1994 XJ sport fouling plugs white residue

Whitish brown crusty resedue on all 6 plugs causing missfireing and rattle at high rpm, what are the possible causes of this i know white plugs indicate a lean fuel/air ratio, i replaced the map sensor and the fuel filter it helped the rough idle but still fouling plugs. My question is where should i start looking? o2 sensor? Fuel pump? Vacuum leak?. My jeep also has no EGR valve or emmisions all have been blocked out or deleted my jeep also has no cat its a full straight pipe, any sugestions would be awesome! Thanks

Id start with the o2 and see if it's bad.


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Yeah i was thinking that then checking the fuel pressure, i also has another question my jeep will randomly emit white smoke, but theres no bubbles in coolant no coolant in oil or vice versa, no power loss, no overheating it just smokes when iddleing for long periods at temp arround 210 its really bizzare could the lean combustion be causing this?

i know that antifreeze in the chamber can cause a lean fuel air mix obviously but ive never heard of antifreeze in all 6 cylinder one two mabie but all 6 it cant be a head gasket, ive blown a head gasket in my toyota 22re and trust me i knew it! The temp guage was off the charts and it looked like a diesel! Hahaha

White exhaust is a sign of lean mixture. You would be able to smell coolant in the exhaust if it was that. Also the rattling is probably caused by a lean condition. You say all emissions either blocked or deleted? you say you replaced map. Technically the whole engine management system is part of emissions including all sensors. Unless you just mean evap, egr, and cat. Otherwise your info is contradictory.

I mean evap, EGR, cat, is it detrimental to run a 4.0 without any of these systems? Or will there be no noticeable differences in performance? I figure it eather has to be fuel system related or sensor related beacuse all six plugs are showing white residue and all look roughly the same with cylinder 1 and 6 being the worst of the lot.

The exhaust dosent really smell sweat it smells, like exhaust �� It dosent smell like antifreeze from my nose anyway should probly do a compression test anyway it never hurts to know

That sounds more like oil deposits than antifreeze. I'd check compression first. Are you using oil at all?

The smoke does have a light blueish tinge, it only smokes upon idle not when driving! Great news here i was thinking it was a Head gasket but it must be valve seals or something much easier to deal with, still dosent explain the white plugs wouldent oil make my plugs black or brown?

You really only suck oil through the intake guides when the intake is at a high vacuum, namely at idle or compression braking. This is a small portion of the time and when up to speed, the oil normally burns off. The white deposit can actually be the residue from this burn off, especially if you are running lean or spend a lot of time at highway speeds.

While valve guides/seals do definitely wear out, normally they don't tend to do it on all intakes at the same time. I have a small electronic endoscope that I use to look inside the combustion chamber to see build up on the pistons and the back of the valves. If the intake is leaking, you will normally see buildup on the back side of the valves.

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Nckthebeast456 said:

Whitish brown crusty resedue on all 6 plugs causing missfireing and rattle at high rpm...

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A combustion chamber loaded up with carbon deposits can cause that rattle and misfire thing. Too bad your Jeep doesn't have a knock sensor.

How long does it take for the plugs to foul?