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02 sensor and misfire issues

2K views 4 replies 3 participants last post by  DynoPax 
#1 ·
Just wanted to share my experience with the first slew of issues plaguing my truck's V6 engine...

Started out with rough idle, then high fuel consumption and a CEL. Codes returned misfire and 02 sensor problems which the dealer adressed with PCM update, 02 sensor swap (3 times!) and all spark plugs replaced, all of this over 6 visits in the last 2 weeks. The high fuel consumption most probably was caused by bad 02, which led to wrong air-to-fuel mixture ratio. This had 2 other adverse effects: accumulation of fuel in engine oil (changed) and in plenum (drained for the most part)...

Now I have a fun time every time I start it when cold, where the starter appears to stay stuck for numerous seconds until engine starts. It runs rough for 5-10-20 seconds then stabilizes. Dealer believes this may be caused by pockets of fuel still remaining in plenum :)4-dontknow:) and should clear over time. I have serious doubts about this assertion but am willing to give it a try. If not conclusive, another visit(s!) will be necessary. Good thing this is all under warranty!

Finally, while wondering about what may cause the engine starting to be so problematic, I verified a few things like the battery voltage for instance. This because these long starts can drain a lot of juice, but I was surprised to get readings of almost 16V with engine off. That is quite high, unless my multimeter was faulty, but verified other car battery and reading was normal (13.5V). Alternator problem too?

Either all issues are cause to effect or I bought myself a truck with gremlins hiding under the hoods! Will update with future results of my misadventures...
 
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#2 ·
You say your getting volt reading of 16 volt, that's about 3 volts too high. Suspect getting an over charge condition. Probable cause, voltage being computer controlled, is that you have a poor connection at the pcm. It's probably going to reflect that your voltage is about 3 volts lower that it really is, causing the pcm to require more charging voltage from the alternator. Your dealer should not really have a problem finding this poor connection as there are only one or two connections that could effect the charging. Maybe even a service bulletin out on it.
 
#3 ·
I had an experience with CEL condition with a 02 sensor that was reading "low voltage"...the first attempt at a resolution was to replace the sensor. After that was unsuccessful, the second stab at in the process of elimination was to replace the power module. Still no joy, so the third fix was to replace the wiring harness. After approx 1,000 miles, so far so good.
 
#4 ·
Replaced battery in multimeter and re-verified, now getting 12.95V... I'll spot-check but it appears my reading was wrong, old multimeter and cold weather make poor combo! Still a rough start but now starter is not "stuck", I have to keep it cranking by holding key fob in until it turns for good...
 
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