Engine/Transmission (1994 - 1998) Poor Mileage Problem

[CThomsen]

The last 4 tanks of fuel I have had a severe drop in mileage. 1st two were 10MPG, changed fuel filter, next two were 12 mpg. Normal mileage is 15-16 year round. Truck starts great without depressing accelerator at all. No new mods since 215 injectors installed in Sept. or Oct. Any suggestions appreciated.

 

[McLaughlin]

No suggestions but if you find a solution, please post your solution. Had the same thing happen to me but I didn't change the injectors. You might check and see if you highway mileage is still good. A few months ago, my truck dropped from 17 to 12 (mostly short in town trips) and I still haven't figured it out. So far, I've checked for water in the fuel (believe I found some), changed the fuel filter, added fuel additives, replaced the lift pump (fuel pressure was marginal), and overhauled the injectors. My last tank of gas was mostly highway and I got 19. 1 (tank before was 12. 7). This tank is mostly the short trips again and I'm way down in mileage (suspect I'm around 13 again but won't know until I refill. ) I'm beginning to believe it has something to do with the initial start up fuel/injector/injector pump operations but am still trying to determine what to do next.

 

[The patriot]

Your timing may have slipped.

 

[WAnderstrom]

I had a sudden drop this last fall and just got around to doing the timing and found it had slipped to about 8*. All is well with it now at 15. 5* Good luck.



How do you check the lift pump? Is there a time when they usually go out?

 

[CThomsen]

If it is the timing, would I notice any changes other than the mileage?

 

[Signal73]

I think you see white/grey smoke at higher RPMS with a power loss.

 

[The patriot]

How do you check the lift pump? Is there a time when they usually go out?

If you do a search under lift pump and my handle, you'll find some info.

Too much to write here.

Eric

 

[Hvy-DCZ]

Any chance of winter fuel being the culprit? I've had a drop, but not as severe as you guys mentioned. I recently went from a badly slipping stock auto to a tight DTT transmission. I expected an increase in mileage, and so far haven't seen it. Hoping it's winter fuel blend. Not sure how long we'll have to wait to see... Mine went from ~16-17 in mixed commuting to ~15. Like I said not severe.



I would really expect power to be down if the timing slipped... . and the white smoke like mentioned before.



I'm thinking some of Lenny's EDM stage 3s might be the ticket for me. Looking for economy, but would like a little extra hp when getting into it.



Good luck,

Hvy

 

[The patriot]

A small drop like that may be winter fuel.

I get my fuel in bulk, so I cant say for sure.

Eric

 

[BOverton]

any resolution to this?

 

[McLaughlin]

I ended up replacing my injectors and added a #10 fuel plate so my results were affected by those mods but I'm getting about 19 highway and 16 city. I think most of my problem was my original injectors.

 

[CThomsen]

With current mods and timing advanced I'm up to 17-19mpg.

 

[BOverton]

Which injectors id you buy?