Cel blinked on, no misfire code, just p0111
05-07-2019, 12:36 PM
#1
Registered
Thread Starter
Cel blinked on, no misfire code, just p0111
So I was cruising at about 50mph in 4th gear at about 3.5k and I had a sudden CEL and loss of power which felt like a fuel cut. It lasted just under a second then the CEL went away and normal driving continued. I thought it was a misfire just based on previous reading, but then I pulled the codes from two different readers and only got a P0111. I did another 20 minutes or so of driving while logging various systems hoping to replicate the issue. I was unable to, and the intake air temperature was completely normal. For what it's worth, I'm running BHR Coils and midpipe. Due to the brief on/off and feeling of fuel cut, was this a misfire that never resulted in a misfire code, or could this have been related to the P0111? Thanks!
05-07-2019, 02:42 PM
#2
What am I doing here?
Join Date: Mar 2006
Location: 2017 Miata RF Launch Edition
Posts: 3,606
Received 649 Likes
on
510 Posts
Misfires won't necessarily set a code even if they cause a blinking CEL. If you had a blinking CEL, you DEFINITELY had a misfire. Nothing else will cause a blinking CEL.
Yah, I'd bet the IAT sensor malfunction is what caused the misfire and poor performance.
The IAT sensor is located inside the MAF sensor and is used to make sense of the MAF data. The MAF sensor is basically just a resistor and the ECU runs current through it and monitors how hot it gets (or how much current is required to keep it at a temperature, I forget which). Since the rate of heat dissipated to the air flowing through the MAF is dependent on the temperature of the air, the IAT data is used to correct the MAF data. If the IAT sensor malfunctions, the MAF data won't make any sense anymore.
As for why the IAT sensor malfunctioned... no idea. The FSM lists three possible causes: IAT sensor failure, wiring failure, or PCM failure.
DTC P0111
Yah, I'd bet the IAT sensor malfunction is what caused the misfire and poor performance.
The IAT sensor is located inside the MAF sensor and is used to make sense of the MAF data. The MAF sensor is basically just a resistor and the ECU runs current through it and monitors how hot it gets (or how much current is required to keep it at a temperature, I forget which). Since the rate of heat dissipated to the air flowing through the MAF is dependent on the temperature of the air, the IAT data is used to correct the MAF data. If the IAT sensor malfunctions, the MAF data won't make any sense anymore.
As for why the IAT sensor malfunctioned... no idea. The FSM lists three possible causes: IAT sensor failure, wiring failure, or PCM failure.
DTC P0111
Last edited by NotAPreppie; 05-07-2019 at 02:45 PM.
The following users liked this post:
BGunner (01-20-2020)
05-07-2019, 07:19 PM
#4
Registered
Thread Starter
Thank you both for the replies. I am going to follow the manual to test the sensor and wiring continuity and cross my fingers the plug was just loose. If I don't see anything wrong and I get another misfire I'll order a new sensor. Is it likely for the sensor to fail intermittently like that? I have a great deal of accurate readings off of the IAT sensor (and others) following that incident.
01-20-2020, 03:51 PM
#6
Those new codes are unrelated to the IAT issue. 2270 may be due to the midpipe (it's the catless model?). But, if that was it, you would have seen it ever since the midpipe went on, as well as P0420.
What all those codes have in common is wiring. The misfire may not have been a misfire, but the electronics cutting out for an instant. Was it a single blink or a consistent blinking lasting a few seconds?
Time to go over your battery posts, grounding points and wiring harness, especially around the midpipe. It's possible to damage the wiring under there when working on the exhaust or the trans.
2270 in particular is a clue to that, "stuck lean" means stuck at 5v -- a short in the wiring.
What all those codes have in common is wiring. The misfire may not have been a misfire, but the electronics cutting out for an instant. Was it a single blink or a consistent blinking lasting a few seconds?
Time to go over your battery posts, grounding points and wiring harness, especially around the midpipe. It's possible to damage the wiring under there when working on the exhaust or the trans.
2270 in particular is a clue to that, "stuck lean" means stuck at 5v -- a short in the wiring.
The following users liked this post:
BGunner (01-23-2020)
01-21-2020, 01:42 PM
#7
Registered
Thread Starter
My car only experienced a single half second pulse of power loss with a blip of the CEL. Looking back it sure seems like it was a misfire. The only code I had was a pending P0111 which has not occurred again since (replaced MAF for the heck of it) and no other relevant codes.
01-22-2020, 01:12 PM
#8
most misfires are imperceivable. Back in the early days it wasn’t that uncommon for 04-05 RX8s to have the CEL blinking all the time under wot and it wouldn’t have been felt or known otherwise. It wasn’t like your situation at all. A bad MAF sensor on the other hand you will definitely know when that acts up.
01-23-2020, 09:43 AM
#9
Registered
Thanks Loki, I'm trying to find it. The '06 has all original exhaust and intake. Last year it wouldn't pass inspection, so Replaced upstream O2, Cleaned some connections (on the MAp *etc) and went on the drive cycle tests for days! I'd turn it off, go drive, at 51 mi.. BANG.. back on. It finally passed but came back on immediately after. It's my gals car, I rarely get time to do a hunt and seek on it, I'll start there today and see if I can run it down.
it has P2096 Po111 P2270 U1900 ( my phone died
that's what it showed last week I checked connections and cleaned Map but didn't get under it to check O2 connections. Thanks I'll get on it- Billy
it has P2096 Po111 P2270 U1900 ( my phone died
that's what it showed last week I checked connections and cleaned Map but didn't get under it to check O2 connections. Thanks I'll get on it- Billy
01-23-2020, 10:24 AM
#10
Thanks Loki, I'm trying to find it. The '06 has all original exhaust and intake. Last year it wouldn't pass inspection, so Replaced upstream O2, Cleaned some connections (on the MAp *etc) and went on the drive cycle tests for days! I'd turn it off, go drive, at 51 mi.. BANG.. back on. It finally passed but came back on immediately after. It's my gals car, I rarely get time to do a hunt and seek on it, I'll start there today and see if I can run it down.
it has P2096 Po111 P2270 U1900 ( my phone died that's what it showed last week I checked connections and cleaned Map but didn't get under it to check O2 connections. Thanks I'll get on it- Billy
it has P2096 Po111 P2270 U1900 ( my phone died
that's what it showed last week I checked connections and cleaned Map but didn't get under it to check O2 connections. Thanks I'll get on it- Billy
11-01-2020, 07:42 AM
#11
Registered
It's been quite a while since I've been on here. I appreciate your help with me TRY-ing to understand the codes on this damned RX8. I get lost with all the lingo. ( CEL/Map/ IAT) etc! lol but every year I have the same issues ;( I'm getting too damned old to mess with it.
But I think I'm going to run down all the wires this month going to the MAF. The RX8 hardly sits still long enough for me to be able to concentrate on the
codes and fix it. Like I said, I do appreciate your insight, you actually sound like someone who might know what I need to do-
Thanks, Gunner
But I think I'm going to run down all the wires this month going to the MAF. The RX8 hardly sits still long enough for me to be able to concentrate on the
codes and fix it. Like I said, I do appreciate your insight, you actually sound like someone who might know what I need to do-
Thanks, Gunner
Thread
Thread Starter
Forum
Replies
Last Post