G0LFII

Went over to my friend's house to try and start up his 993 cause the battery was dead. Put it on the charger and waited for a bit. Once it started it had a continuous missfire. However, the check engine light was not on. Throttle response was very off.

Car drove just fine this past monday in the rain.

Any ideas what can cause this??

He's thinking fouled plugs, but i'm thinking it might be a bad Mass air meter or TPS sensor??

any suggestions


Could a low battery voltage situation cause some sort of electrical fault?

Raceit

Make sure CEL bulb isn't burned out. When your key is on the last spot before starting the engine it should light up all the warning lights.

What's the voltage of the battery if you take a voltmeter to it?

Stealth 993

I hope the distributer belt didn't break. You might want to check that after the CEL light.

g_murray

Yep, check to make sure the CEL bulb is ON when you turn on the ignition! (then it should go OUT when you actually start the car.)

There may be some 'transient' or 'pending' codes stored in the ECU - but 'not enough misfiring' has taken place to actually warrant a REAL check-engine-light (CEL) code to manifest itself.

However, the way you are describing the 'running' of the car, my money is on the CEL bulb being either burnt out or disconnected. The obd-ii system is VERY quick to report (i.e. SNITCH) on any and all 'anomalies'.

Good luck!

Gerry

Uber 911

1. How long has the car been standing?
2. Has the battery been faulty in the past?
3. Whats the voltage across the battery when running?
4. Was there running issues prior?
5. Damp or dry climate?
6. How 'fresh' is the fuel?
7. Any black smoke or fuel smell when running?
8. Last service?

G0LFII

My friend called me this morning. He let the battery charge over night and started it this morning. Still runs like crap. Check engine light finally came on too. After reading a few articles, i really think the distributor belt may have broken. Although i'm a vw/audi tech i really don't know much about porsches.

To answer Uber 911's questions:
1. Car has been sitting for 2 days.
2. Battery tends to die quite often actually, although it's a 1 year old battery. My guess it's some sort of parasitic drain.
3. Not sure what the voltage across the battery when running is since i didn't have my volt meter that night.
4. First time it had an issue running. Actually just did an oil change on it 2 weeks prior. He said i may have over filled with oil cause the gauge in the dash was higher than usual. But the dip stick read lower than max fill line.
5. It's monsoon season right now in Az. Last he drove it home through a storm and it's been pretty humid the past few days.
6. Fuel is pretty fresh about a week old
7. No black smoke or fuel smell when running. Maybe a little rich but no smoke.
8. Last service was a complete engine overhaul about a year ago. Used to be a track car, but since the engine blew he had UMS tuning here in Az rebuild the motor and also repainted the car. Now it's just a weekend driver deal.

I guess he said he just had it towed to a shop instead of trying to self diagnose it. But i just figured i'd ask a couple guys on here incase there was a common failure for this symptom.

Tango635

Well, it'll be interesting to find out what the problem was. Come back and let us know.

Uber 911

Nothing better than a remote challenge..

1. Sat inside or out.. if the latter has it rained a lot?
2. How often does the battery die, what symptoms/cause?
3. Voltage needs to be established
4. Was the dip stick measured with the oil at full working temp with the oil thermostat open?


Distributor belt failure is simple to find, kill the motor pull the HT from one of the coils fire it up it should run, kill the motor put the HT lead back on then do the same with the other coil fire it up. If one of the belts has snapped it'll be obvious.

Stealth 993

If you think it's the dist belt, remove one of the coil wires & start, then repeat for the other side. If it runs better you got your answer. However, it will not run on the broken belt side.