Bad Idle/Shaking/Misfire?? Help!
 

Hey guys how's it going? Well let me introduce myself, I'm Damon and I'm from Orange County cali. I just picked up a 95 sc400 last weekend and it's a steller car aside from one thing.

The motor is not running right, the idle is rough, and it's not making much power... It almost seems like it's misfiring, so I replaced all the plugs/cables/rotors/caps and the problem went away but still wasn't as smooth as lexus usually are. Then I started the car again and the same problem came back in full force.. It smells sorta like gas from the back, I'm not sure if it's running rich or not.. The cats don't glow or anything and there is no check engine light. I'm not sure if OBD1 detects misfire or not? I've replaced the fuel filter as well. If anyone has any recommendations please help me out!

Car is a 95 sc400 with 197,000 miles. The plugs were pretty clean when I took them out, no sign of broken valves/headgasket from what I see

Thanks in advance

Check compression, if its good maybe o2 sensor or see if the maf needs cleaning. Also Check tranny fluid. o2 sensor would be my guess.

It could 1 of a million things MAF, catalytic converter, coil packs, IAC vavle, coil, O2 sensor, vacuum leak, need more information. Go to a pro.

Was it sitting for awhile?

You know I was thinking... I steam washed the engine about a week ago and although it ran fine afterwords, I guess it's possible that water could have seeped into the coil packs... I didn't really spray the maf, and it was just replaced... I wish the check engine light would come on so I could identify the problem.


I just tested the resistance on the coil pack terminals/high tension terminal and they were all within spec... I also disconnected a few of the plugs from the distributor and the idle would change with each a little (I also electrocuted myself lol.)

The car really sounds like it's missing... Could the other electronics unrelated to the ignition cause this? I guess it's possible I have a bad plug, but that seems unlikely...

I'm not sure, it's a possibility?

Why haven't the mods moved this to engine performance section? Need more info on running conditions,what time you drive it,do you beat on the car,other then what you have done what was the service history. Check the IACV or for a vacuum leak. No check engine light it might be along those lines.

I would check the egr valve first , my sc3 had the same problem.... I pry open the egr valve and saw the filter was clogged solid,replace it with similar filter element reset the ecu and now it drives like a charm...GL

:thumbdn: FAIL!!! I did the same thing, thinking i was doing a good thing by cleaning out the engine bay....

try taking the plugs back out and look down the tube of the coilpack...clean it out with some q-tips..and such...a little moisture can cause it to short and wreak havoc on the idle.... or you can be lazy and just wait for the excess moisture to burn off...


good luck!

Yeah same thing happened when i washed my engine bay,ran like crap for at least 3 weeks man. Then i took it out on highway and it was fine from then on.You might have some moisture in the plug department/inspect the intake too from filter to the T/B