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Cat got clogged...please help.

89xjgrey

NAXJA Forum User
Location
Columbus, Ohio
I have a question and hopefully somebody can help me out.

On a recent road trip my cat burnt and clogged up shutting down the truck. From the side of the road, I rammed a rod thru it trying to free it up. A few miles down the road...it shut off again and wouldn't start back up. As it turned out, I fried the computer. After disconnecting the o2 sensor, which burnt up, and replacing the computer...it started up and ran fine for a few miles until I heard a pop and it shut down again. With no more computer on hand, i took the circuit board out of the housing and pried apart the regulators that melted together. Ever since then, it has a very hard time starting and the cpu gets incredibly hot to the touch and then shuts down again until it cools off. What else could be shorting the cpu. I've heard one suggestion that it could be the TPS, but it still heats up when it is unplugged, or the ignition control module. Has anybody else had this problem and found where the fault lies? Thanks.
 
My experience from yesterday leads me to wonder if you are reversing cause and effect.

From the way you wrote the original question, it seems you believe that the clogging of the cat caused the ECU to burn out. Suppose that's not the case.

A friend and I experienced a faulty ignition module (on an '84 4-cyl, so no injection to be controlled). It would run fine for 23 minutes, then die. Once it died, it would not re-start until it had sat for one hour. Then it would run for 23 minutes.

When we pulled the solid state ignition module, the back of the shiny "stuff" that the circuit board is sealed in was blistered, confirming that it was overheating internally.

Now -- applying this to your situation, suppose the ECU was faulty first. Perhaps your ignition wasn't firing fully, and/or the injection was pushing too much fuel. Either or both condition(s) would dump raw, unburned fuel with the exhaust, and that would have to be burned up in the act. Probably wouldn't take much of that to clog the cat.

Trying to run without an O2 sensor causes a full-time righ mix, too, and would also dump unburned fuel into the exhaust stream.

I'm inclined to think that you need a new ECU or ignition module, a new O2 sensor, and a new cat. But I can't quite figure out from your post what you have replaced and what you have simply by-passed. All this "stuff" is interrelated. You can't bypasss essential components and expect the system to function correctly.
 
Well, here's what all went down...

Experiencing poor gas milage...
Cat burnt up...
Truck shut down and would not restart...determined that the cpu fried...
Cut off the cat...
Disconnected the o2 sensor because I thought that it had shorted out due to the back pressure and fried the cpu...
Replaced the cpu...
Did not reconnect the o2 sensor, didn't have one on hand...
When running...cpu still gets hot...strong fuel odor/blue smoke from exhaust pipe...

Possible faulty ignition control module from the start???
 
Don't know what the ECU does when it gets no signal from the O2 sensor. Most likely, it defaults to open-loop (warm-up) mode and operates on a fixed, overly rich air/fuel ratio map. That's actually probably what it was doing before. Poor fuel mileage is a symptom of a failed O2 sensor. (Not the only possible cause, but certainly a possibility.)

Based on your post it sounds like you're driving around with no O2 sensor and wondering why things aren't normal. Why haven't you either re-connected or replaced the O2 sensor? There's no way on earth you can even begin to diagnose a problem when you take a required data input sensor off-line.
 
Reconnected the o2 sensor...according to my checks, the o2 sensor is working fine...but the circuit board of the ecu still gets hot enough to fry an egg...i dunno...i might have to try the ignition control module next...
 
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