1996 850 NA Chug Chug Rough Running

[PeteB]

Ran with logging again.
STFT sometimes at idle wanders from -3 to +3, others from -1 to 4, on revving to 3000RPM
it goes to +7. That video suggests that it is a dirty MAF - I'm going to try cleaning it on that
theory, and to rule out a dirty MAF as the problem.

Does the fluctuation at idle indicate an intermittent vac leak?

Also logged MAF data, light throttle .5 ish, sticking foot into it up to 3000 RPM gave 12 ish,
seems okay to me, anyone?

Coolant temp seems fine, perhaps a bit low around 180 but that seems fine to me.

Why high idle? I think I'm going to try a spray to test for vac leaks.

I probably should mention, tried to remove the Vac tree when I did the PCV job, the
bolt would turn out about 1/4 turn then seemed seized, didn't want to snap it off.
Any tips, I'll hit it with PB blaster a few times over the next few days and try again.

Thanks everyone, appreciate the help.

[PeteB]

Cleaned the MAF even though it looked spotless, no difference.

[abscate]

That's a really minor vacuum leak if you even have one. I believe 10% is typicall when you start getting codes but spikes above that are normal.

Are you still running tough?

[sleddriver]

Is there any sensor that I can check in the scanner to help determine if
there is a vac leak?
Anything to help figure out the high idle?
Does a hot temp of 181 suggest an ECT issue, I thought modern engines
ran hotter?

1. Build yourself a smoker and thoroughly fill intake/engine/emissions system with smoke. This will take some time. However, it will save you much time eliminating all of your vacuum leaks on an old car. Been there, done that.

2. Check the wiring insulation & connectors on:
a. ECT sensor
b. Crank position sensor
c. Camshaft position sensor
Probability is high on an old car, the insulation has crumbled off, the copper wiring has corroded and the bare wires are now touching. This will cause rough running, stalling, poor performance, etc. Exactly the problems you describe. Been there, done this, part II.

[PeteB]

That's a really minor vacuum leak if you even have one. I believe 10% is typicall when you start getting codes but spikes above that are normal.

Are you still running tough?

Hi, sorry, I took a long break from this car, it has sat with a charger on it to keep up the battery.
Our IAC has never had hose clamps on the hoses, did that today no difference.
Idle = 1000 RPM, still chugs, exactly the same way.

I'm thinking of changing the MAF but am not certain if the scanner is indicating that
it needs it.
What else might cause a high idle?

[PeteB]

Our temp gauge is solid at 3 o'clock so I'm not going to go that route for now.
Can I clamp off the vac line to the purge valve to test it, it seems to have been
the problem for this person:
viewtopic.php?t=59014

[PeteB]

High idle was the dash tach being off, actual was 840 and rock solid.

It is Summer, I changed the front motor mount that was completely shot
and the chug chug and roughness seem to be gone.
Not sure if the change in ambient temp has anything to do with it.