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Thread: p0303
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10-05-2010, 05:30 PM #1
p0303
98 Z28 5.7 A4 180,000 miles
Started off with a P0303. I cleared the code changed the plugs and the wires still had a miss but no code. I changed the fuel filter and ran the 3M fuel injection cleaning system through and after that it ran better. Left the driveway wemt down the street - started missing. Checked codes and got P0300 and P0303. I ran Seafoam through seemed to be great. Took it for a test drive and after getting on a few times it started to miss again but no code.
What should I check next?
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10-05-2010, 05:37 PM #2
Are the wires properly seated on the coils -- 2 clicks? Did you test the coils? Any chance you burned a wire on the exhaust? Cracked a plug insulator?
Might try to run the engine at night with the hood up and see if you have any spark jumping around.
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10-05-2010, 05:44 PM #3
02 and cats
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10-05-2010, 05:47 PM #4
No mods on this car. Wires are not even close to the exhaust and seated good and tight. Insulators are good. When I quit it was Dark could not see any noticeable arcs.
Didn't run my hand through there though to check.
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10-05-2010, 05:50 PM #5
After I ran the 3M injector cleaner it was showing an 02 code but I figured that that might be because of everything going through. Ever since I drove it around it does not show the 02 code anymore.
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10-05-2010, 06:54 PM #6
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1999 Formula WS6 M6-sold- 2001 Silverado Z71
try swapping the #3 fuel injector around with a another one and see if the miss follows the injector. Same test can be done with the coil, plug or plug wire.
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10-05-2010, 07:06 PM #7
I will try that tomorrow and see wht happens.
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10-06-2010, 05:02 PM #8
Ok I switched the #1 & #3 coil drove around for a while with a miss. It took a while to trip a code. I am using AutoTap Diagnositic Scanner. It came up with
P0141 H02S Heater circuit Bank 1 Bank 1 Sensor 2
P0157 H02S Circuit Low Voltage Bank 2 Sensor 2
P0300 Engine Misfire
P0303
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10-06-2010, 05:15 PM #9
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Black- 2000 WS6 6spd Hooker LT
More things to try....like Cutlass said, move an injector to Cyl number 3. As far as the P0300, that is a multiple cyl misfire.
Have you cleaned your MAF. Dirty may cause lean issues, which may result in misfire P0300.
You may have a bent pushrod #3. Self explanatory, but sometimes this will have a ticking noise associated with it.
Does it miss only at idle/low speed? If so, rare but could be a barely stuck open EGR. Usually this only causes the P0300, not a specific cylinder.
O2 sensor code P0141 looks like bad B1S2 O2 sensor, and probably same for B2S2. Usually a lean condition won't trip rear O2 codes. Maybe front O2 codes, and rear 02 codes usually don't have anything to do with driveability problems like a misfire. There are some exceptions, of course, like if the rear O2s have shifted so much that the PCM is commanding too much fuel due to the lean reporting (low voltage).
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10-06-2010, 05:59 PM #10
Yes I cleaned the MAF. I will swap the injectors tomorrow and see what happens. Yesterfay after using the Seafoam It ran pretty good for a little while and progressively got worse. Even though it has a noticeable miss it takes a while before the SES comes on. It seems to run pretty good under a load.
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10-08-2010, 06:37 PM #11
Swapped plug wires and disconnected battery and it seems to be running fine. Good enogh that it passed inspection. ??????
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10-09-2010, 05:27 AM #12
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Black- 2000 WS6 6spd Hooker LT
Maybe it was a plug wire not snapped on completely, and now it is.
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