Strange ''Popcorn'' noise

[mudnsnow]

Today my truck started to make a really strange noise. I was accelerating at full throttle and a loud ''popcorn in the microwave'' noise comming from the engine occur, My friend in the car behind me have heard the sound too. I think it's backfire coming from the exhaust, but i'm not sure. And now sometime when i drove the truck at steady throttle at 80 km/h(1800 RPM), the same popcorn sound occurs. Timing chain changed 3 month ago, spark plug,wire,cap,rotor have 1 year. Anybody have ever run through this problem

Engine is a 5.0L from a 1989 Bronco.

 

[v-8power]

Does it start and idle ok?

Could be a timing issue

 

[mudnsnow]

idle is ok, no misfire or popcorn sound at idle or at any rpm with no load. I've also tried in drive with the left foot on the brake to add some load to the engine, nothing special occur. It's a rainy day today..... I will try to put some water on my wire/cap/coil tomorow, maybe i could notice something.

 

[The CDP]

Sounds like there could be some detonation happening... it's often referred to as a "marble" sound - but popcorn could sound similar... normally caused by timing being out - perhaps the bolt on the distributor popped loose... I'd be willing to say you probably have it advanced too far.

 

[mikepotts]

Sounds like there could be some detonation happening... it's often referred to as a "marble" sound - but popcorn could sound similar... normally caused by timing being out - perhaps the bolt on the distributor popped loose... I'd be willing to say you probably have it advanced too far.

x's 2... and bad gas can be another cause.

 

[RangerFabWorks]

yeah thats "pinging" your hearing, either timing is too advanced, your running too low grade of fuel, bad tank of gas. any of these will do this. try throwing some premium in it to see if it helps, if it does then i would back your timing down a couple degrees. if it doesnt, then you may have jumped a tooth with the chain, or be a tooth off.

 

[Psychopete]

the same popcorn sound occurs

My 2.9L used to do that right after I put flow matched injectors in. Idle was slightly higher and it intermittently popped like "popcorn" at steady throttle. Sprayed carb cleaner on vacuum lines, connections, and where the intake and plenum met - and found a vacuum leak on the back runner right by the distributor. Just something to check out...

Pete