My car has had a surge problem since i built a new engine.

had it on a gas analyzer today ,and it surges because its so weak 0.45% at idle.. and thats max on the ecu fuel adjuster if i unplug the lambda sensor the co raises to over 6.00% because its obviously max rich ,but it does idle nice rich not hunting like it does when weak.
the fuel pressure is 3.5 bar pipe off.


so i get home and take the plugs out No 1 plug is wet and black with fuel but all the others are ok/weak white. the problem must be to do with the rich cylinder making the lambda weaken off ,and this in turn is making all other cylinders weak


what can make no 1 rich? i swapped plug and injector and its exactly the same

 

Get the injectors flow tested mate, sounds like No1 is dodgy.

Boschman does it for a very good price

 

As you have changed the plug and injector (or swapped them around)

It COULD be a fucked plug lead or dizzi cap causing a missfire....


OR... ( along shot)

I had a similar issue on my ecu but that was caused by the crank sensor
and/or the phase sensor miss adjusted and also damage on the crank
pulley and causeing the ecu to think the car was continuously starting
causing the first injector to fire twice. (This was on a P8)

 

holy shit!

 

its not misfiring..deffo on all four ,i swapped a lead and made no difference,

need to look at the crank/phase sensor then! thanks!!!

 

Cant be a fuel pressure problem as it would affect ALL cylinders.

Unless your ecu injector 1 driver transistor is dead or dying.

As another test, (for the above)

swap injector plugs over on cylinders 1 and 2 they should just reach.

The car will NOT be damaged by this, but dont drive it hard for more than
a few seconds in case another fault is hiding a bigger problem.
ALso, there maybe a bit of throttle hesitation while doing this at low rpm.

If the fault moves then I would say you have an ecu problem or as I suggested
above a crank/phase sensor issue.

 

wouldnt it misfire if the no 1 driver was dead?

i will try this thanks for your help mate!

 

If the driver was on the way out, they can act like a delay so extending the actual pulse without the ecu knowing.

Had the same probelm once on an L6 ecu and that uses the same drivers as L8 and P8.

 

ahh i see! is the fault fixable or is it new ecu time? if it was this

 

Piece of piss to fix

(If it is the problem)

I have over 300 of those transistors for that here

 

Bugger, This isnt a for sale post

 

do you do ecu testing?

 

Yes I can test it for you, but I would just check the Phase, Crank sensors
and the crank pulley all look ok first !

 

wil do mate! im sure i do have a wobble on the crank pulley.

i just thought if it ran on all four it must be ok

 

See if Doug (L8ECU) would lend you an L8 as I dont have any myself
just to make sure.

*** Doug assures me he isnt a trader despite the name

 

if needs be i could get a L8 of someone easy...

i'l check these things first though! thanks for you help

 

I have one on the shelf if you require, James



JJ

 

But all was well before you rebuilt the engine?

If you unplug the ISCV does teh engine speed stay in the 900s? If not, fix that first as the engine needs to stay above 800 for the loop to work correctly due to teh breakpoints ive used in teh map. However... this sounds a wierd one, but dont dont discount a faulty FPR spraying fuel into teh plenum via the compensation pipework.

 

you haven't connected the iscv plug to an injector by mistake have you?

 

deffo not mate

 

it all seemed good before the build stu, makes me look toward a sensor set up being more likley?

 

Right so....

i get home today ,and remove spark plugs 1 and 2, cleaned them so they both look identical, gave the cylinders a min or two for the excess fuel to evaporate so both piston crowns are dry....

swapped the injector wires as simon suggested and ran the car for a few mins

the problem stays with no 1

i did the test a few times to make sure..and same results every time, no 1 plug gets wet and the crown is also wet.... didnt go black as i didnt run it for long enough, plug two looks clean and dry


so i now have checked... plugs and cap lead etc... base idle with iscv unplugged is dead on 900rpm, and idle is now uneffected when the iscv is plugged back in, fuel pressure, pressure tested for air leaks at 1, 2 and 3 bar, swapped injectors over and done the above test and still have one rich cylinder no 1....



what can it be? fuel reg as stu suggested?

im wondering if i have stumbled on the reason my engine melted no 4, as i may well have been weak

 

Swap the point where the fuel pressure regulator gets its vacuum with
say the dump valve and see if the problem moves.
Also, with the engine going see if petrol comes out with the pipe off.

If this isnt the problem, You may have a valve or cam issues

 

compressions are dead even across the four cylinders, if i richen it up to say 2% by unplugging the lambda sensor... the engine runs sooo sweet i cant see it being a mechanical issue

i will check the vaccum but its got a seperate plug on the plenum


ohh this car

 

JTECHSAFF,

Just reread you post above, any failure in the closed loop system
(If there is one) will cause the system to revert to standard maps settings
and run slightly rich across all cylinders.

Besides above about 2 to 3 psi, the closed loop control will be deactivated anyway.

Swapping the injector wires shows it isnt an ecu problem IMO.


Barring any mechanical issues....
The more I think about it, I am going with an ignition related issue.

Did you swap the cap, lead and rotor arm ?

 

the cap and arm are new, and i swapped a lead over.

doesnt misfire at all though, deffo always on all four, at hte moment its actually running ok, but still rich on no1

just done the above test mate and no fuel comes out the reg pipe, and didnt make a difference swapping vaccum

 

maybe its a lifter problem? one not opening enough? and causing the fuel to drop onto the cylinder rather than spray in?

 

It is possible to part ignite a cylinder with a weak spark.

I am sorry to say its sounding like a mechanical issue ......

Could be a tappet or valve not seating properly.

Compression tests are done at low speed and at relatively low pressures
so may not cause the problem to appear.

DONT rip it apart just yet, I will have a think and I am sure others will
add suggestions too.

 

thanks mate... thankfull for your help here

when the engine was apart it had cosibro valve guides and seat were cut and lapped in by a local firm who are well trusted

 

have you tried swopping number 1 and 2 injector unit round, to rule out a duff injector?

Bri.

 

yep done that mate

 

does anyone know what pins on the ecu are for injectors one and two so i can compare the duration just to double check its not double firing?

 

JTECHSAFF,

How are you going to measure the duration ?

 

18 INJECTOR 4
32 INJECTOR 2
33 INJECTOR 3
35 INJECTOR 1

 

my carlo fandango multimeter can measure injection pulse in m/s

 

No it cant

Low impedance injectors on the weber ecu's have strange driving signals
that will fool 99.9% of duration testing multimeters and give false readings.

The ONLY way of doing it properly is to use an oscilloscope - Sorry

Try it and let me know the results.

If you can wait till Sunday, I can come down to you and we can
check over your car thoroughly with my scope and diagnostic equipment.

 

cool!

i have got a scope, but im sure you know alot more about this then i do!

 

i swapped the lifters tody and got the running in oil out of it.


made no difference

 

Shit news matey - hopefully Simon will be able to diagnose this on Sun.

JJ

 

not sure what will happen, im on my stag night on saturday, but hopefully i will survive