Newbie questions...

Just bought a 97 Riv with 25k on it...I have a question or two.I was going through the receipts the previous owner gave me and found he had some trouble with cylinder #3 misfiring,and throwing the p0300B code.Apparently they ran compression checks and all cylinders were O.k. as far as static compression goes.However they did a comp. check with engine running and found #3 to be low.It was suggested in the notes from the mechanic that a cam lobe,or valve were suspect...or carbon build up.Mind you this service receipt was 5yrs and 46k miles ago.The car runs great and has gobs of power,not to mention it looks immaculate inside and out...so I bought it.Anyhow,I did notice that if I lay my hand on the engine I can feel a TINY occasional stumble (I think),but I don't hear anything unusual.Not to mention when I hit the accelerator the car moves without any hesitation or stumble either.I don't know anything about these engines at all.I am no stranger to doing my own work,but it was always wrenching on V8's.Are these little V6's supposed to feel like a sewing machine at idle,or is a little vibration felt with a hand on the supercharger normal?Thank you in advance. Don

First of all, let me say Welcome, and screw you for such a great find!

I'm not the greatest authority on here for internals, but I have read that the middle cylinders (3 &4) run hotter, and can have problems from valves, to just the damned lame intake manifold gaskets... and the latter is probably your problem, if you do, indeed, still have a problem.

If your Check Engine light is not lit, you're probably OK... I don't want to scare you, but one section of the service manual has this to say:

The PCM has the ability to detect a misfire by monitoring the 3X reference and camshaft position input signals from the Ignition Control Module. The PCM monitors crankshaft speed variations (reference period differences) to determine if a misfire is occurring. If 2% or more of all cylinder firing events are misfires, emission levels may exceed mandated standards. The PCM determines misfire level based on the number of misfire events monitored during a 200 engine revolution test sample. The PCM continuously tracks 16 consecutive 200 revolution test samples. If 11 or more misfires are detected during any 10 of the 16 samples, DTC P0300 will set. If the misfire is large enough to cause possible three-way catalytic converter damage, DTC P0300 may set during the first 200 revolution sample in which the misfire was detected. In the case of a catalyst damaging misfire, the MIL will flash to alert the vehicle operator of the potential of catalyst damage.

madrivage wrote:

Just bought a 97 Riv with 25k on it........Mind you this service receipt was 5yrs and 46k miles ago.

am I drunk or does this math not add up?

Oops...I meant 125k.Well here's a little update.I ran 2 cans of seafoam in a full tank of gas,in the crank case (barely 100 miles and will change oil 2morrow),and over the course of 2 days I have pulled 2 bottles through the vacuum line into the top end of the motor 1/3rd of a pint at a time of course.Quite a bit of smoke came out the first two times,then it was quite a bit less by the third time.Anyhow,it feels like it's quite a bit better,it wasn't really bad in the first place,I wouldn't have really noticed it if I hadn't read the damn service invoice! The service engine light did come on after the seafoam treatment through.It went out a few hours later.Then came back on again today.It wasn't on when I bought it,I figure I really cleaned up a bunch of crap outta there and probably got the o2 sensor a little dirty or something.I'm pretty sure it'll clean itself up like it did the other day.

I lived with a tiny occasional stumble for roughly 120k miles, so I wouldn't worry too much about it. you can try the seafoam treatment if you get a chance though.

madrivage wrote:

Oops...I meant 125k.

Oh, then forget what I said about "Screw you"...

As far as the motor, yes, these even-firing, balance-shaft motors are generally VERY smooth... That's why I complain that with all the electronic nannies, they didn't include a program to prevent you from grinding your starter when the engine is already running!

I would venture that the most common fix on this board is not Seafoam, but rather cleaning the MAF sensor... Do a search, and you'll find all sorts of info on the Mass Airflow Sensor. Most of these engines, unfortunately, use Security Torx screws, but once you pull it out, all it takes is a gentle spray of electronics cleaner (NOT carb cleaner) to clean off the the MAF sensor. You can also spritz the passages while you're in there...

Cleaning the maf was my next move...it is running pretty damn smooth now compared to before already.I just knew that seafoam would clean a lot of chit out o the motor so I did it.I wasn't expecting it to work miracles by any stretch.