I have been having some problems with the way my engine has been running lately. I am only getting about 11 mpg around town and on the hwy. When the engine is cold it almost acts like it is misfiring. I have replaced the plugs (NGKs gapped to spec), replaced the air filter, ran seafoam through the intake plenum and gas tank and it helped, at least for a little while. When it started getting worse I went back and checked the resistance of all of the wires and coils (thinking that there was an electrical problem) and they checked out ok. I know that a failing O2 sensor could be causing bad gas mileage, and I have read the people have had problems with their O2 sensors failing after running Seafoam through the intake. That wouldn't cause the engine to miss, would it? Another thing, the ecu is not throwing any codes so I am not sure of the next step I should take. BTW it is the 3.4

Thanks

 

clean the MAF yet?

 

Yes, I forgot to mention that. I cleaned the MAF and throttle body and checked all vaccum lines.

 

anyone?

 

loose plug wire or a coil going out maybe? check the codes.

 

IM having the same problem with my 95.5 tacoma. 5vz-fe engine. Just got done rebuilding it after a number one spark plug blew out and while in the machine shop found out my number six hole was about the same way as my number one was.

Mine idles fine and cross checked camshaft and crankshaft sensers also.


Im thinking its a bad cat on mine have you checked yours?.

 

No I haven't checked the cat on mine, but pushing 200,00 miles things are bound to start going bad. If I get a chance this weekend I will take it off and give it a look. Doesn't a bad cat usually throw a code? My brothers 2.7 had the CEL go off on his Tacoma, he took it to the mechanic next to our shop and they said the cat was bad.

 

I have been told sometimes it doesnt give a code.

mine is a 95.5, 174,000 miles,

Funny thing is mine its throwing no codes at me.

One side note to this after i posted.

I was running and looking at the data off the Ecm i noticed my OS2 senser was running not where it should be now i thinking it is the cat now. one was 66 and other one was bouncing from 44 down to 6.

I think mine is a bad cat now.

 

check compression you may have a weak cyl.

 

Thanks for the suggestions, I am going to check what I can this weekend. I am really pressed for time during the weekdays.

 

I did a compression check on mine everything is with in spec.