Replacing 1st gen LS400 MAF with 2nd gen GS430 MAF?

[och]

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.

 

[JLondon141]

Shared Knowledge

I know that there is a big difference between those two type MAF sensors, but you could also run a resister in place of the MAF itself, this would give it a constant temperature all the time, or you could get a manual switch that allows you to change the amount of resistance, either way, this could help you diagnose the MAF.

Now I bought a 92' SC400 with 98K miles with similar problems, and I started with plugs and wires. OE Wires, no problems with the ohm's on the originals... However, when it comes to the plugs, I come to find out that the Original plugs call for Iridium type plug. I started with a basic platinum, and it felt like how you said. Lag at 3/4-full throttle about whenever, dead stop or while cruising, and I tried performance Platinum 4 trodes. After trying several different gap sizes, I put in some NGK Iridiums at OE gap. Throttle response under a load has been great ever since.

I have an O2 Sensor out, so mine runs rich at the moment, but I tried a variation of different intake systems, and the MAF is calibrated for the original intake system, with box and all, but some modifications can be done. I replaced the box with a turbo cone filter and it ran perfect at idle, but after reaching about 20-30 mph and hour it would bog completely down and act like it was going to stall. Went back to the box with a K&N and modified the ram box in the bumper to get a little more air flow and it ran perfect. The air flow and turbulence of the intake air has to be just right to make the resister in the MAF to work correctly.

Another cheap and easy improvement I found was very functional. The PCV (Pressure Control Valve) tells the vacuum of the engine where to place the timing, and will also throw the timing off, as well as increase manifold pressure and make it burn a little more oil being pushed through the worn valve seals. After replacing it, (mind you, it's a lot easier if the engine is warm), I notice a great improvement in throttle response, timing, overall performance, and less oil consumption.


Hope This Helps You Buddy...