The cap can't be put on 180* out right? Most have that notch to make sure.

So can you trace your steps back to anything else you did between it running well and acting up?

 

ok guys either way I think it's time to change some parts and these wires also are not in good shape. Ignition coil, wires and spark plugs first. Then, if not, MAF sensor will be next. what do you think? Just motorcraft parts are pretty expensive (((

 

I'd start with wires. Try it - then coil (though I don't think they wear out that much. My F150 is 29 yrs old with 253k and has the original coil). And still don't understand how a bad coil can cause a spark through an open valve to backfire in the intake.

Can you save money with aftermarket wires like Granatelli or something? I've always just shopped em at an auto parts store.

 

Well, there was an engine repair works because of a head gasket leakage and oil problems. The car was in garage for about 5 months. After changing some engine parts I thought it will be a great if I'll change spark plugs also. After all we were unable to start the engine because of no spark condition. Ignition coil didn't worked. We finally managed to start the engine by connecting brand new battery and after that the car was working good. Right after 1 or 2 weeks I've discovered this problem. Then distributor died. Changed distributor, engine started, but now facing this problem. Engine itself runs great, good power, great sound, but this backfires....

 

Check timing. If no timing light, etch the distributor and motor where it is, turn it either way just a little and try it. Also what does the cap and rotor look like? Check for arc tracing marks.

 

Well, I'm far away from any of those stores. I'm getting parts from 1 to 2 weeks right after I place order. So I can't experiment, I'm just trying to buy one thing one time.

 

We have checked timing with stroboscope, rotor and the body are in right point. Dizy is new, rotor is new.

 

Wait - you changed the whole distributor by taking it out and replacing it? Not just the cap?

I'm betting your 180* out.

 

yes, whole dizy, but I'm saying this problem started before changing it. thanks guys for you help I really appreciate that!

 

ok, if not coil, what else can cause backfires through intake? Dead MAF will cause RPM to go randomly up and down, so I can't tell it's MAF. EGR? not really, what else?

 

Firing through an open intake valve is the only way. Think about it.

Either an intake valve is not closing completely like it should (stuck valve, bent valve, lifter failing, bent pushrod perhaps, pushrod not seated in rocker arm correctly, cam timing not set correct) when the plug fires,

or the ignition timing is off (intake valves closing properly but distributor in wrong, plug wires not connected in proper firing order, arcing in dist cap so a wire fires at the wrong time or two wires are firing simultaneously), allowing a cylinder to spark when a valve is open.

Mechanically those are the only ways a cylinder can fire into the intake.

 

This sounds very interesting! I found worn wire together with another while I was checking wiring order a minutes ago. hmm...

 

but I still think why it happens mostly when engine is cold. Also, as you say, valve not closing, in this case it will backfire always, regardless whether or not the engine is warmed up.

 

I'd start with wires as well.

 

Yes - unless it is a sticky lifter that works better once the oil is warm.

That used to happen more often back in the day than today. We used to add additives to ease a sticky lifter.

Maybe you can tape up that bad wire and re-route it so it doesn't overlap another, and try the engine then.

 

I'll isolate damaged wire tomorrow and check it. I like your opinion about sparks more than valve )) I don't want it to be valve!

 

same story (

 

Checked all the wires and the cap?

 

Yes. Some techs here are saying that the bad or mismatched spark plugs can produce this problem as well as bad wires. Not sure about coil, but it seems that when spark plugs aren't able to pass high voltage it stays around coil and that's why it's illuminating. When they are warmed, they work better. Not sure but close..

 

Motorcraft coil
Motorcraft spark plugs
Motorcraft spark plug wires
Motorcraft water temp sensor

on their way
wish me luck guys