Fpr

[jayssupra]

How do you no if your Fuel pressure reg is on its way out, i've just been for a drive and when i get to about 3500-4000 rpm the car starts jumping and spluttering when this happens my AFR reads 10.5, i now this is overfueling, also about 4 weeks ago i fitted a bosch 044 fuel pump,could this cause my old stock FPR to give up the ghost, on tickover AFR is 14.5. my car is a T67 single with Apexi ecu

[Wez]

I run a stock reg and a Bosch 044 and have been for some time.

 

What are you using to control the fueling as I see you have a T67 and the 3500-4000rpm range is where the stock sequential system kicks in.

[jayssupra]

Apexi power fc, which has been on the car for about 2 years, with no problem

[jayssupra]

What are the signs of your FPR failing

[MartinBattye]

What are the signs of your FPR failing

 

has this happened since fitting the new pump??? was the old pump a stock one or an 044.

 

if it was stock then its most likely on the old pump fuel flow at high injector duty was falling below the required..

now with the larger pump the system has necessary flow at all times.. hence the overenrichement your now seeing.

[jayssupra]

Old pump was a walbro 255, this problem only started today

[MartinBattye]

it wouldnt be the normal course of failure for the FPR to be increasing pressure higher than usual.. (giving your rich mixture)

 

have you changed anything else on the car?

 

an over rich mixture like what you are describing (check to see if your have black smoking also) would suggest (if the tune hasnt changed) that something is restricting airflow thro the motor.

[Ian C]

Not sure how you've reached the conclusion that the FPR is at fault, the best way to test it is to monitor your fuel pressure - not many people have the kit to do that though.

 

AFRs will go rich due to a misfire if it's not caused by an injector failing to open. The misfire sends unburnt fuel into the exhaust where the O2 sensor reads it and reports a rich condition. Do you by any chance have an AEM AFR gauge? I suspect you do

 

A breakdown of coil packs or a dodgy connection to one is the most likely cause of a misfire coming out of the blue with no changes. You get it in the midrange which is the high torque region where most load related misfires take place.

 

-Ian

[jayssupra]

Yes i have a AEM AFR gauge, and 10 is the lowest it reads so it could be lower, also yes i do get black smoke coming out the exhaust at the sametime the car splutters and reads rich,

[Ian C]

Yes i have a AEM AFR gauge, and 10 is the lowest it reads so it could be lower, also yes i do get black smoke coming out the exhaust at the sametime the car splutters and reads rich,

 

Yeah it'll be way richer than 10.5, but they don't tend to read much lower than that.

 

My money is on an ignition problem, probably coil pack related if your plugs are OK.

[jayssupra]

Cheers mate will get local garage to check next week

[MartinBattye]

Not sure how you've reached the conclusion that the FPR is at fault, the best way to test it is to monitor your fuel pressure - not many people have the kit to do that though.

 

AFRs will go rich due to a misfire if it's not caused by an injector failing to open. The misfire sends unburnt fuel into the exhaust where the O2 sensor reads it and reports a rich condition. Do you by any chance have an AEM AFR gauge? I suspect you do

 

A breakdown of coil packs or a dodgy connection to one is the most likely cause of a misfire coming out of the blue with no changes. You get it in the midrange which is the high torque region where most load related misfires take place.

 

-Ian

 

that is incorrect... a misfire is indicated on the wideband by a leaner than normal situation.... since incomplete combustion has taken place there is excess oxygen in the exhaust gases.. remember a wb02 is an oxygen sensor.. it only works perfectly if there is complete combustion

[Ian C]

"The sensor does not actually measure oxygen concentration, but rather the amount of oxygen needed to completely oxidize any remaining combustibles in the exhaust gas. "

 

http://en.wikipedia.org/wiki/Oxygen_sensor

 

So if a truckload of unburnt fuel goes through, it says "hmm, I need lots of oxygen to combust this lot, I'll report a very rich condition".

[MartinBattye]

thats a very nice article.... but it says nothing about AFR readings under a misfire condition...

[Tricky-Ricky]

This may help,

One thing to keep in mind about wideband O2

sensors is that they can be fooled in the same way

as a conventional oxygen sensor by air leaks

between the exhaust manifold and head, and by

misfires that allow unburned oxygen to pass through

into the exhaust. Either will cause the sensor to

indicate a false lean condition which, in turn, will

cause the computer to make the engine run rich.

 

Taken from here, http://www.tayloredge.com/reference/Chemistry/oxygensensor3.pdf

[Ian C]

thats a very nice article.... but it says nothing about AFR readings under a misfire condition...

 

It wasn't supposed to, nice deflection attempt. You brought up the function of an O2 sensor, not misfire diagnosis. Thanks for the patronisation, maybe I should MSN you to bone up on that thar techie stuff.

 

I'm going off my personal experience - I've seen enough misfires myself to realise the O2 reading is useless as a diagnostic in these cases. I've seen it go rich, others apparently see it go lean, whatever - you can't draw any conclusions as to the cause of the misfire from it.

 

-Ian

[jayssupra]

Checked coil packs they look fine, also have changed the plugs, took the car for a drive and it's still running rich when i put my foot down, not just at 3500-4000 any time i put my foot hard to the floor, after i took the car out i removed the plugs and they were all pitted with black crap, is this a sign the car is over fueling,

[Ian C]

Yep, sounds like it. Do you experience rough running at all times or only when you're flat out? If you warm the engine up, then sit in neutral and rev up the engine, does it struggle to catch the idle when the revs drop and nearly stall?

[pistonbroke]

Does it only missfire at WOT?, if you get to the same rev range with 3/4 throttle, does it still missfire?

[jayssupra]

Yep, sounds like it. Do you experience rough running at all times or only when you're flat out? If you warm the engine up, then sit in neutral and rev up the engine, does it struggle to catch the idle when the revs drop and nearly stall?

 

Never thought about it before but yes if i rev the engine and let the revs fall 7 times out of 10 it will stall, the other times its all over the place then fine, yes car only runs rough and over fuels when i put my foot down,