Engine Touble, Oscillating Idle, Stall when stopping, Etc, Please Help
 

The basics: 2008 Lancer ES. No mods. 91k miles. Regular oil changes, etc. Last oil change was at 88k.

The problem(s): When the engine is cold and it is started things seem fine (slightly high idle due to cold engine). I drive off and after a few minutes of town driving (getting to freeway) I'll get up to about 2500-3000 rpm and then come to a stop at a signal. Engine will nearly stall and sometimes actually stall. No MIL. Restart engine, idle oscillates for 15-20 seconds, finally evens out. I drive off and rinse-repeat. If I can prevent stall by keeping the the RPMs up (let tranny slow the vehicle and only press clutch when RPMs around 1k). Once the engine has been warmed up, there are no issues. No idle issues, no stall issues. This has been going on for about a week (with some attempted resolutions noted below). Most recently under heavy acceleration I will get a MIL accompanied by the Brake light on the dashboard, but the light nearly immediately clears itself. I'm thinking maybe fuel/air mixture or vacuum (see below) but can't confirm (again see below).

Attempted fix(es): Cleaned the air filter (K&N). Pulled the EGR valve and cleaned, new gasket. Purchased a ELM327 reader (Bluetooth) and paired it with my phone to try and get some more information. At idle vacuum holds steady at about 20-21. Under heavy acceleration I can get see the vacuum drop to pretty much 0. I have to wait until the morning to get cold vacuum readings. Also cannot find any stored error codes. Did the Starter Fluid vacuum leak check, nothing found (but still not 100% on that).

Any suggestions? Anyone else have this happen to them? My next steps are going to be take off the throttle-body and clean. Going to replace the spark plugs as well, since I'm sure they are due, but unless i find one (or more) fouled, I can't see that as the issue.

Update: Cold start still had some idling and near-stall issues. Vacuum readings were about the same as when warm. Replaced the spark plugs, they were a bit dirty, but not too bad. Added some fuel injector cleaner to the gas, but it will probably take a while before that will do any good.

The MIL I was getting was in fact just a CHECK warning along with the BRAKE light. Check brakes ... duh. Looking around I found this usually happens when brake fluid is low but its not. In fact I just replaced the front calipers two months ago, bled the lines and topped off the brake fluid. So I am thinking that the near 0 (or actual 0) vacuum reading during acceleration is causing the the brake system to complain (since there is no vacuum to help the brake booster). So I am back to it being a vacuum leak.

I stuck my head under the hood and eventually convinced myself I can hear a hiss on the passenger side compartment, but I can't tell if its a vacuum leak hiss or just my imagination. On top of that I am no mechanic so I am not sure which of the half a dozen hoses would be vacuum lines (if any) and how to test. Is starter fluid still a valid check outside the intake area? Any other low-cost ideas for checking vacuum leak?

Anyone else have the issue of check brake during acceleration? How did you resolve it? Please help, a stalling engine is no fun and if its a brakes issue then I'm nervous about driving it on my daily commute to work.

your vacuum should be close to zero at WOT, zero vacuum means intake manifold pressure is equalized to ambient atmospheric pressure, which is what you'd expect with the throttle wide open. is there a difference in idle between the clutch being disengaged, and clutch engaged but transmission in neutral?

CrAnSwIcK: Not that I have noticed. I'll check for this specifically when I leave work this evening.

Also, the brake fluid was about 1/2 of the way up from min to max, I topped it off and the Check Brake light stopped coming on. So that sensor is quite touchy, at least for me.

Idle vacuum still holding steady at 20-21. WOT drops to 0 but only long enough for the gauge to show it was the min (max since its all neg) value. The visual reading is typically 1+. Highway driving vacuum is around 8-12. Letting off the throttle brings it up to 25 until it settles back at 20-21.

It appears to be idling at 500rpm. Shouldn't I be at 700 or so? Maybe my idles are just too low. Idle is ECU controlled isn't it? Any way to adjust? Unplug the battery and let the ECU reset?

If its not vacuum, then my next step will be getting to the throttle body, and possibly IAC valve. Clean them up and see if it helps. Unfortunately I don't think I can get to that until this weekend.

Update: Unplugged the battery to reset the ECU when I got home from work yesterday. Left it unplugged overnight. Plugged it in in the morning and everything was great. High idle in the morning at 1300. Settled into 700. Never dipped below 500 (when coming to a stop).

However, when I began my commute home it started back in almost immediately. Idling at 500. Stalling twice while stopping. Oscillating idle, 400-700. So it appears the ECU is 'learning' something that is effing things up.

I know the idle is ECU controlled but is there any way to adjust this? Would I have to take it to a shop? I'm almost to that point right now.

I do recall that I used to have the 'problem' of the engine keeping a high idle when pressing the clutch. Although that was labeled as the engine idling high to prevent catalytic converter damage with 'spirited' drivers. If only I could get that to go back into place.

Check for air leaks at the MAF and the whole airbox.

Check the PCV (if you have one) replace if it doesn't 'rattle'.

[QUOTE=GaminKWB;9757849]Update: Unplugged the battery to reset the ECU when I got home from work yesterday. Left it unplugged overnight. Plugged it in in the morning and everything was great. High idle in the morning at 1300. Settled into 700. Never dipped below 500 (when coming to a stop).

However, when I began my commute home it started back in almost immediately. Idling at 500. Stalling twice while stopping. Oscillating idle, 400-700. So it appears the ECU is 'learning' something that is effing things up.

I know the idle is ECU controlled but is there any way to adjust this? Would I have to take it to a shop? I'm almost to that point right now.

I do recall that I used to have the 'problem' of the engine keeping a high idle when pressing the clutch. Although that was labeled as the engine idling high to prevent catalytic converter damage with 'spirited' drivers. If only I could get that to go back into place.[/QUOTE

I am having the exact sane problems with my 2008 Lancer ES! Please tell me you found a fix for it? I'm losing my mind!

I am having the exact same problems with my 2008 Lancer ES! Please tell me you found a fix for it? I'm losing my mind! Help!!!!!!

I think I'm having a similar problem with my 2011 ES and I might have something to add to the conversation.

I have an Injen intake for mine (the long one) and when it is attached, everything is as expected, but when I swap the vehicle back to stock for any maintenance, my idle is at that 500 range and it has stalled on me once or twice.

Maybe this might help narrow it down?

Never found a solution. This became a safety issue for me and I traded the vehicle in.

Be warned, this issue occurred to me (and my fiance) more than once while making a turn during city driving. Making a turn at any speed usually means downshifting (and sometimes holding the clutch in for a few seconds) in preparations for accelerating out of the turn. During this process the vehicle stalled. This loses all power-steering. Not good when you are mid-turn at a fairly busy (or small) intersection.

With the safety issue involved I was done. We didn't have a second car so we didn't have the option of leaving it in a shop while the issue was diagnosed and repaired. It was out of warranty so its not like a dealership would be of any help. We washed our hands of this car and moved on.

Good luck in your search to fix the issue, but be wary of turns while shifting.

Any idea or cause what may cause this?
I've had for sometime (month) the same problem in a Lancer ES 2008 with Injen CAI, the CAI has been since new.
But the stall problem began a month ago the big problem as mention before is when the car stalls making a turn during city driving. I'm still not planning to wash my hands & get rid of the car, just want to found the reason of the problem.

Could it be the MAF or a faulty relay?

I'm starting to believe this was a big problem with the 9g lancers. I have a 08 ES with only 80k on it. Justs started acting up today. Been trying to figure it out for hours now. Starting to lose my mind! I cleaned the MAF, throttle body, checked vaccum leaks which nothing came up. Starts fine, begins to idle at around 500 range, then acts like it's gonna stall out then revs up to 2k on it's own then back down to 500. It'll come out of it for a bit then back to the same ****. While shifting through 2-3 it loses power then jumps back in and goes again. Possibly bad fuel? Been reading forums on this and not everyone seems to figure it out. Would rather not take it to the dealer. Any help? Anyone!

Same Problem Here w/2010 ES
 

I am having the exact same problem in my 2010 Lancer ES coming to a stop the idle drops to 300-450. It has stalled twice at lights.

09 GTS Same Problem
 

I am having the same problem with my 09 Lancer GTS. I brought the car to the dealer and they could not find a resolution. I have reset the ECU, changed the transmission fluid, changed the air filter on the RRM intake, cleaned the throttle body, and changed the oil.
Car in park idles erratic and stalls when coming to a stop. My wife says she can hear a hissing noise coming from the passenger side but can't find the location.
Any help would be appreciated.

I looked into this forum topic just now and I can see that everyone here bought an aftermarket air filter/intake system. But that has nothing to do with this problem. I used to have an older car that did the same thing and it left me dumb-founded until a parts vendor suggested changing the ECU relay. So I did and the problem went away. Maybe changing the ECU relay can fix it since there doesn't seem to be any mechanical issues with these cars, leaving an electrical issue with fuel, emissions, and intake controls which are all managed by the ECU. Another thing, check all wiring and grounding that are connected to the ECU, fuel and intake systems.