my motor blew due to cylinder 1 running lean (melted piston, spark plug, and destroyed the cylinder). after the rebuild, we had a new o2 sensor and got all the injectors cleaned and checked, and after about 20 miles, spark plug in cylinder 1 was white and the rest were just fine.


any suggestions?

What are your compression readings? Do a Comp. Test and get back.

It could be due to the #1 cylinder having a higher compression than the rest of your cylinders. If #1 is at 220 and the rest are sitting around 190, then the gap on your plug for the #1 should be slightly smaller than the rest of your plugs.

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If one cylinder is higher comp than the rest then you looking at a head with a Tapered mill. Compression would have to be a very large difference (1.0 full point)......I highly doubt that is the case.

Back to reality........


Swap the injectors around. I know you said you cleaned them but you didnt say how. Did you have them cleaned and flow tested or did you just run alcohol through them.

Verify fuel pressure is proper. Low pressure will make the injector flow less. Why only one cylinder? Could be a multitude of things. Cylinder 1 is closes to TB therefore air charge could be slightly cooler temps which make it more dense requiring more fuel.

Check the injector wiring. If you have wiring going bad or connectors that are corroded, the connection/wire will act liek a resistor and force the amperage to favor the opposing injector, in this case injector 4.

Verify coolant and IAT sensors read correctly. Both are very important to air fuel mixture.

Verify you have the same pl;ugs ina nd one isnt an oddball that got swapped around in packaging.


MOST IMPORTANT, do not judge the visible part of the plug at WOT situations. The plug if sized properly will appear lean. At WOT the Plugs run just hot enough to clean themselves off. When checking WOT plug conditions you need to look for a fire ring deep down in the plug porcelain. Easier if you cut the thread section off with a cutoff tool.

Disclaimer: All info is given and judged based on Factory motor. If you are running a setup with higher/lower compression and forced induction then results and recomendations will vary.

Sorry, now that I've graciously been given directions back toward reality, and the fact that you're only off by a couple of psi., I would lean more toward injectors. It was my next thought, but seeing as how I've jot jack for Rep. around here, I must need pointed and laughed at.

Have your injectors tested by a reputable shop. Make sure that they are all flowing at the same rate.

As far as it being highly unlikely that a comp. difference would change anything....Yeah.....If on cylinder was off by 30psi, it would cause a HUGE difference in combustion characteristics inside of the cylinder. That, coupled with a sloppy gap job would undoubtedly cause lean conditions. Because the some engines don't have a specific operating compression, it leaves a lot of room for error that the ecu can't always compensate for. Especially when it's fighting unfavorable conditions. Just learned all about this in Engine Performance.

Go Before Show, Wakka Wakka, Your Honduh's Effin' Slow!!!
Ask Me about 420A RWD FTW!!!