Alright guys I’m hoping you can help me out with this because I’m lost at this point. I have a 1994 Ford F-150 XLT 351W E40D Trans. Just over this past spring it’s been starting to misfire and it just keeps getting worse. I’ve done the basic tune up (plugs,wires,cap,rotor, made sure it was right firing order) and still nothing. I changed my fuel pressure regulator and it has perfect fuel pressure. Redid all my vacuum lines as well. Still misfiring….. it seems to only misfire when warmed up and if you listen to the exhaust it sounds like a puffing sound. It doesn’t seem to misfire while driving but it definitely has a loss of power. Some people were saying bent valves so I did a compression test. 3 cylinders 135-140 and the rest in the 120s or low 130s. Will that cause anything and if so what would be my problem? If anyone could help me with this PLEASE let me know. Thanks for the help y’all

 

These are the compression tests
1- 145 5- 130
2- 120 6- 125
3- 140 7- 120
4- 130 8- 130
Forgot to mention I also changed the EGR and the sensor on top and the EGR solenoid next to the other ones. Also changed out the ignition coil, map sensor, and TPS

 

Have you ever checked the codes? For the most part you're shooting in the dark.

 

Ive checked the KOEO codes but not the KOER codes. I was planning on doing that tomorrow

 

Sounds to me like you should change your Coolant Temp Sensor also your Intake Air Temp sensor as both can cause misfires due to not being able to properly fuel the engine when the computers not being fed the correct temperature info of the air or water due to a faulty sensor.

I had to change my what I know is new but wasnt very reliable IAT yesterday as it was 65 degrees out and the intake sensor was reading 104 degrees and I didnt start the truck yet.I found this info on my Moates dashboard info which is alot more easier and more accurate than using an ohm meter and a temp gun to read the sensors for reliability as the info Im being shown is interpretted how the system reads the sensors to get feedback.

Every once in awhile the truck would intermittently buck out of nowhere were my symptoms which I thought could of been fuel or timing related issues that shown up after the weather cooled heavily but turned out to be as already metioned ;-the IAT..

Another thing to note is the CTS doesnt fully control the ECU until it hits 195 degrees unless you can get into your ECU and change the temp parameters to work with a lower temp thermostat so just in case you didnt know you also need a 195 degree thermostat installed in the truck for it all to work correctly too.




Good Luck

 

So what codes did it give? In general, if it's throwing KOEO codes, it's pointless to try running the KOER ones until the KOEO tests pass.

And Yes, you need to have the engine fully warmed up and the thermostat open before you run the KOEO tests, if you really want valid tests.

 

Ok thanks. I already put in a new coolant temp sensor but I have not done the IAT valve yet. Of course it’s not in stock anywhere so I’ll have to order it

 

I have zero codes. I check every single week and there’s nothing. I had an egr code for the longest time but I figured that out and now it’s gone. I’ll run the KOER tests today and see if there’s anything

 

If you're not getting any KOEO codes, I'd venture to guess you've probably got a ground issue. If you haven't already, go through and clean all of them.

 

Ok thanks, will do. I’ll put up the codes later today

 

Update: I checked the KOER codes and still nothing. I timed the engine to make sure that’s all good and it is. Cleaned ALL grounds and still nothing. Anyone have any suggestions? I’m so lost at this point. Please help me out!

 

What happens if you disconnect and cap the EGR vacuum line and take it for a test drive? Any difference?

Do the same thing with the O2 sensor, disconnect it and drive around for a day.

 

Ok, I’ll try that out on Tuesday. Wont be driving the truck tomorrow but Tuesday I’ll try it out. Thanks for the help. I’ll keep you updated!

 

Update: I capped off the egr and still did the same thing. I will do the O2 sensor when i go to work tomorrow. What are the chances of a bad lifter. I do have a lifter tick. Also, could it be a fuel injector? Do those injectors tick when they go out?

 

Exhaust leaks can sound like a tick as well as the EGR tube. Use a long piece of tubing and go around the components and listen for the tick with the hose. Of course be careful of the fan etc.