Hey all, over the summer I began the process of reviving my 94 F150. It sat for a while and I replaced a whole laundry list of items. The motor now has gt40 heads and a Comp 35-349-8 cam with trickflow springs. The heads were disassembled, cleaned, checked, reassembled, and tested by a local machine shop before installation. My issue is the motor seems to idle roughly. Almost like a miss by cyclic if that makes sense. It revs great with no hesitation at all. When driving, it seems to pull ok but the seat of the pants dyno thinks it is low on power. Motor now has 500 miles on it.

Work done:
GT40 Heads w/ trickflow springs
Comp 35-349-8 XE264HR cam
New motorcraft Cap, rotor, copper plugs, and wireset
Plug wires routed correctly per the many documents I found on here
MSD 6A Box
New timing chain
Water pump
Thermostat
Fan clutch
Radiator
All cooling hoses
Base timing at 10 degrees spout out
New IAC
Long tube headers
Dual exhaust
All smog items removed
Replaced all vacuum lines
New fuel filter
Cleaned injectors with new o rings and screens. Tested for operation on the bench


KOEO Codes 636, 565 (CANP not installed), 10, Continuous 332, 556
Will clear all codes and repeat plus do KOER tonight

Tested:
IAC
TPS
HEGOS
MAF
Timing
Coolant temp sensor
All normal ranges
Spark plug wires ohmed out less than 7k each.

Fuel pressure at 32 engine running with vac applied, Jumps to 42ish with vacuum removed and capped. Pressure stays after engine turned off.


Used my handy IR thermometer to check the header tubes:
1,2,3,&4 all around 340 degrees
5,6,&7 all at 500 degrees
8 at 420 degrees
Would this indicate a lean condition on those cylinders?


Exhaust smells strong, but no black smoke or soot at tail pipe. I plan on pulling the plugs this weekend to check them now that I have put some miles on the motor. I may redo the compression test as well, unless someone smarter has a better direction to go in. Thanks!

 

check the O2 sensors? May be running rich because of those. Never mind. missed it in the list.

332 is EGR flow
556 is fuel pump circuit failure. clear those and see if they come back.

636 transmission oil temperature switch reading high voltage or opened wiring

 

KOER test:

311 Thermator / air system fault during test (All missing, not really surprised)
225 Knock sensor fault during dynamic response test.

Could it be a faulty knock sensor or is the knock sensor picking up on something?

 

is your timing set correctly? the dynamic response test, did you floor it briefly when you were supposed to? (engine at normal operating temp) when I say floor it,it means from idle to wide open and back to idle in about a second.

It could be a faulty knock sensor ,or you just didn't floor it when you were supposed to. If it is the knock sensor detecting something,check your timing.

 

Timing set at 10 degrees with spout out. I floored it right after the indication to do so. I ran the test 3 times and got the same result, but there is a chance I am just timing the WOT wrong. I am initiating the test with the innova 3145, and I will try just the jumper today.

 

Code 225 just means the knock sensor did not "sense" any pinging during the test. This is not that unusual and is typically not a problem. If you run premium fuel, live at a higher elevation, cool/cold ambient temp. or have the timing retarded there may not be any pinging for the knock sensor to trigger. Even at seal level with 87 octane and correct timing you may not get any pinging during the test.

If the knock sensor were faulty it would only allow pinging with the engine under load since the computer is not pulling any timing. It will not cause idle quality/missing issues. The other part of this story is good lucking finding one if you want to go down this bunny hole.

 

Gotcha. I was just worried that a failed sensor would send a constant knock indication to the computer and cause it to pull timing.

 

If in doubt...unplug the knock sensor. No harm, no foul.

 

That is a good idea. I am going to clear all the codes again and drive her around and rerun the diagnostic tests. I cant do the compression check till Saturday when I have more time. Does anyone thing it could be a too restrictive muffler or exhaust? Its another WAG that I was thinking about. I have long tubes to 2.25" dual exhaust to real quiet dynomax super turbo mufflers and side exit in front of the drivers rear tire.

 

I recommend you solve Code 636 before moving on.

 

Quick update. I found a bad vacuum connector on the EGR solenoid (explains 332). Brand new, not 500 miles on it and it looks like it fell apart. Replaced all of the new hard lines with vacuum hose. Runs noticeably better. Not sure it is fully correct but it is an improvement. I have to put some miles on her before I run the self tests again to see if the other codes return.

 

Is this an SD or MAF truck. Either way my experience says the motor will never idle factory smooth with that cam.

 

It is MAF. I expected a different idle witht the cam after reading all of the recommendations on here, especially from you. This issue was a noticeble roughness that was not there initially. I am hoping it was the garbage vacuum connectors I used. I should know more tonight or tomorrow. Thanks!

 

As an update for this, it wound up being an ignition problem. I found corrosion on the power and ground wires for the MSD 6A, and the Accel coil that has been on there since I bought the truck 18 years ago. I cleaned the ground point on the fender by the battery as well as the 12v connection on the solenoid and re-terminated all of the connections between the MSD and the coil. This solved 90% of my issue and the truck immediately revved smoother and pulled harder. I replaced the coil with a Motorcraft one and replaced the new Autozone wires because they were questionable with a set of 9mm Ford performance parts ones with dielectric grease and proper routing. I think I may have some additional wire corrosion somewhere as the truck runs just a little rough only when its wet out. I will try and track that down soon. As a bonus I went from 9mpg to around 16mpg after all the work. Next time I resurrect a vehicle I am just replacing everything lol.

 

Great Job! You didn't just throw parts at the problem but went by looking at what could be or was a contributing issue and eliminated that which was known and suspected!!!!!!!!!