I’ve had great experience using Seafoam in the past with other cars, but not this time. After using Seafoam in my 00 AP1, it has been misfiring. It sounds like a racecar with a huge cam but definitely doesn’t drive like one lol. Any insight would be greatly appreciated. I’ve spent countless hours researching online.

I put around 2/5 of the bottle into my oil crankcase and put the rest into my near full tank of gas (didn’t have time to put in brake booster). I drove around 80 miles and the car has never felt better. The next morning, after driving around 5 minutes, all of a sudden it starts misfiring and threw CELs (flashing) (P0303, P1399 P). I did an oil change and the oil was very, very black. The spark plugs seemed fouled after treatment with a small amount of oil on two of them. I went ahead and changed out all 4 plugs with no noticeable improvement.

I understand that 2000/2001 model S2000’s are known to have unusually high oil consumption. Honda claims that burning 1 quart every 1000 miles is “normal,” which is right around what this car tends to burn. I used to use Amsoil signature series 10w-30, but swapped over to Mobil 1 10w-30 after realizing Amsoil burns just the same.

Before you share about how Seafoam can damage valve seals/piston rings/blah blah blah please read:

http://www.yotatech.com/f105/sea-foa...-truth-160613/

I’m currently waiting to receive an upstream O2 sensor I ordered. I was considering replacing my cat first since it’s possible that a bad cat can damage an O2 sensor. If I can’t figure this out by Saturday, I’ll be dropping my car off at Ballade and spend money I don’t have.

 

Is there a cel? What are the codes?

I would use seafoam in this car, but not in the crankcase. If I really felt the need to do that, I would do it as part of an oil change and not actually drive the car with that in crankcase. Maybe around the block, with no vtec.

 

Ok, clearly I cant read, and unfortunately cant edit. I hate that the mobile app doesn't let you see the post you are replying to...

 

Have you ever adjusted your valve lash? I had a similar misfire problem, adjusted the valve lash and now it runs perfectly. Fairly easy job to do:

https://robrobinette.com/S2000ValveAdjust.htm

 

Thank you for your reply. Yes, Ballade Sports adjusted my valves and installed the Ballade timing correction gear less than 3000 miles ago.

I contacted Seafoam directly and here's the response:

It could be an oxygen sensor but if the computer did not set an O2 code I would guess the o2 sensor is fine. Have you had the converter checked for back pressure? If the back pressure is over 5 Lbs. pressure, then the converter is plugged and can cause the engine to run as you described. I would guess that your car has over 100,000 or 200,000 miles on it and the problem may be the converter. An easy way to test this would be to loosen the exhaust manifold to pipe flange, normally located at the front of the engine on a 4 cylinder engine, to create an exhaust leak before the converter, start engine and if the motor runs normal then it’s the converter. Other than that is all I can think of.

Jim Davis

Technical Director – ASE Certified Automotive Technician

Sea Foam Sales Company


Will try creating an exhaust leak and see what happens. I'm currently at 121K.

 

What's this timing correction gear your talking about ? Or is it the chain tensioner ?

 

https://www.balladesports.com/produc...orrection-gear

 

Turned out to be my coil packs, car runs perfect now. Towed the car to Ballade Sports ($170 ouch). Compression checked out perfect. They also adjusted my IACV and a bunch of other stuff I forgot.

Cost to fix:

$150 catalytic converter (Walker carb-legal)
$85 OEM upstream O2 sensor
$50 OEM spark plugs
$354 OEM coil packs (Ballade Sports; incl. diagnosis/install)
$170 towing

Total: $809

Wonder if I could have gotten away with replacing just the coil packs.. Meh this car is totally worth the cost of ownership.

Thanks to anyone who responded.