byrdman454

Thanks for the clarification on the o2 sensor. It makes sense now.

I pulled the rest of the gasoline out of the tank. The color and smell is a little different than a fresh batch I just bought, so i am hoping he got a bad batch. Should know sometime today. I know my nephew said the car started running rough as he pulled in to get gas, but I am hoping it was something else he was feeling and bad gas is the actual problem. Will update you all on the findings...

rexpontius

I'll keep my fingers crossed...

fbarnhill

It sounds like you could have gotten some water in the fuel. When you get close to the bottom of the tank you can sometimes get some. If that is the problem then it will cure itself after running it out or draining it and adding new gas. You will still have to run the stuff out that is already in the lines.

That is what it sounds like to me...

Good luck,

Podguy

This is not so true these days and was common in changing weather times like winter in the north east. Today almost all fuel contains some ethanol which will absorb any moisture in the fuel and allow it to pass through the system.

fbarnhill

Good to know Dan. I just know that in my old 79, she ran perfectlly but once in a while she would just spit like crap for a few minutes. A few runs to WOT and a few miles always settled the issue. I had replaced all fuel lines, removed and cleaned the tank while replacing all the lines, I cleaned all the screens in the dist etc... In my old Mopars, this used to happen once in a while. I guess, I am not keeping up with the times. But I am working on it.

Podguy

There are other things that can get in the gas besides water. The CIS system is very sensitive to fine particles especially with the WUR. I am not sure the 85 is quite the same, but a good hard run can often clean things out. Just be sure there is not anything functional wrong first.

byrdman454

Another update...
Siphoned as much gas out of the tank as possible. I had to go out of town after this, so my brother attempted to run the car with the new gas. He put in a gallon of fresh fuel. He did indicate there was a color and odor difference. He also burned a little for a test and the older gas left a nasty residue while the fresh gas did not. I did not see it, so take this at face value.

He started the car with about 1 gallon of fresh gas with the older gas that I could not siphon, so I assume the lines were full as well as some in the tank. He ran the car for about 5 minutes applying throttle trying to get it to clear out and the cats got red hot and caught a piece of cardboard under the car on fire! He immediately shut it down and removed the cardboard. No fire damage to the car (thank goodness). The next day he decided to run it again to try and get more of the fresh gas in the lines. This time he ran it only at idle for about 20 minutes. The cats did not get hot at all.

Not sure what to make of all this. The car idles at the correct RPM and shakes a little, but you really notice the rough running when applying throttle. It has a rich smell out the tailpipe and blows smoke. Do you think the new gas is making a difference or is it that the problem is tied more to off idle conditions? I told him to put more of the fresh gas in the tank to dilute the old more and keep running it until we are sure there is fresh gas getting to the engine. We will have to look for something else if the fresh gas does not help.

rexpontius

Dont think it is the fuel if the cats got red-hot, sounds more like fuel dumping in the exhaust if you'd ask me.

Have you checked fuel pressure and fuel dampers (for leaks in diaphragm?)

Cheers

byrdman454

Pulled all the vacuum lines off the dampers. There was no sign of any fuel or liquid. Can these fail any other way without fuel going into the vac line?

I have not checked fuel pressure yet...

byrdman454

My brother put the rest of the new gas in the car. Let it idle for 30 minutes and it did not get any better, but the cats were not red hot. He then put the car in gear and revved it up some and a few minutes later the cats were red hot again. I think the car would have ran the old gas out by now. I do not think this is the problem.

Does anyone have something else to check? The only thing I can think of trying is swapping the stock chips, regulator, and plugs back into the car.

Mako 928

I did not see in your first post that you checked the timing on the cams. Did you do this?

WICruiser

Sounds like it is dumping fuel for some reason. The excess fuel makes the engine run rough and when enough of it gets into the cats and lights off (takes some initial heat) the cats will burn the excess fuel making a lot of heat and the exhaust red hot. Easy way to burn up the car if you do not get it resolved.

If your do not have leaking diaphragms you may have a leaking injector. Did you pull the plugs to look for any black/sooted conditions? It could be one or two or if the bad gas fouled the injectors they might not seal closed. Start by looking at all of the plugs for differences in color and let us know what you find.

Hilton

Tell your brother to stop running the car before it catches fire. Seriously. Red-hot glowing cats can burn the car down. For steel to get red-hot its seriously warm down there, and other bits on the car can start to burn.

It sounds like an ignition problem., despite your initial tests, I'd go back and check spark again at each plug.

Podguy

I disagree with Hilton. The only way for the cats to get red hot is from processing too much raw fuel.

Think about this for a minute. Before cats were invented cars used air pumps to injected air into the exhaust manifold to burn off excess hydorcarbons and lower auto emissions. Cats were implemented in 1975 almost univerally. Auto pollution in the LA basin peaked in 1980 and has fallen ever since. An air pump may reduce hydro carbons by 15% a cat reduces hydrocarbons by 95 to 98%. The cat is really a miracle, but it has to do a lot of work. If you flood the cat with excess hydro carbons it will works its magic to clean the mess up. The result of too much raw fuel is the cat getting hotter and hotter as the catalyic effect takes place. To get red hot the car has to be dumping a lot of fuel. You either have a bad injector or the LH is increasing the injection open interval. Since the car responds to throttle I would look at the dampers, regulator and injectors next. It is also important to note that all injectors open at the same time. Taking a plug off an injector may not help you locate a faulty injector as it might be stuck open.

I think you are very close to solving your problem. This is stuff is science with a little 928 voodoo thrown in.

byrdman454

I was thinking about the MAF last night. I took the MAF and swapped it onto my Dad's '84 Euro and the car fired right up and throttled fine. I thought this was a conclusive enough test, but now I am second guessing myself. When I got this Euro running, we put an adjustable regulator on it to up the fuel pressure since these Euro's run lean. Even before we had the MAF rebuilt, the extra fuel pressure would mask the used MAF. I am going to swap the Euro's rebuilt MAF onto the '85 just to be sure.