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H3 Engine mist

Ronin

Member
Messages
9
Location
Southern Middle TN
Just purchased my 1st hummer and H3. Has the I5 engine and was a great find. One owner garage kept in great condition. I get home with it a couple days later the engine starts to hesitate between 3rd and 4th gear when slight acceleration. It finally threw a code of P0420. Changed the O2 sensor. Now my engine is hesitating a little more than before. Engine when starts sounds great but when idling it some times sputters once or twice then smooths out. During normal driving it hesitates during travel from time to time without throwing an engine code. No check engine light.
My question is would it be advisable to start with my plugs, and clean the MAF and the TB and try it again before changing my coils etc?
any help would be greatly appreciated.
Thanks
 

alrock

El Diablo
Staff member
Messages
10,426
Location
Scottsdale
Well, it sounds like you might have a bad catalytic converter. But, did you change both O2 sensors? There's one before, one after the cat. Also, did you use an OEM sensor or aftermarket?

Never a bad idea to clean the MAF, TB and inspect/change the plugs, but it seems the problems are likely elsewhere. It's also not unusual for the first cat to separate from the exhaust manifold in the I5 H3 - I've seen large gaps there. If air is pouring out of the manifold at the cat, the two O2 sensors are going to be confused.

Also, what year is your H3? The cats are set up different in 06 vs. other years.
 

Bigunit

Hammer Down!
Staff member
Messages
6,558
Location
Arizona
By the symptoms you describe, it could be the camshaft actuator solenoid valve (GM part #12615873). I'm about to replace mine. This has been a common issue with the GM I5 engine from what I've been able to research on the "internets".
 

alrock

El Diablo
Staff member
Messages
10,426
Location
Scottsdale
By the symptoms you describe, it could be the camshaft actuator solenoid valve (GM part #12615873). I'm about to replace mine. This has been a common issue with the GM I5 engine from what I've been able to research on the "internets".
Probably wouldn't have an issue like that if you washed your truck :wink:
 

H3-Me

Member
Messages
9
Location
Central Oregon
Your supposed to wash these H3's?? :huh: Nobody told me that ..!!
Just throwing it out there. But, Ronin could have some bad gas..?? Might pull the O2's and see if there is a greenish/yellowish tint, could be something else...??
 

JPaul

Well-Known Member
Messages
2,400
Location
Way up north, UT
I can't recall, but I think I ended up just getting electrical cleaner by Ideal from Lowes (I do electronics as well so it's multipurpose to me) for cleaning my MAF sensor on my Ford Police Interceptor when I had it, and "carb and choke" cleaner for the throttle body. They should have cleaner specific to the MAF though at any automotive store, though it might just be a can of electrical cleaner.
 

Ronin

Member
Messages
9
Location
Southern Middle TN
My H3 is a 2006 model with 120,000 miles. Today I have the check engine light back on. I've been told by several start with the plugs and then clean the MAF and TB and then start with the coils. When I start the vehicle now it idles like a kitten, and when began to accelerate on the road the vehicle then mist and hesitates off and on when driving. The H3 has never seen mud and was driven on the road by the original owner and was garage kept dust only under the hood.
 

SuperBuickGuy

Well-Known Member
Messages
3,403
Location
Woodinville, WA
a plugged converter will do this too.... get a temperature sensor (the laser ones) and check the outside temps of the catalytic converter... should be at least 300 degrees.... if not, there's the start of your issues. When I say "start" I mean there is more to check after the cat is fixed - cats last a long time, and the only reason they don't is if there is oil in the exhaust or it's been running very lean
 

JPaul

Well-Known Member
Messages
2,400
Location
Way up north, UT
Running rich could cause issues as well. Extreme example, I destroyed a cat once because I washed the engine of a Police Interceptor I had, water pooled in the spark plug wells and shorted out one or two cylinders long enough that I got the cat on that side glowing bright orange in daylight because it was burning the extra fuel inside the cat... Of course it wasn't on the side the cat was all buggered up, so I ended up replacing both. Been very hesitant to wash engines after that...
 

chaos254

Well-Known Member
Messages
577
Location
United States
My H3 is a 2006 model with 120,000 miles. Today I have the check engine light back on. I've been told by several start with the plugs and then clean the MAF and TB and then start with the coils. When I start the vehicle now it idles like a kitten, and when began to accelerate on the road the vehicle then mist and hesitates off and on when driving. The H3 has never seen mud and was driven on the road by the original owner and was garage kept dust only under the hood.
Same code?
 

Ronin

Member
Messages
9
Location
Southern Middle TN
Yes it's throwing the same code again. After driving it around this afternoon to double check it has progressively gotten much worse on the mist. When I accelerate or call on the motor it then runs fine. I haven't checked the temp of the upstream and downstream side of the cat yet and will do tomm after work.
Lets say it is the cat then what would be a comparable cat to replace it with. I've noticed Forman makes one for 399. Is that comparable to replace it with etc.
i would like to get it replaced and or repaired very soon for I haven't it owned it for a month yet and I'm frustrated because I'm not enjoying it because of the ghost I'm chasing.
 

alrock

El Diablo
Staff member
Messages
10,426
Location
Scottsdale
Your H3 has two cats. One in the exhaust manifold, one in the first exhaust pipe. If it is a bad cat, you'll need to figure out which one before you go buy anything. Asking again - you said you replaced an O2 sensor but there are two O2 sensors. Did you replace them both or just one? Did you use OEM? I have a bit less trust on aftermarket ones, in part as I watched a friend replace about 3 Bosch ones before he went back to the Jeep dealer and got an OEM one to get rid of his error codes. (They went away initially but the Bosch ones failed quickly)
 

Ronin

Member
Messages
9
Location
Southern Middle TN
Your H3 has two cats. One in the exhaust manifold, one in the first exhaust pipe. If it is a bad cat, you'll need to figure out which one before you go buy anything. Asking again - you said you replaced an O2 sensor but there are two O2 sensors. Did you replace them both or just one? Did you use OEM? I have a bit less trust on aftermarket ones, in part as I watched a friend replace about 3 Bosch ones before he went back to the Jeep dealer and got an OEM one to get rid of his error codes. (They went away initially but the Bosch ones failed quickly)

I replaced the upstream O2 sensor. The code was showing sensor 1 bank 1. From what I understand that's the one closest to engine. I haven't replaced the second sensor as of yet. I'm going to look at cat with a laser on the front and rear side of the cat this afternoon. The O2 sensor I put back in was a Bosch.
 

chaos254

Well-Known Member
Messages
577
Location
United States
The O2 might have caused the concern but at this point your going to need a new cat:

DTC P0420

DTC DESCRIPTOR

DTC P0420
Catalyst System Low Efficiency

CIRCUIT/SYSTEM DESCRIPTION
A 3-way catalytic converter (TWC) controls emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). The catalyst within the converter promotes a chemical reaction, which oxidizes the HC and the CO that are present in the exhaust gas. This process converts the HC and the CO into water vapor and carbon dioxide (CO2), and reduces the NOx, converting the NOx into nitrogen. The catalytic converter also stores oxygen. The powertrain control module (PCM) monitors this process by using a heated oxygen sensor (HO2S) that is in the exhaust stream after the TWC. This HO2S 2, also referred to as the catalyst monitor sensor, produces an output signal that the PCM uses to calculate the oxygen storage capacity of the catalyst. This indicates the ability of the catalyst to convert the exhaust emissions efficiently. The PCM monitors the efficiency of the catalyst by allowing the catalyst to heat, then wait for a stabilization period while the engine is idling. The PCM then adds and removes fuel while monitoring the HO2S 2. When the catalyst is functioning properly, the HO2S 2 response to the extra fuel is slow compared to the response of the HO2S 1, which is located before the TWC. When the HO2S 2 response is near that of the HO2S 1, the oxygen storage capability and efficiency of the catalyst may be degraded below an acceptable threshold.

IMPORTANT: A new converter with less than 100 miles on it may set P0420 due to out-gassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 hour may correct the condition.

If the ECM detects the degraded condition DTC P0420 sets.

CONDITIONS FOR RUNNING THE DTC


  • DTCs P0030, P0036, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0128, P0130, P0131, P0132, P0133, P0134, P0135, P0136, P0137, P0138, P0140, P0141, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0220, P0300, P0315, P0326, P0327, P0336, P0340, P0341, P0442, P0443, P0446, P0449, P0452, P0453, P0455, P0496, P0506, P0507, P0601, P0602, P1133, P1516, P1621 are not set.
  • The engine has been running for more than 10 minutes .
  • The engine speed is within 100 RPM of the desired idle.
  • The engine coolant temperature (ECT) is between 69-125°C (156-257°F) .
  • The barometric pressure (BARO) is more than 72 kPa .
  • The catalytic converter (TWC) calculated temperature is between 500-700°C (932-1,292°F) .
  • The vehicle is in Closed Loop.
  • The intake air temperature (IAT) is between -20 and +100°C (-4 and +212°F) .
  • The battery voltage is more than 10.7 volts .
  • The throttle position (TP) is 1.5 percent or less.
  • The short term fuel trim (FT) is between -10 and +10 percent .
  • The engine load must be stable.
  • Test the catalyst by performing the following procedures:

  1. Drive the vehicle, engine speed above 1,500 RPM , for at least 60 seconds .
  2. Idle the engine and keep the vehicle in DRIVE, or depress the clutch pedal for a manual transmission vehicle, to activate the diagnostic. Within 60 seconds , the air fuel ratio will transition rich, below 14.1, for up to 7 seconds , and then may transition lean, above 15.3, for up to 7 seconds .
  3. Verify if DTC P0420 has passed or failed this ignition cycle with the scan tool.

    • This diagnostic attempts one test during each valid idle period once the above conditions have been met. This diagnostic attempts up to 12 tests during each drive cycle.
CONDITIONS FOR SETTING THE DTC


  • The PCM determines that the efficiency of the catalyst has degraded below a calibrated threshold.
  • This diagnostic may conclude in as few as one test attempt. However, this diagnostic may require as many as 18 test attempts, which would require at least 3 drive cycles. Each test attempt may conclude within approximately 7 minutes .
ACTION TAKEN WHEN THE DTC SETS


  • The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
  • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC


  • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
  • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
  • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
  • Clear the MIL and the DTC with a scan tool.
DIAGNOSTIC AIDS


  • Inspect for the following conditions, which may cause a catalytic converter to degrade:
  • An engine misfire
  • High engine oil or high coolant consumption
  • Retarded spark timing
  • A weak or poor spark
  • A lean fuel mixture
  • A rich fuel mixture
  • A damaged oxygen sensor or wiring harness
  • The catalyst test may abort if the vehicle falls outside the conditions for running the DTC.
  • The catalyst test may abort due to a change in engine load such as the A/C or engine cooling fan cycling.
  • A catalyst may be temporarily degraded if a fuel with high sulfur content has been used. Drive the vehicle at highway speeds for 10 minutes and retest the converter.
  • If 6 tests have been attempted and the DTC has not run or passed during this key cycle, turn the key to OFF for 30 seconds . Perform the Conditions for Running a second time.
  • A maximum of 12 tests per key cycle will run if each test is a combination of pass, fail, or abort tests.
  • After a code clear, the catalyst test will run once if the test is a pass.
 

Ronin

Member
Messages
9
Location
Southern Middle TN
Ok. After coming home today I checked the cat and it was flowing air as it should in the first one. The temp range was from 275-325 back and forth. Checked the rear cat and it showed temps at the front and back as nearly the same with very little jump at around 275 give or take a couple.
Then Cleaned my MAF with crc MAF cleaner and reset the battery along with clearing the code and test drive it. Ran fine for the time I drove it approximately 25 mins and temp came to normal operating temp. I'm going to be in it all day tomm so I'm going to see if it helped it or bandaged the problem.
The o2 I put in it was a Bosch. Should I have out in the ngk which is twice the money? Thoughts etc. previous said the would take it back beings the cap was missing when I put it and I have a ngk ordered and should arrive first of next week
 
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