Hanging Idle All Of The Sudden

[dubster99]

Coming home from dinner tonight, my car all the sudden developed a hanging idle. I've been driving on this E85 tune for months, and tunes in general for a while with zero issues. I haven't changed anything since going e85, or done anything on the car except an oil change.

I was getting off of the freeway and came to a stoplight, and noticed the idle was hanging at 1500rpm. I thought it was maybe just an anomaly. It did it again at the next light. I left it in 5th gear coming up to the next stoplight to get the revs under 1000 before putting it into neutral. Then the revs jumped back up to 1500. At the next stoplight I shut the car off, started it up, and it idled normally at 650-700 rpm. As I rounded the corner and pulled into my street, I put it in neutral and coasted. It went up to 2K rpm this time. I threw it into 5th with the clutch in, and the idle dipped a bit. I put it into first to get into the garage, and idle went up to 2k again.

Where should I start? Nothing has changed. Reset the ecu? Flash stock tune, and then this one again? I've never had this issue. Mods are in my sig.

Sponsored

 

[Lonmon]

First thing I would do would be to check for any loose or disconnected vacuum lines. Any intake leak could cause this. After that datalog it and check with your tuner.

 

[dubster99]

Wouldn't that cause a bouncing idle? This is a constant idle at a high rpm, almost like the rev hang is there permanently. RPM's aren't dropping when I shift. When I pulled into work this morning and was in third gear, it didn't want to slow down even at low speed. It was just staying at about 2k and moving forward. When I pulled into the lot, RPMs were low from having it in third at low speed and under braking, then jumped to 2500 and stayed constant.

 

[Lonmon]

I usually see a bouncing idle from low coolant through the idle control motor or a faulty idle control motor. I have seen intake leaks cause high idles, an intake leak is similar to opening the throttle more slightly. It would be odd for a tune that was fine for months to suddenly cause idle hang but I would recommend contacting your tuner for advice. A datalog of this would go a long way to figure this out.

 

[dubster99]

14 hour day at work means I didn't have time to disconnect the battery for a reset, or datalog. When I drove home, it was doing the same thing intermittently. However, when I exited the freeway I put the car in neutral and coasted. The Rpms were about 1800, then slowly dropped to normal, and then zero. Yes, zero. The engine shut off and run power came off. I pulled over and the car fired right back up.

Tomorrow I'll try a reset and see what happens.

 

[Merchant Marine S550]

Ever get this fixed? I'm having the same issue.

Thanks

 

[350sexZ]

Same exact thing happened to me, but I was getting lean codes . My maf sensor went out. My fault tho, I didn't tighten the air filter tight enough and guess after driving around for awhile it feel off
I just put my stick intake back on and got it warranty replaced. The rpms would hang, and also go up by itself during idle.

Sponsored