Hey everyone-

I'm looking for suggestions to help me diagnose a problem that came up yesterday morning with my car. It had no prior symptoms/issues "leading up to" this, it was an out of nowhere thing. I apologize in advance for the long story, but hopefully it helps!

6/22, A.M.: I went to start my car to go to work; it cranked and turned over, wanted to start, then just died. RPMs maybe touched 700. Tried to start it a second time, same result. Sat there for a second, swearing to myself, and tried a third time, and it started no problem. I didn't pump the gas or anything. Drove fine, etc. all the way to work.

6/22, P.M.: Go to the parking garage to start my car to go home; same deal...crank, then die. I tried starting it again, this time trying to "catch" the RPMs by giving it a little gas, and that worked to get it started up, but the second I let off the gas, RPMs dipped too low and died. Time number three, I started it up, holding a steady 1100 (or so) RPMs for 30-40 seconds, then tried to ease off the accelerator to let it find idle. It sort of idled; usually, after start up, it sits around 1000 RPM until I'm up to operating temp., then dips to 750 or so. Now, it just fluctuated between maybe 500-700. I drove it home, but had to feed it gas whenever I reached a complete stop. As I drove, A/F was in the usual upper 14's, and my vacuum responded as it typically does with my input on the accelerator (I stayed out of boost). However, the car was noticeably sluggish. In the normal rev range of 2k to 5k, the car acted fine.

That night, I came to evoM and searched around (where else would you turn? ). There are a couple threads from 2003 regarding some Evos that had a similar sounding problem; some things that were suggested in those threads were:
-leaking vacuum line
-bad ground somewhere
-failing idle tensioner pulley
-failing AC compressor pulley
-failing coils
-fouled spark plugs

I went out to my car that night, popped the hood, and pushed/pulled on the accessory belt; it did give somewhat, maybe a 3/4in. or so as I moved it (wasn't stiff/tight..how tight should it be?).

6/23, A.M.: Went to try again this morning, same crank+die. Tried again, feeding a little gas, and it started, and it even managed to find its normal idle (1000, then down to 750). I popped the hood to see if the belt was slapping or shuddering, it looked ok. Went in the car, tried turning on the AC, killed it instantly. Started the car a third time, fed a little gas (AC off now), and it started, but had the same erratic idle from yesterday. I gave it gas to hold 1000 RPMs, turned the AC on and blew ice cold. Turned off the AC then eased off the gas, but it still wasn't finding normal idle. Fortunately, my roommate has the day off of work and offered to drive me to work, so I shut 'er down.

Recent factors that may have influenced/agitated this:
-Recent rain (no hydrolock, I haven't hit any 2ft. puddles)
-Got really hot
-Got really humid
-Just filled up with gas (thought I'd throw that in there)

Has anyone else had a similar problem? What are some "at home" things I can check or test? Note: I don't have a volt/ohm meter, so I can't test circuits/sensors. I'm leaning hardest toward a pulley (electrical) issue; if the alternator isn't being spun as it should, wouldn't that weaken the spark (and subsequently screw up the idle and allow the AC compressor to torpedo the system)?

Thanks for looking and your help!

 

Is your car stock?

 

I'm afraid not (https://www.evolutionm.net/forums/04...-turbo-ra.html)

 

reset the ecu.

I know hackish will comment in here eventually that this is why he is working on cracking the ecu cause the piggy back/5th injector setup inevitably ends up in screwy fuel maps.

so yeah, disconnect battery and reconnect as to relearn fuel trims, and if problem continues, then look into the pulley tensioner or leak in boost line.

 

Didn't realize it was an RA custom build.

Do you have an idle screw on the throttle body? You can try to adjust the idle there...

 

I'll try this when I get home, but I'm highly doubting this is the culprit, due to a) the 5th injector only kicks in when MAP reaches a certain point (not active at idle, so shouldn't be influencing that part of the LTFT table), and b) the fact that this wasn't a worsening problem...it happened overnight. But I'll give it a whirl

Another side note: I am throwing no CEL, and haven't for over a month (prior to that, it was a cat inefficiency code...did the spark plug defouler trick, but I digress).

 

I'm just saying that reseting the ecu is always the best place to start to make sure its not a problem with the ecu and a mechanical problem.

Also its the cheapest thing to do when you're not getting a CEL to direct you as to what the problem is.

 

Alright, update time...odd stuff going on.

6/24, A.M.: Car hesitated slightly, but fully started. Normal cold idle (1000-1100). After driving a block or two, the car started doing an oscilating/dipping idle, but this time, between 1200 and 1400 RPMs. It didn't kill the whole way to work, but it was revving itself atypically high.

6/24, P.M.: Same as yesterday...crank/die. Idle dipped too low and would kill itself off, so I had to feed it gas whenever I was in neutral all the way home. I can imagine other drivers looking at me, frantically looking betwen the road and the tach, my hand going back from the ebrake and gear shift, heel-toeing when approaching a stoplight When I got to my driveway, I eased off the gas, and it idled normally with no load (wasn't moving, RPMs around 800 or so). Turned on the AC, RPMs compensated up an extra 200 (or whatever). Revved it a couple times, and it fell back into the usual idleing "pocket".

6/25, A.M.: Crank+die. I unplugged the battery (+10min.) and reset the ECU. Again, crank+die. Second try, fed it some gas, and it did start. It found idle as I eased off too, but only at around 500 RPMs...it didn't bounce this time, but was a steady 500, and would kill if I wasn't careful.

Tonight, I'm going to follow/trace every vacuum line I can find, see if anything's punctured/melted/loose/etc. Anyone else have any suggestions as to stuff I can check?

 

what about a bad throttle position sensor... or something along those lines

 

^Now I'm leaning toward somthing of that nature, or the idle control valve. Checked all vacuum lines last night, nothing had blown off or was cracked/leaky/etc. Boost still comes on strong when driving. However, it seems like the car can't decide where to idle. Sometimes it will bounce, sometimes it's steady. Sometimes it'll settle around 500rpms, other times at 1200rpms, other times at the ususal 750.

 

Update/Resolution....? (knock on wood)

6/30, A.M.: I took my car to a shop close to my office to help out, they double-checked the vacuum lines and all was good there. They took off the brass-colored throttle control cover circled in yellow below, and cleaned out what they could, lubed it, and put it back together. It hasn't stalled out on me yet and idles as it should, so keep your fingers crossed! This issue never caused a CEL...weird.

And no...the pic below is not my engine