SOLVED: 1988 2.9 5-speed “popping and gurgling” consistently when coasting in gear or down shifting

[GingerKing13]

Hey guys,

1988 2.9L 5-speed 4x4 super cab

intermittently on idle and when driving the truck has a little stumble (flutter in RPM down). Generally it idles and runs smooth but have noticed more lately stumbling a little bit on the highway and stumbling tach and RPM on startup occasionally.

consistently exhaust burps and pops when downshifting or coasting in gear, even just reving it up it gurgles on the way down.

truck has new plugs, coil, distributor, ICM, TPS, IAC valve.

Has anyone ever experienced this??

 

[rusty ol ranger]

Hows the plug on the coil connection look?

 

[GingerKing13]

Hows the plug on the coil connection look?

Plug from distributor to coil looks solid

 

[Uncle Gump]

You replaced the IAC... does it function properly?

When you start it up cold... is the idle raised initially the settle down to a normal idle speed?

 

[rusty ol ranger]

Plug from distributor to coil looks solid

Nah i mean the main plug going into the coil. The black plug with the red and green wires

 

[GingerKing13]

You replaced the IAC... does it function properly?

When you start it up cold... is the idle raised initially the settle down to a normal idle speed?

Yes works as it should and replace by OEM motorcraft.

 

[GingerKing13]

Nah i mean the main plug going into the coil. The black plug with the red and green wires

Its seen better days but the connection is tight on the two terminals.

 

[rusty ol ranger]

Its seen better days but the connection is tight on the two terminals.

Id replace it. I believe that controls your tach. If its bouncing the trouble could be right there

 

[GingerKing13]

Id replace it. I believe that controls your tach. If its bouncing the trouble could be right there

Okay, there about $10 I could do that. What about the capacitor that runs off of one of the green wires and is mounted on the fender liner?

 

[rusty ol ranger]

Okay, there about $10 I could do that. What about the capacitor that runs off of one of the green wires and is mounted on the fender liner?

I believe all that does is control ignition related radio noise. Mines been gone for years

 

[alwaysFlOoReD]

Would a leaking injector cause this? Easy test is hold the gas pedal to the floor and try to start the truck. It's the "clear flooded engine" procedure. The engine should turn over but not try to start.

 

[rusty ol ranger]

Would a leaking injector cause this? Easy test is hold the gas pedal to the floor and try to start the truck. It's the "clear flooded engine" procedure. The engine should turn over but not try to start.

Its possible but an injector shouldnt make the tach bounce...unless hes also getting a notable RPM difference when it happens

 

[GingerKing13]

Its possible but an injector shouldnt make the tach bounce...unless hes also getting a notable RPM difference when it happens

The tach doesn’t “bounce” by itself. It does follow the engine rpm as it stumbles or hesitates, or surges, etc.. I can feel the fluctuation as it appears on the tach.

 

[rubydist]

I would take a good look for an exhaust leak before the cats. There may be more than one issue here because that should not cause the bouncing tach, but can certainly cause the burble or however you want to describe the noise on decel.

 

[GingerKing13]

SOLVED: Replaced the ICM and it idles perfectly, no lag in throttle input, and no more popping on the decel. Thanks for the input guys.

FYI: My ICM screws were PHILLIPS head! not 7/32 or a torx.