I have a highly modified 2000 Camaro with a drivability problem I cannot get fixed locally, my tuner who did the tuning (Greg at Livernois) has no idea, my two mechanic friends have no idea. No codes set, used Snap-On scanner, Tech-II scanner, and autotap. Can’t see anything wrong, no huge amount of misfires or anything unusual. Here is what is wrong:

2000 Camaro, lots of mods….drivability issue and performance issue-
382 Stroker built/installed by MTI, Rossler 4L60E transmission, FLP headers, ORY, no cats, two 02’s in headers, none past the headers (no sims either, tuned out), X1 cam, no AIR stuff, recent running at Livernois Motorsports. Car ran fine until 9-16-04, then it ran for ****! Here is the story…

Car was running fine, changed plugs, changed oil and filter, tranny fluid and filter, cleaned nitrous filter, new fuel filter, did front brake pads, polished out headlights, added metco valvecover breather…
Drove fine, had nitrous in the line (didn’t race anyone that night), shut the bottle and hit the button (ran hard for a second, then flooded with fuel), check-engine light came on, drove it for a few minutes to clear everything out, light went out, felt fine. Next day, too friend for a ride, ran weird, idled high, very unresponsive, rpm’s came up real slow (like an ultra tight converter or something)…tried it on and of the bottle, same response until above 5,000 rpm, then the rpm’s came up faster. When driving, car would accelerate on its own all the way to 45 mph or so and stay there (from a dead stop with no gas being applied), when shifting into neutral at 45 mph, the rpm’s would climb to 1500 or so, and then slowly fall. If you hit it on a 40-50 roll, it would accelerate slowly until 5-5500 rpm then it would pick up speed.
Here is what I have done (unsuccessfully) to address this problem:
Disconnected/reconnected battery after every change-
Replaced IAC with another IAC from a good running, same year Camaro
Cleaned IAC
Replaced TPS
Checked for intake leaks with carb cleaner (none found, no surging at all)
Autotap- no codes
Snap on scanner- no codes
Had friend rev engine to 1800 rpm or so, disconnected IAC (per mechanic friend), car was more drivable down low, did not want to idle high or go to 45 mph on its own, but still felt sluggish (again like a ultra tight converter)
Went to Livernois to have car re-tuned…used a brand new ECM, did the tuning, made good power (dyno pulls were at 70 mph and above) made 580 rwhp and 644 tque so engine is not damaged, and everything ran great on the dyno-
Test drove it and the exact same problem as before with drivability. Tried replacing Metco breather with standard oil cap, seemed to help lower the idle a little but no major difference. Put foot on brake and foot on gas…floored gas…rpm’s went to 1800 at WOT on the brake, did not go above 1800 rpm’s or spin tires. At this point I thought it was the converter, so I shipped it back to P.I. for a check. Everything checked out fine, they rebuilt/restalled to 4000 and sent it back. Put 3.42 gears in rear end, and I believe the computer is now set to not lock the converter at all until 3rd gear at about 50 mph. Now car drives the same, can tell the converter is looser, goes to 2400 rpm on footbrake with gas FLOORED, will not push the car or break the tires loose. Also installed brand new IAC motor, cleaned TB real good. Rechecked for leaks (went through a whole can of carb cleaner) all over intake, TB, basically whole top part of engine compartment.

I will likely have to take it somewhere to get it looked at (I am in NE Indiana), and have sent an email to APE to see if they can do anything. Suggestions?

 

still have the stock PCV system?

if so, you can't run an open breather. What are your fuel trims?

Normally a hanging idle/self drive condition it an uncontrolled air leak. Something that the IAC has to chase and often can't completely control
.

 

Thanks for the input...I did notice that it was slightly better with the stock cap instead of the breather. I do have the stock pcv system as of now. I know it sounds like some sort of vacuum leak, just can't find out where....I will replace the breather with the stock cap. What mods have to be done to the pcv to use the breather?

SDB

 

Tuned open or closed loop?

 

cosed loop I believe

 

Your PCM may be learning. Check very carefully for intake and exhaust leaks. Those will cause alot of problems in closed loop tuning. If none can be found, try tuning it open loop or set your main VE table to stock except for the first two columns. Multiply those two by 70%.

It sounds like a lean condition to me. Be careful with this. How do your plugs look?

Good luck.

 

The PCV system gets a fresh air source from the hose on the side of the TB, just infront of the blade. Draws it through the crankcase and back into the manifold just behind the TB. If you add an open breather you're letting it pull unmetered air into the manifold. That will bypass the IAC and drive your fuel trims way up.

If you want to run a breather you basically have to remove the PCV system. There's a reason it's sealed and metered.

Running an open breather IS a vacuum leak

 

Exactly

After you put he right oil cap back on,reset the computer.

 

One day I'm going to draw a diagram using a LS1 pic to show how everything is connected. I figured that out while trying to diagnose the lean codes after my ATI install. ATI uses a blow through MAF setup and relocates the fresh air tube so it's not metered, simple bastages.

 

Thanks for the input...I will try that again...I hope this fixes the problem...could be looking at two separate problems...bad converter and the breather. Chris PE told me that they had a similar problem with a LS1 that was running a Vig converter. Replaced the converter and voila, problem fixed. If the breather doesn't do the trick, then I think I will get a Neil Chance converter.

SDB

 

Have you checked the o2's since the N2o incident? It sounds to me like you blew one out. The would not effect your WOT, thus the great dyno numbers, but they will screw with part throttle driving.

 

If you could pull a driving-around log file with the most
relevant PIDs, and export us a .csv file, maybe something
would stand out.

I'm still inclined to think a backfire-caused manifold leak,
maybe a crack or blew out the safety plug, or some kind
of damage to the MAP sensor from overpressure?

Thinking that it dynos and runs well when it's well up
into the airflow range and maybe getting by on the MAF,
but has problems down low where there's unmetered air
and/or some problem with the MAP / speed density side.
The MAP might still look "alive" but just be "bent"? Does
your Low-RPM, WOT MAP reading match known ambient
air pressure exactly (maybe read off another handy GM
vehicle and compare same-garage, same-afternoon).

 

02's looked ok physically, and on the scanner, they both ranged from 800's to 200's constantly....

I may go ahead and put two new 02's in for the hell of it...

thanks,

 

Jimmy...

I am not that adept at scanning to do what you say...I don't think its a leak, because we have checked out that with carb cleaner 3 times now. I will replace the breather with the standard cap, change 02's, and reset the computer and see what that does. If that does not fix it, I will replace the converter...I think its the converter from talking to APE, Rossler, and some others.

Thanks

SDB