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Need info on VVT please, timing not right, REALLY bad MPG

mckpaul

By mckpaul
in Ask A GM Technician

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Dnt Senior Enthusiast

Dnt

Posted
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Cylinder #5 (going by memory) is the third from front on drivers side. It is super easy to get the socket on a bit sideways and crack the plug ceramic (ceramic is glass) there is some stuff in the way of getting lined up straight on that side of the engine. Now put away all the fancy scan tool equipment go grab a ratchet and socket and go take the #5 plug out right now. If it has ANY signs of misfire replace it and be dang careful not to damage the brand new spark plug when reinstalling.  BAM all your problems will disappear and you will drive off into the sunset with all your brand new expensive scan gear in the backseat never to be used again. Happy 4th of JULY

mckpaul Enthusiast

mckpaul

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I wish it was that easy, I really do. I've swapped that plug with cylinder 1, and I've had all the plugs out twice for compression test and changing the #5 cylinder valve springs, making sure they were all clean and making sure I put a different plug in #5 the first time, and completely swapping sides of the engine with plugs when doing the springs. The wires and plugs are less than 6 months old and have moved them around as well, and swapped two other coils into the #5 position. Did the same with injectors and #5 now has a new injector. Misfire stayed on #5 through all of that. I've had a noid light on the injector and a spark plug light on the plug wire and neither misses a beat. Got over 170 pounds of compression on #5. While changing springs I took the air pressure off and both valves travel up and down smoothly in the guides. The rockers are rocking with oil coming out on the rocker arm from the rods. I've been beating my head up against the wall over it. But the deeper it gets, the more it seems that, similar to spark timing, the whole misfire thing may be a side effect of something else.

mckpaul Enthusiast

mckpaul

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I'd like to say thanks to all for the input so far. We're going out of town next week so I won't get back to the truck until the following week. I did buy the pdf shop manual which will help. Just want to say I didn't give up or get things resolved without posting what it was, just out of town for a week.

  • 3 weeks later...
mckpaul Enthusiast

mckpaul

Posted
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Well, I gave up and dropped the truck off at a GM certified shop near me. After a couple of days messing with it he called and said he was pretty sure it was a lifter so I told him to go ahead and dig in. He found the exhaust lifter on #5 to have a roller that was kind of chewed up and the cam was damaged as well. I attached a pic of the lifter, I hope it's visible. It's frustrating because No. 5 not even an AFM cylinder. He said the plastic lifter tray wasn't cracked and it didn't appear the lifter had rotated, not sure why it did what it did. However I'm not the original owner, it was a trade in vehicle at a Ford dealership when I purchased it back in November. It may have had repairs prior to me buying it that were done poorly just to make it run to trade it in.

 

So of course that meant new cam and all new lifters. I made sure he got the newest updated GM lifters, replace the plastic lifter trays,  and had him change the VLOM to the newer updated version. Knowing he was going to have the timing chain cover off and would be looking at the oil pump, I had him replace that too.

 

The truck now idles quietly and smoothly, no misfires, and has the throttle response of a new truck.

 

On a side note, a week prior to the repair I put new y-pipe/cats on the truck, bought it online from AB Catalytic, exact bolt up replacement. Since I got the truck back it threw a P430 code, poor cat performance bank 2. The cats are literally 3 week old and only ran a limited amount on the engine with the bad lifter before the repair. I know the cats are good. I don't want to continue on that topic on this thread, I'm going to start a new one on just that subject. Just wanted to say thanks to all who shared their thoughts, and post the solution to the P0305 misfire in hopes it helps someone who finds this discussion later.

No 5 exhaust lifter.jpg

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Happy to hear you got it sorted out.  Have to wonder if the valve train noise was being interpreted as pinging and the ECM was backing off timing as a result. That roller looks like the early beginnings of the Honda V4 bike engine camshaft issues in 82/83. 

dsr611 Senior Enthusiast

dsr611

Posted
Posted
On 7/25/2018 at 9:57 AM, mckpaul said:

Well, I gave up and dropped the truck off at a GM certified shop near me. After a couple of days messing with it he called and said he was pretty sure it was a lifter so I told him to go ahead and dig in. He found the exhaust lifter on #5 to have a roller that was kind of chewed up and the cam was damaged as well. I attached a pic of the lifter, I hope it's visible. It's frustrating because No. 5 not even an AFM cylinder. He said the plastic lifter tray wasn't cracked and it didn't appear the lifter had rotated, not sure why it did what it did. However I'm not the original owner, it was a trade in vehicle at a Ford dealership when I purchased it back in November. It may have had repairs prior to me buying it that were done poorly just to make it run to trade it in.

 

So of course that meant new cam and all new lifters. I made sure he got the newest updated GM lifters, replace the plastic lifter trays,  and had him change the VLOM to the newer updated version. Knowing he was going to have the timing chain cover off and would be looking at the oil pump, I had him replace that too.

 

The truck now idles quietly and smoothly, no misfires, and has the throttle response of a new truck.

 

On a side note, a week prior to the repair I put new y-pipe/cats on the truck, bought it online from AB Catalytic, exact bolt up replacement. Since I got the truck back it threw a P430 code, poor cat performance bank 2. The cats are literally 3 week old and only ran a limited amount on the engine with the bad lifter before the repair. I know the cats are good. I don't want to continue on that topic on this thread, I'm going to start a new one on just that subject. Just wanted to say thanks to all who shared their thoughts, and post the solution to the P0305 misfire in hopes it helps someone who finds this discussion later.

No 5 exhaust lifter.jpg

Looks about like the #5 lifter on my truck back in January 2017...

8Qizg9I.jpg

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