Im driving an 03 evo 8, with 99,000 miles. As of a few days ago the car has been running like ****. Car idles fine. Driving down the road is a different story. My a/f guage is bouncing from 17 to 12 and car bucks alot. If i give it some throttle the a/f guage will peg to 11 . I have done a boost leak test and everything seems ok, no leaks found..

There was a hose off the EGR valve, but but putting it back on didnt solve the problem. I even did the disconnect battery trick. No luck.

I am at a loss, any and all help will be appreciated

Eric

 

intake restricted? Fuel pump or possible injector problem? First things I'd check

 

check MAF, you running a cat? other mods? map sensor? 3 port?

 

No cat. I moved air intake to lower Driver side front bumper. Maybe I'll put back in original place 3 port?

 

3 port electronic boost controller.

is this a bone stock evo? ever tuned?

 

Car has minor modifications. Has manual boost controller. And car has been tuned

 

bad gas?

 

What a/f gauge do you have? Have you try replace wideband sensor?

 

I thought bad gas as well. Topped off tank Monday and the results aren't any better.
Today I put the intake back to its original spot. (behind drivers headlight. It was down behind bumper on drivers side. I cleaned the MAF sensor today. Went for a ride and drive ability seems better. But once you step on the gas it pegs full rich. Car runs smooth when giving 3/4 throttle After that the a/f starts jumping all over the place and car starts bucking again I have the AEM wide band a/f set up. And I did just replace the sensor.
Would my o2 sensor have anything to do with this?

 

id say dead sensor

my afr gauge was reading all wonky, for me it was battery issue (dead cell)

 

Would that cause the car bucking at cruising speed ?

 

Well I'm back, and still have nothing resolved. I replaced my plugs and also throttle body shaft seals. When doing boost leak test, I could hear them leaking. I now have no boost leak and still have hesitation when cruising down the road. My A/F guage goes from 14 to 17. WOT it pulls hard but guage goes rich and flat lines on guage (AEM wideband)
I have replaced with fresh gas as well
Car idles fine too



Please help before I light a stick of dynamite and throw it in the car

 

My 2 cents:

If the car is bucking and driving like ****, a bad wideband sensor is obviously *not* the problem... so don't waste your time there.

I think some of the other guys recommended checking the fuel pump, injectors, and so forth - that's a good place to start. You might want to do some research on this, but iirc, the Evo VIII fuel pump basically has 2 modes: low voltage and high voltage. I remember reading (at least 3-4 years ago) that one guy actually had a stripped wire in/on/around the fuel pump that was causing it to go crazy when it grounded out over bumps or whatever. It's a long shot, but in either case, check the FP and the wiring - make sure it looks good.

My other suggestion would be that if your car truly is only "lightly modded" then return it back to stock and reflash it with a stock tune (don't forget to save your current tune). Drive around the car and see if it still runs like crap; troubleshoot from there.

Good luck.

 

Thanks for the 2 cents! I didnt even think of fuel pump and related components. That is my next move.
Any idea what fuel pressure should be?
Ill start researching, keep you guys posted
Thanks

 

My money is on the fpr being bad. Had a friends Evo do the same thing.