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Catylitic converters

when do you know they are bad?

The Check Engine light will come on.

Tester

ok question then,91 nissan pickup d520 engine, recent full tuneup and within an hour lost all power…drives but no pickup and struggled to climb 10% grade hill I live on…had to do it in first gear and with a lot of effort…will a bad converter effect in this way

it falls off the truck,on said grade?

try a vacuum test.

good luck

lol I was afraid of that

In your case the Check Engine light won’t come on because of a bad cat. That’s because your vehicle has the OBDI engine management system. But you can check for a possible plugged cat by placing hand near the tail pipe while the engine is idling. The exhaust pulses out of the tail pipe should strong and constant.

But another thing that cause this problem is a weak fuel pump. On my 95 Nissan pickup I just replaced the fuel pump for this exact same problem. No power when climbing a hill. Oh! And if it is the fuel pump. it’s much easier to tilt the bed up to replace it than dropping the tank.

Tester

I don’t think it’s the converter at all. Converters plug slowly, so the symptoms would take a while to develop. Also, if it were plugged badly enough to get the symptoms you have, it would be accompanied by a very bad smell, and the engine would likely run quite poorly.

I think it’s more likely that there is an electronic issue of some sort - a failed sensor or something that was damaged in the tune up.