Evo X idle hunt/surge
 

2008 Evo X MR,40000km/s,completely stock.

When pulling up to a traffic light/stop sign engine almost stalls then the rpm bounces up to 1200-back down to say 400,back and forth like that for probably 10-15 seconds.I can pop in into N and it still does the same thing.Dealer can't find the problem.

Anyone experience the same and a suggestion?

You usually see it with an aftermarket intake. Have they looked at your MAF? Also check the vacuum line on the FPR.

+1 remove your engine cover towards the front passenger side for a little vacuum hose that might have popped off

I don't think they checked very much.They told me that there was a service update in the form of a reflash that should take care of it....

I'm starting to think they just pulled the battery terminal off and hoped for the best because I got the surge at the dealership's exit to the main road:lol:

I would have went right back only I was picking it up afterhours and it was only the sales dept open.

Is your A/C on? I sometimes got fluctuations of 500 RPM's with it on, but not the 800 RPM swing you're discussing.

check for vacuum leaks

weird, I have the same idle fluctuations on my '11 GSR. It actually has stalled on me while sitting at a light. outside temp being around 87F. This morning it did it again and it was about 37F in Houston. both at idle while at a light. all I have is a K&N drop-in.

My completely stock 2011 GSR idle hunts all the time too.. Especially when hot outside. All my lines are intact.. I don't know what the problem is.. It's random for the most part.. I just blip the throttle a little to make it calm down.

Mine does that as well but only when I start it. I only experience this when I drive it hard around the city. I have a full TBE, AEM Intake, IC, ICP, and a tune. I dont know why it does that.

BLT!! ( no, not a burger) boost leak test ;)

Check the fuel pressure regulator vacuum hose. There is a huge thread on here and it is a know problem. The hose is easy to miss cause it's so tiny. Just do a search. Read up on it. Then hook it back up then throw a zip tie on it. Happened to me.

Since I know people are lazy here is the LINK

I like being generous :D

Mines popped off twice in 2 years I've never got around to putting a zip-tie on it.

do you have a heat shield blocking the air filter on your intake from the radiator fans?

if you run an open filter and our fans kick on blowing hot air into your intake, it'll cause your idle to stumble or die. a heat shield will fix this

FIXED!

Thanks guys,it was indeed the fuel pressure regulator vac line.

And I think I'll go back and have my eyes re-checked because I can't believe I missed that when checking the oil.......its right there.

Actually I don't feel too bad because the Mitsubishi dealer couldn't find anything wrong with the car......

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