So I've had my 1994 LS400 for a year now, and it's suffering from sluggish acceleration (takes 14 seconds to get from 0 to 60), and it pings when cruising at 1200-1400 RPMs. At these RPMs the pinging is constant, but it also pings on gear changes during hard acceleration, and I hear occasional pings during hard acceleration at upper RPM ranges as well. The car right now has around 110K miles on the clock. I've been trying to resolve this situation for the longest time, and I've done numerous thing, and so far nothing has worked. Here's whats been done so far:
1) Timing belt service done at 80K according to the sticker on the engine (by previous owner).
2) Used numerous fuel system cleaners, such as Techron, Lucas.
3) Used SeaFoam in gas tank, crankcase, and intake chamber (total of three treatments).
4) Replaced fuel filter.
5) Removed and cleaned throttle body - helped to resolve low idle issues.
6) Bypassed powersteering idle up valve - completely resolved low idle issues.
7) Cleaned idle air control valve.
8) Did a full tune up, including new air filter, new spark plugs, new ignition wires, new distributor caps and rotors.
9) Replaced TPS (wasted money on changing from good to new).
10) Replaced passenger side ignition coil (wasted money on changing from good to new).
11) Replaced both main oxygen sensors.
12) Both EGR delete kit, and blocked the EGR system. It made the low RPM pinging even worse, with no power gains, so I removed it.
13) Cleaned PCV valve.
14) Replaced the MAF sensor (going to be returning the new MAF sensor next week, as it's very expensive, and made no difference).
All of this, and with no avail. Of course the car is running very smooth with all that tuning, and the only money I have really wasted, were the TPS and ignition coil, which defenately didn't need to be replaced. I'm going to return the MAF sensor for a refund, and I'm still going to re-install the EGR block off kit once I resolve whatever the issue I'm having.
But this is where it gets interesting. I've been learning the patterns for a while now, and this is what I notice. When the engine is cold, it performs very well, doesn't ping and has quite a bit of pick up, and the colder it is outside, the better it performs. Once warmed up however, it lags no matter what the outside temperature is. The temperature gauge shows normal temperature, so the engine isn't overheating. The other thing is, if I completely disconnect the MAF sensor, when the engine is still cold, it has so much torque that it's comparable to my GS430, it will easily spin tires when punched from a dead stop, and will probably make 0-60 in 7-8 seconds, like it's suposed to. However once the car is warmed up, it starts to lag, and ping harder than when the MAF is connected. Interestingly enough, with disconnected MAF it does not ping when cruising at 1200-1400 rpms, but pings hard whenever accelerating. All of that led me to believe my MAF was malfunctioning, so I replaced it with a brand new unit, which made no difference whatsoever. Therefore, I'm going to be returning the MAF, and trying to further investigate the problem. Right now I'm out of clue what could be causing this, here's my theories.
Bad fueld pump? Bad injectors? Bad ECU? Clogged exaust? Worn out, tired engine? All of these theories do not stand when considering that the car runs well while the engine is cold. I'm pretty sure I'm having a problem with fuel/air mixture, but I'm trying to figure out what may be causing it. With new MAF and O2 sensors, what else can I check?
1) Timing belt service done at 80K according to the sticker on the engine (by previous owner).
2) Used numerous fuel system cleaners, such as Techron, Lucas.
3) Used SeaFoam in gas tank, crankcase, and intake chamber (total of three treatments).
4) Replaced fuel filter.
5) Removed and cleaned throttle body - helped to resolve low idle issues.
6) Bypassed powersteering idle up valve - completely resolved low idle issues.
7) Cleaned idle air control valve.
8) Did a full tune up, including new air filter, new spark plugs, new ignition wires, new distributor caps and rotors.
9) Replaced TPS (wasted money on changing from good to new).
10) Replaced passenger side ignition coil (wasted money on changing from good to new).
11) Replaced both main oxygen sensors.
12) Both EGR delete kit, and blocked the EGR system. It made the low RPM pinging even worse, with no power gains, so I removed it.
13) Cleaned PCV valve.
14) Replaced the MAF sensor (going to be returning the new MAF sensor next week, as it's very expensive, and made no difference).
All of this, and with no avail. Of course the car is running very smooth with all that tuning, and the only money I have really wasted, were the TPS and ignition coil, which defenately didn't need to be replaced. I'm going to return the MAF sensor for a refund, and I'm still going to re-install the EGR block off kit once I resolve whatever the issue I'm having.
But this is where it gets interesting. I've been learning the patterns for a while now, and this is what I notice. When the engine is cold, it performs very well, doesn't ping and has quite a bit of pick up, and the colder it is outside, the better it performs. Once warmed up however, it lags no matter what the outside temperature is. The temperature gauge shows normal temperature, so the engine isn't overheating. The other thing is, if I completely disconnect the MAF sensor, when the engine is still cold, it has so much torque that it's comparable to my GS430, it will easily spin tires when punched from a dead stop, and will probably make 0-60 in 7-8 seconds, like it's suposed to. However once the car is warmed up, it starts to lag, and ping harder than when the MAF is connected. Interestingly enough, with disconnected MAF it does not ping when cruising at 1200-1400 rpms, but pings hard whenever accelerating. All of that led me to believe my MAF was malfunctioning, so I replaced it with a brand new unit, which made no difference whatsoever. Therefore, I'm going to be returning the MAF, and trying to further investigate the problem. Right now I'm out of clue what could be causing this, here's my theories.
Bad fueld pump? Bad injectors? Bad ECU? Clogged exaust? Worn out, tired engine? All of these theories do not stand when considering that the car runs well while the engine is cold. I'm pretty sure I'm having a problem with fuel/air mixture, but I'm trying to figure out what may be causing it. With new MAF and O2 sensors, what else can I check?
