5 pots m20

[shadrack]

today my cars developed a fault, when driving along if you slow down to 1500-2200k revs it seems to develope a missfire and drop onto 5 pots, then as the revs pick up after 2200k it fires on all cylinders and goes again? if reved on tickover seems to sound like on 5, as you rev it, if you pull each plug lead off one by one everything sounds the same, i swapped the coil of the 318 im breaking and made no difference, the rotor rm and that bit round it looks like new....any sugestions my brother said try a new coil as when his golf did this he had a 2nd hand one and no better then a new one cured it,

[Barx325i]

sounds like an HT/connection fault? Not sure though, try testing the resistance of each HT..

[shadrack]

yeh i thaught that but it thaught if it was a ht problem it would have got even worse when i pulled each lead off that wasnt the bad one so it wouls be on 4 pots

[shadrack]

just to add it ticks over fine, its when you blip the throttle or drive under 2200 revs it does it

[Barx325i]

sounds like a random one.. I'd check the dizzy cap, to be sure, check the plugs are tight, check the plug core hasn't separated from the metal shroud (with it running, remove HT and push down on the plug, if it's rattling up and down you've found the prob)

Ultimately check the injectors - you can use a long screwdriver as a sonic probe - press the handle to your ear near your cheek bone and the other end onto the injector - the click will be prominant so if one is a bit vague, this could also be the fault..

Seems unlikely but start from the bottom & work your way through the possibilities. I don't want to waste your time if this is something somone else can pinpoint, but just thoughts.

[sweep]

Remove the plugs keeping each matched to its cylinder and see if any are a different colour to the rest

[shadrack]

will check plugs tomora, to see what they look like its also abit intermitant,

[shadrack]

right so more help needed, my problem is on cylinder 4 as when you remove lead it makes no difference, i have tested swapped leads plugs about, all plugs are sparking and all leads are good, also compression tested it tonight and got 170psi on all cylinders, so im thinking could it be a knackered/faulty injector, also failed mot on emissions got 2100 on hydrocarbons, this fault started night before mot so petrol could be going straigh into exaust, typical when your 25yr old car fails on emmissions and headlight alignment with a comment of that is one clean car underneath for its age off mot bloke! thanks

[Curr946]

Have you checked the plug under the inlet manifold? I had this problem on my touring turned out to be a crappy connection at this plug

[shadrack]

what on number 4 injector? thats my thinking now is no fuel getting to number 4?

[Curr946]

cant remember if it was number 4 on mine but as said the issue was the same and was intermittent and it was down to the plug under the inlet manifold which joins the injector loom to the main engine loom

[shadrack]

Thanks I will check theses and injectors tonight but its deffinately looking like the problem is there

[shadrack]

Just a thaught but reading the wiki about injectors there's some extravagant way of de-pressurising the fuel system, when ever I have done this before I've just pulled the fuel pump fuse with car running let it stop then disconected battery is this way ok on e30?

[Speedtouch]

Are all the spark plugs correctly gapped, and are the threads in the head OK?

My first E30, a 320i, had a stripped spark plug thread on one cylinder, and would sometimes run slightly lumpy.

It may be worth removing the plugs and laying them on the rocker cover, cranking the engine over and checking they all spark evenly.

[shadrack]

also to add there is two wires that come out of the end of the injector wiring loom, one goes down the bottom of the engine and is fastened onto something, the other is just hanging loose?? it has a opposite of a bullet conector on it but i cant work out where it goes or what its for

[Speedtouch]

Sounds like the inductive pickup that goes from a small loop attached to No.1 spark plug lead over to the diagnostics socket.

It's not critical to have it, but if fitted, the Motronic ECU occasionally operates in semi-sequential mode under certain conditions.

[Curr946]

is your temp gauge behaving? on the injector loom there the wires for the blue and brown temp senders

[shadrack]

yeh they connected and fine bu after that there are two wires going past the temp blue and brown and head right down near sump,

[shadrack]

Fault found, wiring to injector 4, at least I know what ill be doing tomoro night!