Need some serious help!

[MyChariot]

Hello all! I'm new to this site and am in need! I have a 99 Explorer Sport, 2WD, 4.0 OHV engine, manual transmission. It has a loud engine knock, which I believe is a lifter(s) tapping. It gets louder under a load (i.e. ac compressor kicking on) and it is always there, no matter what. The only time you can't hear it is when the truck is off. haha Seems like it has gotten louder over the last year. Also, my gas mileage is going to pot. Uses about 1/8 tank for 40 mile highway trip, whereas before the needle didn't even budge. I use regualr unleaded gasoline and always have. Could this be part of the problem? I change my oil on a very regular basis (always have) and use 5W-30. I changed it yesterday and substituted a quart of oil for a quart of Rislone. Haven't noticed any difference yet, but I know things take time. Another thing: it is having a hard time starting. I cycle the key back and forth a few times and then it will start. Seems like it is not keeping fuel pressure. I replaced the pressure regulator about two years ago when I first started having the problem. It's progressively getting worse. Any suggestions for any of this mess I have going on with this truck? I appreciate all of you!

 

[410Fortune]

is the check engine light on?

 

[MyChariot]

No. It has only come on one time ever in its life. Said a bank 2 problem. Replaced O2 sensor and it went off; hasn't ever come back on.

 

[410Fortune]

how many miles?

A knock does not exactly describe lifter noise... that would be more of a tick

how long since the plugs were checked and changed?
You should test your fuel pressure at idle, its simple to do and can eliminate the fuel pump as an issue.

When was the last time you replaced the fuel filter?

No check engine light basically eliminates any of the emissions sensors from being your problem
If your engine is knocking as you say, I would:
check plugs, check fuel pressure

remove valev covers and have a look

consider a compression test also



it may be time for new heads or new engine

 

[BrooklynBay]

Welcome to this forum! Do you always buy gas in the same place? Maybe you went to some shady station where the gas was tampered with. Gas does go bad after a while.

 

[MyChariot]

83k miles. Changed plugs and wires 13k miles ago. Haven't checked them since then.
The fuel filter was changed about 6 months ago.
I live in a small town so we don't have much of a choice for gas stations...it's either the Allsup's, WalMart or Valero. ???

 

[Sams01XplrSprt]

welcome

 

[MyChariot]

Thank you, ecveryone, for all of your help. I'll let you know wat happens when I find out what's going on with it...

 

[skoal_mint]

I have had good results with lucas oil stabilizer.. I never thought it would stop a noise lifter but it did.. I'v used it on 3 vechiles this months and 2 of them stopped making noise at about 10 minutes of driving.

Had one customer from the US, put about a whole bottle in becasue it was really loud. After the oil change the noise didnt change.. 15 minutes later he calls me from the highway and said the noise has stopped and he was happy

 

[Cobraguy]

I've got one other suggestion for you. If it's a rod or piston knock (which this could be) then you can "short" the cylinder and help locate it. However, I wouldn't recommend you start pulling plug wires on these modern ignition systems. See if you can get someone with an NGS tester or equivalent and run a cylinder balance test. The tool shorts each individual cylinder. When it shorts the offending cylinder, the knock will noticeably change or disappear. You can then decide if you want to start pulling plug wires to find which cylinder is bad or just tear it down...as that is what will be required. A lifter tick will not change with this...and as Jamie said...doesn't sound like a knock at all.