1997 f-53 460 backfiring

[JESTIMATOR2]

I have an issue with the engine "backfire/popping" after I rev the engine in park on the deceleration side. I have replaced the plugs, cap and rotor. The wires were done 30k miles ago. The other issue is it runs fine when I first start it up (other than popping on deceleration) but after a few hours on the road I'll notice some hesitation when accelerating and then when I get to my destination it is running so rough I can barely park it! After it cools off I can start it and it runs fine just the popping on deceleration.

I changed the plugs, cap & rotor hoping that was it but with the popping still present I'm worried the problem is still present. It idles smooth as silk and accelerates smooth and clean just does a "pop pop" after a rev up on deceleration.

Any ideas or previous experiences?

Thanks

[TXiceman]

I would check the wire again. Easy way to check them is to pull the engine cover and wait until dark...all light off. Start the engine and look at the wire areas. If you see and areas that have sparks jumping....that is the problem.

Ken

[tln1947]

I experienced the same with my 95 f53 w/460. I found out it needed new wires. Relaced wires with OEM wires and after several weeks had to replace another. With the heat generated with the 460 I bit the bullet and went with a set of Accel 9000 series heat resistant plug wires. To be safe also put boot protectors on all wire boots. All the difference now.

Tim

[ga traveler]

My best engine man always said deceleration backfire was a vacuum leak.

[HotMech]

It sounds like the A.I.R system is directing the air pump output always upstream. This creates the back fire condition and effectively leans out the exhaust gasses, making the computer see a lean condition, and thus try to add fuel to get it right. As it keeps adding fuel, (known as fuel trim) it is acctually creating a very rich condition for the engine to run on, so you might see some smoke, gray to black, and it will run rough, as though the choke would be on. You probably have a bad diverter valve, or maybe just a vacuum hose off.
K.

[Lt46]

Mine pops as well. Just like yours, in park, rev up and it pops as it comes down. Never a problem while underway though, in fact, the popping disappears (or, at least diminishes) once my engine warms up. Until some other symptoms appears I ignore it.

[mpaton]

You may or may not have an air leak into the exhaust system, which would provide air so that unburnt fuel can burn in the exhaust system. However you DO have an air injection system which provides air for that purpose. A test disablement of the air injection system would show a significant reduction in popping. However that does nothing about any unburnt fuel.

The rough running sounds like a more serious problem.

Firstly, you should know that this engine computer can store malfunction codes without setting a check engine light, so you should definitely see if you have any codes set, and if so, correct those issues. You should also ensure the ignition timing is set correctly. This is not so easy as it sounds, for 2 reasons. One is that not all techs know about disconnecting the SPOUT jumper, and the other is that it is difficult to get a timing light to illuminate the timing marks on a class A installation.

There are of course more tests that can be done, but properly performing a code check, AND a KOEO and a KOER test with the ECU is the best start.

[JESTIMATOR2]

Thanks for all the info everyone...I think I'll start with a set of those Accel 9000 wires and boot protectors (thanks Tim) and looking for a vaccum leak! I'll post what I find!

[chboone]

As mentioned in posts #5 & 7, if you have an A.I.R. the diverter valve is bad or not operating properly. Normally bad plug wires will cause a back fire on acceleration, but it won't hurt in install a good quality set of wires.

Chuck Boone

[JESTIMATOR2]

Good point on the diverter valve! I should probably change diverter valve out as well...it is a 97 and sat for about a year before I bought it so it could be stuck....can those valves be cleaned and lubricated or is it a sealed unit? Where is it on the engine? Thanks

[chboone]

If you have the A.I.R., common name is smog pump. follow the large hose to the rear of the engine. You will find the diverter valve some where on the hose. It will have at least one vacuum line attached to it, some have two. There are a number of things that come it to play with the A.I.R. to prevent back fire on deceleration. As mentioned before in post #7 disable the smog pump by removing the belt or the hose from the pump. Run the engine as you have been doing to see if the popping goes away. If it does there is a problem with the A.I.R. system. If it doesn't probably bad plug wires. As mention in post #2, check the plug wires in the dark. If you see arcing, the plug wires need to be replaced.

[teddyu]

I would verify that the distributor wiring sequence is correct. Years ago my 460 was doing the same thing after coming out of the shop. The unit had sufficient power but would back fire on deceleration. Just for Ha-Ha's I was checking everything before going back to the shop. Found two of the plug wires were swapped. Corrected the wiring error and I don't use that shop any more. Fixed the PROBLEMS. Just my two cents.

[subford]

Quote:

Originally Posted by tln1947 I experienced the same with my 95 f53 w/460. I found out it needed new wires. Relaced wires with OEM wires and after several weeks had to replace another. With the heat generated with the 460 I bit the bullet and went with a set of Accel 9000 series heat resistant plug wires. To be safe also put boot protectors on all wire boots. All the difference now. Tim

Tim,

Do you know the part number for the Accel Extreme 9000 set you put on for the 7.5L F53?

The Accel catalog says 9022C and all sellers like JEGS say 9056C.
But the Accel catalog says the 9056C is for the 5.0L.

Thanks

[mustangcar]

its either not enough fuel pressure, fuel pump heating up/binding after a while, your MAP sensor/vaccum hose to it check it,,do a compression check on each cyl, replace ignition wires and confirm fring order, take out each plug and compare see if some of them are whitish.which could be a lean/bad injector