Its a 1990 E150 Symptoms- After starting and warming up, the rpm's will surge to 2500 (guesstimate) then the engine will start to spit and choke and die unless you rev motor. The same will happen during driving conditions, at 35 mph you get off the accelerator and the van will continue at 35 but accelerator pedal is not sticking and returns to its normal position, the van will start to lurch and the rear end start to bang due to motor cutting out and then die if you dont rev motor. It also at a idle will surge between a slow idle and medium idle. This is all intermittent and 10 min. later will run just fine. Its been happening for over a year and sometimes happens everyday and sometimes not for months. The check engine light has never come on but is working and was told by Ford that this model year does not store any codes in computer. I have replaced plugs, wire, cap, rotor, fuel filter, coolant temp sensor, o2 sensor and cleaned injectors. Ford Service says they can change the EVP sensor, Throttle position sensor, and Idle speed control valve, (at a major cost) but will not guarantee or think that will solve my problem and if it is the computer that this year and model is obsolete and no longer can be purchased. $100 seems to be the going rate for a used one that i have found so far. Would a after market chip help in this case? Any help or thoughts are appreciated, thanks!
1990 E150 5.0
automatic
120,000 mi. (60k on new shortblock)