Valve stem seals?

[Clone TIE Pilot]

Started my Regal for the first timd this spring, ran like crap again after it was running fine last year. There was a little bit of mis firing when cold so I thought it was sticky valves, so I added some MMO to the crank case and some in the gas. Ran even worse and got to the point it kept stalling at idle. Took an infrared thermometer to the exhaust headers, most of the cylinders were at mid to high 200s, number 8 was 210 and number 2 was only 177 degrees.

Thinking the worst, I took compreseion readings. Highest was 175 psi which was also number 2, lowest was 160 psi. So the rings and valves seem to be sealing and building good pressure to fire. However, all the plugs were black and wet looking. Probably oil fouling? Guessing my valve stem seals are shot and maybe the Marvel made things worse by thining the oil or attacking the failing seals? It is doubtful all the cylinders would have bad oil rings with good compression readings.

The spark plugs are not old and only have a few miles on them. They should not be fouled already. Does it seem likely its bad valve stem seals? All 8 plugs are coated.

 

[pontiacgp]

I would run the car for a while to see if it clears up, the valve seals can dry out and shrink a bit if the engine has sat dormant for a long time. Also, you are probably aware if you left the ethanol fuel in the system it could be gummed up and water could be mixed with the fuel.

 

[foxtrot]

I would run the car for a while to see if it clears up, the valve seals can dry out and shrink a bit if the engine has sat dormant for a long time. Also, you are probably aware if you left the ethanol fuel in the system it could be gummed up and water could be mixed with the fuel.

I agree, especially with the fuel. I store my car over the winter with a full tank of fuel (With fuel stabilizer). With this in mind, the other day when I started my car for the first time it was running a little rough. This seems to happen every year until I use up the old leftover fuel in the tank. Once I have a fresh tank of fuel it runs fine...

 

[Clone TIE Pilot]

The tank was ran till low before I parked it and I added fresh gas in it before startup. The motor has about 100k on it and the stem seals are likely original. Either way the spark plugs are shot. Thinking about upgrading the stem seals to the positive type.

 

[64nailhead]

Plugs black and wet is different than oil soaked. Sounds like your choke is not operating properly to me - or sticking. The choke not opening will also cause the plugs to be black with soot due to incorrect air fuel mix. The wetness you're seeing, I would guess, is gas from running it to the point where it's stalling.

My recommendation, swap plug number 2 into a different hole, start it and make sure the new home for plug 2 is warming up (firing), then drive it like you stole it for about 2-5 minutes, then return home and make sure the choke is operating correctly. Or, option 2 - same as 1, just with new plugs.

100K mile smog era motors will do what yours is doing IMHO. Those motors were never meat to run 100K, as far as I'm concerned you've done well to keep it maintained to run as well as it does.

 

[bracketchev1221]

Letting a car sit with an empty tank is not good either. It allows bare tank surface to be in contact with the outside temperature and allow condensation to form inside the tank.

 

[pontiacgp]

I run pure gas, the non ethanol type, and I fill the tank at the end of the year. I don't add anything to the gas and in the spring the GP starts up with no issues.

 

[Clone TIE Pilot]

The choke is working and all 8 cylinders have good compression. I did let it warm up and the choke was already open when went to check it as well as for nozzle drip which it also didn't have. The next day, the choke returned to close when l operated the throttle. Made sure the choke, airvanes, and throttle blades were fully opened when I did the compression test. 160 psi on lowest cylinder, 175 psi on highest, and within the 10% margin.

 

[pontiacgp]

It sounds like the engine is in good shape so I'd take it for a good run and see how it is after that. I don't' think it's your valve seals cause it's unusual they'd go all at one time plus if the valve seals are shot you'll get the telltale smoke at start up which you would have seen before you parked the car.

 

[Clone TIE Pilot]

Only other thing I can think of is that either the float or needle valve went bad over the winter, causing a high fuel level. The oil on the dipstick seems ok.