UPDATE: Backfiring thru exhaust after engine cleaning

[pro-five-oh]

Okay so there's this 1987 Mustang GT (stock with 87,000 miles) that occasionally backfires under load. It happened after I powerwashed the engine at a coin-op car wash. The dizzy has the stock rubber boot over it, and I drove the car for a long time afterward to dry everything out. This is the first time I've had this problem, I'm usually good with powerwashing. :)

I'm thinking the TFI module is original and finally bit the dust when it got washed. Any other ideas?

[MichiganTeddyBear]

try this..

at night, hood open.. engine running (idling of course), take a spray bottle and spray it lightly around the plug wires. if you see anything (arcs, a 'glow', ect) i would swap the wires out.

I am thinking a wire is breaking down and your getting a cross-fire situation.

hell, its a cheap test to run too!

[Artbaileyjr]

Pull the distributor cap and spray the inside of it with WD-40.

Art

[pro-five-oh]

try this..

at night, hood open.. engine running (idling of course), take a spray bottle and spray it lightly around the plug wires. if you see anything (arcs, a 'glow', ect) i would swap the wires out.

I am thinking a wire is breaking down and your getting a cross-fire situation.

hell, its a cheap test to run too!

Poured water on the wires while it was running, didn't see any arcing or misfiring.

WD-40 in the distributor? I know that'd dissapate water, but that sounds a little harsh.

I looked at the TFI and the lock tab/plug (that locks the wiring harness to the TFI) is half missing. The orange gasket is still there, but that's about it. More fun for me!

[hypostang]

Wd-40 was designed originally to disapate water............................... ...W=water D= displacement 40

[gadget73]

wd40 works very well as an ignition drier. I know someone who used to load his distributors up with ether (starting fluid) whenever it wouldn't start. Thats something thats extreme.

[Nick]

I found a Mustang owner having problems with his car on the side of the road one day. I eventually pieced together that he had power washed his engine and ran into a running problem. A spray of WD 40 around the inside of the cap and a quick wipe down got him on his way.

[pro-five-oh]

Ok, you guys convinced me its worth a try. WD-40 in the cap it is then!

[pro-five-oh]

Ok, I still have the problem after doing the following:

1. WD-40 in the distributor
2. New plugs, wires, cap, rotor (they were iffy)
3. New TFI (the gooey stuff inside was dried out and cracked)

I will change the fuel filter now, but other than that I am out of ideas. Just to clarify, the problem is a backfire through the exhaust (popping sound) under heavy load below 2000rpm.

Help?

[NYC LS8]

Possibly a just a coincidence, but maybe the fuel pump is on the way out?

[pro-five-oh]

Possibly a just a coincidence, but maybe the fuel pump is on the way out?

You're thinking what I'm thinking. I'm hoping the fuel filter will help. No clue if its the original filter...so that is the next step.

Just about everything is original on the car, every time I mess with it something else breaks. :eek:

[skarhed]

Just about everything is original on the car, every time I mess with it something else breaks.
That's normal, and to be expected. Anytime I go to do something it is guaranteed that 2-3 other items will be discovered along the way.

[hypostang]

Low fuel pressure will cause a lean condition resulting in a backfire in the intake not the exhaust ... It can be mistaken though
just my 2 cents :)

[Fordace]

make sure you didn't cross the paths of wires 7 & 8, seen it before, it's called crossfire induction. Even if they are on the right plugs, the 2 wires should never cross paths because they are right next to each other in the firing order, so keep the 2 wires separated all the way to the plugs on the back drivers side....

try it Pro

[pro-five-oh]

make sure you didn't cross the paths of wires 7 & 8, seen it before, it's called crossfire induction. Even if they are on the right plugs, the 2 wires should never cross paths because they are right next to each other in the firing order, so keep the 2 wires separated all the way to the plugs on the back drivers side....

try it Pro

Thanks for the heads up. I made sure they aren't crossing paths and the problem is still there.

I changed the fuel filter and it might have been original! Fuel came out of one end and Pepsi out the other. I think the car idles better now, but there's still hesitating and popping out the exhaust.

I gotta find a fuel pressure gauge...maybe the pump is on its way out. A few of the plugs where pretty white, like its running lean. The car also ran for less than a second when I bypassed the inertia switch to de-pressurize the fuel lines, I usually get much more fuel pressure/running time than that!

Who knows, I'm running out of ideas. :(

[Fordace]

pro, disconnect the "salt & pepper" shakers and blow dry them with compressed air.

Also, you may have got the TP wet.....:rolleyes:

;) :dunno:

[pro-five-oh]

More info:

1. Fuel pressure with key on, engine off, after sitting overnight: 9 psi

2. Fuel pressure at idle: 38 psi

3. Fuel pressure after turning car off from test: 38 psi

4. When I bled the gauge down to remove it, almost no gas came out of the drain tube. That sounds bad to me.

I can't test the pressure when its moving, but hopefully someone can verify that the fuel pump isn't working very well anymore.

[pro-five-oh]

One more thing: someone put an aftermarket 190lph pump in the tank about a year ago but they didn't change the filter. I replaced it, and who knows, it could have been original. (motorcraft)

[pro-five-oh]

pro, disconnect the "salt & pepper" shakers and blow dry them with compressed air.

Also, you may have got the TP wet.....:rolleyes:

;) :dunno:

Hmmm....its possible! I'll address that after the hurricane blows outta here.

[Michael VII LSC/SE]

Ok, I still have the problem after doing the following:

1. WD-40 in the distributor
2. New plugs, wires, cap, rotor (they were iffy)
3. New TFI (the gooey stuff inside was dried out and cracked)

I will change the fuel filter now, but other than that I am out of ideas. Just to clarify, the problem is a backfire through the exhaust (popping sound) under heavy load below 2000rpm.

Help?

A timing or spark advance issue comes to mind. Maybe a sensor is responding slowly?

That's normal, and to be expected. Anytime I go to do something it is guaranteed that 2-3 other items will be discovered along the way.

I finally learned not to lay all over the car. And few if any technicians ever open the hood.

[Tony T]

Induction, you may have knocked a vacuum line loose when you power washed.

[pro-five-oh]

UPDATE: there's a poor connection at the TFI module. While powerwashing, the locking clip broke (and the gasket is loose) and moisture got in. A can of compressed air fixed the problem...and now I gotta find a new locking clip from the junkyard. Fun!

[hypostang]

UPDATE: there's a poor connection at the TFI module. While powerwashing, the locking clip broke (and the gasket is loose) and moisture got in. A can of compressed air fixed the problem...and now I gotta find a new locking clip from the junkyard. Fun!

How many do you want ???? I can hook you up :)

[pro-five-oh]

How many do you want ???? I can hook you up :)

No worries, there are plenty of them at the local boneyard here. I need to get some other stuff for my Aunt's 1988 Town Car too. But I appreciate it. :)

[Steve Moran]

Pull the distributor cap and spray the inside of it with WD-40.

Art


Ditto to that info. Even if it was not the problem it is good to help keep the spark more directed. Less corrosion on the terminals and all that.