I have a 1997 Buick Park Avenue with a 3800 series II motor that runs perfectly in dry weather. However, in wet conditions, rain melting snow, etc. it will begin to miss and throw out a P0300 OBDII engine code. This is the code for multiple random misfire. If I leave it to idle on its own it will get worse and die out right. Sometimes restarting it is an option though it still runs rough, but I can limp it to somewhere I can work on it. I think its electrical, since it doesn’t seem to get the spark it should though fuel doesn’t seem to be a problem as you can smell it after a bit of cranking.
I’ve been battling with this thing for over a year so far and have replaced the following, ECU, all 3 coil packs, spark plugs/wires(newest parts), mass airflow sensor, cam position sensor, ERG?(emissions deal I believe, mechanic friend put it on) valve. I had the battery trickle charged and tested at an Autozone, I haven’t had the alternator tested yet.
Its a very frustrating problem, as far as I can tell I’ve replaced everything on the ignition system with the hopes that it did the job only to get stranded during the next long rain. It does take quite a while in wet weather for it to start acting up, but once it starts missing a little bit, it doesn’t stop until the entire engine compartment has had a few days to dry. Engine temp doesn’t seem to help the problem dry out. I’d also like to note that I’ve noticed on this latest trouble that the interior lights have been flickering and headlights too. It may have been doing this earlier, but I hadn’t noticed if it was. I’m going to check what kind of voltages the alternator is throwing out next time I have it running.
Any help would be greatly appreciated, I’m at my wits end with this thing and need some way to get to my classes at college.
Normally, a problem like this is caused by aged spark plugs and wires but since you have covered that base and based on the random misfire code I’d hazard a guess the crankshaft position sensor. In many cases of a random misfire code the crank sensor is often the cause.
Also check the junction terminal to make sure the ends are clean and tight on the offchance that a voltage problem could be happening due to a poor connection and throwing the ECM a bit ouf of kilter. All car electrics except for the starter motor windings flow through that terminal. It’s located near the battery positive terminal on the chassis and should have a little cover over it. Just follow the positive battery lead.
Hope that helps.
My thought was the same as ok4450 regarding the crank sensor. This is especially the case because it is low down on the engine. If the lower splash shield isn’t intact it easily gets soaked, and given its age & age of wiring I’m sure its susceptible to water infiltration.
But stop throwing parts at it. If you want to think about the crank sensor first just inspect. Include the lower splash shield in your inspection. Disconnect it, clean up the connectors, & add some dialectric grease. On a dry day, run the car and mist it with some water - see what happens. You could also do something to protect it further from water for diagnostic purposes. Again, pick a dry day and coat the outside of it with some grease temporarily to see if that helps.
Hey guys, I appreciate the timely response and apologize for not having an update sooner.
I ended up having crank sensor replaced and cleaned and coating the battery terminals with terminal spray. I also did the same following the positive cable to the junction terminal and ground to the body and engine.
While doing this last night my mechanic friend and I noticed that the headlights, and to a much more noticeable effect the dome and engine compartment lights, where fluctuating in brightness while the car was at an idle and was running decently. We cleaned up our connections to try and stop this to no avail. The battery state as reported by the car’s computer stated that it had a decent voltage of 13.1 to 13.3 with no large variances unless we rev the motor and only from about 12.8 to 13.6 then. However, when hooked up to an alternator tester the needle was darting around fairly wildly inside the “charging” zone. It never dipped below green zone at an idle, and held steady in the “battery charged” zone with the tester load switch on, but could this random fluctuation from the alternator be a cause to my problems rather than a symptom?
Its a very rainy day outside today, and the car did start giving me the same problems it had been after about 5 miles. I was wondering if maybe I should take a look at the underside of the junction box, where the large bundle of cables, I assume, plug into the bottom of the fuse box there and see about that connection too. I also plan to pull it into the shop and slap the alternator tester on it again and see if the needle is jumping around even more wildly now that its wet, and plan to take the alternator off to get it tested either way.
Thanks again for the help guys.
Alright, pulled it in and threw my tester on it. Whenever the engine would bog down and miss the alternator would drop well into the red zone, but it was stating a fairly steady charge of about 14v if the motor was running smooth. The battery was testing as fully charged.
Also, whenever it does stall it requires a slight pumping of the gas peddle to get it going again, but will still easily flood out if I’m not careful. When (and if) I get the car running again, it will wind up to 4,000rpm and no more in park, but holding the throttle at any rpm steadily, usually around 2500 to 3000, and the car will stutter down in rpm on its own, usually around 500 to 700rpm lower, and then usually bumps back up on its own after a bit. This would normally point to a fuel problem and I’m wondering if maybe my fuel pump is acting up on me. I’m not sure why this would give me a P0300 code though.
Also, the CEL doesn’t seem to work either, and the car just dings twice in quick succession every ten seconds or so when the motor is acting up. Similar to the chime for low fuel but much more persistent. I do know the CEL should be on though, since I’ve had my computer hooked to the car when it was acting up before, but my computer is sadly on the other side of my state right now.
I’ve always found that Buick 3800 engines need to have their spark plug wires replaced on a yearly basis, otherwise you get the exact same symptoms you are experiencing.
I would recommend that you replace them again, and see if things improve.
It sounds like you may need to replace the alternator from what you say. When the trouble is occurring check the AC voltage across the battery and see if it is more than .1 volt AC. If it is then the alternator has excessive ripple voltage and that is causing problems with the engine electrical system. The trouble may be due to a faulty ground to the chassis so it may be a good idea to clean it and the battery connections regardless, even though they may look ok.