I have been fighting fuel cut and miss fires at high rpm. I have replaced wires pulgs, fuel filter. Fuel pump o-ring.

I have a walbro 255 hp in the tank. I moved the aeromotive afpr's gauge on to the wiper cowl to see it while driving. I am losing pressure at about 10 PSI of boost. I also can not build more than 60 psi of fuel pressure.

I also know from my logs that I am getting flat top on the MAS hz at my fuel cut/miss fire. Around 2300Hz

I am running a what I believe is a turbonetics 50 trim (uncertain it could be larger). I am running a SBR internally gated turbine housing. Waste gate can not go lower than 25 psi.

Done boost leaks holding to 25 psi

I have been fighting this since I got the car running two years ago on the 16g it was not soo bad, but on the 50 trim its at much lower rpms. Also the car did run better when I first put the 50 trim on.

I just do not know were to start. I think I have multiple issues. I am leaning towards a new fuel pump and time for SD.

Only major change I made was took off my COP and put the stock coil back on to help with a random miss fire CEL p0300 helped some but not allot.

Sounds like the diaphram in the FPR needs to be replaced. How old is the FPR?

http://www.dsmtuners.com/forums/articles-engine-fuel/399037-replacing-diaphragm-your-afpr.html

The afpr is about 2 years old. If it was the diaphragm why would I be seeing an increase in fuel pressure?

nuclearr said:

The afpr is about 2 years old. If it was the diaphragm why would I be seeing an increase in fuel pressure?

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I would also like to know this...

Dont mean to hijack your thread, but im having the same problem. I cant get my AFRs in the 12s to save my life and im running only 12psi. I need to switch to my stock fpr and see what happens now that these guys have suggested that it might be the AFPR

nuclearr said:

I have a walbro 255 hp in the tank. I moved the aeromotive afpr's gauge on to the wiper cowl to see it while driving. I am losing pressure at about 10 PSI of boost. I also can not build more than 60 psi of fuel pressure.

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Well it said you are losing pressure so unless I missed something? Also what size injectors are you running? and what brand? And is your wally rewired?

FIC 850's. I rewired the pump a few weeks ago, some difference but not much. But I have also read that walbro 255's can internally leak at high pressures when they get older. I did not buy my pump new so I do not know how old it is.

I also know that I am maxing out the hz on my MAS. I do not want to throw money at this thing and it not be what I need.

I inspected the diaphragm it appeared to be in good shape. I may order a new one because its the cheapest part on my possible list of problems.

I see that you have to other cars in the 2nd gen, you could try and swap out a MAF on a other one and see if the MAF might be the problem. Also where do you have the vacuum line hooked up for the FPR? Is it tee'd into anything else or by itself on the intake manifold?

Do you have a wideband? What are the readings before and during the symptoms?

If your AFPR isn't maintaining a rising rate of 1:1 then boost pressure is going to restrict the fuel injectors. That's the purpose of the 1:1 rising regulator, it keeps fuel spraying at a constant pressure regardless of boost pressure. If your base fuel pressure is 43psi and your boosting to 25psi, then your regulator should be at 68psi. Losing 8psi of fuel pressure will definitely lean out your A/F ratio, possibly to the point of damaging results.

Changing the diaphragm is definitely a good start. The Walbro 255 pressure relief valve isn't supposed to open till 85psi. If you have any way to activate the fuel pump without running the engine, you could test the Walbro by activating it and adjusting the AFPR to around 75psi. If you can't successfully reach 75psi with the new regulator diaphragm, I would suspect the 255's pressure relief valve.

What temperature spark plugs are you running? Whats the gap on them? I've had both maf overrun and plugs being gapped too big cause misfires in the upper rpm's. The more boost you run the smaller the gap should be and the colder plug you should use. I also had similar issues running really lean in the upper rpm's and after swapping out a bunch of stuff it turned out that my year old walbro 255 was bad. Dropping in a new walbro 255 fixed all my fuel issues.

Rsawd95dsm said:

I see that you have to other cars in the 2nd gen, you could try and swap out a MAF on a other one and see if the MAF might be the problem. Also where do you have the vacuum line hooked up for the FPR? Is it tee'd into anything else or by itself on the intake manifold?

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I believe I have the boost gauge taped into the afpr vaccume. I have 4 or 5 MAS I will try swapping one this weekend. Also I do not think mine is bad but belive I am at the limits of the stock MAS due to the hrz maxing out in my logs.

WES_393 said:

Do you have a wideband? What are the readings before and during the symptoms?

If your AFPR isn't maintaining a rising rate of 1:1 then boost pressure is going to restrict the fuel injectors. That's the purpose of the 1:1 rising regulator, it keeps fuel spraying at a constant pressure regardless of boost pressure. If your base fuel pressure is 43psi and your boosting to 25psi, then your regulator should be at 68psi. Losing 8psi of fuel pressure will definitely lean out your A/F ratio, possibly to the point of damaging results.

Changing the diaphragm is definitely a good start. The Walbro 255 pressure relief valve isn't supposed to open till 85psi. If you have any way to activate the fuel pump without running the engine, you could test the Walbro by activating it and adjusting the AFPR to around 75psi. If you can't successfully reach 75psi with the new regulator diaphragm, I would suspect the 255's pressure relief valve.

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I know that is not rising one to one. I seem to only get a rise of 15 psi before it drops off. On the current diaphragm I can only hit around 65 psi with the car off and closing the adjuster screw all the way in.

DJ23GSX said:

What temperature spark plugs are you running? Whats the gap on them? I've had both maf overrun and plugs being gapped too big cause misfires in the upper rpm's. The more boost you run the smaller the gap should be and the colder plug you should use. I also had similar issues running really lean in the upper rpm's and after swapping out a bunch of stuff it turned out that my year old walbro 255 was bad. Dropping in a new walbro 255 fixed all my fuel issues.

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I am running brp6es's gaped to .28 need to check them again.

nuclearr said:

I believe I have the boost gauge taped into the afpr vaccume. I have 4 or 5 MAS I will try swapping one this weekend. Also I do not think mine is bad but belive I am at the limits of the stock MAS due to the hrz maxing out in my logs.



I know that is not rising one to one. I seem to only get a rise of 15 psi before it drops off. On the current diaphragm I can only hit around 65 psi with the car off and closing the adjuster screw all the way in.



I am running brp6es's gaped to .28 need to check them again.

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If I read correctly your running 25psi of boost right? If so you should def drop in some bpr7's and possibly try a sliver smaller gap on them. I've also had issues with my old Aeromotive afpr not raising 1:1 with boost. In my case the vacuum port on the regulator was leaking under boost so I had to teflon tape the threads of the port to seal it. I also had issues with the bolts that hold the top of the regulator down on the diaphragm backing out and also causing it to leak. I'm still leaning towards a bad fuel pump. Your issues sound very similar to mine when my walbro 255 shit the bed. I ended up dropping in a new high pressure walbro 255 and it solved my problem completely.

In my old car when I was overrunning the stock 1g maf you could totally see the hz readings in the logs go crazy right when the car starting breaking up and misfiring. If you hz readings are are just maxing out and not actually reading all crazy then I'd say your not overrunning it.

I had 7's before every thing I read said I needed 6's. For pump

I am seeing flat spots in the hz on a graph. At the peaks all flat spots are at the same hz

Upload a log. I want to see whats going on.

For the plugs. 7's with a gap of .26 and never look back.

nuclearr said:

I believe I have the boost gauge taped into the afpr vaccume.

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Re run the boost gauge vacuum somewhere else. The AFPR should have its own vac line with nothing else attached to it.

livedsm4g63 said:

Upload a log. I want to see whats going on.

For the plugs. 7's with a gap of .26 and never look back.

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I can but they are EVOScan logs.

Rsawd95dsm said:

Re run the boost gauge vacuum somewhere else. The AFPR should have its own vac line with nothing else attached to it.

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I do not have any where else to run it. I only have 3 vacuum ports. One goes to the BOV and the map sensor is tied into it, the PCV port, and the one going to the afpr and boost gauge. I have a 6 bolt head with a short runner intake manifold.

OP-

Maybe i missed but what car are we talking about?? The car pictured in your avatar is a 1ga yet your sig shows 3 2g's?

We need to know what MAF you are running.

If you are running a 1g MAF it is easily being over run. End of story.

If you are on a 2g MAF 2300hz is not enough to over run it.

What MAF?




EDIT-- just noticed its throwing misfire code.... OBD2.... 2g.

gimmie11s said:

OP-

Maybe i missed but what car are we talking about?? The car pictured in your avatar is a 1ga yet your sig shows 3 2g's?

We need to know what MAF you are running.

If you are running a 1g MAF it is easily being over run. End of story.

If you are on a 2g MAF 2300hz is not enough to over run it.

What MAF?




EDIT-- just noticed its throwing misfire code.... OBD2.... 2g.

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Sorry for the confusion my Profile pic is of a 90 talon TSI I sold back in 09. I will pull up the log its on my tuning computer and will post it for those who can look at it.

Here is my log I am wrong on the hz I am getting flat tops at 1593.75hz on all my logs.

Check out your ecuload. It looks to be staying at 159-160. When this is happening your HZ stays the same. Is is possible your not seeing load over this? You should apply the patch for 2bit load,rpm etc. just to verify. Upload the rom and xml your using. I want to take a look.

livedsm4g63 said:

Check out your ecuload. It looks to be staying at 159-160. When this is happening your HZ stays the same. Is is possible your not seeing load over this? You should apply the patch for 2bit load,rpm etc. just to verify. Upload the rom and xml your using. I want to take a look.

Click to expand...

You are correct in that I am not seeing load above 150 and the flat spot in the hz is in the same spot.

Well I think I know what you are talking about with the 2bit issue. I can not get my car to run properly on Ceddy's big map. I had to revert to the small map and that is my issue.

Well found out my MAS sucked in the honeycomb and wrapped it around the vane.

So now back to tuning. As that is the reason for my fuel cut. I leaned it out no fuel but but its too lean now.

Are you back to using BigMaps?