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Only firing on 3 cylinders

Posted: Tue Nov 04, 2008 5:05 pm
by hd_andy
Hi all,

I have a 1988 325i and its only running on 3 cylinders. It appears to be running on 1,3 and 5. There is a strong smell of fuel and lots of unburnt fuel going out the exhaust.

There is a spark. I have replaced the DIzzy cap and rotor arm anyway as they both looked in need of replacing.

I swapped over the injector wiring from injector 1 to 2 and that got 2 running again.....

So is there any common wiring issues to be aware of? What route does the wiring take?

Also can anyone recommend a fault code reader?

The check light has also started flashing

Thanks

Andy

Re: Only firing on 3 cylinders

Posted: Tue Nov 04, 2008 5:19 pm
by andrews
Check spark plugs and HT leads, also all the ignition system connections. Their faulty can cause misfire in cylinders

Re: Only firing on 3 cylinders

Posted: Tue Nov 04, 2008 5:29 pm
by SPADGE
Check the connecting plug that links the injector loom to the engine loom as these can be troublesome.
Its located on the right hand side of the engine block beneath the inlet.

Re: Only firing on 3 cylinders

Posted: Tue Nov 04, 2008 5:39 pm
by sati
Check the HT Leads , i had same prob only 1,3,4 were running , swap leads from an escort and its was running fine .

Posted: Tue Nov 04, 2008 6:02 pm
by StuBeeDoo
Sounds like you have a wiring fault on the injector loom. The injectors are in 2 banks of 3 - 1, 3 & 5 and 2, 4 & 6.
Take the loom plug under the inlet manifold apart and clean all the terminals. If that doesn't cure it, next step would be to try another injector loom - one that's known to fire all 6 injectors.
HTH
Stuart.

Re:

Posted: Tue Nov 04, 2008 7:47 pm
by hd_andy
Thats really helpfull thanks very much guys, I will check it out tomorrow.

Andy

Re:

Posted: Tue Nov 04, 2008 8:01 pm
by town325i
if you need an injector loom i have one i no is good you can have it for £15 posted

Re:

Posted: Tue Nov 04, 2008 8:09 pm
by Brianmoooore
Injector loom without a doubt! Check under the lower rubber boot for a rotted wire.

Re:

Posted: Thu Nov 06, 2008 4:42 pm
by hd_andy
Hi again,

I have cleaned up the plug and reconnected it and now it wont start at all!!!

Have disconnected and reconnected a few times and still no joy, I think i have probably broken the wire when I disturbing the plug

Does anybody know what sort of voltage you should get at the injector plugs?

Cheers

Andy

Re:

Posted: Thu Nov 06, 2008 5:47 pm
by zimmer-320i
dont quote me but iirc its 5v

Re:

Posted: Thu Nov 06, 2008 7:04 pm
by andrews
When I claened injectors on mine I used the battery voltage to move injector( i.e. 12 volts, m40 engine). hd_andy, I think you have broken the weakness of injector wiring. Check the nearby to the plug wiring. probably it'll help

Re:

Posted: Thu Nov 06, 2008 7:34 pm
by Ant
its the lower section that breaks, remove the upper plug, remove the lower section and peel the runner boots back on both, should all become clear then

I'm with Brian, Defo an issue @ this connection

FYI there should be 12V at all the injectors with the ig on, engine NOT running,

Repair the loom( cut it back towards the starter til you get good clean wires to connect too !! ) if the same 3 injectors are still "dead" then check for 12V, assuming the feed is OK, then replace the ECU

Re:

Posted: Sun Nov 09, 2008 6:36 pm
by hd_andy
Ok, just an update and a big thank you.

Firstly big thanks to town325i for getting me the wiring loom so quickly - you are a star!

It was indeed the multiplug.

Firing on all 6 again :D

It is however still overfueling. Big clouds of smoke when booting it. The wiring to the ECU temp sender seems ok so I am hoping its just the sender. Going to change it anyway as its only a tenner. Otherwise I guess I need to look at the other ECU senders AFM etc.

All good fun so far though!! Thanks again for your help guys this is a great forum!

Cheers

Andy

Re:

Posted: Sun Nov 09, 2008 8:07 pm
by town325i
glad it helped you out mate

Re:

Posted: Sun Nov 09, 2008 8:52 pm
by Brianmoooore
How well did you check the fresh loom?
A common cause of over fueling on M20's is a different broken wire in the plug and socket.

Re:

Posted: Sun Nov 09, 2008 8:56 pm
by town325i
i never had no trouble with over fueling when it was on my car

Re:

Posted: Mon Nov 10, 2008 9:53 am
by hd_andy
Yeah the loom looks good, might be worth checking the lower wiring loom connector again i guess but it all seemed ok....

Re:

Posted: Mon Nov 10, 2008 11:26 am
by no2lurch
the loom below the multi plug is rotten on mkine causing over fueling problems...

Re:

Posted: Mon Nov 10, 2008 12:30 pm
by Brianmoooore
You say you've changed the injector loom?
It's the engine loom side of the plug and socket that gives trouble.

Re:

Posted: Fri Nov 21, 2008 1:10 am
by Chase007
Any news on this prob mate?

Re:

Posted: Fri Nov 21, 2008 2:08 pm
by hd_andy
Hi guys.

Yes, I changed the ECU temp sensor (blue one) and now no more white smoke!!!!

BUT I now have a small cloud of blue smoke (!). Basically from cold its fine and then when it reaches running temperature you get blue smoke on hard acceleration.

So to me that sounds like rings, going to do a compression test this weekend to find out for sure. Cant understand why that would have happened its only on 117k and its got a pretty comprehensive service history mainly BMW.

It might be replacement engine time next week then! Whats the going rate for a 325i engine and are there any differences to be aware of?

Andy

Re:

Posted: Fri Nov 21, 2008 2:57 pm
by zimmer-320i
i have/get a small puff of blue smoke i think its leaking stem seals but its not bad at all but what to expect froma 20 year old motor that problery had more than a few thrashings!!!

i dought its rings as it would be constant, but maybe brian knows??

tho mine is hardley noticble and only castch a glimse of it some times

Re:

Posted: Fri Nov 21, 2008 5:52 pm
by AlpineAde
zimmer-320i wrote:i have/get a small puff of blue smoke i think its leaking stem seals but its not bad at all but what to expect froma 20 year old motor that problery had more than a few thrashings!!!

i dought its rings as it would be constant, but maybe brian knows??

tho mine is hardley noticble and only castch a glimse of it some times
Under what conditions?

If under deceleration, long periods of idling or on initial start up then seals/guides would probably be a good call.

Other things could be piston blow by/shot rings ~ usually happens under high loads.

Are you sure it's intermittent?

Re:

Posted: Fri Nov 21, 2008 6:50 pm
by zimmer-320i
its very rarely happens, say if im rolling along at 40 and drop down a few gears to over take i have noticed a few times a small puff of clearblue smoke comeout,
dosnt smke under idle or start up nor under most conditions,
(unless the breather pipe has residue init??)
saying that it was only doing that when i first brought it, may have been the thin old crap oil it had,
not noticed it latley but its been getting darker in the evening so maybe why i havent noticed it, so ill keep a eye,
so if it intermitent like now and again what should i be addressing?

and dont say a B25 swap lol :evil:

Re:

Posted: Fri Nov 21, 2008 7:14 pm
by Albinojay
Mine drops down from 6 to 3 when it gets very very low on petrol. I this normal?

Any other car I've owned just conks out lol

Re:

Posted: Fri Nov 21, 2008 8:54 pm
by AlpineAde
zimmer-320i wrote:its very rarely happens, say if im rolling along at 40 and drop down a few gears to over take i have noticed a few times a small puff of clearblue smoke comeout,
dosnt smke under idle or start up nor under most conditions,
(unless the breather pipe has residue init??)
saying that it was only doing that when i first brought it, may have been the thin old crap oil it had,
not noticed it latley but its been getting darker in the evening so maybe why i havent noticed it, so ill keep a eye,
so if it intermitent like now and again what should i be addressing?

and dont say a B25 swap lol :evil:
Keep an eye on it.

Perhaps get a mate to drive behind you and have him keep an eye open when you give it some wellie. See what he reports.

Engine swap? Why would I say that? If you like whatever engine you run, then run it, I say.

The smoke thing has three levels of expense, basically. White smoke = nothing, usually condensation evaporating away from when cold, no biggie. Black smoke = a little more expensive, usually indicating rich running...injector issues, computer issue, sensors, usual stuff. Blue smoke = expensive to bloody expensive, unfortunately. Blue smoke = oil drinking. Think pistons/rings = rebuild, worst case scenario.

Or you could always just source a second hand 2 litre.

But all this is jumping the gun until you see exactly where/how your smoking situation arises. How's the oil consumption? Compression OK? How hard do you push the car?

The real problem is in the "intermittent" nature of your issue. They're a bugger to solve...so that's why I reckon if you can get a mate to have a good look at the car as you drive it you might be able to learn a little more.

Re:

Posted: Sat Nov 22, 2008 3:05 pm
by zimmer-320i
6 TO 3????