i have miss fires on 1 3 5 with 1 being the worst i have changed plugs wires cap rotor fuel injectors and still no fix. the thing is that it will miss for 2 3 days then clear up and miss again and clear up and so on. when the scanner is hooked up to it the oxygen sensor heater monitor flashes for a pending code but it never goes in. at times when it is running good if you go and step on the gas hard it will usually end up making it miss again. ive talked to a few mechanics and there lost about it. and some say its an intake gasket others are saying its the computer or egr valve. can any one help me please. thank you

 

All on one side of the engine would seem to rule out an EGR failure because it should be much more even.

IMG... Well, that is a possibility, but it would possibly manifest itself as a vacuum leak which you can test for.

Have you checked the drains in the bottom of the distributor. If they plug up, it can cause moisture to become trapped in the distributor and cause issues like this.

Also check to make sure that the wires are not working themselves off of the towers on the distributor cap.

 

I did check the distibutor and it was all dry and wires are all on good. another thing that flashes of the scan tool is the evap. but im still stumped on it because im going on day 5 of it running good.hopefully it straightend itself out but i doubt it.

 

my 96 s10 blazer is still giving me problems. I have changed plugs wires cap rotor fuel injectors and intake gaskets. if i baby the truck i can get away with just a occasional rough idle. but if i have to step on it to get out into traffic or whatever it will start to get a really rough idle and put the code in for cylinder 1 missfire. one thing ive noticed is that once in awhile when you just turn the key on if you listen by the intake you can hear what i think is the fuel building pressur or something. I am at a lost with this truck if any one has a good suggestion i would really appreciate it. thank you.

 

Threads merged. Please try to keep the information in one thread. It helps those of us trying to help keep track of what has been suggested and what you have already tried.

 

i am still haveing problems with the truck now i got the p0300 here is the freeze fram data.
calc load 15.69
ect 87
stftb1 50.00
ltftb1 25.00
stftb2 50.00
ltftb2 25.00
map 66.00
eng rpm 1693
speed 76km
maf 31.00

 

Your long and short term fuel trims are maxed out. This is indicating a VERY lean condition is being seen by the upstream O2 sensors and the PCM is trying to richen up the mixture to bring the O2 sensors back into their normal levels.

Do you have any exhaust leaks between the engine and the upstream O2 sensors? If you do, this can cause a false lean condition as fresh outside air gets sucked into the pipe through the leak. This will lead to a very rich condition in the engine, but may still result in a lean condition being read by the O2 sensors.

THIS PDF explains the relationship between fuel trim and fuel delivery in the engine.

 

I was checking the wires on the o2 sensors yesterday and found on the ones by the cat had one wire was wore through the insulation and touching the frame and the other o2 sensor must of gotten a slice in the wire and was corrodid off. so i fixed those and the truck seemed to be running alright now today i got a p0140 code. the freeze fram data is

calc 2.35 ect 87 stft b1 2.34 ltft b1 -3.91 stft b2 0.78 ltft b2 -3.91
rpm 823 map 30 speed 40km maf 5.00

any ideas if the o2 sensor is bad now or something else.

I really appreciate the help thanks again.

I checked for exhaust leaks and there is none. it was the pre and post cat o2 sensors that had the messed up wires.

 

P0140 - HO2S Circuit Insufficient Activity Bank 1 Sensor 2

Was this the sensor which had the wiring damage?

This sensor does not impact engine performance, but if it were blowing the fuse for the heater circuit to all of them, it definitely would impact performance.

I would check the wiring harness over more and see if you can find breaks in the wiring that may interrupt the signal back to the PCM.

 

well the truck ran good for a while and now yesterday it messed up again and still is missing. i put the fuel pressure gauge on and it went up to 60 but when the key is off it loses about 15 psi in less than an hour. i took the throttle body off and it like theres fuel on the injector lines on the drivers side and the intake ports are washed down. does this sound like the whole spider needs to be replaced or could it be the injector lines?

I put the new spider in today and i am still haveing the missfire on cylinder one I dont know what to do now so any good ideas would really be appreciated. thanks

I just checked the compression on cylinder 1 again and it says 120 and if you start the truck and let it run for a few seconds the compression only goes to 60 i am no expert on this stuff does this mean there in a bad valve on that cylinder?