Ok guys i've always came here to read but now I half to ask for help . I have a 1986 f150 4.9 without pollution crap . Pretty bare bones . Ok I have a new engine 2 years old . About 6 mounths ago it started running like crap , like one of the plugs fell out an am about out of ideas . This is what I have done recently . New carb , headers , coil,plugs, wires , cap, rotor button , icm, fuel lines . Its hard to start hot shakes all over . Backfiring threw carb . An Orange spark on all plugs . Any help would b great . But I'm at a loss .thanks .

 

where is the timing at?

 

Ok you throw a bunch of parts at it and still runs like crap.


First thing I would do is a compression test on the motor so I would know all cly are good.


If they all check out good I would then check for vacuum leaks. Base of carb and along the head & intake manifold.


May even check to make sure the timing between cam & crank did not jump along with a timing light check.
Dave ----


edit: I would also check to make sure the cam has not gone flat. A bad/flat exh lobe can make the carb back fire as the exh has no where to go because the exh valve does not open.

 

My first question is, what ignition system are you using? And what carburetor?

 

X2. That is how I found a problem with my engines running capabilities (not to mention extremely horrible acceleration).

 

Ok I couldn't find any vacuum leaks . Timeing is rite on . I hate to think flat loab on a two year old engine . Could it b a fuel pump maybe ? An I remember rite when this happen I'm in a rain storm driveing down the interstate an hit a huge pot hole an broke a big hole in the exhaust manifold . But I don't get the orange spark an no powet either . Yea I'm stumped .

 

Did you perhaps get water under the distributor cap and or sparkplug wires?

 

All been changed .

 

Engine firing order correct? How are the coil's connections?

 

Fireing order rite on . New accel coil . New icm on distributor .

 

So, you're still using the factory ignition system, correct? Again I'm going to ask - what are you using for a carburetor?

 

Yes same ignition as always . Yes same carb but new an only a week old . The only thing that I can think is a burnt wire . Or repace the whole distributor .

 

OK, last question... what, exactly, did you remove when you took off the "pollution crap?"

 

I bought the truck 3 years ago it was already gone an ran great just wore out . So I had a new one put in an did great for a year an a half untill 6 months ago . An its been down hill sence .

 

Well, here are my thoughts....

A 1986 6-banger engine came with computer-controlled fuel & ignition systems. By removing "all that crap," the computer (which runs the show) has become sufficiently freaked out such that the engine is now operating in a crippled state, i.e. is no longer advancing the ignition timing... while it will still run, performance will be severely lacking (e.g. 0-60 MPH will require half a minute) and gas mileage will be poor.

You might pull the computer codes to see what, exactly, it's complaining about, since you apparently don't know exactly what was done.

You can either put "all that crap" back where it was so the computer is happy again, or replace your fuel & ignition systems with non-computer-controlled versions. A common approach is to use the previous-generation's DuraSpark II ignition and non-feedback carburetor, look at "DS2 swaps" (and similar) up in the sticky at the top of this forum and elsewhere on the Internet.

You can also use an aftermarket ignition system, e.g. the General Motors HEI things combined with an appropriate non-computer-controlled carburetor.

I really doubt the engine was/is worn out (this is one of the auto industry's best-ever engines, look it up on the 'net) it just appears that way because the computer is holding it back (because it is no longer getting the correct input from all its sensors).

There is a fairly never-ending supply of these kinds of threads in this forum, where somebody who doesn't know what they're doing decides to "clean up the engine bay" and "remove all that (smog) crap" and the thing then barely runs, they give up and sell the entire thing for cheap.