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Stuck open EGR valve
- juergen.scholl
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3 years 7 months ago - 3 years 7 months ago #42834
by juergen.scholl
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Stuck open EGR valve was created by juergen.scholl
Nissan D21, 2.4 liter, 12 valve engine with a VERY poor idle. At higher rpm engine runs better. In cylinder pressure test showed abnormally high running compression of ~130 psi at idle. The cause is a stuck open EGR valve.
The script graphs show the calculated contribution of each cylinder. With the Egr at fault you can see a pronounced zig-zag pattern for each cylinder. When the cylinders' graph stay above the black horizontal line they actually contribute to the acceleration of the crankshaft, when they stay below this line the crankshaft slows down/decelarates.
Looks like the cylinders fire on one cyle and then the burned exhaust gas dilutes the mixture so much that on the next cycle this mixture won't ignite. On the following cycle this unburned mixture partially is send back to the intake and reenters together with the new mixture the cylinders and now combustion takes place. Next cycle again burned gas dilutes the mixture and this repeats over and over.
Because of higher volume entering the cylinders compression rises. At higher rpm the propotion of burned gas reentering the cylinder becomes less and the engine smoothes out
The script graphs show the calculated contribution of each cylinder. With the Egr at fault you can see a pronounced zig-zag pattern for each cylinder. When the cylinders' graph stay above the black horizontal line they actually contribute to the acceleration of the crankshaft, when they stay below this line the crankshaft slows down/decelarates.
Looks like the cylinders fire on one cyle and then the burned exhaust gas dilutes the mixture so much that on the next cycle this mixture won't ignite. On the following cycle this unburned mixture partially is send back to the intake and reenters together with the new mixture the cylinders and now combustion takes place. Next cycle again burned gas dilutes the mixture and this repeats over and over.
Because of higher volume entering the cylinders compression rises. At higher rpm the propotion of burned gas reentering the cylinder becomes less and the engine smoothes out
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Last edit: 3 years 7 months ago by juergen.scholl.
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