Hesitation when giving gas

Hoping you guys can help, Got a 2000 AC, when the engine gets warm and I come to a stop it hesitates for a few seconds when I give it gas. Only code is a O2 sensor. Has 169,000 mile and thinking the transmission but was hoping maybe the carb or vacuum lines. Any ideas would be appreciated!

 

Could be any number of things, tranny is the last I'd think of, but I may be wrong.

Did you check for any signs of pink foam in the radiator and/or its overflow, or froth on the tranny dipstick?

Anything stopping you from replacing the two O2 sensors on the bank that's showing one as bad, just to rule out it's part of your problem? A pair of Denso sensors can be had for less than $200, last I checked. Not lost on me that it's not exactly chump change, but ....

 

Thanks Shifty! The radiator and overflow show no signs of pink foam or froth. It needs a new exhaust and I was going to replace the 02 sensors when I did it but I'll replace them and see if that helps.

 

Clean air filter & fuel filter?
Clean MAF and throttle body?

 

Curious, did you pull codes after the hesitation started, or only before?

Did the code reader you used only report "set" codes, or will it also show "pending" codes? Just curious if maybe a code is pending.

Checking the MAF resistance could be a good idea also. Maybe see if it's reading high when warm.

Also, checking the tension on the throttle cable. But the part where it only does it while warm wouldn't make sense here.

 

The air filter, MAF & throttle body are clean. Didn't check the fuel filter but I'll replace it since I don't know when it was replaced last since I only had it for 4 months now. Checked the codes when it was cold, I'll check the tension on throttle cable after work tonight. Thanks for the info! Was hoping it wasn't the tranny wearing out.

 

I mean, it always could be the tranny wearing out if it's been used to tow heavy shit its whole life. I've only ever noticed a hesitation to upshift on mine when it's cold and it has less than half the miles.

When people say stuff like, "only happens when warm" or "only happens when cold", sensors specifically are notorious for behavior changes as the temperature changes, so that's where my mind goes. The throttle cable is just something others have brought up here in the past.

Anyway, if you have a basic multimeter than can test resistance, there are some plenty of sensors you can validate by checking the resistance across the two pins, MAF included. You'd need to check the service manual to find out what the readings should be for your year/engine though.

Quick sanity check on the tranny, you could loosen the pan bolt to drain out a quart and check the color, then replace a quart. Or just do a pan drain/fill, replacing with same amount. I take it you checked the fluid level already.

 

I came to find out the back brakes we locking up when they warmed up. Adjusted them back and truck is working fine. Thanks for all the input!

 

Last thing I would've expected was a mechanical system like brakes. Really appreciate the update, it's food for thought in the event someone else runs into the same problem: Hesitation, but no codes posted or pending.

 

I still have to get that O2 sensor in. That's the last thing I expected too. Had another post about the mushy brakes and I put Power Stop pads on the front and now I can lock them up on pavement. You guys really helped!