deviat

Okay fellas, I have a 92 SC400 4.0. While dropping off my daughter this morning for school, (just about when it entered closed loop... maybe right after) I lost power, car started to sputter. Luckily it was only a half mile away, so I drove it home. Catalytic converters were red and smoking, which explains the code 25 I got. Where do I start? Injectors, pump, filter. I've only had this car for a short while. Please any help is greatly appreciated. I have not modded this vehicle in any way, it is bone stock.

masagsxr

What other code(s) do you have? Maybe its just that and the cat needs to be replaced. Also, do you know what was the last service done to the car? It probably needs the whole works (T-belt, water pump, pulleys, plugs, oil/filter etc...)

deviat

No other codes, Service has already been done and is up to date. Maybe not for the O2 sensors, but the cats shouldn't be clogged all of a sudden. The cats are overheating as a direct result of running so lean. I am going to try and get my fuel pressure gauge and check to see what it's getting at idle.

masagsxr

I'm curious to know and see how the cats themselves are tested. It sure is a lot cheaper to replace the O2 sensors than the cat but if the sensors are good and the cat is the problem then thats $$$ out in the trash. Probably not knowing you have a new o2 sensor its just that it is not something you need. I don't believe you can return an electrical part back at the store.

deviat

To test the cats, you use a backpressure gauge and insert it into the O2 sensor holes to test pressure from idle, and it's relatively low. only between 0-12 psi for the gauge.

should only be around 1.25 by 2500rpm.

I really need an osilliscope. Would help MAJORLY with the trouble shooting.

I've had the cats go out on a car before, this was too rapid a change to be the problem. feels more like there could be an obstruction in the fuel tank, pump going out, or a blockage in the fuel filter. I am going to make the 12v bypass for the pump, and see what happens.

deviat

I guess I should specify also that my Tach gauge was jumping around too. Would die completely (engine still running) and then work again.

Thats why i was leaning towards Cam or Crank sensors. I'm having trouble finding info on how to test these two items.

masagsxr

Wow. Looks like you got everything under control.

Look for the manual. Someone had posted it and available for download through rapidshare. If not, PM me. I can upload it to you when I get home. I use AIM or yahoo messenger.

sydwys

Deviat,

Have you ever figured out what your issue was? Oddly enough, I dropped off my daughter at school this morning and experienced the same sypmtoms with my 92 SC400. I limped it home. Cats were definitely glowing and there was a lot of smoke coming from under the car. It ran as if half the cylinders were missing.

V8drummer

iTrader: (5)

Most likely one of your ignition coils, I fixed the same issue on mine.

sydwys

Thanks for the reply. It was indeed the ignition coil - the one in front of the left exhaust manifold. Picked up the part at Kragen for $60.99, installed it in 10 minutes and called it a day. The only damage suffered from the excessive overheating is something getting loose in the exhaust system and rattling around. I will do a few spirited runs and see if it will work itself out. I really don't want to pull the exhaust apart.

deviat

that loose sound in the exhaust are your cats about to go out. i've tested the coils and they are ohm'ing out just fine. hate to replace a part thats not returnable

grindin8o8

when the car is idlig try tapping the maf sensor with a screw driver handle softly. if it sputters the maf might be causing your cats to go bad.

deviat

So far I have tested all vital electronics, coil, cam/crank sensors, FP Ecu. I'm leaning towards the igniters next, More than likely what it is... sucks that they are $150 at the Zone.

V8drummer

iTrader: (5)

You can double check the coils buy unplugging one at a time and starting the car. It's usually the driver's side one that goes bad.

deviat

As i've said the coil's both tested out fine. Ohm'd them both out and they both are in great reading. So i'm leaning towards the igniters. sucks that they are about 5 times as expensive. I'll see if I can get my hand on a pair of good ones, and get it running.