Car skips a beat randomnly at high rev range!!!STARTED AGAIN

[handpaper]

siddiqi1 - It's the idle control valve.
Trust me, I went through exactly the same as you all through this year. Clean it for a temporary fix (may work), disconnect or replace with a known good one to sort it permanently.

[siddiqi1]

Handpaper!!!!

YOU ARE SOOOOOOOOOOOOOOOOOOOOOOOO RIGHT!!!

I checked it today, and its 110% the ICV, WHERE THE HELL WHERE YOU EALRIER MAN!! lol

I was reluctant to admit it at first, as this was a new ICV i.e. used, but will now order a new on the way!!!

thanks so much

Saboor

[Dan318-is]

Sab at least basically every spark and fuel component on your car has been changed

[siddiqi1]

NOT FUNNY Dan.........lol......well to be honest you are right........no harm, im sure it would have been changed in the future, why not just get it out the way in one shot!!!

Ridiclous excuse but well, whats done is done, practically all the igniton system is new par the leads!!!

Its runnig beautfully now, has a wonderful purring nopise and today on the A40 in the tunnel i made a LOT OF NOISE.......love it

Sabs

[SM AUTOS]

I would check the distributor to coil lead.
I had exactly the same problem on a 325i, checked loads of things thinking it couldn't be a lead. When I went to pull the coil lead of it literally fell apart, got a new one, problem fixed!
Always try the easy / cheap stuff first

[handpaper]

siddiqi, check this thread. I changed everything you did, plus (later on) the AFM (twice!) and entire engine wiring loom . I disconnected the ICV one day when it refused to idle smoothly and I didn't have time to clean it; drove it about and noticed that the misfire was gone. I then gave it a thorough test, i.e. ragged it senseless round the lanes for half an hour - it never missed a beat. The ICV stayed disconnected

[siddiqi1]

handpaper,

I thought only i was crazy enough to change so many things! Quite reassuring that is!lol

Do you think that the ICV for some unknwn reason is deciding to fully shut when driving? Even then,though you are right, i cnt figure why it would cause this problem, bcz the throtle is open so it shouldnt matter!

Maybe its somehow telling the ecu that its on idle when in fact its not and hence fuel and timing gets mixed up?

Sabs

[sam325is]

as i said above i have seen the identical problem on a merc. Change of ECU sorted it. i dont see why and icv would change anything.

[handpaper]

I'm not entirely sure myself why it causes the problem, but here's my best guess.
The ECU has a lot of stuff to do and it accomplishes most of it by earthing things; the sparks are created by interrupting the coil negative connection, injectors are fired by connecting their -ve end for the appropriate duration. The ICV is driven in a similar way.
Now the ECU has certain requirements itself, chief among them being the correct power supply; that is, a certain voltage across it to enable it to operate. If the ICV is sticking, it will draw much more current than if it were moving freely; this current must be 'sunk' by the ECU (current is 'sourced' if it's controlled at the +ve end, 'sunk' at the -ve). Being asked to sink a lot more current than normal may not damage the ECU, but may cause a rise in the ECU's ground or 0V, reducing the voltage across the device to a level where it has insufficient to operate, whereupon it shuts down. This removes the load completely (it's not earthing anything), restoring the correct supply voltage, and the ECU starts working again.
Why it should happen at 4-5,000 rpm I don't know and I'm equally clueless about why it stops happening above 5500.

[davidt]

My 325i has suffered with similar issues for a while now, misfires on tickover and at higher revs, also occasional bad starting so after reading this thread decided to change the ICV. Problem is now cured, many thanks you all.

[siddiqi1]

david,

Love it! Nice to hear. This is what the zone is about

Sabs

[gazza]

i have had this problem for a while ....changed the icv ....problem now gone ...yipppeeeeee

[siddiqi1]

I changed my ICV too today, so far so good!!

Nice to see this thread was productive

[siddiqi1]

Guys, it started again

Jumping round liek an australian kangaroooo at randomn points in the rev range!

It starts fine, idles fine, doesnt overfuel as far as i know

Its started after a good 6months; having resolved the problem, its come back

I changed the ICV for a known working one; to no avail!

looked at the injector loom and sprayed some elec contact cleaner for good measure; still the same!

Im suspecting the AFM this time!

Also; i had a electrical mishap; well rather a big one. Prior to this occuring; i had two wires connected at the diagnostic port; becasue my ign switch is playing; well they toched and the wires were smouldering black; they burnt like mad, and melted the diagnostic port out of shape !

Anyhoo; it may be relevant; however i cant see any damage to any wiring anywhere

Any further suggestions guys

[calmac]

If you have not replaced the leads, I would check them.

I have had a very similar problem on my 325, the car did not misfire, but would randomly cut out for a split second when accelerating, felt like engine mounts were going to tear, as well as your neck muscles!. The leads were only a couple of years old, but the resistor caps on 2 of them had failed.

I would at least test the resistance of your leads on a bench, check them against each other, including the king lead.

My 325 ignition system was sensitive to misfires, pull one lead off, the whole system goes funny, I assume all 325's are the same. This was on an 88 touring.

[cliff]

[siddiqi1]

So i just pull the leads off; run them through a multimeter?

Visually im looking for any sort fo cracks i suppose; anything that looks like it could be shorting; what are resistor caps?

Its so sudden that you cant even brace yourself for it; my belt yanks at my chest; it does become annoying!

[calmac]

Pull the whole set of leads off the car and test the resistance of each lead assembly individually with a multimeter.

When I did this, I found that the leads had about 6k ohms resistance, except for 2 that had an infinite (not quite the right word) resistance, basically no continuity between the ends of the lead. Your leads should all have very similar resistance values. The resistor caps are just the part of the lead that plugs onto the spark plug, but also have a built in resistance, rather than the lead itself.

I'm not sure of the specifics, and I may be wrong, but the HT side of an ignition system has to have a large resistance in it, I assume because of the high voltages. This resistance can be in the king lead, rotor arm, plug leads, plug caps or the spark plugs themselves, or a combination.

The 6 cylinder M20 can not have resistor plug leads (because the resistance of each leads is proportional to it's length, and the distributor cap position creates a large range of lead lengths) so they used resistor plug caps on the ends of the leads, I assuming that all m20s were the same as mine here.

I hope I have helped and that my understanding is correct, if not anybody is welcome to correct me.

[calmac]

http://www.realoem.com/bmw/showparts.do ... g=12&fg=05

Item 08 is what I have been calling a resistor cap, the note says that it should have a 5k ohm resistance. It is part of the plug lead, so can't be tested separately from the lead.

[siddiqi1]

Calmac,

thank you so much for your advice; and time in posting, much appreciated! Right so off with the leads then! Im going to test for 6ohms on all including the one from the coil, and then will report back!

[siddiqi1]

have bene looking for sum wher to to poot this to won every one . i had a simaler problem with my car about two yers ago car cept misfiaring randomly did the same as you and replast every finc including the engin wiring loom,ecu,leds,full pump,relay,plugs,leds,cap,rota,ticover valv fingeyand are mas meter but to no avale then wile miy misis was driving ma baby wich i dont normaly let hapan and most setonly not now espesholy sins she has ben resprayd and she reverst it in to a wall .eny way two yers ago it cort alight with her driving it lukaly the poles or garda savill as i liv in span wer right behind her and maniged to cep the flames down untill i ternd up and put it out with a proper firer extwinsher .wilst istarted my resarecshon project i trid to trace the stat off the fiyer wich wos the stater moter wos getin stuc engajed wich corsd the ecu to have to meny volt which corsd the stutering now u wood finc that u wood notic the starter with sum cind of nois but evon low i wos looking for the fult or mis firing for about 3 munthe i never herd the starter moter wining or enathinc.

Now it could very well be my starter! I had a very big electrical mishap ealier this week, involving my starter!! Did you replace the ECU, i dont think my starter is getting stuck engaged; but how do you know; as in how do i find if it is stuck engaged?

Saboor

[calmac]

Just to clarify, the leads should have 5-6 THOUSAND ohms resistance (5-6k ohms).

[siddiqi1]

bimbo question calmac; but do you know what setting i should have the multimeter at to ttest this?

i.e. 20k, 200k,200,200?

[calmac]

20k should be right. So the multimeter will read from 0 to 20,000 ohms, because you are looking for 5-6000 ohms, this gives you the best detail without the multimeter giving you an error.

[siddiqi1]

thanks so much calmac for all your help; Im going to try your advice and will report back with all the readings!

thanks once again

[siddiqi1]

UPDATE:

guys just checked my dizzy and rotor. Like new guys, no cracks or anything; just a little black dust present, but all the terminals were still bright gold.

rotor was in similiar condition too!

havent checked the leads yet; will do that later on!

[cliff]

now way that i now off totest the starter but with the damig it corsd to my car i wood replac it with a recon one . once the fiyer had ript throo miy car the ecu was bernt along with the rest of it .but not to wory she is now looking more butihtal than ever must post sum pics

[AndyTouring]

now way that i now off totest the starter but with the damig it corsd to my car i wood replac it with a recon one . once the fiyer had ript throo miy car the ecu was bernt along with the rest of it .but not to wory she is now looking more butihtal than ever must post sum pics

??? Is this English ???

[Morat]

No, but the guy might have a problem with English. Cliff, if you use Firefox you can get it to install the UK English dictionary that will help you out a lot. People tend to put a lot of store by spelling on the internet since its about the only thing they can tell about you from the written word.

[AndyTouring]

I thought it was all sms "text speak" !

[siddiqi1]

UPDATE:

i fixed it , i fixed it! thank the lord; jsut before summer starts....yeppeeeeeeeeeeeee

Thanks a bunch to Goergen for supplying an AFM within no time! thanks buddy

Replaced the AFM; and boof off she went pulling like the train she is! Though fingers crossed it doesnt appear again!

Im ordering a ECU just for backup in case; but see what goes!!!

thanks everyone!!

Saboor

[georgen]

UPDATE:

i fixed it , i fixed it! thank the lord; jsut before summer starts....yeppeeeeeeeeeeeee

Thanks a bunch to Goergen for supplying an AFM within no time! thanks buddy

Replaced the AFM; and boof off she went pulling like the train she is! Though fingers crossed it doesnt appear again!

Im ordering a ECU just for backup in case; but see what goes!!!

thanks everyone!!



Saboor

Wohoo !! I am absoloutly delighted that your car's sorted dude. It's some feeling right ?

Good work Sabs

[siddiqi1]

ah mate couldnt have fone without your help!

thanks a lot! Now i feel like driving it; otherwise i couldnt be bothered for the ordeal of looking like a plonka jsut going to the shops!

Summer here; and now its all good! Cant wait to book it in and get me bushes done!!!

thanks everyone!