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Bad Miss and CEL at Idle

wvamatt

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wvamatt Enthusiast

wvamatt

Posted
Posted

I have a really bad miss at idle, complete with a CEL light and rotten egg smell. When I accelerate or rev the engine for about 5-10 seconds, the CEL and miss go away. The miss only occurs during idle. Also, when the engine is warm, it is hard-starting. I hooked up a SnapOn scanner, and received a P300, and it showed the missed were all over the board, but primarily on cylinders #7 and 2, mostly on #7. Also, the O2 sensor readings were very erratic. Here is a video of the readings...

 

So far I have...

  • Replaced fuel filter.
  • Replaced spark plugs and wires.
  • Switched #7 coil pack with new coil pack. Miss continues.
  • Cleaned MAF and throttle body.
  • Performed crank relearn.

 

Has anyone had a similar problem and fixed it? Where should I be looking next?

dewfpo Senior Enthusiast

dewfpo

Posted
Posted

How many miles are on your rig.  A rotten egg smell from the exhaust usually means it's running too rich.  That could come from a miss, ignition or faulty injector.

 

DEWFPO

wvamatt Enthusiast

wvamatt

Posted
  • Author
Posted

dewfpo - My truck has 206,000 miles. Would a bad cat co cause a misfire?

dewfpo Senior Enthusiast

dewfpo

Posted
Posted

A bad cat would not, but bad O2 sensors would.  They typically last 125-150k miles before they get too lazy to adapt quickly enough.  If they are original, there's a very good chance they need to be replace.  At least the ones in front of the cats.

 

DEWFPO

  • 1 month later...
wvamatt Enthusiast

wvamatt

Posted
  • Author
Posted

I've been working this problem still. Here's what I've done since my last post:

  • Remove, clean, and re-terminate EVERY ground on the truck.
  • Remove intake and install new intake gasket.
  • New TPS (had REP issue)

I ran a big scan of the truck with a Snap-On scanner.  Here are the results. Does anyone see anything that could be causing my miss at idle?

 

Quote
Engine Data
ENGINE SPEED (RPM): 469-657
TPS(%): Fluctuates between 4 and 11 at idle. Consistent with throttle open.
MAP (inHg): 13.2
BARO (inHg): 29.8
Open/ CLSD LOOP: CLSD
HO2S B1 S1(mV): 61-842
HO2S B1 S2(mV): 78-812
HOS2 B2 S1(mV): 35-829
HOS2 B2 S2(mV): 816-942
 
HO2S B1S1 HEATER (Amps): 0.80-0.86
HO2S B1S2 HEATER (Amps): 0.58-0.60
HO2S B2S1 HEATER (Amps): 0.76-80
HO2S B2S2 HEATER (Amps): 0.52-0.54
DCEL-FUEL-C/OFF: NO
POWER ENRICH: NO
A/F RATIO: 14.6:1
 
ST TRIM -1(%): -4-2
LT TRIM -1(%): 13-14
ST TRIM -2(%): -4-2
LT TRIM -2(%): -15--13
 
COOLANT (*F): 159-174
START UP ECT (*F): 129-129
INTAKE AIR (*F): 62-64
 
MAF (gm/Sec): 4.94-9.95
MAF(Hz): 2469-3266
ENGINE LOAD(%): 3
ARP(%): 0
 
MAP (inHg): 12.1-14.7
MAP(V): 1.62-2.05
SPARK ADV (*): 7.5-30.0
 
CMP SENSOR - HIGH TO LOW: 1976
CMP SENSOR - LOW TO HIGH: 1977
DTC SET THIS IGN: YES
VEH SPEED (mph): 0
 
ST FUEL TRIM B1(%): -5-0
ST FUEL TRIM B2(%):-10--4
LT FUEL TRIM B1(%): 5-5
LT FUEL TRIM B2(%): -12–12
 
FUEL TRIM LEARN: Enabled
FUEL TRIM CELL: 17
 
INJ PWM B1 AVG(ms): 3.40-4.68
INJ PWN B2 AVG(ms): 2.35-3.25
 
EVAP PURGE(%): 16-22
EVAP VENT SOLENOID: VENTING
 
FUEL TANK PRESSURE: 7.39
FUEL TANK LEVEL (%): 32-39
 
 
Misfire Data
MISFIRE CYL 1: 0
MISFIRE CYL 2: 1
MISFIRE CYL 3: 10
MISFIRE CYL 4: 101
MISFIRE CYL 5: 4
MISFIRE CYL 6: 28
MISFIRE CYL 7: 12
MISFIRE CYL 8: 3
 
MISS HISTORY 1: 0
MISS HISTORY 2: 39
MISS HISTORY 3: 903
MISS HISTORY 4: 4268
MISS HISTORY 5: 100
MISS HISTORY 6: 1154
MISS HISTORY 7: 227
MISS HISTORY 8: 479

 

dewfpo Senior Enthusiast

dewfpo

Posted
Posted

Things that look a little off to me (but I'm not an expert) : 

MAP = 13.2 (I would think it should be around 14.7 or so)  although the 13.2 might correlate directly to the 29.8 BARO reading.

HOS2 B2 S2 (looks out of whack)

Engine Load =3% (that's unrealistic, it's usually higher than that even at idle)

LT Fuel Trim B2 = -12-12 (That looks out of whack as well).

 

That Bank2 S2 O2 sensor looks like it may be dodgey.

 

cylinders 4 & 6 are your worst offenders that they are next to each other.  Have you sprayed any unlit propane or carb cleaner around the intake gasket between those 2 cylinders?

 

DEWFPO

 

  • 2 weeks later...
wvamatt Enthusiast

wvamatt

Posted
  • Author
Posted

I’ve been scanning and working to try and diagnose/fix this problem. Cylinder #4 is by far he worst offender, and it makes me think that it’s missing very badly, causing the other to also miss sporadically. I put a new coil pack, wire, and plug on #4, but the miss is still there. It misses at idle on the scanner, but when I open the throttle and the engine speed increases over 1,000 rpms, the miss goes away and all cylinders fire. 

 

My bank 2 LT fuel trim numbers are getting worse, which is making the truck idle even more rough. I’m now wondering if I have a leaky #4. This could explain the hard starting (losing fuel pressure in between starts) and miss at idle (leaking enough to flood the cylinder at idle and cause misfire, but not enough to flood at higher engine speeds). Also, the negative fuel trim on bank 2 and the O2 sensor bank 2 readings seem to indicate a rich bank 2 condition also.

 

What do you think? Am I on the right track, or should I be looking somewhere else?

Raptordude Enthusiast

Raptordude

Posted
Posted

Have you replaced the bank 2 O2 sensor? All of what you said seems to indicate an O2 sensor issue. The fuel injector for #4 may be bad as well. Pop a new O2 sensor in there and see where that gets you


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wvamatt Enthusiast

wvamatt

Posted
  • Author
Posted
Have you replaced the bank 2 O2 sensor? All of what you said seems to indicate an O2 sensor issue. The fuel injector for #4 may be bad as well. Pop a new O2 sensor in there and see where that gets you


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Raptordude- I have 2 oxygen sensors on bank 2. There bank 2, s1 and bank 2, s2. I’m assuming one is before the cat, and one is after. Which one would I try first?


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dewfpo Senior Enthusiast

dewfpo

Posted
Posted

Before the cat, the second sensor's job is to primarily see if the cat ahead of it is doing it's job.  The sensor before the cat, reads the exhaust gases and gives the ECM the data.  That data along with data from other sensors will allow the ECM to adjust the mixture.


DEWFPO

Raptordude Enthusiast

Raptordude

Posted
Posted

Yep, the upstream (1st sensor) is the one that gives readings to the ECU to adjust fuel trims. The second one (downstream) is only to monitor the condition of the cat. If the 2nd one goes bad it will cause a check engine light but won't effect driveability at all


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swathdiver Senior Enthusiast

swathdiver

Posted
Posted

Still working on this?  Drop the Y-Pipe and look at the cats, or buy a bore light with camera and stick it in the O2 sensor holes and look at the cats.

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