Here's the problem.. My car loses power when hot and under load. Climbing hills will basically stall the engine unless I proceed very gently. Too much gas will cause the engine to cut-out, pop, and lose RPM. The problem is not evident when the engine is warm. But after 30-40 minutes of driving it's completely hopeless.

It's an 85 LG4 with a quadrajet. The plugs and wires have been changed recently. I haven't looked at the fuel system. I threw a code 14 and 45 a few days back. Gas milage is roughly 13 per gallon.

The catalytic converter is black. Should I go ahead and get it swapped, or is there something else to check first? Does a roasted catalytic converter cause more backpressure? The car has hedman hedders, but stock exhaust otherwise.

thanks

 

since you have headers and a carb you might need to adjust fuel mixture...headers installed after manifolds have been on, may need to adjust fuel mixture a little to the richer side.....but I have been known to be somewhat mechanically declined

 

Q-Jet,

Your ECM is trying to tell you something. Your eyes (and probably, nose) are apparently in agreement. The '45' is for a rich oxygen sensor reading. The blackened cat converter is telling you the same thing. The "13 per gallon" is also a good indication. Face it - you're running too rich.

The '14' is for a coolant temperatuire sensor that is reading too high (zero resistance at the sensor). This is an important sensor for engine control, and when it fails, the ECM reverts from teh normal 14.7:1 fuel mixture and normal spark advance to about 12.5:1 fuel mixture and almost no spark advance. You need to investigate and repair the coolant temnperature sensor (CTS) and its circuit. That alone may solve the other error code(s) and your drivability problems. Once the fuel mixture is returned to normal and the vehicle is driven for some miles, the cat converter may burn out the excess carbon and HCs and return to normal operation. I wouldn't advise converter replacement until you repair the CTS and drive the car for a few weeks.

You'll need to test the resistance of th eCTS at a known temperature. Compare it to the table:



If the sensor tests within acceptable limits, test the wiring harness to the sensor for shorts and wire/insulation damage.

 

SUCCESS!

No more codes, and adequate power. This board has helped to save my car...

Beyond the direct advice that I received, I also did a lot of work on the vacuum lines, many of which were hardened to the point of being useless. It's clear that my pvc valve was totally inoperable. So this brings me to my next question... If car's pvc was shot for such a long time, does this mean that the engine is full of sludge? If so, then what's the best way to deal with that? I've done some searches on using water through the carb to clean / decarbonize the engine; and I've read some posts that refer to 'Top engine cleaner'. Does anyone have a suggestion? Or should I just drive it a while and see what happens?

thanks

 

PCV valve is just a method of "tree hugger - friendly" crank case ventilation. I doubt that would contribute to the buildup of sludge in the engine.

There is a way of using ATF in your oil to give the engine a good, hard cleaning. I don't remember off hand how its done, but send a message to RB83L69 and he will tell you how. He was the one who's post I read about doing it.

 

Actually, it definitely will cause sludge buidup.

What PCV does, is to circulate fresh air into the motor, and draw all the combustion leakage, condensation, etc. out. The ash and leftover heavy unburnt hydrocarbons is what forms sludge, along with broken-down oil. And under those conditions the oil reaks down faster, because all of that stuff dissolved in it is an acid.

ATF will definitely eat any sludge out of there. Just run a quart of it instead of a quart of oil; change the oil about 500 miles after you first put a quart of ATF in it, and then whenever it starts looking unusually black and funky, up to a normal change interval. ATF is very high detergent stuff, and will dissolve all of that gook and suspend it in the oil; that's a whole lot better than having it come off in chunks and plug up the oil system. Try it. You won't believe how black and thick the oil gets and how fast, from the ATF eating all of that funk out of the motor. Just make sure you change it when it starts to get really gross, and keep a quart of ATF in it until it quits coming out all funkified.

I run ATF in my older cars' oil all the time that way. I'm not sure if it has any long-term ill effects, as all of my cars are fairly new. I even have one with only 210,000 miles on it (my wife's 91 Cadillac). The oldest engine I have is a 305 in a 78 El Camino with only 345,000 miles on it that we've had since about 85 or so, with ATF in its oil most of the time; once it gets broken in good, and I've had a chance to collect a couple more decades of data on it, I'll let everybody know how it works. The intake has never even been off this motor, although it did toss its timing gear at about 315,000 or 320,000 miles. And the dealer wouldn't even warranty it!!! They just don't understand customer service these days.

 

LOL