empirehorn Posted June 10, 2003 Posted June 10, 2003 I have a 95 sc400 with 120k on it, and it runs fine and strong, but when you are just cruising at about 40-50, it will stutter ever once in a while and feel like it is about to stall. If you give it more or less throttle, it is fine. Any help with this?
K9crew Posted June 10, 2003 Posted June 10, 2003 I had the same problem on my '95 with 51K miles on it. After changing the plugs, plug wires, distributor caps, rotors and fuel filter the engine is very smooth. Since I had to disconnect the battery the car is in the "relearn" stages at the moment so I've experienced an erratic idle at times (the engine actually stalled at a light yesterday!). However, the "miss" that I was getting at idle and the stuttering that you mention have both gone away. I would advise you to buy the ignition wires from Lexus. They're more expensive but worth it since they come preconfigured i.e. the wires are routed in the plastic guides that bolt to the heads. The Bosch wires that I bought from thepartsbin.com were the wrong length ... I had to return them. The rest of the items are worth buying online since they're quite a bit cheaper. :)
AWJ Posted June 11, 2003 Posted June 11, 2003 K9crew - there is a fuel pump ecu that causes stalling when it acts up. There is a diagnostic test for it - I can try to locate. If your car drops out on you intermittently - this may worth a check. empirehorn - I would recommend a complete tune-up on your vehicle first including fuel filter replacement. Then if symptoms persist troubleshoot accordingly.
K9crew Posted June 11, 2003 Posted June 11, 2003 AWJ, Thanks for the information. Yes, I'd appreciate the test procedure for the fuel pump/ecu. I had wondered if fuel delivery was the problem but there are so many complex systems on these cars that I was at a loss for where to begin. There is no doubt that the plugs, wires etc made a difference to overall performance but the engine dying at a light was quite alarming. I just put it down to the computer relearning since I'd disconnected the battery. The repair manual mentions "drivability problems after battery disconnect ... “ but I didn't expect that to include the engine stalling.
AWJ Posted June 11, 2003 Posted June 11, 2003 Try this - I must credit London Bill, this is his original site. The link may not take you directly. So look to the left and click on electrical - then up top, fuel pump ecu. There is an explanation there. Keep in mind these are the RHD backwards fellas - so the ecu is on the drive side rear passenger compartment for us. But the diag procedure and high voltage override should be the same. I have not tried it because it has not acted up on me yet but others have. So without further a do; I present the link Enjoy.
K9crew Posted June 12, 2003 Posted June 12, 2003 AWJ, I didn't check out the fuel pump ECM yet but I did manage to flush and the replace the fluid for the hydraulic engine fan this morning. The oil in the reservoir is supposed to be DEXRON II but it looked and smelled like brake fluid. I filled it with Mobil 1 synthetic ATF (nice red color now). I followed the bleeding procedure outlined in the manual. The car is running very well (VERY smooth) except on occasion it still stalls at idle. It died this morning when I hopped out to check the fluid level (HOT) in the hydraulic fan reservoir. Just before I got out I noticed the battery light come on for a second or so then it went out. I'm wondering about the alternator now since that could be the cause of the noise/vibration that I'm feeling. I'll take the alternator apart this weekend to see what's going on. Bad input shaft bearings could be felt in the cabin as a low frequency vibration. Despite the two main problems that I'm experiencing I'm still impressed with this car. :)
AWJ Posted June 12, 2003 Posted June 12, 2003 Yea - troubleshoot your alternator. Have the guys at the local parts store do there test. They usually do them for free and can tell you what is up with the alternator. That is easier and best to rule out as the problem first.
kvh73 Posted June 13, 2003 Posted June 13, 2003 One additional thing on the alternator - if you've replaced the power steering pump, you may be faced with an alternator repair within the next year. The reason is the repair shop will sometimes get power steering fluid in the alternator during replacement (it's mounted directly above), or the seal on the power steering pump will leak after replacement and again get fluid in the alternator. So if you've done that replacement recently, that may help confirm your failing alternator theory. When I took my Lexus into the dealership and told them I was having electrical problems the first thing they asked me was if I had recently replaced the power steering pump - I had done so about 8 months earlier. The alternator was indeed defective and I had no more problems after they replaced it.
K9crew Posted June 13, 2003 Posted June 13, 2003 kvh73, Thanks for the information. I don't know if the previous owner had a PS pump leak or had the unit replaced but I did notice oil/dirt all over the PS pump body. I sprayed it with Brake Clean (the alternator was covered with rags at the time) and it's remained clean for a few weeks now so I don't think the pump is leaking. I have an appointment this morning with a local electrical shop that specializes in charging systems. They can tell me if the alternator is defective. :)
K9crew Posted June 13, 2003 Posted June 13, 2003 I had my charging system checked this morning and according to the tech everything's ok. I was surprised that he simply connected a meter of some type to the battery terminals and checked the system at idle. The factory manual mentions testing the alternator output at 2000rpm ... but I guess his meter is a lot smarter than a standard volt meter! I think I've narrowed down the intermittent stalling-at-idle problem enough to say that it only happens when the transmission is in neutral and when the engine is hot. Usually when I'm waiting at a light I put the trans in N to reduce trans temps but I noticed that the rpm drops slightly in N compared to D. When the engine's cold the rpm are higher so that could explain why the engine doesn't stall in N when cold. I'd better take a look at "adjusting the idle" in the factory manual to see how the ECU controls idle speed. :(
AWJ Posted June 14, 2003 Posted June 14, 2003 K9, I'll bet it is the fuel pump ecu. Follow that procedure in the link (it might be in the manual too) and run the pump in high voltage mode. Then try to recreate the stall. I'll bet you don't stall. But the fuel pump relay has also been found to be weak and cause this problem by others as well. Consult your manual. You'll find it. Good luck.
K9crew Posted June 14, 2003 Posted June 14, 2003 AWJ, Thanks for the suggestions. I'll do the test tomorrow. I read the link that you posted and the author mentioned that it's not a good idea to run the fuel pump on 12V for long (I think this was based on his intuition rather than on something that he read in the manual). Anyway, it'd be nice to set the pump at 12V and then drive like that for a day or two to see if the idle problem goes away. :)
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