There are a few ways of finding a vaccum leak, here are the ones that I know of.

Use a hose with one end on your ear, move the other end around the engine bay listening for a sucking sound.

Another is soapy water, it will bubble and move toward the leak if it is close, but dont use too much....

The final (and most risky) one that I know of is using propane and blowing that around gasket sealing areas etc. You will know of a leak because of the engine rpm rising slightly (due to more fuel being added)

Chris

 

Tried the hose technique, couldn't find anything at all......

 

What about your intake manifold gaskets? Are you using any oil? Could be leaking from the lifter valley and pulling air and oil into the runners in the heads. It will definitely cause a vacuum leak.

That bad of a leak would definitely cause a rich condition. Once it hit closed loop, the PCM would see a bunch of extra air in the 02s and add fuel to compensate for a percieved lean condition. It would really muck up the fuel calculations, lets just put it that way.

 

did you change your o2's??????????

 

Yes I changed the O2's.

The problem with the rich condition is that you can see that the computer is trying to lean things out. The LTerms in Datamaster dump down to the bottom end at 108, showing that the computer is trying to take fuel away, but still can't compensate for the really rich condition.

 

Well, that's it. I can't find anything, and I've got signals pointing to several possible things, and just don't have the time nor patience to work on it anymore.

The thing that pisses me off the most about this though is that if the fix is expensive, there goes the paintjob I've been wanting for so long. And the car NEEDS it too. If I have enough left over after the fix, I may put a 12 bolt in it though. We'll see. I gotta get it freaking fixed first.

 

To locate vacume leaks I spray carb cleaner around the gaskets, ports and hoses, if there is a leak the cleaner will get sucked in and cause the idle to drop.
I noted that originally you had said that you blew an oil seal on the opti before all of these problems started cropping up, I had a optically triggered Accell ignition years ago that would fail when oil vapor from a small leak on my intake would accumulate in the cap enough till the optical sensor was "blocked" by the oil film and cause the car to cutout. After it sat for awhile the film would break and the car would start and run fine until the next time. It took me forever to find what was wrong. If the opti was contaminated with oil, you could be experiencing a similar situation that only occurs after the opti warms up and oil vapor causes some misfires which could create a rich condition.
Just a wild *** guess but I know your searching desperately.

 

93Z4ME -- That was a good post, but I've replaced the opti. That was the absolute first thing I did.

 

No prob, wish I had another idea for you.

 

It's cool, I really appreciate everyone's help in this. It's been an uphill battle since August.

Now it's surging at idle a little bit, and my IAC doesn't seem to be working either. Kinda pointing me in the direction of a vacuum leak, but I can't find one. I'm just praying that it's not an internal short block item. I had $4000 saved for a paintjob, but I may end up having to dump 1-2K of it for the fix.

If it's something head/valvetrain adjustment related, I very well may be contacting the person who did the heads and install.

 

Here's a question. I am pretty sure you checked this already but are the valves adjusted correctly? If they are too tight and are hangin open that would cause some pretty crappy vacuum readings. What is your MAP reading at idle?

What about the timing chain, could the installer have gotten it off a tooth or two?

 

The timing chain hadn't come off since the previous dyno, at least not that I'm aware of. Does it come off for the crank seal???

Valves should be good again. They were good the first time around, and don't just mysteriously go tight for some reason. Collapsed lifter on the other hand, could be a possibility.

 

I've had a very similar problem that you are having happen to my car after I put in long tube headers (BLMs hitting 108 and sterms bottoming out when the car stumbles). Had that stumble problem too. I have datamaster logs that show that 108 blms and the sterms getting really low (around 45 or so but not 1 like yours )

I think I read someone say like you would be in 4th and hit it and it would stumble. I bet it stumbles up until a certain rpm right? THat is probably where it goes into PE and clears up.

I fixed mine by replacing the o2 sensors in my car. Now i know you told someone you already had. BUt I just wanted to ask if there where brand new or had been used.

Reason I ask is, I did the same thing. I replaced mine with someones used ones, and it didnt fix it WHen I bought new ones it fixed it for awhile and it came back.

I had pcmforless do a tune on my car to lean it up as it was running rich. (I had also put some gtp stage 1 heads on my car as 1.6 rr as well as the headers).

Now since I have had this tune and one more new set of o2s, the car has been fine for several months.

My though process on why the headers screwed up my car was this. Since the o2s are farther down the exhaust now, and with no cat to give it any kind of backpressure to keep any heat in. the o2s never got hot enough. That coupled with a ruch running car just killed the o2s pretty quickly. Now with yours being a 93 I know they arnet heated unless you converted to the heated kind.


I dont know if anything I have typed above has helped you or not. I guess all I should have asked was if you used new o2s when you replaced them. I dont think I would have ever found my trouble if it wasnt for datmaster showing me the o2 Mv hardly moving at all in closed loop and finally getting a o2 fail code.

BTW, does your car once it gets into closed loop swithc to open loop and back to closed loop again? My datamaster logs showed that too.

Good luck with it. I hope something I said my help you in some way.

Jason

 

I actually bought brand new Delco O2's and they didn't help.

At idle, the car will bounce in and out of closed loop a couple of times before settling completely into closed at about 4 mins of run time. I'm not running LT headers, just ASM Mid-Length's, and I do have a Random Tech cat on there, so heat loss isn't really a problem.

The car is at FBC right now, I'm looking for words sometime this week about possibilities as to what the deal is.

 

Keep at it, you'll get it!!! Ok, end inspiration, and on with the ideas....

I would have at it with the carb cleaner... The vacum leak is a major pita, and will skew all the measurements if you have one. Make sure.

Next, have you considered doing a compression test to rule out valvetrain issues? Stuck vavle, misadjusted rockers, etc?

Also, on your datamaster logs, what are the other sensors reporting? MAP, and such? Does everything else coorespond to a rich condition?

This is a 93, so is it still speed density only? Just a couple thoughts man, good luck.


-Paul