very poor fuel mileage

[heyhar]

thats one of the more ignorant things to say. feel free to post productive reply's in this post other wise dont.

WOW, Mike, you only have about 6600 posts of trying to help people...If that's ignorant, just continue to be as rude as you can be!!

 

[cruiser54]

I have had the connector at the MAP give me problems, especially if the locking tab is broken/deformed. You can tighten up the female terminals with a pocket screwdriver so they grab the pins tighter while you're at it.

 

[ruger81]

Hmm, I think you kicked over the wrong rock here sir!

YOU asked how to test an O2 sensor in this thread a day ago. Your very next post in this thread said you replaced the O2 sensor, with no mention by you of having tested it first. There are also others that have jumped into this thread with posts, that I was also addressing my "test first, and how to test an O2 sensor" comment to.

If you wish, I will glad to avoid answering any further posts or questions you post asking for help. Sorry to have waisted your time and rattled your cage with my "ignorant" post. LOL

so thank you ecomike for your help, and im sorry for using the word ignorant in my post.
i searched and found ur thread on how to test it before buying a new one... if that was not directed towards me then i apoligize.

my big issue is that it tested bad but with out the computer know something was wrong.. dont know why!

aslo my map test's ok also. im wondering yet still why it test ok and i have such bad fuel milage. i have not yet installed it cause if i dont have to have it i would love to save 60 bucks..

 

[Ecomike]

Some O2 sensors as they age are slow to respond to changes in O2, so they eat more gasoline due to a slow lazy O2 sensor, but they work well enough to keep the computer from throwing a OBD-II code. An O2 sensor can work at cruise, while hot, but get cold at idle and waist gas if the internal sensor heater is not working right.

 

[Ecomike]

so thank you ecomike for your help, and im sorry for using the word ignorant in my post.
i searched and found ur thread on how to test it before buying a new one... if that was not directed towards me then i apoligize.

my big issue is that it tested bad but with out the computer know something was wrong.. dont know why!

aslo my map test's ok also. im wondering yet still why it test ok and i have such bad fuel milage. i have not yet installed it cause if i dont have to have it i would love to save 60 bucks..

IIRC, the O2 sensor reads high voltage when rich, say .9 volts. If only .05 volts of that .09 volts get to the ECU/PCM, it will fool the computer into thinking all is well!!!! A porr connection, voltage loss due the resistance in the wire between the computer and O2 sensor is possible.

I just read a cool idea for testing, that would also check for a leaking injector!

"To test further, create lean.... conditions:

• Remove an injector lead and see that the voltage swings in the lower 0 to 0.2V range."

Have you checked the fuel pressure regulator (I forget, does the 92 have one on the rail, or is it in the gas tank by 92?) My renix has one on the fuel rail, and when they rupture they dump raw fuel into the vacuum line.

Might be a good idea to check and clean the ECU/PCM contacts and ground.

 

[Ecomike]

so thank you ecomike for your help, and im sorry for using the word ignorant in my post.
i searched and found ur thread on how to test it before buying a new one... if that was not directed towards me then i apoligize.

No problem, I know how frustrating it is to try and locate what I call Romulan Cloaked gremlins that defy logic running loose in Jeeps!:roflmao:

 

[xjtrailrider]

I got around to doing some testing tonight. My MAP is reading 1.85 volts at settled idle so it will get replaced tomorrow. The O2 is giving me a 8.5 ohms reading on the heater. I picked a new BOSCH off the shelf at Advance Auto and I get the same reading on it. That was with 2 different DVOhm meters.

Is this an acceptable reading? The RENIX manual says 5-7ohms and if it is infinite then its bad but what if its just a little high. Is this just a manufacturer trait?

I need to check the input voltage to the O2 and make sure the ground is good. I'll do that tomorrow after I get the new MAP in.

 

[kastein]

I would think that's manufacturer dependent, yes. 8.5 ohms will still pull approximately 22 watts while the engine is running, 7 ohms would draw around 27 watts. Either seems to me like it would heat the element perfectly fine.

 

[xjtrailrider]

Well I replaced the MAP and checked all the numbers on the O2, it checks good.

My idle is somewhat smoother but still really low, 300rpm. I'll run a tank of liquid gold through it and report back.

 

[Ecomike]

Well I replaced the MAP and checked all the numbers on the O2, it checks good.

My idle is somewhat smoother but still really low, 300rpm. I'll run a tank of liquid gold through it and report back.

Is yours a 1990? If so, just for grins, check and make sure the O2 sensor and TPS connector are conected backwards at the connector. If not then ask Uncle Bob :shiver: if he messed with the throttle body throttle stop?

 

[DaYeep]

Ok, so I have to add something that might be overlooked. Just banging on the CAT is not always an effective way to check it. Find someone with a digital heat sensor and with the engine running and warm, shoot the temp of the exhaust pipe as it enters the CAT, and shoot it as it leaves the CAT....if temp is close to same, CAT is fine. If temp at entrance is MUCH higher than exit, CAT is bad....replace it and benefit from improved mileage. I too had done EVERYTHING, including all the REMIX updates....still bad until I found this little fix. Hope it helps some of you.

 

[xjtrailrider]

Is yours a 1990? If so, just for grins, check and make sure the O2 sensor and TPS connector are conected backwards at the connector. If not then ask Uncle Bob :shiver: if he messed with the throttle body throttle stop?

Checked the connectors, they are correct! I have "properly" adjusted the throttle stop since uncle Bob screwed with it last LOL!

My O2 heater relay was a little weak so I replaced it as well, it was working but was giving me some high resistance across the coil. I've got a solid 13v at the O2 on the orange wire and 5v on one of the black wire's. The other black wire is giving me a good ground using a test light.

 

[cruiser54]

You can also use a vacuum gauge to check for restricted exhaust. Heck, it wouldn't hurt to hook up a vac gauge on it anyways. They can supply you alot of info on your engine.