My newly purchased f150 has sat for the last 10 years. The gas was bad so I have cleaned the tanks,new low pressure pumps and filters, new inline filter,new high pressure pump, injectors were cleaned and checked out good,new regulator. I have replaced the map sensor,egr valve,iac valve,and throttle position sensor. The truck timing is set at 10 degrees and seems to be solid and advances when I increase the throttle. The plugs wires distributor cap are new. The truck idles a bit highat 850rpm, and when I accelerate it seems to miss then surge with power...almost like it is missing. The only code on the computer is a code 42 running rich.I am at a loss...Please help. The motor is the straight 6 4.9 litre. It is a standard,4 speed trans.
Might want to change o2 sensor's, If they are not sending the right single its tell the computer to dump fuel. 1988 was using a fuel density system.
(1989 came out with Mass air flow system)
Check this
I think it might have a TFI module that's not working right. Located under distributor. Its gray and about 4" long and if equip, you need a 4 or 5.5 mm tool to unbolt it. This was a common thing back in the 80's. Its been so long I can't remember if the 4.9 straight 6 had it or not.
T- Thick
F- Film
I- Ignition module
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Thanks wyatt for your response. I have put a new o2 sensor in.
The tfi module does exist on the distributor,,,is there a way of cecking it and would this cause a run rich code.
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