So for a while now I have been having some issues with my evo 9 (SD on Tephra).

The car will randomly cut fuel, and it produces this really uncomfortable bucking. the AFRs go instantaneously lean. When cruising, the AFR reading kind of erratic.

I just bought a Tactrix and evo scan and they have not came in yet so I dont have any scans to look at.

Are there any common issues that could cause this?

I just recently switched plugs maybe 2-3 weeks ago. Put a new o2 sensor in. New throttle body. I have to check the tune with evoscan and then I will be posting logs.

If anyone could lend their knowledge that would be great! thanks!

 

You need to list the mods?

There's lots of common issues.

 

Just a forewarning I bought the car with these mods so and I was never told where some of them came from so if I dont have a brand that is why.

SD Intake
BBK Full
LICP, UICP, Aftermarket intercooler.
Small Battery Kit
Fuel Rail and Injector (I dont know what cc)
Cosworth cams (I dont know if they are 264s or 272s)
Full Exhaust.
Aftermarket Fuel pump (I believe its a 255)

AEM Boost gauge
AEM wideband

 

When the car cuts fuel or whatever it is doing, the throttle also seems to not have an effect. i.e. giving the car more gas does not help it. Most of the time when it happens it happens for maybe a second and then the car goes back to normal or to 10-12 AFR. Sometimes it will happen back to back so it will go lean rich lean rich. Thats what produces the uncomfortable bucking

 

Sounds like same problem im having could be so many things.

Do a Boost Leak Test to get those out of the way, then start checking plug gap, coil packs. Could be clogged injector, bad fuel pump..

 

I had a very reputable Evo guy boost leak the car before he tuned it 3 weeks ago. I brought the car to him but the nature of this issue he didnt notice any issues. Ill pull the plugs and check the gaps but I put new plugs in (gapped correctly) about a month ago.

Im leaning towards fuel pump at the moment because the car was once an e85 car and it could have affected the pump.

I have never had an issue while doing a pull, but that could just be luck.

I plan on switching to a COP unit soon.

Thanks for the help!

 

You'll be outflowing the FPR of course, as they all do.

 

Do you mind elaborating?

 

You need to fit a fuel pressure gauge.........it should be part of the fuel pump upgrade mod.

Then you'll know that before you changed the pump , it was idling at about 33 PSI on the gauge(factory spec in the manual) and now it's idling at 38 PSI on the gauge.

 

Will do. Car came with all the mods on it currently. All i have added are catch cans, ECBC, Coilovers, tie rods, and some other small stuff.'

Evo scan can log fuel pressure correct?

Tuners can also tune fuel pressure right?

 

Looks like you are on SD and if so then you must be running an aftermarket MAP sensor. If your MAP sensor is an Omni 4 bar MAP sensor, try swapping it out for a known working one and report back.

 

This guy goes in all problem threads and says this is the solution, people run Walbro 255 all day with no FRP and no gauge, it's bs.

 

Yea i am on SD. I will do that shortly, thanks!

 

OP, just curious if the symptoms seem to vary based on throttle position? I had the same issues with Tephramod whenever I held TPS around 100% and I'm curious to see what helps your issue



Are there any problems that you can't fix with an FPR and a fuel pressure gauge?

 

Maybe you should fit a pressure gauge to your own car before you comment?

ignorance is bliss.

So they say.





It's just one more problem which compounds all the others.
One that's easy to eliminate.