Dear all,

I am currently experiencing the following behavior in my 2003 Evo 8:

When driving without reaching High throttle, that car drives normally at a boost of 0.5 bar and at the second i reach a high throttle and the boost reaches almost the max (1 bar in my case), the car's engine starts to shake, the car looses power, and i get the service engine light on.

When plugging the scanner, i get the error : misfire in number 4.

I changed the spark plugs. I installed bosh platinum iridium.

The problem remained the same.

I thought it's a fuel issue so i used an injector cleaning solution in the fuel tank and the engine shaking issue got reduced to half i.e. i got more performance and the range of the issue only at very high throttle.

I am wondering if it is a fuel injectors issue, fuel pump issue, turbo issue or even if it's a software issue.

I appreciate any help before i spend my money with mechanics trying to figure out the issue.

Regards.

 

Check to see if the vacuum line came off of your Fuel pressure regulator. That's about exactly how my car behaved, though I didn't get a misfire CEL.

 

Thanks THUB

i will check the vacuum line as soon as possible and i will post back.

Regards

 

At first look, the lines looked normal between the FPR and the FPR solenoid.

I started the car and checked if there's pressure in the line between the two listed above but i found out that there were not.

i realized that the solenoid got 2 lines, one electrical and one mechanical.

i connected the line from the FPR to the second line in the solenoid (mechanical line), the result is as follows:

- the car got more idle
- the starting of the car got much better...it used to take time to start and specially when it's hot.
- the shaking at high throttle is 90% fixed and even sometimes not shaking...

as i understood, the problem of my car was cause of a big amount of fuel not being neither fired nor turned back by the FPR and that's the cause of the misfire.

Is it possible to clean that solenoid? or you suggest better buy a brand new one or even maybe an after market part?

I hope that would fix my problem at 100%.


what do you suggest guys?

THUB, thanks a lot

 

If you had a CEL come on you may have a code stored that may help you with diagnosing the problem.

 

i received this error:


P0505 IAC Malfunction

IAC (Idle Air Control) System Malfunction

any suggestions?

Thanks and regards.