I'm not trying to sound dumb but , I have afew questions. My truck is a 89 4x4 with a 22re, 5 spd. , 134,000 miles. I have had the truck for a while and haven't driven it much because I had a company truck. The a/c has been bypassed , to me it looks like some of the smog equipment is gone and there are some things unplugged. The main thing is the o2 sensor just below the exhaust manifold, it's unplugged. I have looked for the other side to the plug and I can't find it. Also, i have 2 O2 sensors and they are both bfore the cat. None after the cat. Can I wire the front O2 sensor in with the back ? There haven't been any codes with the front O2 sensor unplugged. It just runs like crap. It also has a little black smoke coming out of the exhaust when I rev it up. I pulled the plugs and they look like it's running lean. I'm going to have a buddy check my fuel pressure and timing this weekend. I have replaced the plugs, wires, dist.cap, rotor, fuel filter, air filter.I have also cleaned the TB and the MAF and ran some seafoam through it. As soon as I can afford it I'm going to replace the coil . Any other ideas why it would run like crap? My mileage dropped. Any ideas about the O2 sensor? Thanks for the help.

 

O2 sensor will make your mileage drop. When they fail, the engine defaults to rich. All O2 sensors are upstream from the Cat so that's Ok.

You might make sure your CEL (check engine light) doesn't have a burned out bulb because it should be sending an error with the sensor unplugged.

I have the 3.0 so I hope that someone will 4 cyl experience will chime in. However, you can check the FSM link on the 86-95 page and it will give you more particulars.

Frank

 

you mike check under drivers seat below the truck some body possibly change exhaust man before to a older one 89 4 runners has o2 sensor under driver seat outside 86 had a sensor on manifold check if yours is hooked up to the tailpipe under the floor when i origly changed my engine had 1 bare 02 sensor on manifold and it always would lean out and get hot, wireing somewhat different decided to do swap instead of dealing with real problem beleaved maybe different computer

 

Some of the trucks had two O2 sensors one before and one after the cat... why I don't know... might have been some thing to do with Kali. emmisions...
sounds like the PO did a frankenstein on the exhaust system...
in this case I'd almost want to bring it to a good dealer for a diagnosis...
or else a toyota specialist shop in your area...

 

thanks for all of the help. I checked and the one just before the cat is hooked up. I looked in the Haynes manual and the front O2 and the back O2 sensor appear to be connected somewhere . At least it looks that way i the wireing diagram. Thanks again.

 

Here's a great link to use for troubleshooting. Most of the stuff shown will aply to your truck. I have a 91 and it only has 1 O2 sensor, it's in front of the cat. I'm not knowledgeable enough to talk about different model years. But I bet if you took the vin # to the dealer they could tell you if yours is federal or cal emissions compliant, and whether you should have 1 or 2 O2 sensors. You say that you think part of the smog gear is missing. If so that can surely mess with the way the truck runs. It needs all that stuff to let the comp do its job for running. X2 on taking it to a pro.
Jim
Oops Left out the link http://personal.utulsa.edu/~nathan-b...sm/engine.html

And here'sthe index for the whole book http://personal.utulsa.edu/~nathan-b...fsm/index.html

 

thanks for link.

 

elripster, Iwent out and took the dash apart and found no bulb in the check engine light. I put one in and is does have some codes. I can't tell what the hell they are so instead of miss reading I'm going to run it to advance autoparts later. thanks for the tip about the bulb. I'll let everyone know what the codes are. Thanks again.