Thread: 4JB Engine, black smoke.

Well well well, adjusted the nut, and the black smoke has reduced! Just taken her for a drive and it seems a lot better. First attempt I think I ran it a bit lean, didn't like being at junctions in drive, fine tuned and now seems a lot better!

Well, It appears that overfueling wasn't the problem, still have black smoke on hard acceleration/load.

any other ideas? lol

BTW.
Boost pressure is about 12psi at full acceleration.

Originally Posted by Davehillbo

Well, It appears that overfueling wasn't the problem, still have black smoke on hard acceleration/load.

any other ideas? lol

BTW.
Boost pressure is about 12psi at full acceleration.

Fundamentally black smoke results from incomplete combustion. There are a number of issues any one or all, may be your problem.

Usually not enough air to burn the amount of fuel that is injected. Over fueling can cause this, or on the air side, faulty turbo or turbo adjustment, boost leak, exhaust (turbo side) leak, restriction in air filter or intake, restriction in exhaust system.

Fault injector - spray pattern giving poor atomisation of the fuel.

Low engine compression.

Just how much black smoke???? Alll those earlier 4JB engines aren't very 'clean', especially under full noise, and I forgot to mention the fact that someone may also have adjusted the star wheel and boost enrichment inverted cone in the top cover of the pump....where that pressure line goes in that you teed into for the boost gauge. You can remove that cover and take a gander to see if the diaphragm has been rotated round. Just mark its position before removal.

JC

Well, it pumps out black smoke (dissipates quickly) when traveling at speed (70mph+), can see it out of wingmirror, and extents for about a foot maybe before its disopated? Also does it if I boot it at a junction

David.

how far is your foot down at 70mph???? if it is near the fuel max delivery position then yes, you should expect some smoke. try reducing the fuel screw setting a bit more, if there is a bit of an idle issue after that just adjust the idle stop screw to bring it up.

it sounds like someone has done a lot of fiddling with the pump.

jc

It depends on the situation, but usually with my foot down it will do 90mph, as soon as you let up off the accelerator the smoke dies down. What idle RPM should the engine be set at? I don't think it could really be set down any lower, the engine starts to judder at junctions when in drive.

David.

some of the problem is the torque converter it is to suit a petrol v8, so has a low stall speed. in 'drive' at rest you will need to increase the idle speed via the throttle stop screw, and it is also more than likely why the fuelling was altered in the first place.

jc