Have you checked the fuel pressure? If it dropping and not atomizing through the injectors it would drop mileage. Has power been consistent?

 

You need to check the timing(not sure how) If something is throwing off the timing then that will kill mileage and possibly give faulty cam sensor failure.

 

fuelman, I replaced the regulator 3 weeks ago. power (lack of) is not consistent. even when it was running good, it barely had enough power to break the tire loose. now on wet snowy roads the tire will spin if you try. data logging shows the timing to be consistent until I try a hill then it will retard.

 

something I noticed this morning, small puddles of coolant around and below the fill cap, like it had overheated a little. never saw the gauge move. last night when I got home there was a strange odor, not brakes or a petroleum product, and the whole exhaust system was making the cooling tick sound but really loud and sharp.

I did have to keep my foot into it to hold speed. even slight inclines I had to increase throttle pressure until it down shifted just to hold speed. wtf

still have a cam position sensor code, no cel

 

another update. my way home last night I had to almost floor it to get it to downshift and make it up slight inclines. used 3/4 of a tank to drive about 140 miles.

 

Have you done a compression test and pulled your plugs to see if water is entering the cylinder or look for detenation issues(on the plugs).

 

no. I'm going to have to find a compatent mechanic in my area. dealerships are of no use.

 

Have you cleaned the MAF sensor? A dirty MAF can cause your symptoms.
Does the temperature gauge go up as high as it used to? An engine that doesn't get up to normal operating temperature can use a lot of extra gas.

 

I have cleaned the maf sensor. the truck did have a 180* stat in it. now has a 195*. the 180* was in it when I bought it in jan of 07 when I was getting 11-12 mpgs and was still in it up to 3 wks ago while I was getting 6mpgs. the dash temp gauge is a little higher since I've changed the stat. the power is still going away while fuel consumption goes up.

 

78% max load is normal for stock. What does the timing look like on the data logs, is something pulling it back?

Was there no change with the new cat? You may need to check the exhaust back pressure still...

 

I'm glad the load is right. the timing does get retarded, I will maintain the same load value and the timing will pull back almost 4*. I already have 2* pulled in the 0-2000 rpm range and 2* pulled global, so I'm still getting pinging with almost 8* pulled out.

am starting to think about the fuel station. if the amount of ethanol in it is much higher than it should be ???? I dunno, $200 + a week in gas is just not except able.

the new cat did quiet down the truck and it would rev quicker, but that is all.

 

I've got concerns about 2 things - none of which seem to be regular problems with the V-10:

1. Timing retard doesn't seem right. This is probably because the knock sensors are picking up something that sounds like spark knock and they are backing off the timing to cure it.

2. The cam position sensor keeps giving you problems.

Here's what I'd bet is going on - you've got valvetrain problems.

If it were my truck, I would be having a leak down test and compression test done to see if my cylinders are building and holding pressure. If there's something fishy there, I'd be stripping down the front of the engine to check the timing chains. I have hear of situations where there was slop in the chains and the slapping of the chains would set off the knock sensors. If the chains are good and the valve timing is in spec, then I'd be checking the cams, valve springs, and everything else under the valve covers.

In my opinion, I think that you'll find the problem when you pull the timing cover. The cam position sensor is throwing codes because the cam timing is floating due to a stretched chain. The odor and noise from the exhaust system is from unburned fuel collecting in the cat and overheating it. This will create a potential fire hazard and at the least destroy your new cat.

 

I need to find a decent diagnostic mechanic in my area. most places are r&r.

I did have a leaking fuel tank vent line, weather that contributed to my problems or not??? fixed and changed the filter crossing my fingers!

 

Do you have a post-secondary vocational/technical schools in your area? If so, you may want to talk to them if they teach diagnostics. Nothing like a real life head scratcher to help people learn.

 

well fixing the leaking fuel tank vent line did nothing for my pinging/mpg problem. I did add 2 bottles of dry gas. still getting a solid 5 mpgs when 3 years ago I was getting 10-12. power is still way down.