P1128 P1130 b7 s4 Rough Start

[EUR0tuner]

2006 S4 has a CEL with both codes P1128 and P1130. ****FIX WAS A JHM HIGH FLOW FUEL FILTER****

The car takes 6-7 cranks before starting and when it does it stumbles for a second before smoothing out the idle. Once running it runs just fine, pulls hard and smooth. If I shut the car off and start right away it fires no problem but once it sits for a few minutes its back to the rough start and stumble.

Reading most threads everyone goes with the MAF or Vacuum leak.

Replaced the MAF with a Bosch unit - no change
Replaced the Vacuum Suction Pump - no change
Replaced Fuel pump - no change
Replaced Spark plugs - no change
Smoked engine - no vac leaks anywhere



Ordered a smoke detector kit and ran that to test for vacuum leaks anywhere in the system and there are no leaks anywhere.

Am I right to be leaning towards LPFP in the tank?

When I clear the code it comes back almost immediately, I dont have Vag com but I do have OBDeleven if anyone has experience with that.

Any help or direction would be appreciated.

[Rol-co]

Look at oxygen sensor values and fuel trims. If its at 1 bank swap it to the other bank, injectors can be possible cause but fuel pressure too.

[EUR0tuner]

The fuel trims are definitely maxed out at 25% trying to make up for whatever is wrong.



Looking at the o2 sensors, they seem to change back and forth from bank to bank +/- 4%. I dont know what the sensor voltage should be but here is a few snips of the live data idling.

[Rol-co]

Looks pretty normal except the 25% , the +/-4% telling me the lambda's are working.

[EUR0tuner]

[QUOTE=Rol-co;14982403]Looks pretty normal except the 25% , the +/-4% telling me the lambda's are working.

So it sounds like I am on the right track with fueling being the issue.

Ill pull the fuel rail tonight and visually check out the injectors, but with both banks having the lean issue I cant see all of them being clogged.

Is there a check valve or something that keeps fuel pressure when the engine is off? Seems the only time there is a noticeable issue is when starting the car, once running it does fine.. well after the added 25% that is. So it could be a weak pump possibly?

Sorry very ranty and all over the place.. just thinking while typing haha

[Rol-co]

Yes, bbk has a fuel pressure regulator at the fuel rail, bhf has it at the fuel pump? Or filter unit? Not sure there.
Injectors could be leaking, if you pull the rail the pintle cap's possibly break and fall in, better maybe is to take the top half im off with rail still attached.

[calebtbay]

Yes, bbk has a fuel pressure regulator at the fuel rail, bhf has it at the fuel pump? Or filter unit? Not sure there.
Injectors could be leaking, if you pull the rail the pintle cap's possibly break and fall in, better maybe is to take the top half im off with rail still attached.

I hate those stupid pintle caps!

[EUR0tuner]

I hate those stupid pintle caps!

When I installed the flapper mod, I swapped to the JHM Pintle caps so no issues with them breaking.

Pulled the fuel rail and inspected the injectors, everything looked clean with no visible clogs or build up. Couple little spots with rtv that overhung into the cylinder so I cleaned those off.

Cleared the codes and started it, stumbled really bad for 3 seconds and then smoothed out. We will see how it goes this afternoon.

[EUR0tuner]

Code has not come back but checking the fuel trims there is still an issue and starting still takes several seconds of cranking before it starts.

Edit: Code is back and CEL is on... going to order a new fuel pump and filter

Are there any other options than the VDO fuel pump assemblies ?

[EUR0tuner]

Question on fuel pumps..

Is there any benefit to upgrading to the JHM High flow 255 pump and high flow filter if I am not boosted?

Car has JHM exhaust, JHM Intake manifold, JHM manifold spacers, Jackal Intake, Jackal ECU/TCU tune for reference.

I will not be boosting this in the future, only other mod might be piggies.

[CrickiKaze]

More fuel on tap for pressure but better supply at higher rpm, regulators will maintain the prescribe pressure but a higher fuel pump will help supply fuel if you want a higher pressure.

[EUR0tuner]

Update:

New fuel pump installed
New Spark plugs installed

Still cranks and cranks and cranks before starting. Cleared the codes to see if it comes back after driving for awhile. (edit... codes P1128 and P1130 have come back already)

Something I noticed while waiting for the pump to come in... we had a cold front come in and the car started way faster when it was 50-60 degrees vs when it was pushing 100 outside.

What would cause it to start so much better with the colder weather..

More n more searching has me leaning into 2 possible culprits:
*Coolant temp sensor - saw somewhere the temp sensor controlled fueling based on hot or cold engines, false readings could be causing the lean condition for the codes and a rough start cause not enough fuel..
*Possible weak/bad battery - not enough amps when its hot to give the pump all it needs, doesnt really explain the lean codes though...

Any thoughts?

[EUR0tuner]

She is fixed...

It was the fuel filter.

I installed a new filter about 6 months ago. When installing the filter I accidentally swapped the two lines on the motor side of the filter.. cranked a few times with no start before realizing it and swapped them back and it fired no problem.

Curious if having the lines swapped for just a few somehow did damage internal to the filter which caused it to some how fail.

Either way, new JHM high flow filter fixed the start up issue and the CEL has not come back after a week of driving, fuel trims are normal and she drives perfect.

[Rol-co]

Great!