I just installed a new pump car wouldnt start so i check my fuel pump relay and fuses and all is fine so the pcm is not turning on my pump. so i straight wired the pump and the car starts and runs fine all night long i was driving the next day car keeps stalling at red lights. I have no trouble codes but if i let it idle for a while ill get a code 0420 and after checking its often a bad cat which i dont have one as it turns out and i have all new o2 sensor please help!

 

are there any other odd things happening with the stereo or other things? sounds like a lose or shorted wire. how did you hook in the hot wire and where

 

no the lights are solid the radio works fine never goes or and of the sort. I wired it to a thick white wire under my dash. I think also it could be after i was looking yesterday all around the car while it was idling and after shaking wires to see if that would do something but it didnt i noticed an exhaust manifold bolt broke of and is stuck in the block. The bolt is the last one on the drivers side by the o2 sensor could this cuase it to send different signal to the computer and tell it to idle funny?

 

that would cause a rich condition and foul your plugs, thing is the plugs would still be fouled after the motor cools. a ignition contol module can fail after warming up, coil can fail after warming up, both can do this and work fine after cooling.

 

Were you having this same problem with the old fuel pump, or did you change the pump due to different other symptoms?

 

Ok well would i get a code for a bad coil or spark plug? I changed the pump because I thought it was the pump but after putting in the new one it still does the same thing. Actually after installing the new pump it it worked great for like 30minutes then the p0420 code came on and the car started back up with the usual again.

 

One thing you could do, if you access to a proper scanner, is to look at the output of each sensor when the engine acts up and verify what the sensor are sending to the PCM makes sense for the conditions. Something silly like the ECT sensor showing 60 degrees when you know the coolant temp is up around 80 degrees. Most times when a sensor is telling a lie it won't cause the PCM to set a code because it assumes what the sensor is sending is correct. However; the PCM will set a code if it sees an outright failure of a sensor, such as when it stops communicating with the PCM.

 

Ok after work i will try to do that but also another thing is i noticed when im in park the idle is the same as if it were in drive at a red light does that mean anything? man this car is not easy.

 

Hello everyone got the exhuast on right but it still stalls and now i have no codes no known issues all new spark plugs, wires, etc. even a new fuel pump still stalls.

 

try restarting the computer. unhook battery, both cables, touch them together (not hooked to battery) for 10 minutes. reconnect to battery. should take a few runs for the computer to relearn the normal operation of the system.