Very hard to start when warm all of a sudden.
02-28-2016, 10:02 PM
#21
Drifting
Thread Starter
Thank you. Actually weather has been upper 70s and even 80 and does same exact thing. didn't do this at all when I got the car. Rough idling at stop lights is new too and started at same time. I dont want to change the tune since I know it was good before.
02-28-2016, 10:08 PM
#22
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St. Jude Donor '15
Most tunes are ****
03-02-2016, 11:41 PM
#25
03-02-2016, 11:51 PM
#26
The theory behind this. When you turn your car off, the heat from the engine, and exhaust heat soak th crank sensor, causing the sensor to have much higher resistance. When its high resistance the compter reads that and dont start the car. After the car sits and xools off the resistance in the sensor lowers, you go to start it, the computer sees a lower resistance from the sensor and start. If not mistaken, when the sensor is reading high resistance, it tells he computer. And then the computer don't fire up the car.
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08velocity (06-02-2016)
03-20-2016, 02:10 AM
#27
Drifting
Thread Starter
The theory behind this. When you turn your car off, the heat from the engine, and exhaust heat soak th crank sensor, causing the sensor to have much higher resistance. When its high resistance the compter reads that and dont start the car. After the car sits and xools off the resistance in the sensor lowers, you go to start it, the computer sees a lower resistance from the sensor and start. If not mistaken, when the sensor is reading high resistance, it tells he computer. And then the computer don't fire up the car.
If the sensor is bad wouldn't it have a hard time starting after I run it and let it sit for 5 minutes too ? Should be really hot under there by then I would think. If its a bad sensor it seems like it would affect the startup some when its cold too.... I know that sensor is a bitch to get to or I would just swap to rule it out.
I have been really watching my fuel pressure when this happens. Cold start it goes right to 55 immediately. When it has a hard time starting it reads 35-40 and SLOWLY climbs up to 50-55. Thats when it actually starts but runs super rough for a little while. Once it smooths out the pressure is normal. Now while at a light and it starts getting a little rough out of nowhere pressure seems to be fine. Needle bounces around a little but stays 53-55 range.
You know there must be something to this. Once I start driving it always smooths out. It only gets rough idling at stop lights prob as it heat soaks........ Sitting at a light I wouldnt think the fuel pump would change and according to my gauge the pressure is fine.
I think I mentioned this before but when I can tell it wont start I just turn it off right away. Almost every time it will start on second try. If I let it crank for more than a few seconds it is VERY hard to get it restarted.
Last edited by dllhg; 03-20-2016 at 02:39 AM.
03-20-2016, 12:54 PM
#29
Le Mans Master
Did you check/swap the cam sensor as mentioned before?
I had the same issue on the TT C6, hard to start when warmed-up as well as occasional backfire. Swapped the cam sensor and the harness extension (total less than $100) ans problem solved.
I had the same issue on the TT C6, hard to start when warmed-up as well as occasional backfire. Swapped the cam sensor and the harness extension (total less than $100) ans problem solved.
03-20-2016, 02:35 PM
#30
Drifting
Thread Starter
I never have any driving issues once moving,. Always full power, and smooth. Starting when warm and idling at lights is when it shows up. 1-5 minutes after shutting down it still starts ok. longer then it has the issue. Makes sense I guess if it is getting more heat soaked from sitting there.
03-22-2016, 08:39 AM
#33
Race Director
Take a look at the EVAP purge valve. My Avalanche started to have the same symptoms you describe and that's what caused the problem. It wasn't shutting off so fuel fumes were collecting in the intake and causing the hard starting only when warm. I'm not sure where it's at on the Vette; it was on the front top of the engine on the Avalanche. It took about 10 minutes to change it out and cost about $25. I never had any codes.
03-22-2016, 09:03 AM
#34
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St. Jude Donor '15
There's one on the passenger side front of the engine on C6's. It would be something very easy to change to try (or you could disconnect it and put caps on the connection to the intake just to try and see if it helps)
03-22-2016, 08:52 PM
#35
Drifting
Thread Starter
03-22-2016, 09:10 PM
#36
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St. Jude Donor '15
03-23-2016, 06:35 AM
#39
Race Director
One would think it should but my Avalanche never did; it never even had any pending codes (I tuned it with HP Tuners, which you can also use to check DTC's - the Avalanche was also MP112 Magnacharged). The issue immediately went away when I replaced the purge valve.
03-23-2016, 08:38 AM
#40
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St. Jude Donor '15
Agreed... I'd expect it to, but I'm not sure if it actually would or not. I'm not sure if the computer has any way of telling if it's stuck open or not. My guess would be not though
If you unplug it it def. will throw a code (I've done that one).
If you unplug it it def. will throw a code (I've done that one).