1984Z51auto

Well that test pretty much answers the fuel pressure issue, looks like it is not the problem. Something odd happening beginning at 3100 RPM, if not the cat then valve springs/cam issue? I think you are right to check the cats next.

Bugly87

Bump for the new week.. Thanks 1984Z51 for the response..I guess I'm looking for reassurance here. Is it still possible that my CATS could be at the end of their useful life? The car seems to run decently until just over 3000 RPM's. Im worried about the possible lifter/cam issue... ironically I had a cam issue on another car that kinda bottomed out at 3000 RPM's and I can not afford to fix that here. I also believe that it is unlikely that the EGR valve can be the cause of the car running this poorly. Ill take the cats out to test as soon as I get a chance.

Thanks again for any help,

Kevin

BigDaddy5

Sorry, I didn't mean to imply when I mentioned the EGR valve and referenced the cats that the EGR valve was the culprit. I saw it as a potential sign: if the EGR valve is bad, it's possible that it failed as a result of a bad cat. Cat test should just be as simple as remove it, see if any of the honeycomb falls out, look through it for any debris, then reinstall.

Bugly87

Thanks very much for the reply... I have a question for when I check the CATS...I have what I believe are two pre-cats just after the connection to the exhaust manifolds..then a resonator..then the mufflers. Do I need to cut out the two pre-cats..or just the resonator? I plan on replacing the resonator with a straight pipe anyway? It seems pretty straight forward...lol untill I have at it. lol

Thanks for the reply and the help,

Kevin

BigDaddy5

Do you have stock exhaust on there? You shouldn't have to cut out the cat, it should be bolted on.

It should be:

Mainfold -> Front Y-Pipe -> cat -> rear y-pipe -> muffler -> exhaust tip

Check this diagram out:
http://keenparts.com/Graphics/diagrams/15025.gif

The exhaust should connect at the cat, then seperate again (keeps it from being a true dual-pipe exhaust, but it is what it is)

Bugly87

Hello All,
I was able to remove my main CAT today..When it came down a collection of honeycomb material fell out at the front of the CAT before the screen. I assume that material came from one of the front pre- cats. I couldn't see through the converter so I began to hollow it out for now. I could not see through most of the honeycomb material that came out in big chunks. Put it back together and now it runs like it should...much improved power and acceleration. No stumble at 3000 RPM's. After a while I got a SES code. I assume it is converter related. What is the consensus here in regards to a hollowed out CAT? Should I replace with a new one? Not too worried here in PA as emissions for this year is a visual only.

Thanks very much for all of the help along the way,

Kevin

BigDaddy5

I did the same, hollowed out my cat, and no problem. I don't have emmissions, so no big deal. SES code is probably due to the EGR with the hollowed out cat. Check to make sure the EGR line is hooked back up right?

Glad it wasn't too difficult to diagnose!

Bugly87

Thanks for the reply. I still need a new EGR valve. The hose is currently blocked. I was going to swap it out last weekend but I was so happy it is finally running well that I drove it all weekend. I have a more pronounced drone now but as of now don't mind it much. Its pretty much a weekend driver.

BigDaddy5

Of course, glad it's fixed! My gut says you probably got gummed up in the EGR, which gummed up your cat, and once you cleared it all and were able to break 85/90mph, the computer was finally detecting the problem with the EGR. That's just me spitballing without knowing the codes, etc.

But at least it runs better than before, one problem solved!

VetosVet

Fuel pressure looks ok. Although I don't know what you mean by "accelerated to WOT...." Does that mean you gradually pressed the pedal or that you accelerated at WOT to a certain speed?

So check for exhaust back pressure. Also make sure that it is timed correctly. My '84 you have to pull a certain wire or it will actually be retarded several degrees. I know because I pulled the wrong wire. When I found the right one, I needed to advance it about 16 degrees to get the right setting. It behaved as you described until it was right.

Holes in exhaust generally won't cause back pressure. Baffles coming loose in muffler will.