Basil2000

Posted this in performance driving section but thought may get more views here



Today 15mins into my second track session my car (2015 stock z07 m7)all of a sudden started to lose power. It was 88deg out and i thought the car was just hot and went into limp mode although there were no messages of that on the dash. I let the car cool down and went out for the 3rd session and car still had no power on first lap so i pitted and loaded it on the trailer and headed home. Just checked my data on Cosworth toolbox and said max oil 266 and max water 230. Seems kind of low for limp mode. Going to call dealer tomorrow. Just looking to see if anyone has had this issue. I’m booked for Watkins glen July 15 and 16 so i hope this is am easy fix. Definitely thinking i need to add auxiliary radiator.

23/C8Z

yep.. also it's possible you have some IC pump cavitation..

Mr. Gizmo

High probability that’s the op’s problem.

Op can search threads on it. My car had the problem. It pulled power when it had cavitation on the street car running 190 degrees water temp and 180 degrees oil temp.

Basil2000

How do you know if you have a bad catalytic converter? I was wondering if this would cause the car to act like this. Car is bone stock. Have been tracking car for 3 years. Dropping car to dealer on Monday but trying to educate myself before then. Thanks

Road machine

It's not your cats....they don't go suddenly. I agree with the guys above. You have air in the intercooler. When the intercooler bricks get hot two things happen. 1st you get a much less dense charge, so you lose power. 2nd the car pulls timing to keep detonations down, and you lose power. Neither is limp mode, and does not set a code.

Thomasmoto

yep.. also it's possible you have some IC pump cavitation..

This would be my first thought as well.

Poor-sha

If the car had been performing well on track you don't magically get air in the intercooler but cats do suddenly fail - I've been through several. The weld splits in the cat piper where it makes the sharp bend and exhaust gas shoots out the break throwing the sensor readings off and having the car pull massive power. In at least one of my cases it started shooting hot exhaust gas toward the knock sensor and melted the wiring connector so it was dripping like candlewax. You often can't see it unless you pry back the heat shield but if it gets bad enough you can hear a ticking under the car from the exhaust leak. I've posted pics in other threads but can't find them at the moment.

Basil2000

Thanks guys. My local Chevy dealer has a corvette tech that does my track prep. He is going to take a look at it on Saturday. I will let you know what he finds. I appreciate all of the experiences.
ken

badhabit_wb

Mine did the same thing, It didn't throw any codes but it was so weak it couldn't pull a fat baby off a tricycle. I re-bled the ic and got most of the air out of the tank and never had it happen again. I thought at the time it was a converter but they were fine. You can't hurt anything by getting as much air as possible out of the intercooler tank and all you've got tied up is your labor.

Bill Dearborn

How low did speed drop? Limp Home is a top speed of less than 35 mph. I used to get a 10 to 12 mph drop in top speed in 4th with my 15 Z06/M7. Then after discussions with GM Engineering found that I had to bleed the intercooIer so the air pocket in the reservoir was reduced to the size of two quarters. It is easier to do the bleed if the mechanic uses the vacuum bleed tool specified for the ZR1. I just finished the NCM event at VIR on Mon/Tue. Monday temps went to 98 degrees. Tuesday temps went to 92. I did notice some drop off in top speed on both days but it wasn't as much as before, maybe 5 mph.

Check the ECM to see if there are any codes. You may not have a CEL but there may be some codes like P0300. If you have that code there should be a history file that will tell you how many times a misfire occurred and on maybe which cylinder misfired. For 88 degrees your coolant and oil temps aren't that bad. I have the aux radiator and saw a max coolant temp of 221 and a max oil temp of 261 on Monday afternoon. I wasn't pushing as hard as I normally do as I had a student with me and I was showing him the line I use. On Tuesday afternoon I had another instructor with me and was pushing harder for more laps and saw a max coolant temp of 217 and max oil temp of 262. My lap time was 6 seconds faster than the previous run I mentioned.

Bill

Basil2000

I was still able to drive fast but just couldn’t put the power down to pass or pull out of a corner. The car was almost sputtering when first getting on the gas. Someone I know was behind me and said car sounded bad like it was miss fireing. Car starts up and sounds good but when I rev it, it sounds bad until rpms come back down.

Bill Dearborn

That sounds like an ignition system problem, bad plug, loose plug wire or a bad coil.

Bill

23/C8Z

Agree with Bill on that one.

Doubtful cavitation or cat failure.

Log the car and post it up here if it keeps happening after the visit to the shop. I hope it does work for you though good luck.