Misfire -under load and high temp

[RobP]

Bit of a chin-scratcher this one.
Car accelerates cleanly across the rev-range (throttle mashed to the floor) when the engine bay is relatively cool.
In the footage below -ignore the absolute boost figure. The guage is inaccurate. On a rolling road test a few days ago (where of course the car behaved impeccably)it boosts to 1 bar.
http://s5.photobucket.com/albums/y185/robprice/?ac...

However about about 30-35mins driving with a fair bit of heat soak about, I pick-up a misfire (engine stutters and stumbles) usually but not exclusively at peak boost (4-5Krpm) but you can drive through it. Again see below (although the sound gives a better indication of the stutter)
http://s5.photobucket.com/albums/y185/robprice/?ac...

Fuel pump (Bosch Motorsport)is brand new
Wiring all in good order and 'upgraded'
Plugs - brand new cooler running NGK 7s being used with gaps checked and rechecked (so it's not blowing a spark out a full boost).
All vacuum/breather pipes are on correctly and not leaking.
Coil-sets checked out and seem OK.

Any ideas?

[NickyTwoHats]

I had this.

Turned out to be a loose wire in the connector block drivers side at the side of the engine.

Others will suggest (probably rightly) that this will be plugs or Lambda sensor.

[JLSELAN]

I wouldn't be so quick to dismiss your boost gauge reading.
It is very common for these cars to overboost when driven on the road even though no problem seems to show up on the dyno. The engine/drivetrain dynamics of the two situations are different enough so that it is necessary to use a conservative boost setting on the dyno in order to ensure that overboosting does not occur in road-going situations. Overboosting can cause a lean-burn situation, with associated engine damage--especially at high operating temps.

[mgbond]

JLSELAN said:

I wouldn't be so quick to dismiss your boost gauge reading.
It is very common for these cars to overboost when driven on the road even though no problem seems to show up on the dyno. The engine/drivetrain dynamics of the two situations are different enough so that it is necessary to use a conservative boost setting on the dyno in order to ensure that overboosting does not occur in road-going situations. Overboosting can cause a lean-burn situation, with associated engine damage--especially at high operating temps.

DaddySummo had an interesting boost issue, on the Dyno it behaved as it should (0.75bar ish) but on the road it was hitting 1bar. He had an air leak?

Bondy

[RobP]

Thanks guys - if the turbos are over-boosting and the ECU notices this and 'shuts it down' then wouldn't this happen all the time? The car behaves impeccably for the first 40mins (with engine nice and hot) but things start to go awry once the general heat soak pervades the whole engine compartment. To me this would seem like something electrical is getting flaky when hot.
Maybe the only way to really see if it is a fuelling/ignition or sensor issue is to wire it to a 'puter and test it on the road.

[Adrian W]

or invest in an afr meter

[daddysumo]

Rob

My car has exactly the same symptoms as yours ! I did all the same checks and found the rear fuse holder near the ecu to be corroded so replaced that with a weatherproof one. The car was better but still the prob was there.I put it on r/r and the A/F went through the roof (16)when the stutter occurred and the fuel pressure droped to 30 psi so all indicating lack of fuel.
I re checked things on the fuel pump side including the earth from the upgraded wiring.The next time I drove it all
was fine untill I had nearly 100 miles done then noticed when I cornered it happened then after a few more miles it would do it more frequently.
The fuel gauge was 'showing' under a 1/4 of a tank so I put fuel in and immediately the prob was gone, I drove it on the bumpy lanes etc with no stutters !
So maybe either the pump is getting hot, mine is insulated btw which Im not sure is a good idea and the new fuel in the tank helped to cool it, or my gauge is lying and I was running out of fuel and what was left was sloshing around in the tank, or the tank/pipework has an obstruction in it ?
Hope this helps I will investigate further !

Steve

[RobP]

daddysumo said:

Rob

My car has exactly the same symptoms as yours ! I did all the same checks and found the rear fuse holder near the ecu to be corroded so replaced that with a weatherproof one. The car was better but still the prob was there.I put it on r/r and the A/F went through the roof (16)when the stutter occurred and the fuel pressure droped to 30 psi so all indicating lack of fuel.
I re checked things on the fuel pump side including the earth from the upgraded wiring.The next time I drove it all
was fine untill I had nearly 100 miles done then noticed when I cornered it happened then after a few more miles it would do it more frequently.
The fuel gauge was 'showing' under a 1/4 of a tank so I put fuel in and immediately the prob was gone, I drove it on the bumpy lanes etc with no stutters !
So maybe either the pump is getting hot, mine is insulated btw which Im not sure is a good idea and the new fuel in the tank helped to cool it, or my gauge is lying and I was running out of fuel and what was left was sloshing around in the tank, or the tank/pipework has an obstruction in it ?
Hope this helps I will investigate further !

Steve

Thanks Steve - I too replaced all the fuses in the box by the ECU, and on the R/R with a brand new motorsport pump, AFR was smack on 12 across the whole rev range. Vids that I posted were on a straight piece of road with full tank of fuel and the wheel insert removed to maximise cooling. (Wheel insert also has a louvre to help reduce heat build up in the side pod).
My fault only seems to occur when the engine bay is heat-soaked -which is why my instinct is that it's an electrical break down under load. Probably find it's something to do with the horn, such is car electrics!!
Fortunately I have a couple of mates who are expert in these matters so resolution will be forthcoming soon (I hope).

[JLSELAN]

Could it be related to overheating the fuel to near vapor lock? The fuel pump re-circulates unused fuel back to the tank, and pumps that move a high volume of fuel tend to heat it excessively over time. Hot fuel does not atomize/burn well. Perhaps a stock M400 fuel pump will work better.

[NobleNick]

RobP said:

daddysumo said:

Rob

My car has exactly the same symptoms as yours ! I did all the same checks and found the rear fuse holder near the ecu to be corroded so replaced that with a weatherproof one. The car was better but still the prob was there.I put it on r/r and the A/F went through the roof (16)when the stutter occurred and the fuel pressure droped to 30 psi so all indicating lack of fuel.
I re checked things on the fuel pump side including the earth from the upgraded wiring.The next time I drove it all
was fine untill I had nearly 100 miles done then noticed when I cornered it happened then after a few more miles it would do it more frequently.
The fuel gauge was 'showing' under a 1/4 of a tank so I put fuel in and immediately the prob was gone, I drove it on the bumpy lanes etc with no stutters !
So maybe either the pump is getting hot, mine is insulated btw which Im not sure is a good idea and the new fuel in the tank helped to cool it, or my gauge is lying and I was running out of fuel and what was left was sloshing around in the tank, or the tank/pipework has an obstruction in it ?
Hope this helps I will investigate further !

Steve

Thanks Steve - I too replaced all the fuses in the box by the ECU, and on the R/R with a brand new motorsport pump, AFR was smack on 12 across the whole rev range. Vids that I posted were on a straight piece of road with full tank of fuel and the wheel insert removed to maximise cooling. (Wheel insert also has a louvre to help reduce heat build up in the side pod).
My fault only seems to occur when the engine bay is heat-soaked -which is why my instinct is that it's an electrical break down under load. Probably find it's something to do with the horn, such is car electrics!!
Fortunately I have a couple of mates who are expert in these matters so resolution will be forthcoming soon (I hope).

Ok. I've had something that sounds similar to both. Started off only in sixth gear at first, then generally got worse and worse till I was experiencing it through all the gears, but always under load. Had all the usual stuff checked and still there. Eventually it got worse, but easier to diagnose because it just seemed like the engine was being starved of fuel.
In the end it turned out to be water in the fuel! The petrolcap lock had corroded and water was going directly though the lock into the tank, through rain or washing.
Clean and drain tank, new filter and new petrol cap--No problems. I think the dealer did well to diagnose it!!

[steve1]

Rob,
Can I just ask what gap you have in your plugs, the NGK 7's need to be gapped slightly smaller than standard plugs.

Steve.

[NobleGuy]

NobleNick said:

Ok. I've had something that sounds similar to both. Started off only in sixth gear at first, then generally got worse and worse till I was experiencing it through all the gears, but always under load. Had all the usual stuff checked and still there. Eventually it got worse, but easier to diagnose because it just seemed like the engine was being starved of fuel.
In the end it turned out to be water in the fuel! The petrolcap lock had corroded and water was going directly though the lock into the tank, through rain or washing.
Clean and drain tank, new filter and new petrol cap--No problems. I think the dealer did well to diagnose it!!

That is a good spot on their part. Probably the last thing I'd ever think of.

[joust]

steve1 said:

Rob,
Can I just ask what gap you have in your plugs, the NGK 7's need to be gapped slightly smaller than standard plugs.
Steve.

Could be, as if the coil is heating up it will become less efficient, and consequently provide slightly less HV input the the spark plug.

Anyone know what the gaps are for each type of plug fitted?

J

[steve1]

As far as I know, the standard plugs should be 40thou. but the 7's should be between 30-35thou.

Steve.

[RobP]

steve1 said:

As far as I know, the standard plugs should be 40thou. but the 7's should be between 30-35thou.

Steve.

Steve - yes, they are all set and checked at 32 thou.

An update - with the car plugged into a laptop and an expert sitting in the passenger seat, it was found that the fuel pump was momentarily cutting out completely at (and only at) full throttle. So the engine wasn't running lean and misfiring, but basically it was not working at all for a couple of short periods between 4-5K rpm. Bit like hitting the rev limiter, only you can drive through it. This event didn't occur when you accelerated hard, only, as I said, when the throttle was mashed fully to the floor. It was so predictable and consistent that a duff ECU was suspected. We swapped the ECU with a spare (with my map programmed in) but found exactly the same symptoms on a 3rd gear run.
So looks like max engine torque is causing a break in the electrics, either physical due to the turning moment of the engine shorting something - or due to an overload on some brittle piece of wiring.
So next step is to double check all earthing connections and wire the pump up directly and see if the problem goes away. If not, we'll then piggyback a spare engine loom and see if that does the trick. If it doesn't I think it's back to the new horn theory...(!)
Sincerest thanks to AdrianW, Yellowshed and Skip (and to suggestions on the forum) for helping sort this out.

[NickyTwoHats]

Look at the connector block drivers side wheel arch....

[Adrian W]

NickyTwoHats said:

Look at the connector block drivers side wheel arch....

It's an M400 the ECU is not in the wheelarch as in the 3/3R

[daddysumo]

Ok Closure on my problem........ To cut a very long story short.. the valve in the fuel tank breather pipe was malfunctioning which stopped air entering the tank as the fuel was being used, causing a vacuum inside the tank which completely stopped fuel leaving the tank and so giving the symptoms of a defective pump when infact the pump was ok just not getting any go go juice to pump.
Once the faulty valve was taken from the pipe all was restored to how it should be and sitting in traffic on the way back from Brands and running the fuel down to almost empty and all still ok ! I will of course replace the faulty ford fiesta/escort offending part

Steve

[hollowpockets]

RobP said:

steve1 said:

As far as I know, the standard plugs should be 40thou. but the 7's should be between 30-35thou.

Steve.

Steve - yes, they are all set and checked at 32 thou.

An update - with the car plugged into a laptop and an expert sitting in the passenger seat, it was found that the fuel pump was momentarily cutting out completely at (and only at) full throttle. So the engine wasn't running lean and misfiring, but basically it was not working at all for a couple of short periods between 4-5K rpm. Bit like hitting the rev limiter, only you can drive through it. This event didn't occur when you accelerated hard, only, as I said, when the throttle was mashed fully to the floor. It was so predictable and consistent that a duff ECU was suspected. We swapped the ECU with a spare (with my map programmed in) but found exactly the same symptoms on a 3rd gear run.
So looks like max engine torque is causing a break in the electrics, either physical due to the turning moment of the engine shorting something - or due to an overload on some brittle piece of wiring.
So next step is to double check all earthing connections and wire the pump up directly and see if the problem goes away. If not, we'll then piggyback a spare engine loom and see if that does the trick. If it doesn't I think it's back to the new horn theory...(!)
Sincerest thanks to AdrianW, Yellowshed and Skip (and to suggestions on the forum) for helping sort this out.

Bringing this one back folks,

after trying all sorts and failing i managed to get my car to cut out on demand while the mechanic was in my car this morning, some of you may remember when i bought my car i complained of the interior light comming on while the engine came on boost...

well this has become more frequent and what i thought may have been the fuel pump/a misfire, has been identified by the mechy as the engine cutting out for a second or two while pressing on (similar to RobP's situation above), possibly caused by a perishing engine earth, it doesn't happen on the rollers, just on road when the engine will flex in its mounts more and bumps and vibrations have a chance to affect things.

They can't look at the car till next week but incase i get the chance does anyone know what wires to im to look for and are they easily replaced?

As always much appreciate the help

Graham

[RobP]

hollowpockets said:

RobP said:

steve1 said:

As far as I know, the standard plugs should be 40thou. but the 7's should be between 30-35thou.

Steve.

Steve - yes, they are all set and checked at 32 thou.

An update - with the car plugged into a laptop and an expert sitting in the passenger seat, it was found that the fuel pump was momentarily cutting out completely at (and only at) full throttle. So the engine wasn't running lean and misfiring, but basically it was not working at all for a couple of short periods between 4-5K rpm. Bit like hitting the rev limiter, only you can drive through it. This event didn't occur when you accelerated hard, only, as I said, when the throttle was mashed fully to the floor. It was so predictable and consistent that a duff ECU was suspected. We swapped the ECU with a spare (with my map programmed in) but found exactly the same symptoms on a 3rd gear run.
So looks like max engine torque is causing a break in the electrics, either physical due to the turning moment of the engine shorting something - or due to an overload on some brittle piece of wiring.
So next step is to double check all earthing connections and wire the pump up directly and see if the problem goes away. If not, we'll then piggyback a spare engine loom and see if that does the trick. If it doesn't I think it's back to the new horn theory...(!)
Sincerest thanks to AdrianW, Yellowshed and Skip (and to suggestions on the forum) for helping sort this out.

Bringing this one back folks,

after trying all sorts and failing i managed to get my car to cut out on demand while the mechanic was in my car this morning, some of you may remember when i bought my car i complained of the interior light comming on while the engine came on boost...

well this has become more frequent and what i thought may have been the fuel pump/a misfire, has been identified by the mechy as the engine cutting out for a second or two while pressing on (similar to RobP's situation above), possibly caused by a perishing engine earth, it doesn't happen on the rollers, just on road when the engine will flex in its mounts more and bumps and vibrations have a chance to affect things.

They can't look at the car till next week but incase i get the chance does anyone know what wires to im to look for and are they easily replaced?

As always much appreciate the help

Graham

Graham - iirc the main engine earth strap is at the rear of the engine/gearbox to the chassis. Not particularly easy to get to unless you have very bendy and strong arms as it is placed in the centre of engine bay. During the process of excluding bad earthing we put another strap at the front of the engine to the battery earth as well.