running lumpy, ht leads, whats that hanging off it

Wed Mar 30, 2011 10:21 am

Hi guy recently changed the leads on my car. When I got the car it used to run spot on, it's been parked up for 3years now runs like a heap of sh!4. Even before changing the leads. No I have put the new ones on I noticed a difference on one of the original leads the was a clamp which plugged into something on the block, what is that lead for? And any suggestions why it runs crap.

Wed Mar 30, 2011 10:29 am

pulse generator if its a later car..the pre facelift didn't have them ...have you bought the wrong leads

Wed Mar 30, 2011 10:33 am

Yes its a later car. But it was running dodgy before these leads were put on

Wed Mar 30, 2011 10:49 am

Can a mod move this to the technical section

Wed Mar 30, 2011 12:23 pm

et voila!

Did you test the resistance of the old leads before you removed them?

Wed Mar 30, 2011 1:19 pm

Nope. What are the values?

Wed Mar 30, 2011 1:37 pm

Oh yea its an m40

Wed Mar 30, 2011 1:55 pm

The sensor on the ignition lead is an early form of cam position sensor, and tells the ECU which of the two cylinders that move up and down together is just about to begin its intake stroke and which is about to begin its firing stroke.
With the signal and under certain conditions, the ECU will fire the injectors two at a time, instead of all four together, which it has to do when the signal is missing.
The car should run perfectly well without the signal, but slightly better with it.
It's unlikely there was anything wrong with your original leads, unless they were physically damaged, but even then, it's best to replace the damaged one with a genuine second hand one.

Wed Mar 30, 2011 2:10 pm

Nice one brian I still have the OEM leads. What could be the cause of running so lumpy? Would a video help anyone diagnose the problem bearing in mind that it ran sweet when I got it and only done a tops of 15miles since then. Things which have been changed are the blue temp sensor and the leads.

Wed Mar 30, 2011 7:34 pm

Many things can make an engine run 'lumpy'. If it's just at idle, then the most likely is an air leak letting unmetered air into the inlet plenum.

Wed Mar 30, 2011 9:36 pm

If you accelerate it drops like it wants to cut out then comes back to normal idle, I'd also say when it gets warm not hot it runs a bit lumpy, on startup it stinks of fuel from the exhuast, and I've sprayed wd40 onto every hose and makes no difference to running.

Wed Mar 30, 2011 9:41 pm

Oh yea I also have changed the rubber from the intake to afm

Thu Mar 31, 2011 7:04 am

Check the instructions with the leads, you can normally remove one boot to install that sensor.

Thu Mar 31, 2011 9:29 am

I just uncrimped one end of the lead and slid the sensor over the new lead. it wouldn't fit without completely removing the end of the lead though, there's not a lot of clearance and it's a tight fit on the lead itself.

Thu Mar 31, 2011 11:10 am

The thing with mine was that it was cracked and as soon as I removed the lead from the block it just disintegrated where can I get just that lead? And I still don't think it will solve the running issue

Fri Apr 01, 2011 9:36 am

Sat Apr 02, 2011 8:21 pm

i have a video of the running shall i upload it

Fri Apr 15, 2011 11:55 pm

anyone, its so bad that when you go to pull off its cut out you have to rev it over 2k so it doesnt cut out, things that have been changed are blue temp sensor, leads new spark plugs

Sat Apr 16, 2011 12:41 am

The fact that your exhaust is reeking of petrol would indicate that not all of it is getting burnt, so spark is the first place I'd be checking - are you sure that your new leads are connecting to your sparkplugs properly? Aftermarket leads often require you to leave on the larger, removeable connections that top some sparklugs, whereas for OEM leads you have to remove them. Are you getting a proper "click" when connecting them? Do you have to put in a bit of effort when disconnecting them?

Also (if the M40 is the same as the M20), where the sensor lead (the one that you are now missing) conects to the main loom, there should be another identical connection - except this one will be for the crank position sensor. Did you disturb this when disconnecting the pulse sensor connector?

Sun Apr 24, 2011 1:11 am

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