Rough Idle... (1 Viewer)

[BTLSHP]

I have read the rough idle threads here without finding a precise match, but I have a sense we are generally pointing towards fuel system but would like ideas.

1994 Series 80, 228k miles original. No CEL

Cold start yesterday morning and this morning was fine. Normal high idle then fall off is a couple stages as engine warms.
After a 30minute highway drive and 3-4 hours resting in the sun car started ran rough as imaginable. Idle returned to smooth normal after light pressure on gas pedal.

Again, 15 minute drive, parked car for an hour in the shade car started but ran horribly. Light touch on accelerator and it was fine.

Started and ran just fine from cold start this morning.

Any immediate ideas?

 

[SmokingRocks]

check for vacuum leaks, if 'unmetered' air gets sucked into the intake after the air flow meter it will cause this condition. This is very common

 

[BTLSHP]

Thanks! The car underwent open heart surgery a week ago to replace a 29-year old pesky-heater-hose. I will begin looking in that area.

 

[ppc]

What is the condition of the throttle cable? It sounds like it is sticking. Try pressing the accelerator pedal a few times before trying to start.

 

[BTLSHP]

What is the condition of the throttle cable? It sounds like it is sticking. Try pressing the accelerator pedal a few times before trying to start.

Ha! My dad, the original owner, and I were looking at it last week. He says he is big on preventative maintenance -then defers everything. Superficially, there is no more sheathing left, the visible part of the wire appears ok -- but I am well aware that these wires bulge when they start to go. Good thought

 

[LandLocked93]

+1 throttle cable.
I fought the same thing for about 6 mos, adjusting the cable at the intake. Once warm, the idle was high. Adjust it back. Then idled rough at cold start, slight tap on the gas and idle returned to normal. Back and forth, and so on.
New cable and no issues since.

edit:also replaced the gas peddle assy at the same time. That hinge was flat worn out, requiring immense pressure on the gas peddle to get it to move. A couple hour drive and me hammys were clapped out. This too was resolved by replacement of that assy.

78120-60080 - Rod Assy, Accelerator Pedal
35520-60110 - Cable Assembly, Throttle