Engine/Transmission (1994 - 1998) Smoke and reduced MPG

[Tom Trujillo]

I have noticed that since adding an ATS Manifold and a 4" exhaust about a month ago that the truck smokes more (at startup) and my MPG has dropped quite a bit - about 50 - 75 miles to the tank.



Is this normal ?

 

[fortunate1]

I don't think that sounds right...

Are you sure that you're not enjoying your new exhaust growl too much? That's about a 1. 5 - 2 mpg drop.

 

[bmoeller]

Never saw a difference in startup smoke or mileage with mine. Although, mine smokes plenty anyhow, so if it added a little, I doubt I'd notice. lol



Have you double checked the mounting bolts for the manifold? They're known to come loose sometimes. I've had to tighten mine up some before.

 

[McLaughlin]

What was your original mileage and what did it drop to? I recently had the same thing happen to me I was getting about 17 mpg and it dropped to about 12. It didn't happen for over 1000 mi after installing the manifold and about 500 mi after the exhaust so I don't think those were the cause.



I'd really suspect an exhaust system/manifold leak some place.



When I figure out whats going on with mine, I'll let you know.

 

[Tom Trujillo]

Double checked mounting bolts and still nice and tight to 32'lbs.

 

[Tom Trujillo]

Thats what I figured the first tank and then I made sure I wasn't "enjoying" it.

 

[Tom Trujillo]

Since I got the truck new I could count on 18mpg in all round driving, tank and tank out. I am around 14 now. I will make sure to track the next tank full to get another check. The thing that still surprises me though is the amount of smoke at cold startup. blackish blue. Then it dwindles away as the truck warms up.

 

[McCRam]

When I put my ats and 4in exhaust on I think it helped my mileage slightly, It definatly didn't hurt it. Maybe you have already checked, but make sure you are not getting any leaks into the fuel system. Gaskets and fuel lines git brittle with age, not just mileage. Its also possible you could have gotten a bad tank of fuel and clogged your filter.

 

[mechanic]

I find your problem interesting. I have a 98 as my signature shows, and have gotten from 15. 5 to 18+ out of it since I got it. My 94 with a TST #6 got from 18. 5 to 19. 5 under the same conditions, and only smoked if I jumped on it at low RPM. It also pulled like a bear. The 98 pulls very good, though not quit as strong at the 1800 to 2200 RPM range but pulls hard from around 1400 to 2650 RPM. But it smokes when cold and smokes to much when hot if the RPM is not at least at mid range. Therefore the interest in yours. How is your boost pressure and did you change the turbo exhaust housing? Mine has a Banks housing and waste gate, and I think that it is part of the smoke problem.

I have found that by not throttling hard when the revs are low, I can reduce the smoke and increase the mpg.

I will watching to see what you find.

 

[Tom Trujillo]

Actually I did not change the turbo or the housing at all - its all stock. All I did was the ATS Manifold, new gaskets for manifold and turbo to manifold, and the 4" exhaust. Thats why I think its so wierd, unless by coinsidence something else happened at the same time.



Some one else mentioned a possible clogged fuel filter, I have a Prime-Loc with the gauge and the gauge is in the green so I assume the filter is fine.



Quick question, what is the accuracy of the air filter minder that comes from the factory, I have owned the truck since new and I have never seen that indicate anything other than o% used. Then again, I change filters once or twice a year. This is a very light duty truck - never worked etc.





Tom

 

[sewman]

Well it's getting that time of year f/winter fuel. Mine drops about that much too.

Bob

 

[Vaughn MacKenzie]

Tom sounds like you're sucking air from somewhere. When was the last time you serviced the prefilter and replaced the O-rings including the one on the top side of the preheater?



Vaughn