Not sure if this is in the correct section, but feel free to move the thread if so.

Anyway.. I've recently bought an evo 5 and it was running with out any problems until the past few days.
Originally is was jus a rough idle, and would seem to "hunt" or "cough" a bit every 10 seconds or so.
It developed into not being able to rev over 3k without the engine dying and not being able to accelerate any further, and feeling like it was misfiring or having problems with fuel starvation.
I'd recently run the tank quite low with the light on about a day before, i figured it had picked up dirt in the tank and clogged the fuel filter, so changed that and also the spark plugs at the same time just incase they were old and were being blown out by the boost and causing the issue. This has improved the issue but not fixed it at all.
Still cant boost or use high revs for any period of time as the car starts to cough and splutter and lose all power.
Sorry for the poor description but the problem is quite random.
Maybe a dying fuel pump? I've checked the A/F ratio and it doesnt seem to be leaning out at all and is still quite rich (about 13:1 - 10:1 under boost).
Boost is set to 15psi.
I've reset the ECU and gapped the plugs to 0.8mm

Ideas anyone?

 

What are the mods on the car, sounds like you have aftermarket cams, which could explain the idle to an extent.

 

Have you checked your coil packs to see that they're functioning properly?

 

i think the car is pretty stock from what the guy i got it from was saying, like engine wise.
today it has been better after changing the fuel filter and spark plugs, but still cant sustain full boost as it will cough and misfire it seems. Still has a rough idle though.
not sure if this is related or not, but if im at idle and i tap the accelerator it wil go up in revs and then drop down and almost stall, then settle out again to its rough idle.

how would i check the coil packs? im guessing if they have an issue it would be under high load?

 

mods wise, boost controller, piggy back ecu (although no corrections made at all on it so it isnt effecting anything), A/F monitor.
Owner before me had a vta blowoff valve which i have plumbed back into the system how it should be. impossible to find a stock one.

 

One of your injectors may be clogged or not spraying properly/fully.

 

1. Boost leak test. (It sounds aLOT like a BL)
2. Check spark. You can see plenty of vids on how to test coilpacks on youtube etc.

 

cool, will have a search tonight and see how we go with the coil packs. Guessing youtube/google for how to do a boost leak check too haha.

i had a thought it may be a blocked injector after replacing the fuel filter helped a bit. should i run injector cleaning in the fuel to try and solve this?
I know with my last car the fuel pump system had issues at one stage and wouldnt switch to high load mode, and i had to give it a constant earth. Are there similar problems like this with evo 5's?

 

It sounds exactly like a boost leak, so I'd start there. You'll need a compressor and a way to connect it to your turbine inlet.

Basically, take your intake assembly and disconnect the BOV from it (so the BOV assembly stays connected to the UICP. Disconnect it all the way to the turbo, so you're looking straight into the turbine. Then buy or make something like this: http://www.siliconeintakes.com/index...aaf15b3f89bc50

Basically a way to connect the compressor to the turbine and pressurize the system. You'll want to listen for leaks. If you have a boost controller (as you mentioned) you'll need to block that as well since its a controlled leak.

I'd say you should be able to get it to 18 or 20 psi... listen for leaks through the whole system. Some air will come out of the valve cover (breather areas) so you can expect that. Spray all of the connections on the IC pipes etc with some soapy water. Some slow bubbles are fine, but anything major is no good. You should see the pressure drop at roughly 1psi every few seconds. If you hear air leaking... you need to examine it, and address the leak.

The fuel injector cleaner probably isn't worth it unless its a last resort. Check air/fuel/spark first.

So...

1. Boost leak test.
2. Check the plugs, wires, etc.
3. You've checked most of the fuel... you could have a bad injector but you'd see that on the sparkplug.

There should be a better how to on here about boost leak testing.

I'm putting most of my money on a boost leak though.

Good luck m8!

 

Thanks heaps, will have to give it a go.
although wouldnt a boost leak just cause the system to no be able to get up to the set boost amount as easy or as fast? i wouldnt have thought it would cause misfiring issues as well?

 

check those plug gaps.

 

currently they are gapped to 0.8mm .. think i should go smaller?

 

I'm having what sounds like the same problem what did you find was causing your car to run like that?

 

yes! .8mm is .031 gap; stock evo gap (for 8/9) is .020 - .024. .031 would be hard to get even with a powerful coil-on-plug setup

gap those plugs down to .5-.6mm and re-test the car

 

I didnt read everyone post but just incase they didnt say this....

check your psi once I had my fuel pump replaced and didnt realize the last owner had put in a 255 and a shop put in a stock one. I was running too high psi for the fuel pump so it wouldnt go past 3k it would just sputter like crazy eventually I swapped it myself with a 255 and got a retune then problem solved.

I am not saying its your fuel pump but maybe your boost controller is malfunctioning and your putting out more psi than your fuel injectors or pump can handle. (or injectors may need servicing)