i have a 92 sc400, i have replaced the o2 sensors, distributor caps, rotors, spark plugs and wires, and i just got done putting on a new upper intake manifold. but after i put it all back together it will start with a really rough idle around 3-400 rpm but it doesnt have enough power to move after i put it in drive or reverse. any advice will help! thanks.

 

It sounds like a mass airflow sensor (MAS), try cleaning it but make sure you use a very specific MAS cleaner or you can damage it further. If that does not work then you will need to replace it. When I cleaned my MAS it worked for a few minutes then it went back to rough idle so I had to replace mine. Good luck!

 

i wiped off my mas, i will have to try getting a little more in depth

 

Sounds like it could be a bad catalytic converter.

 

I would check a few things regarding your issue:

• 1) Bad Catalytic Converter (maybe take it off and throughly clean it?)
• 2) ECU could be going bad, known to go bad on these cars and it cant regulate the idle RPM correctly.
• 3) Dirty or defective (MAS) Airflow Sensor

I just had to send my ECU to be rebuilt because I had irregular idle, no check engine light on startup, and odd shift times, and sounds like you have similar symptoms. Definitely check the other two thingsfirst!

 

Check your ignition coils

 

You probably lost a coil, unplug them one at a time to find the bad one. If you unplug and no change that's the one. There were 2 other threads with this issue today

 

92-94 is karman vortex hot wire type in the SC's and uses a thermistor, a platinum hot wire, and an electronic control circuit while the MAF in 95 and later also has an intake air temperature sensor (IAT) integrated into the housing. The hot wire type can only be blown off with compressed air. If you spray it with MAF cleaning liquid, it will permenently damage the AFM hot wire sensor due to the exposed wire and sensor.

If your SC is 95 and later, feel free to spray down the MAF with liquid cleaner.

 

thanks for all the help, i will have to check that stuff out. i cleaned off my mas so i ruled that out, next stop is to check the ignition coils. now if im not mistaken, the 92 doesnt have ignition coils it only has the spark plug wires. correct me if im wrong but they are one in the same correct?

 

as far as a bad cat, i checked my exhaust flow and it seems normal. the problem only started after i replaced my intake manifold and replaced my spark plugs. so im thinking it would have to be something to do with either one of those

 

Are you sure you got the firing order correct? If the spark plug wires are mixed and mingled your car will run awful.

 

it was running just fine before i changed spark plugs, and i only took one off at a time when i changed them so there was no way for them to get mixed up

 

Are you sure you got the length of each one correct? If they weren't exact, your engine wont run up to par.

 

i didnt change the wires, just the plugs. i will double check once i get a chance

 

Close but not correct. 92-95 is Karman maf. 96 And up is hotwire. You aren't supposed to clean the Karman with maf cleaner generally. The hotwire you can spray on the maf cleaner all day long. Both have air temp sensors also but thats not the problem.

You have 2 ignition cols. the wire that goes into the 2 distributors are the leads from the 2 coils. One of them is bad. Unplug one at a time to find the bad one. Report back. No need to look everywhere else it happens all the time.