1996 850 GLT - stalling, sluggish and rough idle

[850corb]

OK, checked all the vacuum lines - for the most part they seem fine. The only one that was broken looking was the line that goes from the vacuum tree to some sensor/valve on top of the fan shroud. Its not actually on the the diagram that erikv11 linked to, so I'm not sure what it is/does. Its the yellow line in this photo. I replaced it with a rubber vacuum line - I assume this is fine to do?

Vacuum tree

Took it for a drive after changing that and it drove fine - but it isn't a Thursday so it would have driven fine anyway...

Is the IAC the shiny piece of equipment in the front of the photo with the two thick lines coming out of the top and the bottom? If I take it off and clean it, can I just replace those clamps with the screw down type clamps?

The MAF that is on there is a Bosch, I have ordered another one from FCP anyway so I'll see how that goes when it arrives.

[erikv11]

Hey Erik, what's your source for those red vac hoses, and are they silicone?

The red lines are silicone. I made comments in there about sources, scroll down that thread a bit.

[erikv11]

@ 850corb: that white line is a vac line for the SAS, it goes to a solenoid valve at the fan and then that purple line (barely visible in your pic) goes from the solenoid to the SAS valve, back near the exhaust manifold.

Check the top of the thread there is some explanation that the info refers to non-SAS cars. But also, there is a diagram at the very top of the thread that shows how to route the extra lines for SAS, if you want to keep it.

And yes and yes on the IAC and its hose clamps. Clean it out real well with carb cleaner. Work in a well ventilated space.

[erikv11]

Oh hey - I would clean out the throttle body while you are messing around in that area, too.

[SUPERBRIK]

The fuel relay is in the fuse panel (The part you need to remove with a torx wrench) it is usually pink in color and I think has 102 stamped on it. It is in the forum of repairs and I haven't found it again, but the cheapest test is to run a jumper in line M see if that stops the problem. Don't throw money down the hole chasing repairs. A MAF, which is expensive, should not be the start of your troubleshooting; that and oxygen sensors should be held for the last ditch effort. There is an elbow vacuume line on the right(passenger side), that will throw codes. You can get a fuel relay at the wrecking yard for the price of a fuse or make a jumper (only suggested as a temporary fix) for when you stall; but, I need to echo the previous comment of cleaning the throttle body, MAF and checking the vaccuume lines first, change the fuel relay, then plugs, drink a beer, change out the MAF then the O2 sensors.

[draser]

I'd run another parameter scan to see changes in fuel trim, be aware that it takes some driving and time for this to change.

[850corb]

Ok, cleaned the throttle body, IAC and replaced the spark plugs. Spark plugs looked normal when I took them out. The pipes that connect the IAC to the air hose and vacuum tree, while not loose, were quite easy to remove, so I'm wondering if they need to be replaced? Didn't get a chance to look at the fuel relay, but will try that this week.

Took it out for a drive, didn't have any issues. The fuel trim values were looking a little strange. The LTFT has gotten worse, down to about -15% from -13%, but was actually as high as -21% while driving. STFT was quite variable too, at one point +20%, I don't know how normal this is though.

[850corb]

Thought I'd just post an update - ended up replacing a couple of vacuum elbows (mostly related to the SAS), the IAC hoses (and cleaned the IAC), fuel relay and MAF. MAF was possibly overkill, but as it was such an intermittent problem it made it somewhat hard to diagnose, and I didn't want to wait for it to fail again. And basically I justify the cost by telling myself its still cheaper than a new car payment... Anyway, it appears to be running fine now, idle is smooth, acceleration is normal, LTFT is down to around -3% and its made it through 2 Thursdays without any issues!

Thanks for all your advice, I'm def going to have more questions for you all at some point