1987 FX-16 has alway had a cold weather running problem

[smewr]

Hi, I've owned an 87 FX-16, manual trans, for 18 yrs, it has always run poorly below 40F for some reason. I have rebuilt the engine, had the injectors cleaned, new plugs, wires, compression is perfect etc... it had this cold weather running problem before and after the rebuild... I tried cutting a hole in the air box, and blocking the fresh air inlet so the intake air would be warmer, breathing engine compartment air instead of outside air, no change. I have all new sensors, good thermostat, etc. Typically, I start driving and after about 15 minutes on the highway, especially just as I lift on the gas, the engine will buck, and if I mash the gas to the floor, it will accelerate without bucking. I was thinking maybe it's induction icing.... but can't tell. It has the original TPS (they're damn expensive) and MAF unit. It's also never shown a fault on the fault sensing system. Above around 40F it runs perfect, and is a joy to drive. I rebuilt the distributor (which finally ended the oil drip), and the plugs always look perfect. I can't figure this one out, anyone out there ever seen this problem before? Thanks ! ! !

[taroroot]

Get a multimeter and actually measure your TPS and AFM. I've got 4 AFMs from my FX16's and other 4AGEs, all bad. The AFM has to be seriously screwed up in order to throw a code in the ECU so it may be bad but you won't see a code.
If I recall, there's also a temp sensor in the AFM.
Just to be sure, check for vacuum leaks too. My friend had a temp related problem that was a leak, when the engine warmed up the leak closed up.

[smewr]

Thanks for the great info.... I will follow up on your suggestions ASAP......