91 22re 4x4 automatic,i have been working on this truck for three weeks now and still cannot get the ignition timing to advance.i have replaced the the distributor,igniter,coil tps and computer,bit still no change.my wiring looks excellent can,t seem to find anything,just hoping somebody might have some other ideas,thanks for looking

 

Did you put the jumper in the diagnostic box?

 

yes,jumped the correct connectors,set timing at 5,then remove the jumper,timing will not advance,even when i rev the engine.

 

Usually that means it is a TPS problem. Make sure it is in spec.

I would also check the pick-up in the dizzy itself.

 

replaced the distributor with one out of my 94 that i know is good,and all the tests on the tps including ohms checks and voltage checks seem to be within specifications,maybe i will take the tps out of my 94 and try it,jst as a last resort,thanks for looking.

 

well as a last resort i installed the tps from my 94 which works great , but once again it did not fix the problem,does anyone have any other ideas as to why i have no timing advance,i geuss i,m completely out of ideas,thanks for looking

 

the igniter needs a signal from the cpu, on the iGt connection... the igniter defaults to no advance when it doesn't get that signal... unfortunately you may need an o'scope to see that signal, or perhaps a multimeter with a frequency counter(?).

since you have already swapped out the igniter, could there be a break in that wire, going back to the cpu? ring it out.

 

when i read the fsm it says to check voltage at the igt - e1 terminals,voltage should be .7-1.0 volts,mine is reading 8.8 volts.had a friend check the square wave voltage at the igniter,there is a pulse,but he says it,s hard to see because the high voltage has it out of range,i,m really confused

 

my craftsman 82040 has a frequency meter, i'd really like to see what that signal looks like on a vehicle that runs... it could be a good thing to know for troubleshooting purposes.

unfortunately my trans is out, and my garage looks like a farking yard sale, so it'll be a couple of days before I can look at it :-(

you could still do a wiring integrity test... it's a long shot, but unplug both ends of the harness, make sure that the wires ring out to the cpu, and that there aren't any shorts that go to ground or to the 12v battery side.

 

The IGF signal "should" just be a pulse at the ignition frequency; your frequency meter will just read the number of times/second a plug fires. Since it's a low duty-cycle pulse, a typically slow meter will average down to the 0.7-1.0 volt spec.

If you're getting 8.8 volts on IGT, you either have a very wrong duty cycle, or it's riding on top of some errant signal. Both bad. Hard to say for sure without an oscilloscope, but knowing the waveform isn't going to tell you how to fix it.

The IGT comes from the distributor. You say you replaced it; with a new one? Or one from another vehicle? Are you sure the distributor is producing the right signal?

 

when we checked the waveform with a snapon advantage tester on the 94 it looked exactly like the waveform should look,but swapped the distributor and igniter to the 91 you could barely see anything on the screen,it was way down at the bottom of the screen and a very tiny signal,i geuss i will check my wiring again,thanks everyone for the responses,sbarrett any other ideas anyone,please chime in,i really appreciate the help.

 

after many weeks of searching for the problem, i decided to replace the igt wire from the igniter to the computer,and it fixed the problem,much to my surprise,so if anyone else has this problem,be sure to check the wiring very carefully,thanks for the help forum members.