my dear old 84 4x4 (22r,carb) is failing cal. emissions test.only 170 k mi,changed everything i could,(cat.convert,oxy sens. etc.,)any ideas?
Kind of hard to even make a guess without knowing why it’s failing.
CO, HCs, NOX, or what? Or all of them?
Is is to be assumed by the converter and O2 changes the problem is NOX related?
sorry bout the tags,technical glitch, yknow.the failures are in co & hc,local mech said it was dumping too much gas, so i had the carb rebuilt.still at 265hc &3.56 co
is my timing off? valves out of adjustment? or are my rings just toast…
To pass, you need to do a full tune-up. On this truck, That should include spark plugs, ignition wires, cap & rotor, Check timing, adjust carb and check to insure proper operation of the accelerator pump and the auxiliary accelerator pump. I know the carb was just rebuilt, but the auxiliary accelerator pump is the most trouble-some part. I had mine go bad, and let raw gas get sucked in through the vacuum lines.
The carbs on these truck used an undersized accelerator pump to help reduce emissions. They added an auxiliary accelerator pump operated by vacuum to help when the engine is cold. A thermo vacuum switch will turn it off when the engine is warm. However, when the diaphragm in the pump gets old, it could tear or break, and it will allow liquid fuel to get sucked in through the vacuum lines, and directly into the intake manifold. Once running, if you pull the vacuum line, you can see wet fuel inside the line. This AAP is located directly on the opposite side of the mechanical accelerator pump.
You should post the high limit on the HC and CO, it looks like just a CO failure,your HC is not that high,you could get out of this with just a idle mixture adjustment.
BustedKnuckles has the right idea. I would only add that you can disable the AAP system by pinching off or jamming something into the vacuum hose that goes to the AAP housing. I found my 79 truck with the 20R engine started and ran just fine with this modfication.
Just rebuilding your carburetor won’t help if the fuel metering device is stuck. You may have to replace that electric device. On an 87 Mazda four cylinder, the top of the carburetor (with the valve in it) cost me $400. A smog certified mechanic should be able to tell you if your carburetor is similar.
Oil burning could do it but you did not state if this is the case or not.
Plugs, plug wires, retarded timing, etc. etc. could all be responsible for this.
Hopefully the carburetor was rebuilt correctly. They’re simple devices if you really understand the principles behind them.
Pop the top off of the air cleaner, start the engine, and allow it to idle.
Do you hear any faint crackling sounds from the carburetor? If so, look down the throat of the carb. and note if you see any gas dribbling from the emulsion tube. If so, back to the drawing board on the carb. overhaul.
try your egr valve