The Mustang Forum for Track & Racing Enthusiasts

Taking your Mustang to an open track/HPDE event for the first time? Do you race competitively? This forum is for you! Log in to remove most ads.

  • Welcome to the Ford Mustang forum built for owners of the Mustang GT350, BOSS 302, GT500, and all other S550, S197, SN95, Fox Body and older Mustangs set up for open track days, road racing, and/or autocross. Join our forum, interact with others, share your build, and help us strengthen this community!

Engine has an intermittant stuttering/ignition problem with no codes

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

So I have been tracking my 13 Boss for the last 3-1/2 year and have had a PRS engine harness upgrade from the get go. The motor ran flawlessly up until last fall. On the last run of the season the engine started to hesitate/stutter almost like it was running out of fuel. It only lasted a brief moment and then ran fine. I always run with nearly a full tank of gas, so I know the fuel system isn't pulling air.
During my winter preps I went ahead and changed the plugs for good measure and they looked just as they should.
Last weekend I had the same issues only now the issue seems to be getting more frequent. In the middle of the second day, I decided I needed to park it until I figure out what is going on.
Since this is an intermittent problem, I am leaning toward an intermittent electrical problem.
The engine wiring harness has been a weak link in the past and is fairly cheap to replace, so I am thinking my first step is to replace the engine wiring harness along with the cam solenoids and crank sensor.
Has anyone gone through this and have any suggestions on how to trouble shoot this problem before I pull the trigger on these parts?
Thanks.
 
Have you checked into the spark plug coils? See if you can isolate which cylinder is misfiring and then swap the coil with a different cylinder.
 
So if it were misfiring, I would think I would be getting a code. But, I haven't gotten a single code except the precat codes that I get because I've got LTH on it. Could it be a fuel issue?
 

302 Hi Pro

Boss 302 - Racing Legend to Modern Muscle Car
2,009
441
Southeast
These conditions are tough to diagnose. Is it possible to recreate this condition while data logging?

Keep an open mind during inspection and testing. Look at fuel pump lines, kinks, melting, and fuel pump electrical supply. Some of these items will not throw codes.

Good luck during your inspection.
2HP
 
Ok, so this weekend I'll check the fuel lines and fuel pump connectors and clean the crank sensor. I'm not sure about the coils since I am not getting any codes, but can do some testing after I clean the crank sensor and see what happens.
 
I had the same problem at Laguna Seca last year. Turns out the cold air intake was a little loose at the throttle body, and every time it would shift a little (due to cornering, braking, etc) it would leak some air and mess with the MAF sensor. Tightened the clamp and no more trouble. I could not "see" that it was loose, but once I started feeling around, it was obviously loose.

Hope it's that simple for you.
 
898
544
When we were talking about the issue this past weekend, I forgot that I had a similar issue last year. It turned out to be poor electrical connections in the charging circuit. Specifically, the battery cable lug on the negative ground cable of the battery relocation kit came loose creating a poor connection and ground. This resulted in a voltage fluctuation that played havoc with the PCM and misfire circuits. The car kept misfiring and going into limp mode with no codes.

It is still worth checking everything mentioned above.
 
Well I took the car out this morning and had no issues. I think I am going to clean the crank sensor and change the fuel filter and go from there. Maybe I was starving the car of fuel on the track, but I normally don't let the tank get that low. If I do find something, or it manifests itself, I'll let everyone know. Thanks for all the great suggestions.
 
I am thinking that might be the case. If it were anything electrical, I would getting codes left and right, but I wasn't. I'm going to change the throw out bearing and send the transmission off to be serviced. I'll throw in a new $250 fuel pump/filter while I have everything apart. (ugh!)
 

TMO Supporting Vendors

Top