What do you guys think about this:

1990 F150, 4.9 line 6 with a 5 speed. I purchased the truck about 2 weeks ago, truck ran fine with no problems except that the clutch was about to go. I replaced the clutch, go to start the truck and it died right after starting, restarted it and it ran fine but it had no power at all and this continued for about 3 days. The other night I went out and looked at it thinking maybe we knocked something lose when doing the clutch. Everything looked good, fuel lines were straight, nothing dangling anywhere, I jiggled around a few vacuum liines, and beat out the air filter some (it was dark so couldnt tell how dirty it was) and the next day it ran waaay better but it still has a significant power loss especially in the upper rpms and it has a small miss now. It has a new fuel filter, spark plugs, wires, distributor cap, ignition coil. I'm not sure if this is a fuel delivery issue or maybe something with the timing. I'm purchasing a new air filter tonight maybe that'll make a difference but any advice would you guys could offer would be great!

 

Welcome to the site!

Struggling in the upper RPM range can be a sign of airflow restriction - kink in the exhaust pipe, plugged cat, plugged air filter, etc. Also could be timing, but unless you moved something - would place it lower on the list of things to check.

When were all the new ignition parts installed, and what brands of parts? Looking at the possibility of a crossed plug wire, or a failed/failing part as a potential culprit.

Could be a fuel issue, although I would place this lower on the list of possibilities.

Pulling the computer codes is always recommended as a good place to start. If codes are present, then you have something to chase down. If no codes are present, then you have a pretty good confidence that the problem lies with something the computer doesn't watch or monitor - such as a bad plug or wire.

Good luck, and keep us posted!

 

Thanks!

I'm unsure of the plug wires/distributor brands as this was done by the previous owner and I didn't ask. The ignition coil is an MSD brand and I put that in 2 days ago, to my understanding the plugs/wires/dizzy are a few weeks old at the most. I'll take a look at the exhaust as we did have to lift the tail pipe up a little bit with a jack because it was in the way of the crossmember, we didn't put alot of pressure on it but ya never know. As far as trouble codes go I know I have to jumper a wire from the STI connector to the EEC harness (whatever its called) could I do so by using a paper clip?

 

Here's a how-to link for reading codes -
https://www.f150forum.com/f10/how-re...es-obdi-10907/

I get persnickety about ignition parts - have had some bad experiences with the bargain-basement / store-branded stuff.

 

Thanks for the sticky, lots of good info. My truck has a check engine light on it so once I jumpered the two connectors for the KOEO test would I just watch my CEL flash or do I still need to hook up a voltmeter?

 

Voltmeter isn't needed unless you don't have the check engine light or if it is blown out.

 

Error code scans & Fuel pressure test. Is the new coil a stock replacement voltage or upgrade? If you burn out on the flash count method:http://www.handsontools.com/Equus-In...ol_p_5574.html $22.77/ ships next day.

 

I was messing around with it some today and noticed a hissing sound coming from the backside of the engine, its hard to pinpoint where its coming from over the engine noise but I've narrowed it to the EGR valve or that little 2 way vacuum valve directly below it, I never noticed it before but then again I never listened for it either. I sprayed a soapy water mixture on the hoses but I didn't see any bubbles. I also unplugged the EGR connector and took it for a spin expecting not to make it far but it didn't drive any differently than how its been except that the engine light was now on, plugging it back in didn't make a difference in performance either. Is it possible I have a faulty EGR valve? Next day I have off I'll get on to scanning for error codes.

And ymeski56, the coil pack I have is "supposed" to be a little better than stock, its an MSD. I've used them before and have never had problems with them.

 

The hissing would probably be a vacuum leak, and soapy water won't do crap. You can't see bubbles when they're sucked in. Use a length of hose as a stethescope to listen where the leak is coming from. There will be EGR codes if there's a problem with it.