Engine starts, won't idle. No codes or CEL. **SOLVED!**

1BADM6 · #1 03-03-2018, 10:36 PM

After fiddling with the HID's yesterday I start the X and the idle starts fluctuating and dropping every so slightly with each fluctuation until the motor dies. I started it again. It starts fine and I can rev it and control rpm with the pedal but as soon as I let off it dies. This morning it ran fine after cold start until it went into closed loop then it repeated the same as yesterday until it wouldn't idle. i removed the air inlet, MAF, checked the throttle and cleaned everything, sensors and connectors. Checked butterfly at throttle body, buttoned it all back up and fired it up with the same issues. I disconnected the MAF and it ran like shit, super rich. I scanned 3 times today with my Foxwell Nt510 and there is no CEL, no codes, no module faults outside of the 3 I'm aware of, lights, cluster and air suspension which are on the list to be repaired soon. I even did a idle test through the throttle body set to 1,000rpm and it would fluctuate between 800 and 1,000 just up and down, up and down. I didn't do a thorough wire inspection beyond 12" of the connectors at the MAF and throttle body. I have a new MAF on the way because it's been about 70k miles since it was replaced. Anything else I should be looking for? Runs great cold but shitty during closed loop. Throttle is smooth, no misses, just won't idle. I can rev it and it dies. Starts right up and dies unless I control the throttle. Thanks in advance.

80stech · #2 03-03-2018, 10:49 PM

It should run reasonably well with maf disconnected. If it's super rich with no maf then start looking for things that will cause that. Fuel pressure reg, air charge temp, coolant temp etc.

80stech · #3 03-03-2018, 10:56 PM

I guess if problem is more so in closed loop then o2 sensors might be suspect but you would think you would have a code if that was the case.

1BADM6 · #4 03-04-2018, 03:58 PM

Today I'm going to disconnect the MAF before it gets to closed loop and see what happens. I'm doing airbags as well and a couple other things. There are so many things involved with air intake. I was disappointed when there weren't any codes. It runs really well with just my foot controlling idle too, no stumbling or roughness.

1BADM6 · #5 03-04-2018, 08:00 PM

Fired her up on a cold start this morning with the MAF disconnected and it didn't want to run, plugged it back in and it idled good for a while until closed loop. I scanned it again and finally got a code for the DME, 'DME Signal, hot-film mass air flow sensor'. So it looks like I was on the right track. I have a Cardoni MAF showing up today but I'm going to order a separate Bosch or Delphi sensor just to have. I don't trust cheapo parts but I've had decent luck with Cardoni products in the past. Hopefully this solves it.

1BADM6 · #6 03-04-2018, 10:48 PM

It was the MAF all along. It took 4 separate scans to pick up the code. I ordered a cheap MAF from Oreilly's because I need to get to job tomorrow, that's if $140 is considered cheap. There were cheaper ones for less than $100 but I didn't recognize any of the brands. I'm loving this Foxwell scanner. It can do all sorts of things.

BladeX5 · #7 03-05-2018, 10:09 AM

Don’t throw away the OEM. Buy CRC MAF Cleaner and you’ll probably get it back on track. Mine was doing the same and after cleaning it the problem dissapeared. The reason you got a code was more likely you disconnected the maf sensor with the car running. Not necessarilly because it was faulty

1BADM6 · #8 03-05-2018, 10:00 PM

Quote:

Originally Posted by BladeX5

Don’t throw away the OEM. Buy CRC MAF Cleaner and you’ll probably get it back on track. Mine was doing the same and after cleaning it the problem dissapeared. The reason you got a code was more likely you disconnected the maf sensor with the car running. Not necessarilly because it was faulty

Did that a month ago and it worked, different issue, didn't work this time. I cleaned it twice, checked filter, intake and throttle body. It was done. Codes were cleared each time I scanned.