Okay guys, new here. Got a 92 LS400, lotsa lotsa miles. Just started running rough with a surging idle (100-200rpm) it runs fine when the idle is up i.e. no misfire. However, it misses under load and when the rpm's drop. I also have no CEL which puzzles me. Just put brand new NGK plugs in today, seemed good while it was in the shop, drove home and half way home started having a rough idle at stoplights and obviously missing under load. When I took the timing belt covers off it was pretty dusty under there, and being this is my first actual foreign car it's got two distributors?! Please help!

 

when I bought my 90 It had the same issue replaced both distributor caps and rotors 8 new ngk plugs and new wires and the car has been driving awesome ever since,make sure you get the firing order from your local auto parts and check your wire placement see if its that too

 

Was doing the distributor caps hard? I've had muscle cars all my life so this is totally new.

And how much did the caps, wires, and rotors cost? The NGK's were mo*****in 105 bucks!

 

nah the cap was 3 8mm or 10mm screws don't remember and once you take of the cap the rotor is only two screws the same size super easy I think the caps were like $12 and the rotors were like $8 and the ngk spark plugs were $26 for all 8 and the wires I think are bosh and I spent like $115 on them but do everything first before you change the wires because u can save that money if the old ones are good

 

Yeah good thinking. I also read up that it could the AFM thats causing the plugs to foul and miss. I havent had the car not 5 days and I'm already crying inside

 

I was the same way when I picked mine up not running but after two weekends working on it fixing small problems I am very happy with the car now just have some patience trust me I was the same exact way when I picked mine up

 

Yeah I picked the car up and it was running like a dream but now it's just missing like hell. Still drive-able and really missing no power at all, just needs a little TLC. Love the car though, been into the VIP stuff forever.

 

Clean your throttle body.

 

Well it probably doesn't help I snapped off a vacuum line when I was taking off the intake pipe to do plugs. I sealed it, but I have no idea what that vacuum line when to. It idles fine at stop lights and things for a minute and then when it misses the rpm's drop and surge back up. Looking at the 1UZ makes my head hurt. So complicated compared to things I've built before. I looked into replacing the distributor caps and rotors, and I'm gonna do it when I get the time to, because theres alotta stuff that needs to come off i.e. hoses and things. What's weird is it was running absolutely great when I first got it on friday.

I accidentally put 87 in it in Oregon and drove back up here on it and drove it on 87. Could that be my problem? I'm using premium like I should now, but could using 87 be causing my misfire as well? And if so, what product do I use to clean it out?