Hey, So got a 93 SC400 and it’s just super sluggish. Going up hills is a struggle. I’ve still driven her only from shops and back, but again so sluggish.

Acceleration is not there at all. I’m no technician, but I figured it would be good to replace the plugs & wires, fuel injectors, and relief back pressure.

The cats were hella clogged I had them cleared out. which made it feel a bit better, but issue still persisted. Sparks & wires honestly didn’t notice much of a difference I’d say it ran better, but eh. Fuel Injectors I can say that helped a lot I did have a leaky injector so I made sure to not run her too much and only from shops to work on her. But still sluggish.

I’ve been thinking it could be either an Ignition Coil or the Ignitor? What do you guys think?

FAQ:
No check engine light
Idles steadily at 800rpms

Update: 05/04/24

Checked my throttle body and both TPS Sensors with multimeter their all good. ignition coils still havent arrived I noticed yesterday when doing the test on the tps sensor that the connector too my passenger side Ignition coil is melted (photo will be attached). So, I’m going to replace both Ignition coils, both ignition coil connectors, and Fuel filter. Then I’ll do anot her update! Hopefully this can help someone with the same problem!

 

Have you ensured that the CEL works (lights up at Key ON)? Otherwise, the absence of a CEL isn't meaningful.

In my experience, a) ignition coils will lead to stumbling in the 1500-2000 RPM range, rather than general sluggishness, and b) knock sensors will cause what you're experiencing. The latter should trigger a CEL.

 

This might be too obvious, but is the ECT set to SNOW? There's a switch in front of the gear select that clicks into power or normal, but is a button press into Snow. There should be an indicator in your instrument cluster if you're in Power or Snow but if some cluster lights are out, you might be in Snow mode without knowing which makes acceleration at low speed very slow.

 

Hmm, how would I check if the knock sensor is bad? Maybe it’s worth replacing just to be sure. Also what do you mean by CEL? All dash lights work fine if that’s what you mean.

 

don’t believe this is the issue my cluster lights up fine. And I haven’t noticed a snow mode. Definitely will check just to make sure.

 

CEL = check engine light. It should illuminate at Key ON, then turn off. If it doesn't do that, then the lack of a light during operation does not mean there are no stored codes.

 

check English light does work. I fixed the sluggish issues it was the Coil packs that provide spark.

 

Solution: Ignition Coils if your SC400 sounds like a tin can 4 banger and it’s slow check your ignition coils. I replaced both the coils and both connectors on the coils.