Help with idle surge/stall '99 E350 5.4 4R100

[SteelheadJones]

Okay, I followed carringb's advice and disconnected the trans controller harness this morning. No change.

I did, however, see all this dirt/grease in the connector that's mounted on the trans. Do you think it could be the problem? If so, any ideas on how to clean it out?



This was the cowl ground strap as I found it...



I thought the exposed wire might be the problem so just in case I re-taped it...



This was the mounting hole and bolt. Could so little rust be the issue?



Here's where that strap mounts to the motor. Could the old oil be an issue?



Here's the frame ground strap. Dirty, but I doubt that's the problem?



And finally, the shift solenoid. Looks like it got dragged on the ground at some point. Could it be the culprit?



By the way, I also disconnected the harness at the solenoid just to see what would happen. The van wouldn't start.

[carringb]

Oil or missing tape on the ground straps shouldn't affect anything.

But that much grime in the trans connector could be causing issues. I'd definitely clean that out first. Just pick up a can of CRC (or store brand) Electric cleaner, or MAF cleaner which is handy to have anyways, and just blast that grime out there. Clean out both ends.

If still no change, then the next step I'd try is disconnecting the tailshaft speed sensor. It might even have a "OSS" tag on the wire harness.

Also, did a little more digging, and Mark Kovalskly (retired 4R100 controls engineer) has an old post saying a bad rectifier on the alternator can cause pulses to be picked up through the OSS circuit and be interpreted as speed.

[carringb]

One more thing... I see an open positive battery terminal in your pic. You are test running this with the battery installed, right? Not jumping it and running only off the alternator?

[SteelheadJones]

Originally Posted by carringb

But that much grime in the trans connector could be causing issues. I'd definitely clean that out first. Just pick up a can of CRC (or store brand) Electric cleaner, or MAF cleaner which is handy to have anyways, and just blast that grime out there. Clean out both ends.

MAF cleaner worked a treat. Unfortunately no change.

Originally Posted by carringb

If still no change, then the next step I'd try is disconnecting the tailshaft speed sensor. It might even have a "OSS" tag on the wire harness.

I think we may have a winner. Apparently I was wrong earlier when I said all the harnesses matched up. This sensor sits unplugged on top of the tailshaft - with no harness to plug into it. Dang it!



Would the Abbott controller r27d suggested solve the problem?

Originally Posted by carringb

Also, did a little more digging, and Mark Kovalskly (retired 4R100 controls engineer) has an old post saying a bad rectifier on the alternator can cause pulses to be picked up through the OSS circuit and be interpreted as speed.

If the sensor/harness doesn't solve the problem I'll consider this. Would I need a new alternator or is the rectifier a serviceable part?

Thanks carringb, you've been super helpful!

[SteelheadJones]

Originally Posted by carringb

One more thing... I see an open positive battery terminal in your pic. You are test running this with the battery installed, right? Not jumping it and running only off the alternator?

Yes, I just pull the cable out of habit after testing things so I don't run the battery down while I'm not driving the van.

[SteelheadJones]

Update. I found this other article and decided to swap the single sensor harness I have from what I think is the OSS on the extension housing (at the front of the trans) to what I think is the VSS on the tailshaft.

So from here...



To here...



And voilà!...

https://drive.google.com/file/d/1C07...ew?usp=sharing

Now I just wonder if the open OSS on the extension housing will be a problem?

[carringb]

Great!

You could squeeze some RTV in the open sensor to keep in clean, then you'll be carrying a spare speed sensor in case the one in the rear diff gives you any trouble while you're on a trip. Ford shipped some of the transmissions with a blank-out plate, but I see no problems just leave the spare sensor in there.

BTW - I think you were plugged into the TSS (turbine speed sensor), and you should now be plugged into the OSS (output-shaft speed sensor), which should be correct. The TSS was used on diesel F-series to control torque converter lockup, but the E-series V10 uses an RPM-vs-TPS algorithm to control it.

[SteelheadJones]

Awesome, thank you! I'll try the RTV. Fingers crossed the speedo works when I take it on a test drive. And thanks for schooling me on the TSS/OSS/VSS distinctions.

[SteelheadJones]

Well, success was fleeting. I'm having the same issue the guy here was having. Anything above a crawl and the speedo shows me doing 30-60 mph.

So...plugging into the rear sensor fixed the Park/Neutral surging problem, but now indicated speed is way higher than actual.

I'm thinking this replacement 4r100 is one from a 2001+ gas van as discussed here. The tech says:

"If you choose to leave this trans in the vehicle you will need a new wire harness and PCM from a 2001 model or install a 4r100 with a VSS sensor instead of an OSS.

VSS=gear driven
OSS=magentic reading sensor"

I'm basically a harness short; and my PCM expects only one harness to be there, not the two I need.

[Twoxentrix]

Carringb - Have to say your diagnostic instinct and overall knowledge continues to impress. Each time you chime in someone benefits... I learn more in the process.