Help please

I have my 1990 Mazda b2600 nd I love this truck but it is wierd at idle sounds fine but has check engine light and when I go and accelerate it the light goes away and when I hold it like at any higher rpms for a steady while it comes back on. Someone help me and also when I turn the truck off it rattles the hole car and engine shakes pretty bad but only when turnin the truck off

So.......is the engine "dieseling" (continuing to run) when you turn the truck ignition to the "OFF" position?

Anyone know:
Do they have a light for the cat? Or does it come under the engine check light as well?

If its not dieseling, when you turn the engine off and it shutters my guess is that it's likely due to worn engine mounts, which is just a cube of rubber on the engine mount that is supposed to absorb all of that.

My truck does it, I don't think there is any mechanical issue.

The cat does not have a warning light and also I'm pretty sure it has no sensor to flip the CEL..

ok cool thanks and i also have a check engine light but when i press on the throttle it goes away but if i hold the throttle it comes back what could it be im thinking it might be the tps..throttle position sensor

Did you ever resolve your problem?

If you were getting the check engine light intermittently, then you need to follow the procedure for retrieving the codes to see what the truck was telling you is wrong.

Not sure how you plan to pull a code unless the light flashes in a certain pattern. These trucks dont have an obd2 port. I'm not sure what would cause the light to go on/of... Kind of an odd issue.