Ok guys, I have a 90 F150 300 6, 5 speed. I have a sputter happening. 1/4 throttle and it starts to sputter. Floor it and the sputter goes away, but it goes into a full power suck at that point. Idles fine of course. I took a look at my plugs, wires, cap and rotor and everything looks fine. They are not very old. I decided to try the EGR trick to see if it ran better. I disconnected the green line and took it for a drive. It seemed to run slightly better but not a lot. The thing that got me the most was that every time I've heard about doing this trick it says the check engine light will come on during your drive. Not a big deal because you're just testing to see if it runs better prior to doing an EGR delete or the EGR smaller whole trick, but in my case it never came on. I drove it for about 4 or 5 miles and the check engine light never came on. It made me think that perhaps there is a vacuum issue, so I started replacing obvious old vacuum lines, however that did nothing. I guess at this point I was mostly curious why it would not throw a trouble code or check engine light with the EGR valve unplugged? Does that clue lead me to another possibility? Thanks.

 

Early 1st gen EFI vehicles like this are very slow to react to problems, it may take several drive cycles to even set a code and not all codes will trigger the CE light.
But your testing has eliminated the EGR as a potential source of your problem, good work there, I suggest you test fuel pressure next and pull codes to see if anything electronic has been flagged, your stutter could be ignition related.. the ignition module and PIP sensor are potential sources, and if fuel pressure was low the engine will run lean which could produce the same type of problem.

 

There are a couple of things I have forgotten. This truck sat around for many many years. I resurrected it about 5 years ago. Fresh plugs, wires, cap, rotor, and while driving ut very little over the years, I have replaced the computer, the and the egr valve. At first, I thought the clutch was slipping because I had changes the oil and I thought perhaps the new oil somehow has broke through the rear main and was leading to lack of power...yeah, not it. It has seemed to be lacking power for a while and I'm still not sure the egr trick won't help with part of that, but the one important thing that I forgot to mention is that this seemed to get worse after a car wash. I thought something electrical got wet and would dry out. Didn't seem to dry out. So I thought maybe water got in my gas tank somehow...added a lot of Lucas fuel system cleaner...didn't make a dent in it. I'll hook up a code reader and see if it is storing a code...even with no light. It's running so bad, I'm almost afraid to drive it around that much. Yesterday, while doing the egr trick, it was much harder to start. Also, does it matter if you plug up or not the egr itself? I plugged the line, but not the egr. Also, it talks about unplugging the battery to reset the computer, but that's after you do the egr delete or 1/8 inch hole, right, not just on the test? Okay, thanks guys.

 

You could be having an issue with the throttle position sensor having a dead spot. It can be check voltage/ohm meter to make sure it has I nice smooth reading signal output.

 

EGR trick?
When you plug or remove the line to the EGR valve, that makes the pintle valve not move on the EVP sensor
When the processor sees that, it will lock the timing et al, and run like ****
The "trick" is to leave the EGR valve and its EVP alone and just shut down the port size with a piece of beer can
That original EGT valve port is about the size of a nickel; if you drill a hole in the beer can aluminum the size of a pencil, you will notice a performance improvement

 

Excellent point, and something else I forgot, I hooked up my Tester and checked the TPS, and it looked like smooth sailing all the way up and down the throttle. It idles fine, but lately, whatever it is, it is getting worse. The idle is still okay, but much harder to start and I never really noticed it when I was sitting in the truck just revving the engine, but lately, it seems to have gotten worse with a bog even just revving the engine. Before, it seemed to be 2nd gear where it was most effected, now 1st is a struggle at first to get going.

 

Yes, my plan was to do the trick, but I read you can test if it helps at all by just disconnecting the line and plugging the line. I didn't noticed much of a difference at all. Maybe even a worse difference when it came to starting the truck. Driving it, I noticed some difference to the positive, but not that much. I thought maybe I missed a step in the part where you plug it and drive it to see if that is a difference at all. I didn't disconnect the battery, and I didn't plug the nipple on the egr. Does that part matter for testing if it makes a difference at all?

 

The EGR system isn't your problem, why are you stuck on this?

 

2x on this. If you don’t have a check engine light or any codes showing up when you scan it I’d be checking the tps personally. It’s free to test. The PIP Would also be a good thing to test IMO like someone else said here. Both can cause the symptoms you mentioned but anyways… always a good idea to check for codes.

 

With a vehicle that has been sitting for extended periods the #1 most common issue is weak or dead fuel pumps, so a fuel pressure check should be at the top of the list. A motor will run with only 20psi fuel pressure but it won't have any power because of fuel starvation. The 300 in particular requires 55-60psi at the fuel for correct operation.

 

So, I would love to say I have it figured out, bot no such luck. I do have updated info.

1. I have 2 codes. 34, and 67. Is it possible that 34 is from unplugging the egr and plugging it? I rehooked it and pulled the battery cable, but maybe it did not reset?
[size=16px]34[/size][size=16px] [/size][size=16px]EVP voltage above closed limit.[/size]
AI says 34 could be a tps, however I tested it and it gave smoother numbers up and down.

67 is supposed to be a neutral safety switch thing, but I think that is an old code.

Okay, more info...i put a fuel tester on it. What a fiasco. The tester would not go far enough in to get a rating but eventually, I got something.
1. Key on, not running...pressure started at 10, but after 3 minutes, went up to 22lbs.
2. Running, started very low, but over about 4 minutes it worked it's way up to about 39 lbs.

I'm honestly thinking of hitting the fuel filter first.

Any thoughts after the new info?
Thanks

 

OK good work with the testing. You are however running into a couple common problems I will address.

1. The fuel pressure testing issue is common, the fix is easy just remove the shrader valve core before attaching the test hose. The shrader valve is the same as one found in a tire valve so it can be removed with the same kind of tool.


2. There seems to be an issue with new EVP sensors where the pin is too long and it actually produces a reading that is too high for the valve in the closed position. You can test the resistance value of the sensor with a multimeter(engine off and sensor disconnected) or probe the pins for the sensor voltage with it connected, and if it does seem to be a problem try another or modify the one you have.

 

On the fuel PSI test when you first turn the key to on / motor off the fuel pumps should run for a few seconds to "prime" the system and then hold.
When you start the motor the pumps should run all the time and the PSI should be with in spec.

When you said the motor was off key on the PSI was low and them went high was strange, was this because of the valve in the fitting?
I never heard of this before and why I asked.
Dave -----

 

Yeah, I honestly think I was so frustrated trying to get the fuel tester to work, I kind of screwed it up a bit. It is possible either others have tried to fuel test this truck and somehow some old O ring residue was in Schrader Valve area or maybe the O ring that was in mine was tearing apart and leaving parts in there, but I was having to use a pick to get debris out of the valve even though it had a cap on it. Anyway, after cleaning it out, changing to another O ring in my gauge, I finally got it to start working. By then, I had already relieved the pressure from the line. As a matter of fact, how this worked was I thought priming the unit would fill it quickly, but it was doing nothing. So, once I got the gauge working, I just started the truck and even had to rev it up a bit to get it working a bit smoother, and then the gauge started working. It was pretty much at no pressure, but slowly worked its way up to 39 lbs while running, but it took about 3 minutes. It didn't go higher. With how slow it moved, I thought 1 of 2 things...Either the pump is struggling, OR the fuel filter is clogged. A clogged filter could cause it to rise slowly, at least in my mind, however any of the Fuel Regulator or others things I guess could theoretically cause some of that, but I am thinking clogged filter or bad pump. Thing is, I of course had just filled the tank thinking it could have been bad gas... so if it's the pump... well, at least I have a lawn mower jack, so it should fit right under there to help take out of the tank if I go that route. haha

 

Yes to clogged filter or a weak pump, the filter is easiest to change so that should be the next thing done. And before tackling the in-tank pump it's a good idea to test power at the pump connector, if it isn't getting full battery voltage it's pumping capacity will be reduced. A good pump will produce the required pressure almost immediately.