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· Registered
2 Posts
Discussion Starter · #1 ·
I am looking for some info to try to help out a friend in need....

His 94 HB with the 2.4 failed NOX test standard is 3.0 he failed at 5.6
it had a horrible misfire and we replaced plugs, wires, cap and rotor, it also had a cooolant leak causing it to overheat, that was repaird and now runs at a steady 180-185 degrees. After these repairs it is still at 5.6 and failing. I am not very farmilliar with nissan's EGR system, but from what i can tell it is operating fine, when idleing I apply 5-6 inches of vacuum directly to the EGR valve and it stalls the engine which tells me the EGR system is flowing. When driving it is getting up to 4 inches of vacuum to the EGR valve which seems that should be enough to flow enough EGR to control NOX output.....Am i missing something?
Any help/advice or experience with this issue would be appretiated

· Fearsome Fabricator
213 Posts
NOx is controlled by the EGR. High combustion chamber temperatures cause NOx.

The BPT valve (back pressure transducer) controls the application of the EGR, and is connected to a wee metal tube that threads into the manifold at the back of the block (intake side) - a wee hole in the tube often carbons up stopping the EGR from working. Remove the wee tube, poke the hole clear again, and repair/replace the probably rotten section of rubber hose.

The BPT valve itself is quite expensive, but the plugged tube is far more common.

There is also a solenoid that connects vacuum to the rest of the EGR system. I've forgotten the tests for it. The tube... the tube...
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