Hey guys,

back again with the same issue.

I am having some throwbacks to what the problem might be. Can someone please help me diagnose?

1.Car starts fine during cold start, fuel is delivered.
2. Car runs fine for the most part
3. as soon as you give it above 2,500 rpm or more the car then goes into some limbo and starts to idle rough (misfire I presume)

4. Car then idles rough for a couple minutes but given gentle throttle the car will go back to idling just fine.
5. Car does not drive at all car will stall and die.

6. When started after it dies the car has a rough time starting, I usually have to prime the fuel 3-4 times.

7. Car starts after the fact idles roughly then goes to a smoothe idle afterwards

Note No smoke or bad smells coming from the exhaust, car has no Check engine light or anything...

This is on a 1998 Evo 5.
Car has:

Aftermarket charge piping
Aftermarket intake : HKS RS Intake
Aftermarket Boost controller, HKS Valve controller
Aftermarket O2 housing
Aftermarket cat back exhaust

Everything else is pretty much stock

NEED HELP PLEASE!

 

check your vacuum hoses to your fpr

 

MAF sensor perhaps?

 

get new spark plugs and gap them close 0.28 or 0.32. my car used to do the same and that solved the issue for me.

 

get new spark plugs and gap them close 0.28 or 0.32. my car used to do the same and that solved the issue for me.

 

Fuel pump?
Maf?
Measure fuel pressure if possible.

 

Spark plug wires

 

Really sounds like vacuum to me... but hard to say. You'll just have to go through things one at a time..
Another option is a dead Coil. Also MAF as mentioned is a definite possibility.
If it is just the plugs they must be really really bad...

 

Do you have a non-recirculated BOV? I have seen an issue like this where sometimes the BOV sticks partially open some of the time causing intermittent poor behavior.