6250 to 7000 RPM Light - Strange Behavior

[guevoncito]

Hi All,
Would like to see if anyone with a 13/14 has encountered this issue, and if there is a good long-term fix.

My car will warm up to operating temp, and then the 6250 to 7000 RPM light will turn off. Normal. Then when driving around, the light will come back on, and sometimes turn on/off like it can't make up it's mind. It eventually comes back on and stays on. Then if I stomp on it a little, it will turn off until I let off the gas. No CEL and no codes are thrown. I was totally expecting to see some O2 sensor codes, but nothing.

I'm running E85 with Dynatech long tube headers. I know there are issues with the O2 sensor placement being at 90 degrees, but so far no O2 related codes. I also have a 4.0L whipple and generate 24-25 psi of boost at WOT.

I see another thread about this subject where O2 sensor codes were found:
6250 light stays on.

Car seems to run fine. It's just annoying to see this happen and not have any "smoking gun" that points to a specific problem.

Has anyone else had this issue?

I have a spare set of upstream O2 sensors that I'm probably going to install. I'm really curious about anyone else's experience with this.

I'm also considering installing heat sinks to pull the sensor tips back a bit to hopefully improve the exposure to moisture. Has anyone else done this successfully and did it improve the life of the O2 sensors?

Thanks,
Chris

 

[LS WUT]

@Vinnie_B @1Kona_Venom @2011 gtcs @biminiLX @Norton

 

[2011 gtcs]

I know this sounds silly, but are you running 02 senor wire extenders for your front A/F sensors? If so, that may be causing it. The factory A/F sensors will reach on headers.

Some other things to look at, make sure your IAT2 sensor by your supercharger is plugged in all the way. Since you did a blower swap and have upgraded injectors I wasn't sure if you messed with it

Do you have a colder thermostat?

 

[guevoncito]

I know this sounds silly, but are you running 02 senor wire extenders for your front A/F sensors? If so, that may be causing it. The factory A/F sensors will reach on headers. View attachment 1820403
Some other things to look at, make sure your IAT2 sensor by your supercharger is plugged in all the way, since you have injectors I wasn't sure if you messed with it.

Do you have a colder thermostat?

Thanks for the reply.

I'm pretty sure there are extensions for the front sensors. I will have to get under the car to see for sure.

And I do have a 170 deg thermostat installed with updated tune for fan on/off.

Will also check the IAT2 sensor. The Whipple was just serviced with a complete rebuild, so maybe something didn't get reinstalled correctly.

Thanks,
Chris

 

[2011 gtcs]

Thanks for the reply.

I'm pretty sure there are extensions for the front sensors. I will have to get under the car to see for sure.

And I do have a 170 deg thermostat installed with updated tune for fan on/off.

Will also check the IAT2 sensor. The Whipple was just serviced with a complete rebuild, so maybe something didn't get reinstalled correctly.

Thanks,
Chris

Was this going on before the whipple rebuild?

Definitely check the IAT2 sensor. I remember when I did my 3.6KB I had a similar issue.

Also look at the A/F sensors, you don't want to run and extension harness on the 13/14s. Hopefully it's something simple to fix.

I run a 170 thermostat in my car and don't have any issues, so you should be ok there. I was just making sure you didn't have a 160 in something like that.

 

[guevoncito]

Was this going on before the whipple rebuild?

Definitely check the IAT2 sensor. I remember when I did my 3.6KB I had a similar issue.

Also look at the A/F sensors, you don't want to run and extension harness on the 13/14s. Hopefully it's something simple to fix.

I run a 170 thermostat in my car and don't have any issues, so you should be ok there. I was just making sure you didn't have a 160 in something like that.

Thanks again. Going to check all of these things over the weekend when I can get the car up onto the ramps.

I had one occurrence of this before the Whipple rebuild, but it was a while back (6 months) and there was a code for the O2 sensor at the time. Cleared the code and didn't have any issues again....until now.

I suspect that it's related to the work done to the Whipple. It came off and went to Whipple for a rebuild.

I have also noticed that the O2 sensors just dont last that long with long tube headers and E85. Plus my O2 orientation is not ideal at 90 degrees vs 45 degrees.

Fingers crossed for something simple.

Thanks,
Chris

 

[Vinnie_B]

I got your back @LS WUT .........


Chris,

1.) First thing I would do....DATA LOG reference values and compare them to OEM specs at HOT IDLE/ 30 MPH/ 55 MPH. Especially ECT, CHT, O2'S ect that would effect engine is at temp.......Keep an eye on your engine oil temp as well!! That light goes out once coolant temperature reaches 170°F (77°C) and oil temp is in the green .I would also data log VPWR for any voltage issues.

I dont like to guess but you could be dealing with something simple of something much more complicated. Things to consider.....

1. Failing/erratic or Input sensor that is not secured properly
2. Failing PCM/Instrument Cluster module. *Need to run them thru a diagnostic self test with something like Ford IDS/ Forscan to verify there integrity
3. Possible corrupt firmware in the PCM/Instrument cluster modules
4. Network issue (Need to run a Network Test for data transfer issues between modules)





ENGINE OVER-REV Note: Engine torque and maximum rpm are limited until coolant temperature reaches 170°F (77°C). Warm up is indicated when the redline indicator band starting point changes from 6250 rpm to 7000 rpm. Your vehicle is equipped with an over-rev feature to increase the performance range of your Shelby GT500. When conditions permit, over-rev is indicated on the tachometer with redline marked at 7000 rpm. If conditions limit over-rev accessibility, the band is illuminated red from 6250 rpm to 7000 rpm. Once the engine is warm, the over-rev feature allows eight seconds above 6250 rpm up to 7000 rpm. If the eight second time limit is exceeded, the maximum engine rpm is reduced to 6250 rpm until both of the following occurs: • Engine is operated for at least 15 seconds below 6000 rpm • Engine rpm falls below 5000 rpm. Do not operate the engine at high rpm and low load for sustained periods of time, as damage may occur.

 

[Vinnie_B]

You might consider reaching out to B.J McCarty @ Venomous Tuning. He knows these GT500'S better than anybody

Venomous Tuning

3080444

venomoustuning.com

 

[Norton]

Thanks for the tag, @LS WUT.

Have not encountered this issue, so not much to offer beyond what others have said. FWIW, I've run a Reische 170' Tstat for almost 25K miles and a little over seven years with zero problems, so I don't see that as the problem.

I'd focus on A/F sensors and extension harness first, broadening the investigation from there... Good luck!

 

[guevoncito]

I got your back @LS WUT .........


Chris,

1.) First thing I would do....DATA LOG reference values and compare them to OEM specs at HOT IDLE/ 30 MPH/ 55 MPH. Especially ECT, CHT, O2'S ect that would effect engine is at temp.......Keep an eye on your engine oil temp as well!! That light goes out once coolant temperature reaches 170°F (77°C) and oil temp is in the green .I would also data log VPWR for any voltage issues.

I dont like to guess but you could be dealing with something simple of something much more complicated. Things to consider.....

1. Failing/erratic or Input sensor that is not secured properly
2. Failing PCM/Instrument Cluster module. *Need to run them thru a diagnostic self test with something like Ford IDS/ Forscan to verify there integrity
3. Possible corrupt firmware in the PCM/Instrument cluster modules
4. Network issue (Need to run a Network Test for data transfer issues between modules)





ENGINE OVER-REV Note: Engine torque and maximum rpm are limited until coolant temperature reaches 170°F (77°C). Warm up is indicated when the redline indicator band starting point changes from 6250 rpm to 7000 rpm. Your vehicle is equipped with an over-rev feature to increase the performance range of your Shelby GT500. When conditions permit, over-rev is indicated on the tachometer with redline marked at 7000 rpm. If conditions limit over-rev accessibility, the band is illuminated red from 6250 rpm to 7000 rpm. Once the engine is warm, the over-rev feature allows eight seconds above 6250 rpm up to 7000 rpm. If the eight second time limit is exceeded, the maximum engine rpm is reduced to 6250 rpm until both of the following occurs: • Engine is operated for at least 15 seconds below 6000 rpm • Engine rpm falls below 5000 rpm. Do not operate the engine at high rpm and low load for sustained periods of time, as damage may occur.

Thanks Vinnie! Great info. I will be relieved once I can find out what's causing this strange behavior. The Whipple came off, went out for repair, and was reinstalled. Thinking it's related to these changes and something with the reinstall.

Thanks,
Chris

 

[VNMOUS1]

You might consider reaching out to B.J McCarty @ Venomous Tuning. He knows these GT500'S better than anybody

Venomous Tuning

3080444

venomoustuning.com

The 6250/7000 can be modified in a custom tune

Sent from my SM-S918U using Tapatalk

 

[2011 gtcs]

The 6250/7000 can be modified in a custom tune

Sent from my SM-S918U using Tapatalk

Good information. I never knew that

 

[guevoncito]

The 6250/7000 can be modified in a custom tune

Sent from my SM-S918U using Tapatalk

Thanks BJ. I have a dyno session scheduled with the tuner for right after the first of the year. Hopefully this will provide some answers and a clean bill of health .

 

[biminiLX]

Big power setup with a 4.0L at 24-25#
Does the car rev clean to 7000/above 6250 when the light comes back on?
I’ve never noticed the rev limit light go back once it’s warmed up at 7000 limited is reached.
Probably best to wait until the dyno session but definitely datalog if you’re going to test high RPM pulls.
Good luck.
Any pics of this beast?
-J

 

[guevoncito]

Hi Everyone,
Update. The light still stays on all the time now. Car was on the dyno yesterday with datalogging. Tuner is happy, car is healthy. Still no real answers for the 6250 to 7000 light. No codes or CEL.

Here is an interesting side note related to the blower rebuild. The blower rebuild seems to have improved the blower's efficiency. On the 2.875 pulley and 24-25# of boost, it previously made around 975 HP and 915 Torque. On the 3.75 pulley and 17-18# of boost, it previously made around 830 HP and 760 Torque.

With the blower rebuild, the 2.875 pulley made just over 1200 HP and 1000 Torque. With the 3.75 pulley, it made just over 900 HP and just under 800 Torque.

The 2.875 setup was way too spicy for my taste, so I opted to stay with the larger pulley. Also worried about the transmission lifespan at the 1200 HP range. Plus the traction challenges. Just not fun to drive.

We're still tracking down the issue with the RPM light. The tuner couldn't find anything or force it to behave. Current suspicion is the oil temp sensor.

Main concern has been mitigated about the car's health after the blower rebuild and reinstall.

If we ever figure out the RPM indicator issue, I'll post back. Thanks everyone for the inputs and guidance!

 

[biminiLX]

Glad she’s healthy!
Good news on power too, that’s what I’d expect from a 4.0L at that boost.
-J