The problem:

11 mpg no matter how easy I drive it, loaded or unloaded under any condition... still 11. I put my face to the exhuast to quickly sniff and I nearly lost my eye sight. I've been around rich running engines but not as rich as this. It took 30 seconds of blinking and putting water in my eyes to stop the burning.

Now it's harder to start. It takes about 5 or 6 cranks to fire it up when it used to only take 1 or 2.

Here's what i've done to the truck:

K&N FIPK, no cats, stock EFI manifolds, walker down pipe, single in dual out raven side exit (before wheels) exhaust system, removed the A.I.R. system and blocked the head with plugs, 172k miles, 3.73:1 gears with SVT locker out of a Cobra, M5OD.

With every performance mod I made the truck got progressively slower... Now i've got a truck that sounds excellent, is slower than stock and gets worse mileage... what a waste... I sure hope that when this rich running problem is corrected, the performance parts I put on the truck will come alive...

Is there a solenoid or sensor or something that controls the mixture that could be stuck?

I'm really desperate for help and don't want to sell this truck... I just want to fix it and enjoy it... i'd be thrilled with 15 mpg highway.

Thanks a million guys, any ideas welcome no matter how goofy or far out there it is, i'll try anything recommended!

 

Quick thought... could a faulty EGR valve create those symptoms listed above?

I sucked on the valve and it held vaccum... but maybe there's something wrong with it still?

Thanks!

 

How old is the O2 sensor?

Check for codes.

 

The O2 sensor is a Bosch brand and is about 4 months old or so. The check engine light is not on at the time, but i'll run it by Autozone tomorrow and have the codes checked.

 

Went to Autozone and it pulled no codes.

I'm going to try cleaning all electrical connectors and blocking off the EGR completely as well as the vaccum line for testing purposes. I'm expecting the check engine light to come on but hopefully it'll run better and I can further diagnose the problem.

Does anyone know where the part number is located on the EGR valve? Autozone sells two for my truck, $75 or $95.

Thanks!

 

Ok... I went ahead and traced the outline of the EGR gasket on an RC Cola can and stuck my 'new' gasket against the intake with the real EGR gasket between the 'new' gasket and the EGR. I started it and lo and behold it has more power and most of the irritating hissing that it did when you'd rev it up and let off the gas is gone. Besides blocking the EGR I pulled the line off the vaccum block right below the EGR and just plugged the block (the EGR port) to eliminate the possibility of the line being bad.

Experiment time... It now has more power but still takes a little bit to start it. The exhaust note sounds alot more healthy and it actually sounds more like a beefy small block now. I'm broke at the moment and can't afford to fix this thing the right way for the next couple of weeks... soooooo... can I get away with running the truck like i've got it right now? I figure anything's gotta be better then the huge leak and the raw fuel smell coming out of the exhuast...? What's the worst that can happen with this block off plate? I ran it for about 20 REALLY hard miles, harder than I usually drive it and the temperature stayed right at a quarter like it always does and when I popped the hood, the engine felt as hot as it usually is...

The exhaust smells alot less now! I'm going to clean the O2 sensor connector and am putting in new plugs and flipping over to my full rear tank to see if fuel consumption goes down.

The "Check Engine" light is on... but if I start getting decent mileage i'm just going to take out the bulb.

Anymore advice would be greatly appreciated!

 

I've been running with no EGR for almost 6 years. Don't worry about it too much. You'll get better mileage with it hooked up and functional.

The SES light is on because you unhooked the vacuum line from the valve. If you leave it hooked up the valve will still open, but no EGR will flow. If the valve doesn't open the EPS knows the valve isn't open and throws the code.

 

i think if it is completely blocked off it'll still throw a code.

Leaving a small 1/8" hole in it is the more common method. Mine still passed emissions with this restrictor plate in it. I'm not entirely positive that it'll throw a code if it doesn't flow that little bit.

 

So the RC Cola can works for now. I didn't pierce a hole in it and the check engine light is still going... but i'm happy to report that i'm through with my first tank of gas since the "RC Cola" EGR block off plate mod and i'm getting 15 mpg up from 11... and that wasn't even driving it lightly or babying it at all. I had a head wind for atleast 1/2 of those miles and only about half of that were actual highway miles with A/C on max most of the time.

Once I get the new EGR valve and solenoid next month i'm hoping mileage will go up. I read on another post that eventhough the mileage will improve with the block off plate over a leaking EGR valve, it will go up even more if everything is connected and 'fresh'. As a side effect to this experiment i've noticed that the exhaust and area surrounding the whole truck smell like crap... not raw fuel like before just carbon monoxide smell... but all around the truck when idling with the windows down... needless to say i'm going to get the EGR and solenoid on as quickly as possible to get rid of this problem!

Thanks!