hi guys i have a 91 300 6. About a month ago i noticed it cutting out at higher speeds, we replaced the fuel filter and it still cutout pretty bad at cruising speeds. Just replaced distributor cap and the cutout is still there. It sometimes will trip the check engine light. Its very sparatic, sometimes it runs good and other times its cutting out big time

Any ideas to what could be causing my issue??
thanks

 

Check fuel pressure and check the codes.

 

i pulled the codes. im guessing they are 2 digit? if so they are
33-throttle position sensor(noisy/harsh on line)
45-coil 1 primary circuit failure
43-oxygen sensor

 

Yea, any of those 3 could do it. I'm not sure which one I would do first. Coil and coil wire probably. If you have an aftermarket tach hooked into the coil wire, unhook it and see what happens.

 

<table border="1" cellpadding="2" cellspacing="0"><tbody><tr><td>33</td> <td> </td> <td><center>X</center></td> <td><center>X</center></td> <td>EGR valve opening not detected.</td></tr></tbody></table>
You can at least for the moment disregard that one, its not the reason for it cutting out and as long as its closed remains so its not a big deal can deal with the larger issue first.

<table border="1" cellpadding="2" cellspacing="0"><tbody><tr><td rowspan="2">45</td> <td> </td> <td><center>X</center></td> <td> </td> <td>DIS coil pack 3 circuit failure or coil 1 primary circuit failure.</td></tr></tbody></table>
Don't have a coil pack, not a DIS system. Might be problem in primary circuit to the coil you do have, power cuts out due to problem in ignition switch and or wire between the two for example. Be worth minute to check out the connection and test the coil, intermittent connection type issue wouldn't be limited to cruise speeds so not likely the problem. Coil yes connection with it no not so much.

<table border="1" cellpadding="2" cellspacing="0"><tbody><tr><td>43</td> <td> </td> <td><center>X</center></td> <td> </td> <td>HEGO lean at Full Throttle.</td></tr></tbody></table>
Points to one of first suggestions, check fuel pressure and while at cruise speed (provided of course passes tests at idle.

45 to 60 psi at idle vac line connected at fuel pressure regulator (50 to 60 psi KOEO), KOER vac line disconnected at FPR pressure should increase 5 to 10 psi.

Now it might be 33 and 43 are directly related, factory plastic vac lines are cracked/broke and leaking (possibly eliminated at some point) and or metal vac reservoir on passenger side inner fender rotted out = little or no vac to anything/everything needs it.

Now vac line to FPR is direct from intake, what is supposed to be and what is after some 20 odd years isn't always the same, if not sure definitely worth a look see a look see make sure all vac lines are routed as they should be and air tight.

Code descriptions based on assumption that you ran KOEO and CM test/check, KOER was not done.