toyoman13

hi guys maybe you can help. i have a starting problem with my 93 4runner v6 4x4. when its below 50 degrees outside i have no problems. when its over 50 degrees i will start it it will run for a second just fine then it gets bogged down. every time i hit the gas pedal it act like it does know i am hitting the gas. it just stumbles and some times back fire. i have to drive it for a couple of miles before it will before it will drive right. it doesnt do it from and cold start it only does it when i drive get it warm then let it sit for about an hour. if it sit longer it fine. please help.

abecedarian

Hmm....

I'd be inclined to think there's a vacuum leak or similar, possibly the auxilary air valve is malfunctioning, causing you to have a lean mixture when cold but not too cold, but I'd lean that way only because you say you have a "backfire", which I assume you mean a misfire up through the intake.
However, the coolant temp sender to the ECU could also cause a similar condition as could the throttle position sensor.

Does it run fine once warmed up?

toyoman13

once its warmed up it feels like it has a little miss but nothing mayor.

toyoman13

the backfire does sound like it comes from engine and not the exhaust.

toyoman13

where is the coolant sensor for ecu located.

94svt50

Mine did the exact thing. It ended up being the o2 sensor, I had just replaced it with a generic one and it caused the exact same problem. Switched to an oem brand and it cured the problem, but occasionaly it does a similiar thing anytime I get moisture in the o2 sensor connector. I just hit it with some electric parts cleaner and it takes care of the problem. This has something to do with temperature and at what point the ecu switches from closed to open loop with its information gathering from the sensors.

toyoman13

if i unplug the O2 sensor would that be a good way to test if its the problem.

94svt50

No, there really is no good way to test without specialty equipment. If the sensor is old just replace it, it should fix your problem and could give you a bit more mpg.

toyoman13

ok. i have been getting 15 mpg on the highway when i'm use to getting about 19 mpg. i'll let you know if it helps.

94svt50

Just dont use the Bosch sensors, try to get the Denso brand. Side by side there is a big difference in how far the sensor sticks into the exhaust flow.

toyoman13

Replaced the 02 sensor still have the same problem. abecedarian you said something about some other sensor. do you know the spec for those sensor so i could check them.