HT leads

Sat Jan 03, 2009 5:01 pm

I got a set of replacement leads for my 89 325i. Went to change them all and the plugs. on no6 there is a connector around the lead running to a connector near the diagonistic plug.
Has anyone figured out what this does as my new set does not have this.
currently feels like there is 1 cylinder down but I think its a bad lead to plug connection. but cant seem to make it work better until I manage to get leads all sorted.

If anyone has the haynes manual the connection can be seen in picture on page 1.18 pic 15.11a

Any help would be great. I miss my cylinder!

Sat Jan 03, 2009 5:03 pm

Not needed to run. Diag back to the ecu..

Sat Jan 03, 2009 5:05 pm

These leads don't usually need replacing. There are two types. One with the inductive pick up and one without. Sounds like you have the wrong set.

What were the symptoms that led you to change the leads?

Sat Jan 03, 2009 5:06 pm

So its only for diagnostics. And I can have my motor running sweet again!

Very fast reply. Was thinking it could be for ignition timing return for the ecu so it knows where it is and will keep it in check.

Sat Jan 03, 2009 5:13 pm

I initially changed the plugs as was just doing a service. When I put in the new plugs I could not put on the tops of the plugs the part that makes the connection. This then left me with a car that seemed underpower and had a hessitation around 2k revs esp when at 50mph in 5th.
Decided to change leads aswell as I think they are original.

Is the pickup just magnetic and has 2 wires running to the sensor?

Sat Jan 03, 2009 5:46 pm

Forgive me if I have this wrong but you need to unscrew the little caps on the ends of the spark plugs to make them connect with the original leads. I doubt there is anything wrong with the original leads.

Sat Jan 03, 2009 5:52 pm

I did this but this left me with the cylinder problems. have tried other plugs as i 1st though that 1 was faulty. just dont seem to be making the right condition when cap is off. just that the problem arose after i changed the plugs.

Sat Jan 03, 2009 10:08 pm

You do realise that some plugs need the outer part of the connector unscrewed and discarded?
The inductive pick up on the plug lead is the M20's equivalent of a cam position sensor. Like most engines, it will run without its input to the ECU, but will run better with it.
It was used for diagnostic purposes only on very early management systems.

Mon Jan 05, 2009 10:04 pm

ok back to the magnetic pick up. this should just be a pulse sensor that works by the induction from the spark plug lead.

this is a continuous band of metal in a plastic case. is this a certain type of metal or is it magnetised?

any help always useful

Mon Jan 05, 2009 10:11 pm

I think the ecu batch fires injectors until it sees the pulse from that pick up and then fires them in banks of three ( but i could be wrong on that )

Mon Jan 05, 2009 10:24 pm

that does explain the running its just not right at cruising speed and would explain some of the carbon on the plugs.

need to try to get my sensor back on but not shelling out £75 for new ht leads! was thinking cut the sensor and resolder in on the lead. I no heat on ht wont go well

Mon Jan 05, 2009 10:39 pm

I have a new set of leads cap rotor arm that only done about a hundred miles before i converted to a M50 engine are you ever around dublin .

Mon Jan 05, 2009 11:19 pm

I can be around that end of the country but it might be a few weeks. normally involves a run to the airport. any excuse to get the 325 out on the road!

will keep you in mind esp cause id love a look at an m50 in an e30 in person.

Mon Jan 05, 2009 11:31 pm

I wont have the e30 with me some fecker tried to rob it up here so its back home in mayo .

Mon Jan 05, 2009 11:51 pm

thats not right. if they had any sense they wouldnt touch a mans pride and joy.

i think double barrel is the only job for scum like that.

if im down ill def give you a shout.