hello there i have 2004 evo 8. i am having bogging issues and no boost at all. the car will rev up with no load beautifully but under load the vehicle will start bogging kicking back firing on load after 3500 rpm. i have already replaced plugs wires and checked for boost leaks. checked all wiring sensors and vacuum lines. no check engine light. i have been running diag with my scanner for two days now and everything seems fine. the only thing i might assum is causing this problem is the fuel pump cutting out when its time to feed with tons of fuel in boost range. the car is pretty much stock. just has downpipe and exhaust. PLEASE HELP I AM GOING NUTS!! ALL HELP WILL GREATLY APPRECIATED IN ADVANCE. THANK YOU

 

Also forgot to mention that after replacing plugs and wires the car will to one or two good pulls before starting to bog out and start doing the same thing.

 

So you plugs are failing only after one or 2 pulls? What AFR do you see at the peak boost? What are the plug gaps?
Post close up pics of the fowled plugs.

 

Thank you for responding so quickly. Not sure how you gap the plugs never had to deal with that before. But the plugs are brand new. When the car boosts on the first pull it is i believe around 13 psi when i know it should be at around 15. And for the afr what is the best way to check that. Can the plug gaps really cause the car to react like that? And also can it not be the fuel pump not sending enough fuel especially when its time for full boost? Also for got to mention the car has a 153k miles on it and the fuel pump has never been serviced. It would be a great help if you can help me to learn how to gap the plugs if that is the case and also help with how to get a proper afr reading.

 

Try to gap the plugs down to 0.020" and report back.
And yes a WideBand o2 readout would be awesome to have to troubleshoot these type of issues.

 

so what should afr reading be?

 

Cruising and Idle should be about 14.7:1 and should be able about 11:1 in Boost. On 93 octane that is.

 

yes, your plug gap will do that if your gap is too big. gap it to .020-.024 range and try again. if you dont know how to gap your plug, there are many how to videos on youtube. check them out. let us know how it goes and good luck!

 

thanks alot for the responses guys greatly appreciated. i gaped the plugs to .022 and it is still doing the same thing. also the plugs are brand new 2 days old and only driven for a total of 5 mins. and they are already black. looks like it is running extremely rich. any suggestions on how to fix this problem or the cause of this problem?

 

Bring it to a pro tuner. Don't drive it that rich much longer.

 

so that is what the problem is? it seems to be rich. correct?

 

the only reason it was driven was testing purposes. it was not driven regularly. lol i would be a pretty stupid person to drive the car that way.

 

It does appear to the end result. But the rich condition could be caused by many things. Boost leak, coolant temp sensor failing, FPR failing, injectors sticking, or sparks simply not strong enough to ignite the fuel mixture.

If you don't have a WB O2 installed you are just shooting in the dark.

 

but if i take it to tuner they will be able to spot the problem right away correct?

 

what plugs are you using?