Mr. Hyde... Sudden Rough Running 2.9L?

[john keefe]

Bob, I found that one of the bolts at the EGR-TB connections had backed out a little when I was disassembling the clean the TB, but hasn't made a difference now that it's back together.

Ed, worth a check. Do you recall if clockwise delays shifts, and counterclockwise firms them up? Or, vice-versus? Found conflicting opinion on Ranger forum.

[Ed Lijewski]

Clockwise for firmer, later shifts; ~ 1/4 turn only at a time.

Good luck.

YMMV

[john keefe]

Thanks Guys... thought the ECT would be it, but testing the old against a new, and swapping the new one in anyway didn't work.

So far, I've swapped out or tested almost everything. I don't know what's left... Basically, I've eliminated almost everything else except EGR, EGR position sensor, EGR Control valve, and the TFI module. But a bad TFI wouldn't cause this, right? It'd be almost a no-run scenario?

Does this help or convince you guys... With the intake hoses off, you can hear the IAB is pulling in air. When I unplug the FPR to test it, the RPM's go up slightly, the IAB shuts off, and everything returns almost to smooth normal. When I plug that vacuum line, the IAB actuates again, and idle goes to crap immediately. The IAB wiring tests fine per the manual, a known-good IAB swap helped at first, but now its back to crappy.

I haven't tested it to see if that same thing happens with any other vacuum line. But, that should point to the EGR, right? If its stuck open, the IAB and EGR is too much air flow. I don't know why the additional air from the vacuum line causes the RPMs to jump slightly, or shut off the IAB, unless the EEC is then reading off-idle conditions for the instant you've got all three sources of air going on.

But, it should point the the EGR or its ancillary components as the problem, right?

[john keefe]

I've got the EGR nuts soaking in Liquid Wrench, 'cause they won't budge. So haven't been able to test it, or see if the pintle is stuck. Holds vacuum, though.

[Ed Lijewski]

Wonder if the Manifold Air Sensor is the cause?

YMMV

[john keefe]

I pulled the manifold air sensor and cleaned that off with TB cleaner. It was caked pretty good. No difference, but I guess that doesn't mean its not kaput.

[Ed Lijewski]

I know from experience what a PITA getting the EGR off usually is...

Maybe consider this: disconnect the EGR pipe fron the TB. Make a temporary plate from any metal at hand with screw holes matching the pipe retainer, and block off the TB there and to see if the engine runs differently.

YMMV

[john keefe]

Block-off plate... great idea.

Any tips on removing the EGR? Everything's still frozen. No chance to undo the pipe to block nut at the EGR until I can get it in a vice. I'm guessing it'll have to be disconnecting the pipe at the block connection. Do you have to drop the steering column?

[Ed Lijewski]

No magic here; daily dose of penetrating oil (Liquid Wrench et al), rapping lightly nut and pipe with hammer/wrench. Repeat 2/3 times or more daily over a few days. That worked for me.

(Have no ideas to offer re disconnecting pipe at block.)

YMMV

[Ed Lijewski]

Re the MAP, the ECU looks to it for data re the density/mass of the air charge at the intake in order to correctly adjust fuel/air mixture. The MAP takes the place of the VAM on the XR. A MAP found to be crusty would be suspect (condensation can collect in the hose from intake); spraying it with any kind of cleaner might damage it internally. A defective MAP might produce symptoms you've described.

Just some thoughts.

YMMV

[john keefe]

AND THE WINNERS ARE.... Ed Lijewski and Jeff Herson for "MAP sensor."

Didn't throw any codes related to the MAP, still looked good cosmetically, and tested fine via all the troubleshooting protocols in the Manual. But, figured got nothing to lose at this point by swapping in yet another "known good" spare. Runs perfect now. Swapped the old back on just to make sure, saw the same symptoms.

While it pissed me off, I started to think that 30 yrs. is a damn good lifespan for an electrical component/sensor sitting over a hot engine, and subject to whatever crap and has been flowing through the intake manifold all those years.

Ended up swapping a few other suspect sensors along the way, so hopefully I won't have many surprises for a while. Still can't get the EGR to budge. Maybe spraying again repeatedly with liquid wrench when hot will do the trick. Good thing that wasn't the problem this time, but time to get prepared.

Did find a couple slow leaking vacuum lines to the EGR, and the EGR solenoid, probably from heat due to poor routing on top of the valve cover and heater hose. But, replaced those with new, 5.0mm German made braided fuel/vacuum hose from a high performance shop nearby. This stuff is very well made, not the cheap thinwall replacement hose at the national parts stores. BTW, I found out you have to ask for Euro spec hoses... the 7/32" inch stuff is a smidge too large. Bought enough to eventually redo most of the lines around the engine, figuring heat and 30 yrs of abuse will take a toll on the other hoses soon enough.

Funny how, literally overnight, a perfectly running sensor can go out, with no symptoms. What's a little troubling is that it threw no codes. Oh well, shouldn't bitch when its finally solved. Now to tweaking the shift points.

Thanks Again to everybody for chipping in with all the advice.

[DPDISXR4Ti]

AND THE WINNERS ARE.... Ed Lijewski and Jeff Herson for "MAP sensor."

Glad you figured it out. I've found that the EEC-IV era internal diagnostics are not so great at always pointing a finger at the problem. That's especially true when compared to modern vehicles which almost always allow a "parts-swapper mechanic" to simply pull codes and replace parts.

I guess a MAP sensor should be added to the list of parts to keep in the glovebox.

As for the EGR pipe, too bad this group buy has passed, but you might want to consider getting one any way....
http://forum.merkurclub.com/forum/viewtopic.php?t=26213

I've used mine at least 10 times now and find it very effective.

[john keefe]

As for the EGR pipe, too bad this group buy has passed, but you might want to consider getting one any way....
http://forum.merkurclub.com/forum/viewtopic.php?t=26213

Geez... @ $649.99 ? That's some serious jingle when you can't find two nickles to rub together. What does that translate into number of curse words per job doing it the old fashioned way? Looks like a great tool, but since its a loop, how would you get it over the pipe and onto the EGR bolts when both ends are frozen?

[Ed Lijewski]

Open up the defective MAP sensor for possible indication to what failed.

Re the EGR valve the difficulty is finding a tool among the typical assortment weekend wrenchers have available that lets one gwt good purchase on the pipe nut and then good leverage for freeing it up. (Was there a Rotunda wrench for this purpose?) I don't recall exactly what I used but a thin medium size pipe wrench along with a thin adjustable pliers--and frequent doses of Liquid Wrench and tapping on the nut--probably did it for me. (I clearly recall the moment I got the nut to move miniscually knowing the rest would be easier.)

YMMV

[DPDISXR4Ti]

Geez... @ $649.99 ?

Wow, they've really jacked the price up since I organized that group buy. I think what I arranged I had the price for us down to around $300. He asked that I remove the pricing details after the group buy; I guess I got him at the right time shortly after the product was launching and looking for exposure.

For items where the coils won't work, they have a "rope" that you can wrap around whatever you want to heat. I've used that a couple times.