98 Mustang GT 4.6 / Hesitation, while cruising between 40 -70

[Mike554]

This issue is driving me insane, everytime I drive this car ONLY when it's HOT( not cold, first 15 min)it will hesitate or have a slight buck when I'm crusing between 40-70. I really don't have a problem ( or atleast it's not noticeable) when I accelerate, but it has been RUNNING RICH. I have replaced Wires, Plugs, Fuel Filter, Fuel Pump, Coils, EGR, TPS, O2 Sensors, Mass Air, K&N Air Filter, Main Computer, (all top brand names). I also use Z-Max every 6000 miles for fuel injection and engine, Mobile 1 15000 miles synthetic oil( change every 7500) and I still can't fix the problem. Someone please steer me in the right direction so I don't have to bring it to the dealer and be at their mercy.

Thanks,

Mike

 

[Gtwo]

Any codes?
Scan it and let us know.

 

[nyuk98gt]

Mike554:

Couple things. First, test the ECT sensor. There's one for the gauge and there's the ECT sensor. The computer uses ECT for a lot of things and a bad sensor will give the car some issues. Next: is your transmission an auto or manual? If auto, the torque converter can lock-unlock, depending on speed and load on the engine. You can test this by slightly touching the brake pedal to keep the torque converter unlocked. If this is the problem (locking/unlocking) then a modified tune will take care of it.

HTH,

Chris

 

[evolucion311]

Mike554:

Couple things. First, test the ECT sensor. There's one for the gauge and there's the ECT sensor. The computer uses ECT for a lot of things and a bad sensor will give the car some issues. Next: is your transmission an auto or manual? If auto, the torque converter can lock-unlock, depending on speed and load on the engine. You can test this by slightly touching the brake pedal to keep the torque converter unlocked. If this is the problem (locking/unlocking) then a modified tune will take care of it.

HTH,

Chris

This 4.6 also has a cylinder head temp (CHT) sensor in addition to the ECT, if I remember correctly.