Since the gap size has a direct affect on the spark plug's tip temperature
and on the voltage necessary to ionize (light) the air/fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability
in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need.
A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximizes burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.
With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think.
|
Do twin electrodes need gapping?
No, because no hard you try, you will never get the gap exactly the same on multi-electrode plugs. Remember that the spark will take the shortest route and if one gap is closer than the other.....
If in any doubt, replace them. They're not expensive from Vauxhall themselves, or if you want them through the post, try http:/www.autovaux.co.uk
|
thx Dave, what I'm doing is going to Vauxhall parts in next few days and comparing the gaps on their plugs, if wider then I'll know I'm right.
Platinum range twin electrode spark plugs can't be gapped anyway, as far as I know.
Vauxhall parts have just confirmed the gap info in my book is right, so the mystery about whether the NGKs I've got are right or wrong ungapped deepens.
But NGK's website does say gapping may be necessary, check manufacturer's specs.
See www.ngkntk.co.uk/technicaltips/sparkpluggap.asp
|
Yet this link from NGK's own website describes the plug as pre-gapped
www.ngkpartfinder.co.uk/car_commercial_extra.php?i...2
Really confusing (for me anyway).
But the gap ain't right according to the handbook p200, unless the handbook refers only to single ground/electrode plugs.
|
|
|
Regarding the plugs, just fit a new set from the Vauxhall parts counter - I don't have any truck with spurious ignition parts, they are more trouble than they are worth, and frequently get in the way of diagnosis. (In other words, I would bin the NGKs!)
The coolant temperature sensor is relatively easy to check - it has high resistance when cold, and lower resistance when warm. Typically, they fail by going open circuit, and are high resistance all the time.
If you backprobe the coolant temperature sensor wires and measure the voltage across the sensor while the engine warms up, you will see;
initially something like 3 or 4 volts when the engine is really cold
this will drop as the engine warms up
at about 1 volt, you'll see a sudden jump, and the voltage will go back up (don't worry - this is the ECU stepping up the supply voltage to the sensor to increase the resolution when warm)
The voltage will then drop a little more from its increased value.
The *best* way to read this is via live data on Tech 2.
As for unplugging the idle speed control valve - well, I'm not sure exactly what that proves!
Number_Cruncher
|
thanks NC
I agree with you on that, absolutely.
But for a chuckle, I'm regapping these NGKs, very easy to do, can't be Platinum ones then, lot of confusing info on suppliers' websites, but I don't think these are the Plats.
Will post again once I've done the plugs and the new thermostat and also once I've been to Vx and checked their pre-gapped plugs with my gauge.
I'll be back in a few days with that info, if anyone else is interested.
|
Just to say widening the spark plug gap has made the idling worse. So that experiment fails, will be going back to the old gap.
Mind the gap! as they say.
|
I have been remiss in not asking and making sure that you had done all the basics.
Have you done a compression check?
Number_Cruncher
|
|
NC, I've heard of them, I've no idea how to do one. Anyway, the garages were supposed to do all this, but when I got the bill they conveniently failed to mention a number of checks they had promised they'd for the money. No wonder they don't take credit cards, so no come back via Consumer Credit Act, got to be the Small Claims.
|
By the time you've paid a garage to do a compression test, you may as well have bought a cheap and cheerful compression gauge like this one:
www.gunsons.co.uk/product.asp?pnid=284&deptid=13&x...3
Then, you can be sure of the results, do a dry and wet test, and still have the gauge for your future use.
Number_Cruncher
|
I may well buy that, thank you. As long as it comes with fairly clear instructions I'll be okay. Years ago I taught myself C41 photo colour processing and printing, this can't be as hard as that!
I think the Haynes has a How To on it anyway, must check.
|
Hesitation yesterday, breakdown mechanic couldn't get the computer to talk to his diagnostics, but he thought the problem causing the hesitating acceleration was the EGR valve.
I've had the EGR valve off today again. Looks in good order. Press the pin you can hear air as I assume the bits inside move and the valve opens or closes.
However, a thought occurred to me.
What if the car's ECU is not doing whatever it's supposed to be doing with the EGR or the EGR electrical part is gone?
Or, put another way: if car's thermostat is faulty (and I think it is), would that make the car's ECU not activate the EGR as the car believes itself to be too cool to need the EGR?
Would that then cause the EGR to in fact not be operating?
If I unplug the EGR the engine management light should come on, I assume. So that may be a start to see if the cables linking the EGR to the car are any good.
Any comments welcome.
|
Leon
In the first post you said that you'd blanked off the EGR without effect.
If you're going down that route, maybe the intake manifold air control system would be more likely?
|
I did blank it off, then someone said you mustn't blank off an automatic. So I removed it but yes I don't think it made any difference.
But I note that the car does not have the idling problem for the first 3 mins or so of any drive, so if the bad manifold gasket is to blame would it not cause bad idling immediately, once the engine has settled to 800 rpm after the auto choke IAC valve warm up ? What happens is after that warm up you can go drive and there's virtually no evidence perhaps no sign at all of a bad idle when stopped for a few mins after. The bad idling comes on later, say 5 or so mins into a drive.
|
For the first five[?] minutes the system operates in "open loop" which is the ECU simply using a pre-programmed warm-up fuelling map without any feedback to tell it how it's doing.
Once the oxygen sensor has reached a stable operating temperature; then the system accepts it's signal and goes into "closed loop" where the fuelling going in is heavily influenced by the amount of unused oxygen in the exhaust.
If there was too much oxygen; then there wasn't enough fuel added to burn with it, so the ECU immediately adds a bit more. Too little oxygen means that there was an excess of fuel that used it all up. This adjustment takes place about twice a second and gives the familiar sweeping profile of an oxy sensor voltage on an oscilloscope.
An oxygen leak into the exhaust [there is a slight vacuum in a exhaust] completely throws the system. The ECU madly adds fuel to try and get the balance right, but it makes no difference as the oxygen isn't coming through the combustion chambers.
Running that rich upsets the idle - it's just like leaving the choke full on.
If you haven't sorted that gasket yet; then don't change anything else.
|
Thanks Screwloose, much appreciate your time.
There's a bit of thumping or thudding when the car idles badly. It then almost stalls and does so with a jolt/jerk, car shakes etc. Don't know if that's of any use in diagnosis.
Problem getting that manifold done is the garage can't do it, they say a broken stud needs to be drilled out on bank one or some such. I've no real idea what they're on about but they say it needs an engineer and the only one recommended to me is miles and miles away. It's a question of getting down there for them to do that work, will have to try and do so though.
Well, many thanks again.
Leon
|
Just checked - the car does not illuminate the eng mgt light if I disconnect the EGR. just by the by. Perhaps I'll start the car from cold and see if the EGR gets hot immediately, if ot does I think that indicates it's got stuck.
But focussing on the exhaust manifold gasket - am told there's a stud gone on the head, so engineer needed. One garage has said it can do it for £140 all in. But they also said to me they very much doubt the idling problem is caused by that.
So round and round I go, but I'll have a punt and hope for the best, whatever happens the manifold gasket has to be done anyway.
|
The exhaust manifold stud problem is common on X20XEVs, seems to affect Omegas and Cavaliers / Vectras despite the engine being mounted very differently in the Omega. Anyway the studs had gone on my last Omega when I put it in for the MOT, lambda was up at 1.032 i.e. marginal fail - did wonders for the fuel economy though. The idle speed was stable.
Is it not possible to just blank off the EGR with a metal plate on these to check if it is affecting the idle?
|
>>Is it not possible to just blank off the EGR with a metal plate on these to check if it is affecting the idle?
That's what I would do - of course, only for testing purposes.
Number_Cruncher
|
|
Whoops! just noticed Leon mentioned that's been tried in the first post. I'm all out of ideas now.
|
|
Hi SpamCan61, I was told not to blank off an automatic gearbox model. I don't know why - just trying to be a smartypants now and I'll have a guess and maybe look daft: is it something to do with pressure on the EGR valve or its associated pipes/ducts helping the auto box decide when to change up/down?
|
Hello folks
Just been to a new (to me) no frills local garage, going to give them a try, got good vibes, he looked scruffy enough to be genuine! He also had the sort of quiet courteous attitude that people who know what they're doing often have.
He offered to take the cover off to have a look for free at the manifold, and I saw the nut has come off the bottom left one nearest the water pump, the stud or screw bolt itself not visible, probably just a small bit of it inside the thread hole, may be a devil for them to get out, maybe not.
If the garage is good, they'll get more of my business as although I can do a few things myself I have a hard job reaching in and stuff like that down to having back pain probs.
Thanks all,
Leon
Edited by Leon on 21/11/2007 at 16:34
|
Garage went significantly over their estimate - but that's no surprise.
Asked what the idling problem was mechanic said "Could be lots of things".
Needless to say, the new gasket on the exhaust manifold has not sorted out the idling.
The only hope is now that the car ecu will re-map and adjust the idling over some miles. But somehow I doubt it.
Thermostat's fixed at least.
Never buying a Vauxhall again, ever.
Regards all,
Leon
|
>>Needless to say...
Why needless to say? It very well could have been the root cause of your problem via the mechanisms that Screloose and I have described. It was an obvious fault that's now fixed and out of the way. A good thing!
Number_Cruncher
|
But it isn't the root cause unfortunately. The low value of the vehicle obviously makes it highly inadvisable for me to spend any more time or money on it. It's been an expensive lesson, I now expect a major component to fail at which point it'll be scrapyard time.
Only hope on the idling now is a bad earth, missed pipe block or hose split, ecu reset/remap, dirty fuel injector. Almost all else are going to not make any economic sense at all.
Thanks for the replies and I hope anyone else with a similar problem gets written estimates or a better set of garages - you might get lucky as sometimes it can just be the blocked throttle body breather and a dirty idle valve.
Signing off and wishing you all happy motoring and better experiences,
Leon
|
It was an obvious fault that's now fixed and out of the way. A good thing!
Yeah, but it improved the economy by 7-9% on my X20XEV Omega running it with the manifold blowing slightly ;-)
Edited by Dynamic Dave on 22/11/2007 at 19:18
|
My car's problem was the DIS / coil pack
along with blocked breathers and idle valve dirt, usual story, but mainly the DIS.
Easy job - replaced in 10 mins.
|
|
Nice to know the final outcome, DIS / HT leads usually cause problems under load rather than idle IMX, but one lives and learns :-).
|
Sure do, SpamCan, and the garages should hang their heads in shame, as they skip merrily to the bank with my cash - with no right to it at all.
But such is life. Still considering if I should sue them, might do.
Should just point out I changed the DIS myself - 10 mins, very easy. Real mechanics are great if you can find them, my garages were obviously staffed by fitters with ideas above their station.
Edited by Leon on 30/11/2007 at 23:48
|
|
Yes, having recently swapped from X20XEV Omegas to an X20XEV Vectra one of the few advantages of the Vectra is that the DIS / CTS / HBV & suchlike gubbins are actually accessible, unlike on the Omega where it's all hidden at the back of the engine, a nightmare to get to.
|
|
Ah, but the Vectra also has plenty of parts that are inaccessible or almost so for the home mechanic, don't worry about that! Just enjoy the ease of the DIS, EGR, thermostat, and temp sensor, not all parts are as easy to get to as those.
|
|
every silver lining has a cloud..;-)
|
|
|
|
