I spent a good part of today trying to help my best friend troubleshoot his 2000 Chevy Blazer. It has a 4.3L Vortec with a 4l60e.
The issue it has is that it has almost no power. It bogs and will not rev above 4000rpm. The transmission will not upshift at WOT unless you let off and get back into it. Once you get it into O/D it has barely enough power to maintain 40mph.
I verified all the sensors on the engine, all are working correctly. The O2 sensors crosshatch nicely. The cat is falling apart and rattles but appears to be functioning according to the bank 2 sensors. It has a brand new ignition system with a new coil, cap, rotor, plugs and wires. The plugs looked slightly dark but were clean and dry. They are gapped to spec at .060". It has 16-17"HG of vacuum pressure and idles smooth / steady. The fuel pressure is around 60PSI key off and around 55PSI under load (which is spec for the CPI). There is plenty of volume being moved by the pump. It'll fill a coffee cup in just a few seconds.
I felt the vac pressure was a bit low and looked for vac leaks but was unable to find anything out of the ordinary. The brake booster does not leak. The HVAC system is air-tight as well. The MAP sensors indicates atmospheric pressure when the engine isn't running and drops down to the same 16-17"HG that my vac gauge indicates. I checked the vac pressure on my 03 Tahoe sitting right next to the Blazer and it read the same both running and not.
The IAS and CTS indicate believable readings. The TPS is calibrated spot on. The EGR appears to be functioning correctly. There are no DTCs set in the PCM.
I'm at a loss. I'm not sure what else to check? I am sure that the failing cat is not doing us any good but I can't see it restricting the engine quite this badly. When you run the engine at WOT it sounds like it is missing fuel or timing. I am not sure if it is going rich or lean. The ignition should be set alright as it was not touched during the tune-up.
What do you guys figure?
The issue it has is that it has almost no power. It bogs and will not rev above 4000rpm. The transmission will not upshift at WOT unless you let off and get back into it. Once you get it into O/D it has barely enough power to maintain 40mph.
I verified all the sensors on the engine, all are working correctly. The O2 sensors crosshatch nicely. The cat is falling apart and rattles but appears to be functioning according to the bank 2 sensors. It has a brand new ignition system with a new coil, cap, rotor, plugs and wires. The plugs looked slightly dark but were clean and dry. They are gapped to spec at .060". It has 16-17"HG of vacuum pressure and idles smooth / steady. The fuel pressure is around 60PSI key off and around 55PSI under load (which is spec for the CPI). There is plenty of volume being moved by the pump. It'll fill a coffee cup in just a few seconds.
I felt the vac pressure was a bit low and looked for vac leaks but was unable to find anything out of the ordinary. The brake booster does not leak. The HVAC system is air-tight as well. The MAP sensors indicates atmospheric pressure when the engine isn't running and drops down to the same 16-17"HG that my vac gauge indicates. I checked the vac pressure on my 03 Tahoe sitting right next to the Blazer and it read the same both running and not.
The IAS and CTS indicate believable readings. The TPS is calibrated spot on. The EGR appears to be functioning correctly. There are no DTCs set in the PCM.
I'm at a loss. I'm not sure what else to check? I am sure that the failing cat is not doing us any good but I can't see it restricting the engine quite this badly. When you run the engine at WOT it sounds like it is missing fuel or timing. I am not sure if it is going rich or lean. The ignition should be set alright as it was not touched during the tune-up.
What do you guys figure?
