Help - limp mode

[AgSurfer]

Got the 2018 Roush Phase II SC GT back from the performance shop Wednesday. Mods were as follows:

2.8" pulley
VMP boot a pump
Long tube headers, w/ high flow cats
Custom tune - for 93 octane
Billet oil pump and timing gear

Car ran fine on the way home from the shop, which is about a 20 minute drive. Car was parked for two days (rainy weather). Last night, I put 93 octane in the tank and added a 32-ounce can of Race Gas Ultra to the gas tank. Drove home, washed the car, detailed it, put it away... no problems.

Today, was having a nice gentle ride - nothing spirited / hard at all - and the car went into limp mode after 5 minutes from the house (I got the wrench symbol and dash said "see manual"). Was able to turn around and get the car back home. The car ran horribly in limp mode and extremely rough during idle. Damn thing was shaking.

I will call the performance shop Monday morning can get the car back to them ASAP; probably have to tow it as don't think it is a good idea to drive the car on the highway in limp mode.

Did the addition of the case gas ultra in the gas tank totally screw something up? Tuner said adding the higher octane gas would be great and no need to adjust the tune, as the computer would automatically adjust timing. I took pics of the gauge readings; oil pressure went down to 20 PSI and vac was near zero. Cylinder head temp was 189 degrees. Also, the supercharger was not hot at all; it was cool to the touch.

Anyone have any thoughts on why "limp mode" showed up? Thanks.

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[engineermike]

The octane booster did not do that.

You need to get the dtc out of the pcm and post it. Sounds like it went into fmem.

 

[AgSurfer]

The octane booster did not do that.

You need to get the dtc out of the pcm and post it. Sounds like it went into fmem.

I don't have the tech to get the DTCs. Will have to wait until next week. Thanks for the quick reply.

 

[AgSurfer]

The octane booster did not do that.

You need to get the dtc out of the pcm and post it. Sounds like it went into fmem.

I acquired a scanner. The following codes were presented:

1. P0124
2. P0120

Thanks.

 

[engineermike]

I would check the TB wiring, unplug connector, re-seat it, then try again and see if it returns.

 

[fmc_smt]

Wait your cht was 18 degrees?

 

[AgSurfer]

Wait your cht was 18 degrees?

Sorry I do not know what means. Can you please elaborate? Thanks

 

[cahouston]

Sorry I do not know what means. Can you please elaborate? Thanks

Your cylinder head temp was 19 degrees?

 

[fmc_smt]

Sorry I do not know what means. Can you please elaborate? Thanks

Sorry , in your original post , you stated that your cylinder head temp eas 19 deg .

 

[AgSurfer]

Sorry , in your original post , you stated that your cylinder head temp eas 19 deg .

My lord - that was a major typo. CHT was 189 degrees. I went back and edited the original post. Sorry about that.

 

[AgSurfer]

I would check the TB wiring, unplug connector, re-seat it, then try again and see if it returns.

Should I clear the DTC codes? Or, just check the wiring / connectors as you suggested and start the car back up without clearing the DTC codes?

 

[fmc_smt]

No problem, with the codes you have either a tb issue or wiring . Did you change the tb or any kind of wiring extension to the tb ?

 

[AgSurfer]

No problem, with the codes you have either a tb issue or wiring . Did you change the tb or any kind of wiring extension to the tb ?

No change in tb. Only wiring I believe was for vmp boost a pump. Maybe they knocked something loose when doing the install of billet oil pump and timing gear. I am calling the tuner first thing Monday morning.

 

[AgSurfer]

I would check the TB wiring, unplug connector, re-seat it, then try again and see if it returns.

Correct me if I am wrong please, but the TB connector on the 2018+ Roush supercharged mustangs is directly behind and slightly underneath the supercharger pulley. If that's the case, I am unable to access it to "check the connection". I can't get fingers in there. I imagine the pulley will need to be taken off and connection checked and/or repaired - if this is the issue.

 

[engineermike]

I thought the roush kit came with a larger tb. Either way it would be very simple and easy to check over the wiring and the-seat the connector and extension if it has one.

Edit, it might be easier to pull the tb off to access the connector.

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