My truck used to get 26- mpg. Moved where speed limit was mainly 70 mph. MPG dropped to 25. Just recently added some injector cleaner (once every 3,000 miles), cleaned throttle body and checked the intake(some carbon but ports still open) and then I started to get 21 mpg. Always do regular tune ups. Has 173,000 miles and runs good, no MIL light. 02 sensors within specs. Any suggestions?
how does the cap and rotor look? I was getting terrible gas mileage when I bought the truck 2 yrs ago (around 15 mpg) looked at the cap and rotor which had build up on the contacts, cleaned them off and I was in the 20s.
My truck used to get 26- mpg. Moved where speed limit was mainly 70 mph. MPG dropped to 25. Just recently added some injector cleaner (once every 3,000 miles), cleaned throttle body and checked the intake(some carbon but ports still open) and then I started to get 21 mpg. Always do regular tune ups. Has 173,000 miles and runs good, no MIL light. 02 sensors within specs. Any suggestions?
Did the 21 MPG start right after the TB cleaning and intake check?
Could something (like the MAF or maybe the O2 sensor) have gotten gummed up from the cleaning.
How did you check the intake ports? Did you pull the intake?
Could you have left any vacuum lines off? Could the gasket be damaged or not sealed correctly?
Do a Search on Seafoam if you think it's a carbon problem.
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Jerry
2004 Frontier, King Cab, XE, 4x1, 4-cyl, 5-spd
The poor mpg did not start right after the throttle body cleaning. It started after I put stuff in the tank (intake and injector cleaner). When I took off the TB I looked into the inspection holes in the intake. There was carbon build up but the ports were open. As for O2 sensor or MAF, I've got no MIL light. If they are bad I should get a light. I am leaning more towards carbon build up. No hesitation and no real power loss though. Thanks!!
The poor mpg did not start right after the throttle body cleaning. It started after I put stuff in the tank (intake and injector cleaner). When I took off the TB I looked into the inspection holes in the intake. There was carbon build up but the ports were open. As for O2 sensor or MAF, I've got no MIL light. If they are bad I should get a light. I am leaning more towards carbon build up. No hesitation and no real power loss though. Thanks!!
Don't be so sure about getting the light. I've got a 1996 that ran like total crap for 3 months before throwing an MAF code. I would first check your vacuum hoses, plugs, wires, etc. Also, clean your MAF and IACV if you haven't already. It's all just routine maintenance.
Have always kept up with tune ups (cap/rotor/plugs, etc). Plug wires have 100K on them so I will change. You mentioned IACV. Not sure what the abbreviation is. I will check the MAP. Thanks!!
definitely get some new plugs, wires, cap, and rotor on there. Sounds they're due to be replaced. What about your air filter and fuel filters? they must be pretty crusty by now.
Lastly, have you ever replaced the PCV valve? It's a $2 part that's a total motherfucker to replace. But it can throw your entire emissions system off balance if it's too old. I finally replaced mine at 145k miles for the first time, and it was pretty oily.
High speed wipes out the good gas mileage. I have a 97 2wd HB that I still get 27-28 mpg the highway on going 65-65mph but if I stay on the interstates running a whole tank of gas out at 70-75 and sometimes 80mph it drops me down to 22-23mph! Mine does seem to be geared pretty low at 3000rpms at 70mph though.
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