i have a 1998 dodge dakota 318 5 speed
throwing a po135 and po443

changed the downstream o2 sensor and the catalytic. also changed the purge solenoid. these changes did not help and it still backfires at low rpms. im wondering what else could cause the evap code and also if i change the upstream sensor will this fix my backfiring problem?

 

P0135 is the upstream 02 heater fault code.

Not sure about the purge solenoid. I'm showing "open/shorted condition in the EVAP purge control circuit." If you've changed the solenoid, check the wiring for damage and make sure all connections are clean and tight.

Check the distributor cap and wires for the backfiring. May want to check the plugs for condition as well too. It could be any number of things.

 

Ok thanks. All the plugs are new. It actually got progressively worse when the cat was changed but thank you for the help. I will check the wiring to the solenoid

 

Do you know about the charcoal filter location?

 

Not sure on a '98 but I think it's under the vehicle, drivers side, in front of the fuel tank.

 

ok thanks. do you how to check if they are bad or is it just replace it and be done?

 

I don't think the canister is causing the problem.

Change the 02 sensor. It can screw up the mixture. Did you check/replace the cap, rotor, and plug wires? The wires don't last forever the insulation does break down after a while. The cap could be carbon tracked.

All can cause a misfire.

 

Check the underside of the coil for cracks. Had this problem with my truck causing it to run poorly. The coil still made spark but it started to weaken casing misfires and backfires. Its an easy and cheap part to replace.

 

Its a brand new cool. It seems like when the engine is warmed up the butterflies on intake close cause the engine to choke. Any ideas on what sensor controls this?

 

There's nothing on the throttle linkage that should do that, not like a car with a choke.

The air bleed for idle is via the IAC in the throttle body.