Cut out at idle and misfire

[PhilH42]

Since replacing a split fuel hose from filter to the copper fuel line and a sleeved exhaust. Nothing else has changed.

I've changed the leads and dizzy cap to be sure but no difference. Arm, coil and amp changed recently and I'm not running extenders. AFM seems ok and I don't think there are any vacuum leaks.

Symptoms are starts up lovely but will just die on idle after a a minute or so, starts back up fine. Will generally run ok but misfires giving it beans and then intermittently just chugging along but not all the time.

I was thinking maybe some crap got in the line but I was careful, or maybe I've kinked/creased the copper line pulling it out the way (b***ard getting it off laying under the car)? I've given her a run a few times to see if it will work through but no luck. Also wondering if I loosened a connection on the fuel pump whilst wedged in the wheel arch or has anyone had an issue like this with a sleeved exhaust?

Any ideas fellas??

[bobfather]

If it's only failing at low revs and working well at high revs then it's unlikely to be fuel starvation. I would suspect the fuel line change was not the cause of your issues and that something else is failing. Have you still got your old HT leads, cap, rotor etc.? If so I would put the old set back on and if the problem disappears you can then refit the new items one at a time to see if any of them have failed. I've had HT lead failure after only a couple of thousand miles. Some leads do not like the hot environment

[Sharpeee]

Mine did something similar and I found ecu connection was damp, dried it out then no problem, might be worth a look

[PhilH42]

bobfather said:

If it's only failing at low revs and working well at high revs then it's unlikely to be fuel starvation. I would suspect the fuel line change was not the cause of your issues and that something else is failing. Have you still got your old HT leads, cap, rotor etc.? If so I would put the old set back on and if the problem disappears you can then refit the new items one at a time to see if any of them have failed. I've had HT lead failure after only a couple of thousand miles. Some leads do not like the hot environment

I did change the leads and cap as a just in case exercise literally this week due to this problem but the symptoms remain just the same...to be fair it was worth changing them as they were getting quite hard from the heat. Their a decent set of black silicon leads from racetech...one could still be faulty of course.

Initially there was a big misfire at high revs only which seems to have lessened but it's still there sometimes,but also now the cutting out (more when cold) and an intermittent misfire at no particular range. It's more at high revs but the cutout at idle is confusing me.

[PhilH42]

Sharpeee said:

Mine did something similar and I found ecu connection was damp, dried it out then no problem, might be worth a look

Definitely worth a look....I've not driven it much since doing the fuel line and exhaust and it's been in and out of the garage (under a cover when out) but it's been very cold and damp. Thanks

[rev-erend]

Sounds like it is running lean.

Fuel in tank?

Blocked fuel filter ?

Wiring suspect at pump ?

Kink in fuel line.

Fuel line collapsing internally.

[PhilH42]

rev-erend said:

Sounds like it is running lean.

Fuel in tank? Yes and fresh

Blocked fuel filter ? Don't think so changed in the last 6 months

Wiring suspect at pump ? Checked previously but yes could be, I was wondering if it could be making and breaking with under force but the idle cut-out wipes that theory.

Kink in fuel line. If I have its going to be fun changing the line!

Fuel line collapsing internally. Thats possible think I left too much slack as well

[PhilH42]

Removed the ecu as suggested and although not damp its seems to have reset itself somewhat. Not misfiring much now just a little bit of hesitation under max load. Not been able to check if its cured the cut out at idle when cold yet.

Did get a bit of a backfire though....still not quite right...timing, fuel pump or fuel supply issues possibly??

[HKGriff]

The idle cut-out and misfire may well be unconnected.

Concerning the idle cut-out, this happened to me a few weeks back. I had inadvertently disconnected the male/female connector for the speed sensor. The m/f connector is located under the armrest/centre console (well, it does on my Griff). If the speed sensor is not sending a message, or the wrong message to the ECU, then the stepper motor may get confused and not allow idle RPM.

The misfire - not sure. Do you have plug extenders? I took two from one bank out, and no problems since.

HTH.

[J400GED]

Could be a faulty AFM.
Try disconnecting the AFM plug on top of the AFM and starting from cold.
See if it idles without stalling.

[PhilH42]

HKGriff said:

The idle cut-out and misfire may well be unconnected.

Concerning the idle cut-out, this happened to me a few weeks back. I had inadvertently disconnected the male/female connector for the speed sensor. The m/f connector is located under the armrest/centre console (well, it does on my Griff). If the speed sensor is not sending a message, or the wrong message to the ECU, then the stepper motor may get confused and not allow idle RPM.

The misfire - not sure. Do you have plug extenders? I took two from one bank out, and no problems since.

HTH.

Its a fair point...it might well be unconnected. Another thing to check is good.

Not running extenders.

[PhilH42]

J400GED said:

Could be a faulty AFM.
Try disconnecting the AFM plug on top of the AFM and starting from cold.
See if it idles without stalling.

Convinced myself its not the AFM as its a sore subject! I'm on number four albeit the last three have been replaced for free each time and are aftermarket. Put a heat shield jacket round the last one and its been fine, but yes its possible! Previous symptoms were always the same...misfire at 3500, but thats not to say this one could be a different set as its been protected to a degree. I've got an OE one as a spare which I will try when I get 5.

I think I've been avoiding this one as I thought I'd solved the problem...the sooner I get rid of the AFM the better I think...bu**er I bet it is now the more I think of it!

Eann's shoving a turbo on her on the 25th and if I could have stretched to it would have gone with an aftermarket ecu fuel and spark....as it is I'll have to wait a bit longer. Just don't want to complicate Eann's job by handing her over half cocked!

[FlipFlopGriff]

Hesitation under load could be ignition amp?
Time to go for a 20AM AFM - the one you need is off an X300 Jag, part number LHE1620AA.
FFG

[ClassicChimaera]

Do you have Rover gauge, you could do with checking your stepper motor position etc odd things happen when the stepper is out of sync.

[PhilH42]

ClassicChimaera said:

Do you have Rover gauge, you could do with checking your stepper motor position etc odd things happen when the stepper is out of sync.

Unfortunately not....should have picked one up ages ago really.

Changed the oil pressure switch as it was leaking so have driven her a bit today, seems fine general driving, only symptoms now are drops a bit on idle every now and again and def hesitation on full foot down around 4000 ish...but only under full load. Going to swap the AFM first and see if that helps at all.

Hmm...yes nothing much been done with the stepper since I've had her!! ts the one thing I've tried to leave alone, as in up to now if its not broken and all that.

Still wondering if the straight through exhaust may have unbalanced anything?

[Steve_D]

You really do need to get Rover gauge it can tell you so much more than just swapping/replacing things.
It also has a function you can use to dismantle and clean stepper motors.
Also get yourself an infrared temperature gauge to point at each exhaust header which will find a misfiring cylinder in double quick time.

Steve

[PhilH42]

Noted Steve....I really do need to get one, I've a collection of parts doing just that!

However on this occasion enigma solved...well not exactly a surprise yes the AFM is Fubar again...thanks Ged for the kick up the a**e I needed to change it over. Runs perfect no hesitation now or dropping idle.

I did find a bare bit of wire going into the AFM so I put heat shrink on it to be on the safe side...not sure if thats a reason why she eats AFM's....I don't think so, its always after a lay up and when the battery goes very low....I now make sure she's trickle charging rather than going almost dead and then full charging.

So when anything goes wrong now or the steering wheel falls off I'm going straight to the AFM

Cheers Fellas for all the ideas.

[ianwayne]

Been trying to chase a bit of a misfire myself. Only when cold though, with rich running. Changed HT leads. Checked voltages and sensors iaw that outlined by ACT here:

http://www.actproducts.co.uk/2011/lucas-14cux-fuel...

The only thing a bit out is that after start up, the AFM voltage is 1.9 - 2.0V instead of the 1.6 - 1.75V expected. Is this critical,i.e. an AFM on the way out?

[Barkychoc]

Did you just change a single fuel hose? Easy to get them the wrong way round if you don't understand the logic of the pressure regulator that needs to be on the line back to the tank.

[PhilH42]

Barkychoc said:

Did you just change a single fuel hose? Easy to get them the wrong way round if you don't understand the logic of the pressure regulator that needs to be on the line back to the tank.

Sorted now thanks...but yes only the hose out, not the return.