Truck running funny sometimes and other times running perfect.
I have a 1990 F-150 5.0L 4x4 with 155,000 miles that has an issue. A couple years ago I had my fuel regulator replaced because it was running crappy. Now it runs good sometimes and others it seems to have power loss and miss or chug. It fires right up every time and idles good but I can smell a lot of fuel when I sniff by the engine even with the hood closed. What to do other than replace fuel regulator and check fuel pressure? It also has a new fuel pump, filter and spark plugs.
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Re: Truck running funny sometimes and other times running...
It sounds like you really take care of your truck,But being that it is a 1990 with the mileage you stated,The only thing that comes to mind about your problem, Is the rubber "O" rings that seal the injectors,They are probably not soft anymore and that might be where your smell is coming from.this could also be your light miss or chug too,But if you do check them for hardness,really check the injectors over before you reinstall them,check the screen on the bottom to see if any rust particles are trapped in there from the fuel tank and lines.
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A backfire usually indicates a timing issue. I recommend a minor tune up, which will include new plugs and wires, as well as checking/setting the distributor timing. An oil change is also recommended after the issue is corrected, as offset timing can cause fuel to remain in cylinder, which then bleeds past the piston rings and ends up in the crankcase with the engine oil.
How long since over-all tune-up? Use a gage and check proper fuel pressure, tbi fuel pressure 9--13 psi. 5 psi won't start and run a v8. In my opinion. I don't know liter size of engine?
Can you check applicable trouble codes? Your obd1, you should be able to check some codes, if your check engine light works. You use a jumper wire between the A & B terminals at your datalink connector, then turn the key just till the dash lites come on, then the mil starts flashing, you count the flashes to get the codes. Your looking for two digit codes.
If you think ignition and or valve timing is off, check it. My info for ignition timing, just says to check the decal under the hood for specs.
Could be a long list of things including dirty injectors or a leaking EGR valve. The coil could be weak or the distributor cap and rotor may be shorting to ground. Has the fuel filter been replaced ? You'll have to go down the list and try to eliminate components to narrow down your options. Does it happen all the time, only when you are accelerating, etc.
if the exhaust blows black when this issue starts,then probably a bad regulator,which the check engine light will come on then go off a few times telling you a code,oxygen sensors...if not,try replacing the throttle position sensor,its tough because its at the bottom of the throttle body,and the screws rust in and sometimes breaks,so the throttle body has to come off.you have to figure out where the gas smell is coming from at least,it could be blowing back into the air breather.also check the vacumn lines(green hose and red hose) on top for cracks.the red should be for the regulator
I had a similar problem @105k. I had changed the fuel filter but it was still sending all kinds of codes that were related to 2 problems. Long story short, the main problem was a bad trigger assembly in the distributor (rough running) and the other was a loose engine to body ground (engine code issue). Good luck, this worked for me, now 171k.