I recently replaced the hydraulic lifters, timing chains and tensioners. I also replaced the water pump, crankshaft sensor, maf sensor, hoses, gaskets, valve guides and seals and re-machined both heads. The passenger side backfires. And the catalytic converter overheats on the passenger side. My 2002 Suzuki xl7 2.7L V6 2wd gains speed very weak and slowly no matter how much I press the gas. I am at a loss. The exhaust system is not clogged anywhere. Any ideas would be appreciated.
RESPONSE
I suspect all your issues are related. The converter is burning excessive fuel making it hot. This can happen from a stuck open fuel injector or fuel being sprayed at the wrong TIME. Back firing happens when the fuel is sparked at the wrong TIME. The engine can only backfire when the fuel is sparked and the valves are open. Also with the engine not wanting to accelerate for you, this can occur with poor ignition TIMING. Do we see the trend here. After you install the timing chain it is recommended that the engine be turned over a couple times and the timing marks re-checked.
Ignition Timing for interference engines
Engines, chain- or belt-driven, can be classified as either free-running or interference, depending on what would happen if the piston-to-valve timing is disrupted. A free-running engine is designed with enough clearance between the pistons and valves to allow the crankshaft to rotate (pistons still moving) while the camshaft stays in one position (several valves fully open). If this condition occurs normally, no internal engine damage will result. In an interference engine, there is not enough clearance between the pistons and valves to allow the crankshaft to turn without the camshaft being in time.
An interference engine can suffer extensive internal damage if a timing belt fails. The piston design does not allow clearance for the valve to be fully open and the piston to be at the top of its stroke. If the belt fails, the piston will collide with the valve and will bend or break the valve, damage the piston, and/or bend a connecting rod. When this type of failure occurs, the engine will need to be replaced or disassembled for further internal inspection; either choice costing many times that of replacing the timing belt.
the timing is perfect. checked it very carefully all three times I rebuilt it to start her up. a lot of work. cant be the injectors, since only the passenger side has this issue and I switched the injectors around from one side to the other without change.
it is simply running too rich. I can smell the raw gas. and if I disconnect the exhaust manifold on the passenger side, the engine purrs like a kitten and revs perfect and beautiful. no issues. sounds like a new engine all around. beautiful!
If the catalytic converter is clogged it will restrict the engine. You stated the exhaust was not clogged however when you remove it, it runs well. Have you tried just unplugging the O2 Sensors? Also you can use a back pressure gauge that plugs into the upstream O2 Sensor hole to check if the converter is clogged.
A failed or stuck O2 Sensor may cause the engine to run rich.
I unplugged the O2 sensors, swapped sides, etc. no change. I really think it’s the computer. do the computers come programmed?
the entire exhaust system is completely clear
No the computer will need to be programmed(flashed) at a dealership.
I will try that. I think that will fix the issue. I will let you know what happens.
thanks
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