420a multiple random misfire

[Aproductions]

Alright so I am trying to tackle this annoying problem/CEL on my new rebuilt 420a.

The car always starts and never dies, just does not idle steady and I have p0300 code.

Now as I understand it the random multiple misfire means that it is not just tied to 1 or 2 cylinders directly. This means the misfire is affecting different cylinders at different times.

I am thinking since the erratic idle that it has to be a vacuum leak at the intake manifold or the EGR tube.

What else could it be? could a bad front o2 sensor cause the bad idle AND the p0300?

I dont think the issue is fuel related because the erratic idle so injectors, pump and filter are considered fine.

Anyone know what I should check?

 

[jayson427]

An exhaust leak will throw the front o2 off and an intake leak will throw the map off. Both of those effect your fuel trims. I would check your plugs/gap and specs on the coil.

 

[eclipse420ags]

Clean off o2 sensor and the idle air control sensor on the throttle body.

 

[jayson427]

The iac wouldn't make it idle erratic like that.

Take some carb cleaner and spray close up to your Tb, exhaust/intake manifold. If it revs up Then There's your leak. What intake are you using? Inspect your throttle plate make sure it's closing 100%

 

[Aproductions]

I know I have an exhaust leak at the flex so I am fixing that first, If the code is still there I will reclean/replace the o2. Then I will move to the vacuum leaks. I know it is all clean and sealed up but maybe the egr or intake manifold has a leak.



Just pulled some codes:

135 02 sensor
134 02 sensor
1294 idle not reached
300 misfire
403 egr

Do you think it's the egr and o2 or could the o2 set all those?

 

[jayson427]

Definitely fix all your leaks and is your egr hooked up? I have mine unhooked so I always get a code. But if your egr is hooked up Then you need to clean it out because that will mess with your idle too. Make sure your manifold is straight/flat and your surface is clean or it will end up leaking later on. Then if you still get the p135 buy a new sensor.

 

[Aproductions]

Definitely fix all your leaks and is your egr hooked up? I have mine unhooked so I always get a code. But if your egr is hooked up Then you need to clean it out because that will mess with your idle too. Make sure your manifold is straight/flat and your surface is clean or it will end up leaking later on. Then if you still get the p135 buy a new sensor.

EGR is hooked up.


it is a fresh build so the head was hot tanked and everything was new, flat and clean. However the EGR itself is used so I will try and clean that up.

Is the code referring to the EGR or the sensor? or either?

 

[jayson427]

The egr code usually means the diaphragm inside is not opening properly.