Ignition timing
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Ignition timing
I've got an 85 f-150 w/302 FI. I checked the base timing and it is at 10 degrees like it should be, I reconnected the spout wire and it jumped to 21 degrees, bouncing around +/- 5 degrees. When i increase throttle it holds steady for a moment then jumps up about 10 degrees, and as i continue increasing rpm, timing increases from there. I have a stumble just off throttle and knocking / power loss, almost like a cylinder isn't firing, at cruise speeds. At stop signs it will rev / almost die / rev/ almost die. I replaced the IAC, O2, TPS already. The smog pump was removed by the previous owner, the vacum lines to the diverter and bypass valves are plugged off and the pipe going to the head has been sealed off. All the symptoms are intermittent, they seem worse if its hot (after 5-10 miles). Does anyone have any ideas what could cause this. Thanks
dan
dan
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From: Virginia
Make sure you check the codes. Even though you replaced the TPS, you could still have a TPS error code, which would point to the wiring. What you could try also is to unplug and plug back in the big connector on the computer. Sometimes they get a little bit of corrosion on the contacts.
Also, what does the idle do when the IAC is unplugged and the engine is started? It should idle really slow. If it won't, then turn the idle screw up a little bit. Try to get it to idle with the IAC unplugged at around 500 rpm. Then the IAC and the computer will take over from the there and give it another couple hundred rpm.
Also, what does the idle do when the IAC is unplugged and the engine is started? It should idle really slow. If it won't, then turn the idle screw up a little bit. Try to get it to idle with the IAC unplugged at around 500 rpm. Then the IAC and the computer will take over from the there and give it another couple hundred rpm.
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I have rechecked the codes several times, I get either 44 or 45 (emissions) and 25 (knock sensor). I had to dial down the idle screw because it was idling way too fast. When I pull the IAC wire when it is running it almost dies, sometimes it does die. It only does it after I've drove it a while slowing from cruise speed, if I bump it to neutral and give it a minute it quits.
I was concerned that the timing at idle with the spout reconneted jumps from 10 degrees base to 21 degrees and doesn't hold steady. Could the TFI or Stator be bad or going bad?
I was concerned that the timing at idle with the spout reconneted jumps from 10 degrees base to 21 degrees and doesn't hold steady. Could the TFI or Stator be bad or going bad?
