long story kinda short I have an Evo 9 and my idle is pretty much makes the car a potatoe. Cold start idle is terrible. It starts up to like 700 rpm and will drop to the point it stalls unless I keep gasing it. Once it warms up it gets a little better but still not where it should be. After warm, I can drive it but once I clutch into neutral to come to a start it pretty much wants to die unless I gas it while I'm braking. Just recently did a boost leak test and took care of a few leaks. Still pretty much the same thing. My next step is to bite the bullet and buy a iac. Tonight I was playing around with it on Evoscan making sure the tps was set correctly and what not. Pretty sure it is. The car was warmed up and idleing at roughly 750 rpm. I removed the vacuum line that goes to the intake mani from the fuel pressure regulator. The car instantly jumped to 1000 rpm and it was ALOT better while driving. It still had a little hiccup and almost stalled tho. Not sure why removing the vacuum line helped me because i took care of all leaks yesterday when doing the boost leak test.. pretty stumped and don't know where else to turn. Like I said I'm gonna try to buy an iac but just wanna make sure that'll be it before I drop 400 bucks on one. Next step would be take it to a shop for a tune.

Evo 9
Speed Density
30r
kelford 272s
fic 950cc
double pumper
sparktech coil non cdi
ets intercooler/piping
tial bov/wastegate

 

Was there anything done to the car prior to this "issue"

 

Nothing done prior to the issue

 

it will take steps on finding the culprit for sure. but its usually down to:
boost leak or vacuum line(s) popped off the intake manifold, and lastly fuel.
So make sure you're getting adequate fuel by disconnecting your ignition cables and removing the fuel feed line and putting the car in on position and check the flow.(have a friend on hand works while observing). if you're running dual maps make sure you're on the right one. Good Luck man.

 

Are your injectors fouled up? If you took the vacuum line off and it got better (which would raise pressure since vacuum would lower it from base at idle), maybe the higher pressure is getting passed the dirty injector nozzles better. This would also make sense if it suddenly started happening. Maybe some gas station had some poor quality fuel which fouled them. I'd run some injector cleaner through the tank and see if that clears it up first - cheap and easy to try. I've had that happen to me before on my Porsche and the fuel injector cleaner fixed it pretty quickly.

Also, if you want to check fuel pressure, get a fuel pressure tester and Schrader valve sandwich plate. I have a permanently installed plate that gives me NPT, and I fitted an NPT->Schrader fitting on it. You place the plate between the fuel pressure regulator and fuel rail giving you an instant Schrader valve to test fuel pressure on.

Thanks!

S.

 

I wouldn't do that (check fuel by flow)... Not only is it hazardous, but when not under pressure, flow will probably look just fine. A couple years ago I changed my fuel pump, and suddenly I was getting very low pressure. I took the lines off to check flow, and fuel flowed fine at zero PSI of pressure (I did it straight off the carrier, with a long pipe, routed completely outside the car, with a spare FPR on it). Put it back on, and it just wouldn't pressurize. Ended up being an O-ring on the bottom of the fuel pump carrier had gotten dislodged when I was changing the pump! I spent hours/days trying to find that (I bought another pump, went back to stock, etc - almost bought an entirely new carrier!), since it was so baffling.

Definitely need a fuel pressure tester if you want to check pump operation.

Thanks!

S.

 

thank you so much for the input! That honestly makes the most sense.. it seems it's not getting enough air or fuel at idle/when the pressure drop.. gunked up injector might be preventing fuel at such a low pressure.. gonna give that a whirl after work today, and I'll report back. Thank you so much for the help!

 

check your IACV also. sounds familiar to when mine died. super low idle, would have to give it gas when the car was cold to keep it from dying

 

yea im gonna buy one today hopefully.. part number is the same as a dodge stratus and it's a lot cheaper then oem mitsu lol.. 400 bucks for a new one

 

You could also hit up a junkyard. You would have a wide choice of cars to choose from when looking for an IACV.

 

actually that's my plan after work.. cross referenced it to 01-05 Stratus/Sebring.. local yard has a bunch of them so I'm bound to find one.. I hope

 

If you want an eBay / Amazon special I have one I'll sell you. It's the standard $25 one found on Amazon normally. I went through two of them, all replaced under warranty, before buying OE. The one I still have is the third replacement and was never installed, I just got the replacement to get the replacement and bought OE.

Personally, I'd go with OE. If you do, make sure to test your current one before dropping $250 or so on a new one only to find out that isn't the actual issue haha

 

Your double pumper will have destroyed the FPR....as they do.

As has already been said, check pressure and flow.

Flow is checked with the return line replaced for a long one to a container, the engine running at idle.

 

the double pumper isn't hooked up.. only running one pump.. but I tested my iac and the valve is stuck.. to test flow at idle it's as simple as you stated? What am I looking for with how much it flows?

 

How did you test your IACV? If you did the "movement test" (i.e. Pulled it out, turned key to on, and expected it to move in/out), that test is not conclusive. I did that test on mine and it didn't move... spent $300 on new one, and the new one did the same thing! In my case (since I was at the end of my complete rebuild) it turned out I had forgotten to bypass the injector resistor pack for the new injectors, but that IACV test is definitely not conclusive.

Do you have a boost gauge hooked up? What vacuum do you show at idle?

Also, do you have a Tactrix cable? It would be useful to run an idle log and see all the parameters. Also, might be useful to go in to SAS mode (which disables the IACV) to see if it holds base idle properly (you need Tactrix cable and EvoScan software).

Oh, also you didn't happen to "clean" the throttle body recently did you??

thanks!

S.