Ticking noise from engine, decreased MPG

[hilltopfarm]

OK, so I replaced my transmission this Summer. In the process I had to take my exhaust manifolds off and I broke all the bolts. I then took the engine apart to get at the head and have the bolts drilled out. Before I did this project I was getting 18-23 mpg, now the best I can get is 18 (its mainly 12-16 mpg). I replaced the fuel pressure regulator, and tested all the sensors (all tested OK). The only thing I noticed that is different is a VERY loud "ticking" noise when I first start up the truck or accelerate. I am perplexed, could it be my lifters or my injectors??? If it were any of these would it decrease my MPG that much??? I also have headers and high flow exhaust which should have increased my mpg...

Thanks for any suggestions as to what it could be!!

 

[jhammel85]

Stupid question but since you removed the manifolds, you did replace those gaskets right? That ticking could just be an exhaust leak.

 

[hilltopfarm]

Yes I did, tightened it all down to spec torque as well.

 

[cocoasranger]

Since you had the heads off, I would recheck the preload on each hydraulic lifter. When the heads are reinstalled, each rocker adjustment nut is turned in till there is no clearance, then turned in an additional amount (something like 1 1/2 turns..check your manual)

This is fairly easy to check and may well be the problem. Good luck.

 

[volrath]

if your hearing it under load and at start up i would say it is coming from your exhaust gaskets or were your y pipe connects to your headers. once the engine is heated up the metals all expand enough to close what ever leak there is until under heavy load where the exhaust pressure is great enough to "leak" again. it isn't all that uncommon for headers to leak a little though.

but it is always a good idea to check your lifter adjustments.

on my old 2.9 it wouldn't tick under heavy load or when i was beating on it but it would tick once it idled back down. but even then the lifters never seemed to affect performance or milage. if they were out of adjestment it could though