Driveability issues.

[mobydick]

I have some intermittent issues with my car. '90 CV Wagon w/302.

1. Idle sometimes rough. Either in drive or park engine idle will rise and fall. Does it sometimes, and then sometimes it is fine.

2. Backfireing/popping during deceleration, especially at higher engine speed and always only when throttle completely closed. As soon as you touch the throttle it completely goes away.

3. Squeal coming from back of car. Sounds like a squealing fan belt, but from the opposite end and only when car is moving. Doesn't do it all the time.

New parts:
TAD/TAB solenoids
EGR: valve, position sensor and control solenoid
Fuel pump
IAC valve and solenoid
MAP sensor
O2 sensors (last year)
TPS (last year)
Complete tune up (plugs, wires, cap, rotor)

Any ideas what could be causing these issues?

[pollock]

If you've done all that work already, then my suggestions to #1 and 2 are probably things you've already considered.

1. Make sure the throttle body is CLEAN.

2. Make sure your timing is set properly.

3. Check rear U-joint and axle bearings. If they roll smoothly you might have to check the pinion and differential bearings too.

[mobydick]

Turns out my mufflers are both blown. They seem to be rotting from the inside out, I think all the baffling is gone. I think this is where the popping noise is coming from.

[johnunit]

How loud is the popping? These things will sorta burble and pop when you let off, especially if you're holding it in first or second at highish RPM, but it shouldn't be gunshot loud.

[pollock]

Turns out my mufflers are both blown. They seem to be rotting from the inside out, I think all the baffling is gone. I think this is where the popping noise is coming from.

Exhaust could be whistling out of a hole in the mufflers, causing the fake belt squeal.