rough running problems

[Redbeard90]

Just wondering if anyone else has this problem or can tell me how to fix it. Engine runs rough, especially when first started, until it reaches a certain rpm. I don't know what rpm because the tach doesn't read right(another problem I'm trying to figure out). I was getting on the highway after work. Got to 3rd gear and pressed the pedal to a point where it was still accelerating and held it there. The truck ran really rough but when it got that certain rpm, it's like something adds a bunch more power and it smooths out almost like it had a dead cylinder and then starts firing on all four again. I've changed the O2 sensor, fuel filter and all 8 plugs. Could it be one of the coil packs? Plug wires? One of the codes I got out of it had to do with loss of dual plug input control. Any help would be greatly appreciated!!


I have recently noticed that when I first start it on a cold morning, it runs perfect. After a few minutes, it's back to running rough. I've been told it could be the ignition control module or crank trigger. Could it be the coolant temp sensor or throttle position sensor? It will run great if it is at full throttle.


Thanks

 

[Redbeard90]

anybody??

 

[fastpakr]

Stop guessing, and stop replacing parts.

Grab the codes you've got and go to your public library. Find the Mitchell book for 1990 domestic light trucks, and look up the pinpoint tests for the first KOEO code you get. Follow the test until you solve the problem, then re-run the codes and deal with the first code you get at that time. Continue until the Check Engine light doesn't come on and you get 111 pass codes in KOEO and KOER tests.

 

[Redbeard90]

I've got the codes and list of what they mean, but don't know what to change to fix the problem. One code was loss of dual plug input control. Where do I look for that? Another had to do with the SPOUT being grounded, I think that's why the tach reads wrong. Every once in a while the CEL goes off and the tach reads right. Is Mitchell available online?

Thanks

 

[fastpakr]

I've got the codes and list of what they mean, but don't know what to change to fix the problem. One code was loss of dual plug input control. Where do I look for that? Another had to do with the SPOUT being grounded, I think that's why the tach reads wrong. Every once in a while the CEL goes off and the tach reads right. Is Mitchell available online?

Thanks

No - the Mitchell manual is not available online. If you want one all the time, you can probably pick one up on Amazon. I got mine for about $10. They're pretty straight forward to use. Just flip to the Ford section, find the code number, and it will point you to a section with a troubleshooting sequence to track down the specific cause.

 

[Bryan22]

I've seen this before on this forum (tach not reading right and throwing a spout code). seems like it usually turns out to be the ICM, you should have it checked.