ok i have a 1990 f150 2X4 3 spd automatic trans.....

whats goin on... ok while im idling it feels as if there is a slight miss....maybe one cylinder....every third time misfires...maybe idk, now while im driving it it idles fine, but if i floor it . . it stutters spits and has almost no get up and go....im gonna change the fuel filter friday but the currnet one isnt that old....i added some water remover so i know its not that...then i added some chemtool to try and clean things a bit...still doing it... i have played with the timing by ear, but it doesnt smooth out like a v8 would....i tired a timing gun and the white line is all over the place!!! i dont know what to do....if anyone has had any similar problems feel free to throw them my way!!!! i can use any help i can get....thankyou

 

Start simple...with the hood up and the engine idling, grab a can of WD40 and start looking (and LISTENING) for a vacuum leak.

 

well i thought i heard a vaccuum leak but i cant find it, whats the wd40 for ??? LOL please let me know how to use your technique there, ok, PEACE and thankyou for reply!

 

Spray the WD40 at all of your vacuum lines...slowly....when you hear the idle pick up, you've found your vacuum leak.

 

no kidding!!!!! why didnt i think of that lol would carb cleaner or eather work too?

 

How ld are the spark plugs, distributer cap, and rotor? I'd have to pull them and get a good look............
Bob

 

Carb cleaner, or starting fluid will work.

As Bob mentioned, there's other things to look for as well, but I always start by looking for a vacuum leak.

 

This is a common issue with EFI 300's. It's got several potential causes from fuel delivery issues to clogged exhaust.

Fuel: even if the inline filter is good one of the pumps could be having an issue. The intank low pressure pump could have a pickup obstruction. The inline high pressure pump could be fouled or failing. Crimped fuel line (delivery and/or return). Fuel pressure regulator could be failing or just have a bad vaccum line. clogged injector(s). Bad fuel relay. Faulty O2 sensor.

Ignition: Cracked or fouled cap or rotor. Failing coil. Plug wires. Fouled or damaged plug(s). Plug(s) that won't stay seated. Failing TFI module.

Intake: Obstructions in the ducting. Dirty filter. Bad PCV valve. Fouled or failing EGR. Bad TPS or IAC in the throttlebody. Damaged manfold causing a vaccum leak.

Exhaust: Anything that is causing additional restriction.

These are just starting points. But all of them can contribute to your issues.

 

omg how disturbing....

ok updating what ive done today:
new fuel filter, new pcv valve, checked for vacc leak, no leaks yet.... new set of plug wires, spark plugs are new (4 months old) with about 100 miles on em, air filter is new and coil is new about same time period....

it is still stuttering but not as bad, i added some fuel additive....cant get name of my head at second.....good stuff though, i only use good stuff.... i bought some carb cleaner to look for vac leaks, first i manually checked all those vac lines w/o taking them off....then used spray to test....maybe my vac pump is goin out? how do i check it? how muc hair does it put out? autozone said it could be the sensor on the top of the throttle body, but its fairly new too, plus i cant affor 70 bucks right now lol hell i spent 40 tonite alone..... new plugs wires made the most noticeable difference though it idles smoother but still drives choppy.... tomorrow im gonna replace the cap and rotorthen go from there, if you guys have any ideas on what i should test next, let me know, thankyou so much for your help! PEACE!!!

 

You don't have a vacuum pump. Your vacuum source is the 'tree' on the passenger side of the intake manafold plenum.

Start with one system (sounds like you've started with both fuel and air) and just start checking everything. Unless you see something that suggests troubleshooting a different system.

Since your next project steps are ingnition stick with it. Hopefully you have a multimeter. Do things like cleaning all plugs with contact cleaner and applying dielectric grease/gel before reconnecting. OHM's test plug wires. At least try to visually inspect the entire engine wiring harness for breaks and shorts.

PULL CODES!!! The computer stores a lot of fault codes that don't trip the CEL. These are actually your best starting point.

 

ok i was told that codes on my truck wont stay in memory because it wasnt designed to store the codes, only when the engine is running, now if i owned a 95 or 96 and newer, there is a memory that stores codes for so many days....

this morning i changed the plug wires and its a little better but not much.. later i will pull all the plugs, i was gonna change the cap and rotor becuase i thought it be like 10 bucks....ya know like it used to be a few years ago lolo, 25 dollars right now for the cheapest duralast cap and rotor, un flippin real!!!!! so im sticking with my old accell one, its still in good shape lol

could it be bad ground maybe......? is there any relays that control anything ignition wise??? what aboput injectors? they shouldnt have junk in them because of the fuel filter right? man id hate to pull them, anyone who has worked one of these fuel injected 4.9's...knows it sucks to take loose all that crap....last time i had problems getting #6 injector to seal lol

thankyou for any help and all previous help, PEACE!

 

a good friend of mine said it sounds like i have some really bad watery gas, so tommorrow im gonna add a bottle of 90% alcohol to the tank to try and dry out the water....ill keep you updated with the results!

 

If your mechanicly inclined, get a good manual. Chiltons and Hayes both are good.

Also visit the Inline Six Forum above Ford Inline Six, 200, 250, 4.9L / 300 - Ford Truck Enthusiasts Forums

Your getting some incorrect information from your friend about Ford computers. The EEC-IV (which is what you have if still stock) stores several previous codes as well giving you ones that currently trip. Both of the manauls I suggested list detailed instructions on how to pull both types without a dedicated code reader. You can also visit Ford Fuel Injection for the same detailed instructions.

Yes, water contamination could cause some of the symtoms you discribe. But...I;m betting you have some system issues as well. It's an older truck, they need some TLC.

Even though troubleshooting diagnostics is a pain, it also teaches you how your truck functions if you do it right. The more you learn, the easier it is to figure out the next problem.

 

well thankyou for the advice, but the alcohol did the trick thus far....its running great....you dont suppose it sitting for 3 months had anything to do with the fuel going bad? dont it take longer to spoil? also as far as knowing my truck, its almost teh back of my hand, i rebuilt the motor myself in a day, by the book at that. everything on it is new except the head, block, crank and connecting rods.... the intake is original but i had it cleaned and the block was cleaned inspected and the deck checked. the head got a complete remanufacture and the guy did a great job. the rest is new..... if i have any more issues with it ill be shure to ask for help here, this is a very helpful forums and im looking forward to being a part of this forums PEACE!

 

OK i needed to update the status of my Pain in the **** ford truck, the alcohol worked for like 2 days, now its sputtering again, i have adjusted the distributor to smooth it out. . . but it still misses and take off S U C K S i can fart it faster than it goes on its own . . . any ideas? i multimeter checked the plugs and they all read ok, cleaned the air flow sensor, and the throttle sensor on top of the throttle body. .. . . or w/e it is lol, no bad vaccuum lines that i can find, and all the electrical is looking in tact, so what cou8ld it be, it was running fine then one day it sputters. . . . idk, planning on a 302 / e40d combo in teh spring . . . will i need to chaneg computers or can u put an older version of the 302 in it?