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1fstavant
11-06-2008, 06:49 PM
possible causes of a bad afr before i was hitting 11.5 now im at 13.0 could a bad fuel filter cause this or a bad fuel pump need help immediately

JumboBlack1.8
11-06-2008, 06:52 PM
Wow....that looks bad......What're the AFRs under all other driving conditions?

1fstavant
11-06-2008, 06:58 PM
fine 14.0-15.0 idle and part throttle 12.1 but wot in 3rd goes to 13.0 just did a compression check and was 180 across the board

djwimbo
11-06-2008, 07:04 PM
does it do it in 4th and 5th as well?

That's a sign of a fuel pump not pushing enough fuel volume top end. Depending on what fuel pressure you run, and what pump, sometimes you can actually push less volume at higher pressures.

does it spike to 13.0:1 or does it taper?

1fstavant
11-06-2008, 07:13 PM
taper a bit...starts at 12 and makes its way up to 13- i didnt want to push it with it running lean like that...walbro 255 with a 3.0 fpr

Don Supreme
11-06-2008, 07:14 PM
Same 15 psi-16 psi?

What pump?

1fstavant
11-06-2008, 07:30 PM
yea 15lbs walbro 255 intank....side note i havent changed my fuel filter since i bought the car and after putting gas in it it started missing like crazy the previous two fill ups

mike-2ptzero
11-06-2008, 07:36 PM
Do you run a maf?

317ssayzarc
11-06-2008, 07:39 PM
Do you run a maf?

Iirc he's ME5 so yes... But so suddenly Mike?

1fstavant
11-06-2008, 07:46 PM
any thoughts? lol im going to change the filter tomarrow but should i be looking at anything else...this just happend like 20 minutes ago after all day of driving fine...or could my fuel pump be taking a shit

1fstavant
11-07-2008, 06:04 AM
bump any input

offroader1006
11-07-2008, 06:07 AM
can you extend your gauge so its visible during a pull?

GetBoosted84
11-07-2008, 06:30 AM
Oh man I think I'm running into the same issue as you:
http://plainbored.com/files/logs/2008-11-07%20(3rd%20Gear%20WOT%20Lambda%20Only)/3rd%20Gear%20WOT%20at%2021-22%20psi%20LOG-01-031-xxx-xxx.JPG (http://www.audizine.com/forum/showthread.php?t=242787&goto=newpost)
My setup is compleletly different from your but I have the same issue. The above log is a 3rd gear WOT pull at 21-22 psi on a GT2860RS with a stock fuel pump, stock 4 bar fpr and genesis 415cc injectors.

I'm subscribed to this one because I want to see what solves your issue. What injectors are you running btw?

Don Supreme
11-07-2008, 06:30 AM
any thoughts? lol im going to change the filter tomarrow but should i be looking at anything else...this just happend like 20 minutes ago after all day of driving fine...or could my fuel pump be taking a shit

It could be -- you need some logging data -

Log some maf values
and
if you could observe fuel pressure during a boosted pull then you could determine if pump / fuel restriction has any role in this.

mike-2ptzero
11-07-2008, 06:53 AM
Iirc he's ME5 so yes... But so suddenly Mike?

Well if his maf starts reading lower then it should then it will happen really quick.

Also if his setup is running his maf near its max reading all the time the maf will tend to go bad quickly.

Don Supreme
11-07-2008, 07:04 AM
He is running a 90mm maf, so I am sure its far far from max... probably ~ 100 g/s +-

mike-2ptzero
11-07-2008, 07:47 AM
He is running a 90mm maf, so I am sure its far far from max... probably ~ 100 g/s +-

Well we know how well those work. Plus since the readings are so low all the time, any slight little change in its readings is going to have a huge effect on the afr.

AudiRacerS4
11-07-2008, 08:13 AM
are you sure you dont have a leak anywhere, my car was doing the same thing I would creep up to 12.8-13.1 while going WOT and I found a small tear in the hose that goes to the FPR.

mike-2ptzero
11-07-2008, 08:24 AM
That could be another cause, he might also want to recalibrate his wide band setup if he can since the wide band 02's tend to read leaner as they get older.

bassed
11-07-2008, 10:02 AM
are you sure you dont have a leak anywhere, my car was doing the same thing I would creep up to 12.8-13.1 while going WOT and I found a small tear in the hose that goes to the FPR.


I think this is a strong candidate, considering you had everything apart and maybe things loosened up after breaking her in a bit.

I do however think Fuel Pump and Fuel Filter being OEM and original may have a huge factor as well. These are the preventative and neccesary maintence/upgrade items to tackle with these cars and the mileage they have.

Don Supreme
11-07-2008, 10:10 AM
I think this is a strong candidate, considering you had everything apart and maybe things loosened up after breaking her in a bit.

I do however thing Fuel Pump and Fuel Filter being OEM and original may have a huge factor as well. These are the preventative and neccesary maintence/upgrade items to tackle with these cars and the mileage they have.

He has a walbro fuel pump.

bassed
11-07-2008, 10:14 AM
He has a walbro fuel pump.

That was directed at Chris, I should have clarified that.

1fstavant
11-07-2008, 07:37 PM
walbro is getting changed out on monday for another walbro...after a fill up it will start studdering at idle which from several sources is what happens when a fuel pump starts losing pressure...but my maf readings are the same and its new so i know thats not the problem...

1fstavant
11-10-2008, 03:49 PM
fuel pump was the culprit...misfires due to plugs gapd wrong now im gonna do another comp check idk if its me or my mounts but it sounds wrong so ill find out

Don Supreme
11-10-2008, 03:52 PM
What sounds wrong.

GetBoosted84
11-10-2008, 03:54 PM
That was directed at Chris, I should have clarified that.

:-) I knew what you meant.

I'm going to get a replacement fuel filter + pump shortly.

1fstavant
11-10-2008, 06:06 PM
um idk it sounded wierd but i think it was my fmic vibrating around...love and hate these mounts...love and hate this car another 300 on top of everthing to get it running ok

TQMB5
11-11-2008, 09:09 AM
i am having the same problems as well. afr is good everywhere but wot. I was thinking more along the lines of a boost leak but i am on a stock fuel pump, so who knows.

b5a4gt28
11-11-2008, 07:26 PM
So you got another fuel pump right?? Now that you switched it out are you're afr's back to 11.5? Im wondering because my car has the exact same problem.

1fstavant
11-11-2008, 07:28 PM
nope not at all...im putting a new fpr on it tomarrow hopefully tht solves it but im worried im destroyin my motor fin with it...
before when id loosen the gas cap id hear air his out...now no air so im assuming the diaphram went sour and at idle holding the pressure till it gets to great at wot and sends it back into the return line which is why it drops to 11.8 and then starts climing up again