PistonHead

My tunes are on the laptop at the shop. I'll see if I can get the latest one sent home and then I'll get it to you.

Thanks,
Brad

PistonHead

Email sent. Thanks!

Wicked94Z

iTrader: (26)

I'm "working" right now, I'll pull it up tonight when I get home

PistonHead

Thanks. I appreciate you looking at it.

PistonHead

Brought it home from the shop yesterday. They threw in the towel. No one can seem to figure this car out.

Later,
Brad

moehorsepower

iTrader: (3)

Whats your COT set at?

PistonHead

If that is the Catalytic Overtemp Protection, where would I find that in the tune?

Thanks,
Brad

quik95lt1

iTrader: (7)

ok well theres some good info in here and it seems all the basics were coverd so ill ask some more unlikely things.......

did you check your valve train over?
any bent pushrods? bent valves? bad valve guides or bad springs?

basically anyting that could be hanging a vlave open?

also how about the ignition? cap and rotor in good shape not getting any spark scatter or transfer in the cap that shouldn't be there?

also....any debris in the fuel rails that may be causeing a volume drop between the entrance to the rail in the back and the crossover in the front??

again i realize these are rare problems im suggesting but it may apply here seeing all of the normal things havent solved it......

i cant see how the tune should affect it personally unless somebody screwed up the cyl. balance tables......

the car should be alble to idle at 15:1 afr withouht any crazy heat numbers i idle mine there to keep the plugs clean and its just fine......

you need to look for a place where extra un metered air could be getting into just those four front cylinders........or obveously a fuel delivery issue.

how about the intake manifold gaskets? sealed well? no leaks?

also exhaust? header gaskets good? no leaks? did you get any of the O2's wet with coolant or anything to foul them out?

just trying to bring some new ideas to the table lemme know...

moehorsepower

iTrader: (3)

Depends what software you are using, Just go through your settings and see if you can find it, usually associated with the fueling or verification tables..

PistonHead

I've had the push rods out and inspected. I've looked over all the springs and re-adjusted the rockers.

Replaced the opti not to long ago. Everything inside the cap looks good.

I took the injectors and fuel rail out of the car and tested them on a bench. Inspected the rails and tried a second set of injectors.

The cylinder balance tables is what the shop was adjusting after they checked everything else. They were able to improve things, but never able to get it even close to correct.

The setup on my car has very little room for leaks. The MAF goes directly on the front of the TB. I have checked all around it for leaks just the same though.

I've pulled and replaced the intake manifold gaskets and had no change.


I have changed out the headers for a different set and replaced the gaskets with Earls gaskets. Definitely no leaks that I can find on the headers.

O2's have been replaced with new ones from the dealer. No change with the new O2's.

I appreciate the help. New or unlikely things are my only option at this point.

I drove the car home from the shop which is at least 30 minutes away. The thing runs like a top on the road. Lots of ***** and runs smooth. Even ran it on the emissions dyno (which it failed of course) with no problems. Brought it home and within a minute or two of pulling into the garage the cats where already orange.

I watched the cats on the emissions dyno and stopped and looked underneath on the road and they where fine.

Thanks,
Brad

PistonHead

I'm using Tunercat and can't seem to find it. I'll look again.

Thanks,
Brad

moehorsepower

iTrader: (3)

I'm at work so when I get home I will check unless someone can chime in

PistonHead

May have found it:

CAT Overtemp Threshold (Low Baro) 801 deg. C

CAT Overtemp Threshold (Mid Baro) 813 deg. C

CAT Overtemp Threshold (High Baro) 828 deg.C

CAT Overtemp Baro Threshold 1 79.625 kpa

CAT Overtemp Baro Threshold 2 99.625 kpa

CAT Overtemp AFR 12.2 AFR

Hopefully that is the info.

Thanks,
Brad

Gojira94

iTrader: (4)

**General safe catalyst temp. limit estimated to be 750C (1382.0F) for cars of the early-mid 90s**

801C = 1473.8F at approx. 6250ft. elevation ("Low Baro")

813C = 1495.4F at approx. 3325ft. elevation ("Mid Baro")

828C = 1522.4F at approx. 400ft. elevation ("High Baro")

79.625kpa = 0.785837651atm = 11.5518134697psi = (approx. 6250ft. elevation)

99.625kpa = 0.983222304atm = 14.4533678688psi = (approx. 400ft. elevation)

http://www.aa1car.com/library/map_sensors.htm :

"When the ignition key is first turned on, the powertrain control module
(PCM) looks at the MAP sensor reading before the engine starts to determine the atmospheric (barometric) pressure. So in effect, the MAP sensor can serve double duty as a BARO sensor. The PCM then uses this information to adjust the air/fuel mixture to compensate for changes in air pressure due to elevation and/or weather."

Pursuant to this line of thinking, what is the elevation where you are in Canada? What are your MAP values/ vacuum readings? Just looking for unturned stones...

Bad94

iTrader: (1)

i found this while searching was this ever cured?

im having this same exact proplem. front plugs are damn near snow white. rear 4 lookslightly darker than they should

quick run down on my combo which everything has 850 miles
stock GM short block
ported LT4 heads
230/236 108LSA lift is just under .600
about 11.4:1 compression
1.6 rockers
gold springs
edelbrock LT4 intake
AS&M monoblade
walbro 255 pump racetronix hot wire kit
FIC bosch 3 30lb injectors
55psi base pressure
gm opti
taylor wires
tr6 plugs gapped at .044
1-3/4 to 1-7/8 headers true 3"duals all the way to the bumper with x-pipe bullet mufflers

idles between 700-750 rpm

i never even knew there was a problem until i pulled the plugs to change them out before getting the final tune done

my BLMs are split at idle but are evened out by 1500rpm. throttle response from idle is ok. its really good above 2000rpm. drives great some surging/bucking on a real light load between 1500 and 2000rpm.

yesterday i took the throttle body off and modded the IAC housing so i could send all idle air through the IAC passage in the intake. BLMs are better but still will split if i let it idle more than 5 minutes.

i have never noticed any glowing headers but they are stainless

its deffently an air flow problem at idle i just havent been able to narrow it down

jasonisdn

iTrader: (1)

have you ever cleaned out the build up in the IAC passages? there are four plugs on the bottom of your intake. remove those and make sure they are clean.

pillarpod

i don't have an answer for you, but that is a badass engine bay

PistonHead

Nope I still haven't fixed the problem Bad94. I'd be interested in seeing how you make out.

I've taken my intake completely apart and cleaned all the IAC passages. Didn't make any difference in my case.

I've since stuck the car up on blocks and picked up a bone stock 2009 Z06. Some day I'll get interested in fixing this problem. Until then I am enjoying driving my new toy!

Later,
Brad

Big Al

iTrader: (1)

My 95 has the exact same problem. No glowing headers but the rear four cylinders are carboning up the header tubes. Read all the above and do not see any clear idea of what would cause this. Someone posted a picture of the front of the intake with the small hole ground off at an angle. What does that do? BTW: I also have a BBK throttle.

Al 95 Z28

96capricemgr

iTrader: (1)

I will be honest, I did not read the whole thread.

Did you adjust the TB blades back to closed and drill an IAC bypass hole like the stocker had?? It needs to be sized correctly by trial and error for your combination.