Error P0306 on S10 1997
 

We got the P0306 error code yesterday. It came suddenly when I started it after a drive to the store. Up until then no indications on anything wrong, it has always run fine and reliable. I noticed that the idle was bad and after a short while the Service Engine Light came on and started to blink.

It smelled a lot of gasoline when I came home. I cleared the codes and let it stand for a few hours to cool down. I then started it and it ran fine.

My wife took it for a drive today, it ran fine for a while and then started to go rough and the light came on again and the smell is there again. It has had really bad mileage when this happens.

This has lead me to believe that there is some issue with the fuel supply when it come up to temperature. Searching the forum I suspect that it is the fuel pressure regulator.

I understand that this is primarily guesswork so far but I would appreciate some leads on what to start checking and replacing. I have a fuel pressure gauge but I haven't done anything yet. Will look at it in a few days.


Thanks


Jan

What are your fuel trims? Have you done the fuel pressure leak down test after its warm and messing up?

George

I haven't checked anything yet, appreciate suggestions.

Will look into it on Saturday, I'm busy until then.


Thanks

Jan

Could it be a leak from the fuel injection spider?

I have now changed spark plugs and ignition wires and the problem is still there.

It behaves normal if you don't drive to far. More than 10 miles and after a stop and then starting it again after 15 minutes or so it gives the error and run on only 5 cylinders. This happened last night, when I came back home I shut it down and started again after 1 minute and then it ran just fine again.

So I have something that come and go. I suspect the EGR Valve, would that be the next thing to check?

Thanks

Jan

First things first! Were any of the spark plugs covered with black carbon when you changed them?

All spark plugs looked clean and had that healthy light brown color.

Then I would doubt it is a miss from being too rich as has been suggested. Check Cam sensor retard - should be 0 +/- 2 degrees. Also report fuel pressure during the misfire. If yours still has the poppet injectors, low fuel pressure could conceivably be causing one injector to malfunction (if it is right on the edge of enough pressure to run).

EGR would not cause a dead miss on a single cylinder.

I had some problem a few years ago and then it got a new fuel pump and filter. It has the new style of injector/spider type that was installed by previous owner over 5 years ago.

The behavior is a little strange since it shows after a drive and after a stop when car is started again, and then can be OK again when restarted. Might be a fuel related problem with some dirt that blocks the injector.


Thanks


Jan

No doubt, intermittent problems can be a pain because they don't always want to do their thing when your all hooked up. If you want to diagnose before swapping parts then get as set up as possible to measure as soon as you have the problem. Check spark - 1" of blue spark. Get your fuel gauge on the Schraeder and check key on pressure and leak down. If you want to check the injectors firing have a fuel gauge and injector pulse tool ready along with the wiring diagram to ground/fire each injector to check balance. The last test is more involved than typical DIY work but I would want to at least try to know if it is or isn't spark before I start swapping parts if diagnosis is just not practical. At that point we can give you some of the more common failures so you can prioritize.