I have a 92 SC300 with 275,000 mile. 3 weeks ago I took a trip of about 350 miles and the car ran great. About a week ago, it started running really rough and when I came to a stoplight/sign, I would have to put it in neutral and keep the RPM's up around 1,000. Ny brother in-law, who was a Toyota tech for 20+ years, installed a new distributor with new cap, new NGK iridium plugs, new plug wires, new air and fuel filters andthe car still runs poorly. I'm about to put a new MAF in but didn't know if anybody had any other thoughts? Maybe the O2 sensor (do they have O2 sensor or air/fuel sensor)? THanks for any suggestions.

 

Is the CEL on, and if so, have you pulled any codes? Good call on the tune up, however, my guess would be a bad MAF or you might be in need of an ECU capacitor service.

 

No codes or engine light on. If the MAF doesn't fix it, I'm going to try a new O2! Does the 92 SC300 use an O2 or Air/Fuel Ratio sensor? I think its just an O2 but not sure.

 

A bad 02 typically won't cause it to run so bad as the engine computer can extrapolate data and continue to run the fuel injection somewhat effectively. Someone else may chime in, but with no CEL on, I'm tempted to say you may have an issue with your ECU. Companies such as Tannin electronics rebuild them for a fair price and many on this forum have used them with great success.

 

Thanks, I'll check that out!

 

Check for vacuum leaks. Does it run fine above idle and under load going down the road? Could be ecu, but check the simple and cheap stuff first.

 

I had a similar problem and it turned out to be the fuel pressure regulator on the end of the fuel rail.

 

Did you ever find a solution to this?

 

Any chance the IACV could be the culprit? Sounds a lot like an issue I'm having with my 92 SC400.