I have my 94 LS400 and I suspect that it has a malfunctioning MAF sensor. I have a spare MAF for it, but it also doesn't seem to work properly. I also have a 2001 GS430, and ironically I have a spare MAF for that one too.
I'm wondering what would happen if I tried using the MAF from GS in the LS. I know LS has a Volume Air Meter, and GS has a hotwire MAF, so they work differently, but I'm wondering if they send the same data to the ECU. Both have a 5 wire harness, which doesn’t fit, but I can splice GS430 harness onto LS400. I can also machine LS400's MAF pipe to accept the MAF from the GS.
The reason I even want to do it, is because I'm having serious issues with power loss and some pinging. I've done a lot of work trying to eliminate it, but so far no cigar. The symptoms are basically as follows. The car has very little torque at full throttle from a dead stop. Also, the engine is knocking at around 1200 RPM’s at very low throttle. Usually it the engine is performing well until it’s warmed up, and then it starts lagging majorly. The engine seems to perform better when outside temperature is around 55 degrees F. When outside temperature is hot, 70 or more degrees, it lags the most, and when temperature is cold, 30 or less, it lags, but sometimes it feels like something “kicked in”, almost like VTEK kicks in, and the engine starts accelerating better. Here’s the trick though, if I disconnect the MAF, the engine seems to perform a lot better, loads of torque, and seemingly no pinging, however not for long. After about half an hour of driving with MAF disconnected, the engine starts lagging and pinging even more. I’ve done a lot of work to resolve it, here’s what I have done so far.
Used Sea-foam treatment in intake chamber, gas, and oil, repeated three times.
Used various injector and fuel system cleaners, Chevron, Lucas, etc, multiple times.
Removed and cleaned throttle body.
Installed Lextreme EGR block off plates.
Replaced both main O2 sensors.
Replaced TPS sensor.
Replaced spark plugs, wires, distributor caps and rotors.
Replaced Air and Fuel filters.
Replaced driver’s side ignition coil.
Cleaned the MAF sensor.
Bought a used MAF sensor to replace the old one.
Of course reset the ECU after every attempt.
All of this work yielded very little result. The engine still lags, sometimes more, sometimes less. The only reasonable explanation that I have for this, is that the engine is either on its way out, but that’s unlikely, because with only 107k miles on it. It idles very well, and at idle it revs without any problems. It doesn’t consume oil, or any other fluids. So I’m thinking it must be air/fuel ratio, the spark plugs are probably getting flooded with fuel, and not firing properly. This would explain the random power surges I get during cold weather. I think this bad air/fuel ratio is being caused by malfunctioning MAF. I know that MAF readings change with temperature, so this would explain best performance when temperature is around 55, and the worst performance in hot temperatures. Even though I tried using a replacement MAF, it was used, so maybe it’s suffering from the same problems as well. It seems like the first gen LS didn’t use the most reliable MAF sensor design, and therefore it was replaced in future generations. The dealer charges around $1,000 for a new MAF, but I really don’t want to shell out that much money if there’s a change that it’s not the MAF. I would almost rather invest in APEXI fuel computer, but before I even do that, I want to experiment with a different MAF.
I'm wondering what would happen if I tried using the MAF from GS in the LS. I know LS has a Volume Air Meter, and GS has a hotwire MAF, so they work differently, but I'm wondering if they send the same data to the ECU. Both have a 5 wire harness, which doesn’t fit, but I can splice GS430 harness onto LS400. I can also machine LS400's MAF pipe to accept the MAF from the GS.
The reason I even want to do it, is because I'm having serious issues with power loss and some pinging. I've done a lot of work trying to eliminate it, but so far no cigar. The symptoms are basically as follows. The car has very little torque at full throttle from a dead stop. Also, the engine is knocking at around 1200 RPM’s at very low throttle. Usually it the engine is performing well until it’s warmed up, and then it starts lagging majorly. The engine seems to perform better when outside temperature is around 55 degrees F. When outside temperature is hot, 70 or more degrees, it lags the most, and when temperature is cold, 30 or less, it lags, but sometimes it feels like something “kicked in”, almost like VTEK kicks in, and the engine starts accelerating better. Here’s the trick though, if I disconnect the MAF, the engine seems to perform a lot better, loads of torque, and seemingly no pinging, however not for long. After about half an hour of driving with MAF disconnected, the engine starts lagging and pinging even more. I’ve done a lot of work to resolve it, here’s what I have done so far.
Used Sea-foam treatment in intake chamber, gas, and oil, repeated three times.
Used various injector and fuel system cleaners, Chevron, Lucas, etc, multiple times.
Removed and cleaned throttle body.
Installed Lextreme EGR block off plates.
Replaced both main O2 sensors.
Replaced TPS sensor.
Replaced spark plugs, wires, distributor caps and rotors.
Replaced Air and Fuel filters.
Replaced driver’s side ignition coil.
Cleaned the MAF sensor.
Bought a used MAF sensor to replace the old one.
Of course reset the ECU after every attempt.
All of this work yielded very little result. The engine still lags, sometimes more, sometimes less. The only reasonable explanation that I have for this, is that the engine is either on its way out, but that’s unlikely, because with only 107k miles on it. It idles very well, and at idle it revs without any problems. It doesn’t consume oil, or any other fluids. So I’m thinking it must be air/fuel ratio, the spark plugs are probably getting flooded with fuel, and not firing properly. This would explain the random power surges I get during cold weather. I think this bad air/fuel ratio is being caused by malfunctioning MAF. I know that MAF readings change with temperature, so this would explain best performance when temperature is around 55, and the worst performance in hot temperatures. Even though I tried using a replacement MAF, it was used, so maybe it’s suffering from the same problems as well. It seems like the first gen LS didn’t use the most reliable MAF sensor design, and therefore it was replaced in future generations. The dealer charges around $1,000 for a new MAF, but I really don’t want to shell out that much money if there’s a change that it’s not the MAF. I would almost rather invest in APEXI fuel computer, but before I even do that, I want to experiment with a different MAF.
