Do i have to gap the spark plugs?

[chivas]

just got a set and i'm planning on replacing the ones in there.
NGK5839


failed NJ emissions:
HC: 234/100 (yeah.. 134 points over)
CO: .75/.50 (not that bad)

i've already seafoamed the motor. change the plugs and what else?

thanks!

[dlmpsy]

If the distributor cap & rotor button hasn't been changed for awhile I would check/clean/replace that. If the O2 sensor is 3 or 4 years old, it may contribute to your emission problems, an old "cat" may also cause problems. Make sure your plug wires and fuel filter are in good shape. I would definately check the new plugs to be sure they are set to the proper gap (can't recall the gap). I would also check for any vacuum leaks.

[fretburnr]

I always check to make sure plugs are gapped.

[chivas]

I always check to make sure plugs are gapped.

what are the spec's and did i get the right plugs?? someone on e30 said they were the wrong ones.

[fretburnr]

I don't know NGK part numbers. The normal replacement plug for M20b25 are the Bosch Super (regular copper plug, no platinum junk) p/n WR8LC gap .07mm (.027")

[jlevie]

Since you are trying to get the car into condition to pass emissions testing.

Yes you need to check the plug gaps. And...

If the plug wires are over 6 years old, replace them and the rotor and cap. Minor faults in the ignition won't necessarily cause noticeable misfires, but they can result in only partial combustion. Which causes high HC.

Adjust the valves

If the O2 sensor has 100k on it or you don't know what its mileage is, replace it. And aged O2 sensor causes the DME to richen the mixture.

If the temp needle doesn't rest close to the mid-mark under steady state conditions while driving at 45mph or above, replace the thermostat (using an 80C unit). A cold engine runs richer.

Check the fuel pressure at the inlet to the fuel rail. A bad FPR that is causing excessive fuel pressure may result in a rich condition.

If those don't bring the numbers into acceptable range, the engine temperature signal to the DME may be out of spec, the AFM could be bad, or the catalytic converters could have failed.

[chivas]

Since you are trying to get the car into condition to pass emissions testing.

Yes you need to check the plug gaps. And...

If the plug wires are over 6 years old, replace them and the rotor and cap. Minor faults in the ignition won't necessarily cause noticeable misfires, but they can result in only partial combustion. Which causes high HC.

Adjust the valves

If the O2 sensor has 100k on it or you don't know what its mileage is, replace it. And aged O2 sensor causes the DME to richen the mixture.

If the temp needle doesn't rest close to the mid-mark under steady state conditions while driving at 45mph or above, replace the thermostat (using an 80C unit). A cold engine runs richer.

Check the fuel pressure at the inlet to the fuel rail. A bad FPR that is causing excessive fuel pressure may result in a rich condition.

If those don't bring the numbers into acceptable range, the engine temperature signal to the DME may be out of spec, the AFM could be bad, or the catalytic converters could have failed.

where to get O2's for a 10/87 iX? everywhere i looked it's well into the $160+ range... HOLY MOLY on that! my 540 didn't even cost that much for each... well, about 3 of them cost $180.

i have to adjust the valves. it's 28 degrees tomorrow, not going to happen. maybe this weekend.

thanks for the heads up jlevie, always enjoyed your replies on all other bimmer forums.