Intermittent misfire - bad wiring?
 

I have a strange intermittent misfire issue. It only happens every once and a while, maybe every 5 mins on average and it only lasts a second or so. I get a temporary rich condition (below 10 AFR) for a second or so which causes the car to stumble. It can happen at idle, cruise or under load. I have a feeling that it is bad wiring/elec connection somewhere, maybe TPS, MAP or Ignition. I am not sure where to start. Anyone ever run into this? It is not a huge problem, just an annoyance but it can cause the car to stall if it stays rich for too long under idle. Also, if it happens at cruise or under load, it can cause the car to jerk due to the stiff clutch.

Thanks!

Re: Intermittent misfire - bad wiring?
 

bmp 4 u

Re: Intermittent misfire - bad wiring?
 

OK, I think it is my TPS. I was looking at the TPS voltage at idle when it started to misfire. It basically stayed at .45 to .5v but would drop to .2 or .1 and sometimes below .1 when it misfired. The swing in voltage was probably adding too much fuel. I messed with the throttle cable so that it idled a little higher and that seem to make the voltage more stable. Not sure what would cause the voltage swing through. Any ideas? Batery voltage maybe? ELD?

Re: Intermittent misfire - bad wiring?
 

so hook up a voltmeter to the 5v signal @ the tps, see if it drops when the problem occurs.

Re: Intermittent misfire - bad wiring?
 

ahhh, good idea. If it stays at 5v when the TPS output fluctuates, that rules out general battery/ELD/external problems and isolates it to the sensor.

Re: Intermittent misfire - bad wiring?
 

well, it could also be the signal return wire, or the ground wire. This will just eliminate the 5v reference.