986 runs rough and gives misfire codes.....

[wad]

Guys, trying to diagnose an issue that just cropped up after a reasonably long highway drive.


Boxster starts fine but has rough surging idle and eventually stalls, can rev it but its pretty obviously misfiring....

and then it throws P0300, p0301, p0302, P0303 Misfire on all cylinders of bank 1, this is ruling out a coil pack or spark plug for me.

I also get P0130, which is an oxygen sensor and some P1313, 1314, 1316, 1317, 1318, 1319

CEL Flashes so I am trying not to run it until I can figure it out.

The engine seems to have a pretty loud Vacuum leak so I am taking off the Oil Filler tube as there is a minor leak form the o ring to the engine case and it would be nice to clean that up, would the oil filler system/dipstick cause these symptoms?

The other thought I had was bad gas?

Any help here would be great as I am baffled and would like to get her going again.

I might replace the 02 Sensors, just wondering why that would cause such misfires if one of them was bad? Is this a symptom?

[JFP in PA]

Originally Posted by wad

The engine seems to have a pretty loud Vacuum leak................

You have misfires codes for just about every cylinder, and I think the above is where you should start before replacing anything.............

[wad]

Ok, cleaned up the small vacuum leaks I heard. Started it and it runs rough, hard to keep it idling. Also lots of pops, sounds like backfires not banging in the engine as they are only at low rpm and not constant.

It acts like a vacuum leak but there are none.

Any other ideas guys? Maybe a timing issue of some kind?

[wad]

its also giving codes P0300 P0301 P0302 P0303
Miss fires on all cyl on bank 1, I did previously get a code on the O2 sensor on that side, if it dies would it throw off that bank that bad?

[wad]

I have cleared up all of the vacuum leaks.

I have replaced the O2 sensor that was throwing the earlier code.

I have checked the Coil packs and replaced the spark plugs.

All I can think of now is a timing chain issue? its a 5 chain so I doubt it.

How about the timing advance solenoid?

What are the symptoms of this going bad and does the whole head have to come off to fix it?


The car starts but is very hard to keep idle, pops and spurts under 2000 rpm, once over 2000 rpm it is much smoother.

But lacks power and pops and almost bangs? I hope its not a valve hitting the piston!!!

Yikes

Anyone?

[wad]

Originally Posted by wad

I have cleared up all of the vacuum leaks.

I have replaced the O2 sensor that was throwing the earlier code.

I have checked the Coil packs and replaced the spark plugs.

All I can think of now is a timing chain issue? its a 5 chain so I doubt it.

How about the timing advance solenoid?

What are the symptoms of this going bad and does the whole head have to come off to fix it?


The car starts but is very hard to keep idle, pops and spurts under 2000 rpm, once over 2000 rpm it is much smoother.

But lacks power and pops and almost bangs? I hope its not a valve hitting the piston!!!

Yikes

Anyone?

Scratch the valves hitting, its definitely backfire, I have headers so it sounds pretty tinny once it backfires into the muffler.

I am also wondering about fuel, going to change the fuel filter as I am not getting any timing codes and when gas is pressed it is a struggle to get the rpm's up.

A question about the fuel system, where is the fuel pump and does the filter feed bank 2 before it feeds bank 1 just by fact of plumbing?

Maybe there isn't enough fuel left for bank 1?

I get misfire codes O2 sensor (P0130) and sometimes a MAF code, I sprayed the MAF and also unplugged it with no change.

[steveng1993]

Well this one time on my e36 bmw this vacuum hose connector popped off from under the intake manifold. Car ran pretty much like yours.


How much vacuum is yours pulling now, thats where I would start.

[bell]

You need to stop throwing parts at it and do a good smoke test.......

[wad]

Originally Posted by bell

You need to stop throwing parts at it and do a good smoke test.......

Well, after a lot of hunting and listening and spraying starter fluid, I found that the intake gasket(s) on the right(Pass) side have some leaky moments.....

Got the car back up to smooth and the thing that helped the most was a battery disconnect and letting the ECU remap the fuel delivery....