P0200 and p0300 error codes

[LEG]

2003 yukon xl 1500

 

Replaced: plugs, wires, injectors, fuel filter, fuel pump.

Re-tested: coils, wires

Cleaned fronts side of throttle body (didn't remove) as best I could.

 

Scanner was telling me cylinder 2 and 8 misfire, with code p0135, swapped o2 sensors (bank 1) misfire switched to 7 and 8 cylinders. Still p0135 error on scanner, checked wiring on 02 sensors that I could see, no apparent damage

 

Misfire's only at idle, when I apply gas misfire's go away

 

Read on the net, could be idle air valve (can you clean that, rivited to throttle body, shoot cleaner in that tiny hole?), maf sensor (cleaned that) all little wires good, no apparent vacuum leaks

 

Disconnected battery  to try to reset iac valve, no change...

 

What am I missing?

[Doug_Scott]

Only asking since you didn't mention it, you did clear the trouble codes didn't you?  They are history, and need to be cleared manually after dealt with.

[Jsdirt]

Misfire at idle that goes away with throttle is a dead ringer for a vacuum leak. Probably intake gaskets, but could be a deteriorated hose somewhere, too.

 

I use a spray bottle full of water, or a water bottle with a hole punched in the cap in a pinch,  and hose down all the gasket surfaces one at a time, ENGINE COLD (leaks will be worse then, if they're intake leaks). If the leak is big enough, you'll hear the water getting sucked in. I do one section at a time, listening. Also have your scan tool up with your short and long term fuel trims in graph form - if you see the trims dive back towards zero, you're on to the leak. Spray all the vacuum hoses as well - it'll find those, too.

 

Since the misfires swapped sides with the o2 swap, maybe its not a vacuum leak. Strange one here. You could probably be safe in replacing that o2, so long as the heater wires will light a halogen bulb (should blink at varying brightness, since it's a duty-cycle controlled circuit).

 

Not sure if the o2 and injector codes are effects rather than causes, since they're circuit codes, but that's always a possibility. I'd focus on the misfires first, then go to the o2 next.

 

Did the new injectors get rid of the 0200?

[LEG]

Yes, did reset of the error codes, just came back. Scanner gives me p0135 , so I swapped sensors, still p0135. Checked connectors for corrosion, none.  Sensors have been in for about a  months. Misfire started about a month ago. Tried injector cleaner. Problem went away, came back shortly after filling the tank again. Did the cleaner routine again. Same results. That's why I thought for sure it was the injectors. Changed them and still the same. They didn't really swap sides. was all along. 2 went to cylinder 8.

 

Thank you for the replys!!

Edited October 13, 2019 by LEG
Typo

[Jsdirt]

That's why I always tell people to run a halogen lamp with the heater wires to see if it has the capability, and do a continuity check of the sensor itself. 9 times out of 10, people get lucky winging a sensor at it, so they get on the net and say, "It needs an o2" (also a running joke in repair circles) any time the money light is on.

 

You either have a wiring, connection (up at the computer, or at any splices or junctions that may be present), or an actual computer problem regarding the sensor code. Same exact thing could be true of the injector. They may be related - a computer ground that only has 50% of it's capacity and is trying to run at 100% is going to cause all kinds of strange problems.

 

There's a reason private shops get over $70 an hour - this stuff takes ALOT of time to track down, and the more money you have invested in diagnostic equipment, the faster you can find things (sometimes). In most cases 3/4 of the diagnostics charge goes to research - once you figure out how the system works and what the actual problem is, it could be a 5 minute fix. 

[LEG]

Sent the truck to the dealer, 2 days later the only thing resolved was $140 being relieved from my wallet. They had no clue, wanted to start by replacing the injectors, all of them!  I said no thanks. Replaced the old injectors back in, misfire on cylinder 8 went away, so back to 2 and 7 misfire, checked for leaks, none I could find, swapped coils, nothing, re checked wires.

 

Found something interesting though, with the mass air flow sensor disconnected the misfire goes away, plug it back in and it's back, same 2 cylinders. I tried it several times, same result each time.

[riverbanks]

What's the MAF reading at idle in GPS

[LEG]

It's reading .01 lb/s. Thought that was the problem, when disconnecting and reconnecting so I replaced it. Still the same. It's almost like it need about 20 more rpm at idle.  Scanner says 560 is

recommended, it's hovering around 550ish.

[riverbanks]

I do g.p.s, just easier for me,grams equals litres of motor at idle,this way I don't have to remember much

[LEG]

4.53 grams

[Jsdirt]

I'd carefully clean it. Its under-reporting just a bit.

[riverbanks]

A couple posts back,he replaced it,but with what brand?bad luck with duralast,and back to unplugging it, should you check for battery voltage at plug,pink wire?

[LEG]

Yeah, it is a duralast brand, with connector plugged in and connected to positive terminal of battery, meter set to 2, I'm getting .07 reading on pink wire. Didnt try with the stock one because the plug in/unplug results were the same.

 

I am super appreciate of the help this forum is providing!

Thank you!!

Edited October 25, 2019 by LEG

[riverbanks]

I won't buy them anymore,not for Chevy anyway, nickname"don't last"

[Jsdirt]

Still better than a Dorman product any day of the week!

[LEG]

Thanks, but what should the voltage reading be on the maf pink wire?