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

Scorpio / Scorpio Cosworth Discussions - Questions, problem resolution, general talk, technical tips and modifications.
john keefe
Level 3
Level 3
Posts: 250
Joined: Sat Sep 02, 2006 1:13 pm

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

Post by john keefe » Sun Aug 12, 2018 3:58 am

So, literally overnight, my Scorpio went from a perfectly running engine which easily passed CA smog two weeks ago, to not being able to hold a start, hold idle, and very rough running when I mechanically fixed the throttle opening, with surging up and down almost rhythmically. Gotta' get this back running ASAP, & don't really have time relearn the whole EEC-IV troubleshooting curriculum. Any ideas would be appreciated.

Had NO symptoms of any sort before this happened. Other than still plagued by A4LD shifting slipping issues. Vacuum line to the modulator is good, though I do have to "peddle" the RPM's sometimes to when it slips shifting into 2 or 3 (shifter in 3 or D), but no issues if I manually go through gears.

Does NOT seem or smell like its running rich. Does NOT sound like any misfiring. Just missing badly, and sounds like a bad vacuum leak.

Here's what I've done, or tested so far:

No Codes, in both KOEO, and KOER.

No vacuum leaks. Tested lines with a vacuum pump and closing off ends, then by spraying brake cleaner onto every vacuum line, every intake-related gasket, injectors, IASC, TPS, etc., etc. with no difference in RPM.

No fuel injector leaks. Spraying with brake cleaner produced no changes. Stethoscope on injectors showed all are clicking.

IASC (Idle air bypass) checks out good for voltage and resistance.

Base Idle (SPOUT disconnected) is fine, @ 10 deg. Jumps up when SPOUT reconnected.

Fuel pressure seems OK, though haven't yet tested the FP regulator. However, it's a recent replacement along with the fuel line. Has been working great so far... though identifying this will be problematic when it won't stop surging.

Cleaned off ALL battery grounds, checked connections. No difference.

Changed fuel filter. At least it now holds idle, but still runs rough.

New ign. wires, cap & rotor. Plugs are fairly new, and gapped properly (done just before SMOG); no sign of rich or lean on any of them.

Leads me to think it could be the used FPR going bad, or a sudden malfunction of either the TPS, or the TFI module, or maybe Engine Coolant temp sensor? I don't have a spare TPS, but before I get to the point of (needlessly out of desperation) wasting a ton of time I don't have trying to shotgun a solution by replacing every actuator or sensor with spares, any and all ideas would help.

THANKS!!!

Ed Lijewski
Level 8
Posts: 7153
Joined: Thu Sep 04, 2003 5:53 pm
Location: The Belly of The Beast

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

Post by Ed Lijewski » Sun Aug 12, 2018 6:55 am

Quick thoughts: EGR stuck open. (Or intake gasket leak.)

YMMV
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!

john keefe
Level 3
Level 3
Posts: 250
Joined: Sat Sep 02, 2006 1:13 pm

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

Post by john keefe » Sun Aug 12, 2018 12:14 pm

Thanks Ed. Think I got all the intake gaskets sprayed, but worth another check. Hadn't thought about the EGR being stuck open. I'll give that a shot first thing.

Ed Lijewski
Level 8
Posts: 7153
Joined: Thu Sep 04, 2003 5:53 pm
Location: The Belly of The Beast

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

Post by Ed Lijewski » Sun Aug 12, 2018 3:11 pm

If you haven't, I'd also check the vacuum hose end at the vacuum modulator. (Re your trans shifting issues, might also replace the modulator if you haven't already done that.)

YMMV
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!

john keefe
Level 3
Level 3
Posts: 250
Joined: Sat Sep 02, 2006 1:13 pm

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

Post by john keefe » Sun Aug 12, 2018 3:31 pm

Already checked the modulator (very recent new, adjustable), and the hose. Heck, don't want to spend time under the car unless I have to, so I haven't had the chance to play around with adjusting the modulator to see if that will help with the shifting. Maybe time to do it now, after I get this running.

john keefe
Level 3
Level 3
Posts: 250
Joined: Sat Sep 02, 2006 1:13 pm

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

Post by john keefe » Sun Aug 12, 2018 3:34 pm

Not sure the EGR tested good. I put a vacuum on it while running, and it made no difference to the rough idle. Either that means it's open all the time, or if it's working properly, then introducing exhaust gases wasn't the cause of the rough running. ???

On a flyer, I swapped the IAC for a good, known spare, and it cured about 80% of the problem. Still running a little rough, but at least it will start and hold an idle. Idle @ 900 RPM seems weak, though. Don't want to bump it up until I have some way to calibrate the TPS.

Little or no RPM fluctuations, like it was before, as if hunting for the correct fuel/air under a vacuum leak. But, still not back to where it was the other day.

Ed Lijewski
Level 8
Posts: 7153
Joined: Thu Sep 04, 2003 5:53 pm
Location: The Belly of The Beast

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

Post by Ed Lijewski » Sun Aug 12, 2018 3:55 pm

Have you removed to thoroughly clean the throttle body?

YMMV
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!

john keefe
Level 3
Level 3
Posts: 250
Joined: Sat Sep 02, 2006 1:13 pm

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

Post by john keefe » Sun Aug 12, 2018 4:56 pm

Did that a year or so ago when I replaced the heads. No gunk now, very little ash/carbon buildup as far as I can see through the inlet bores.

john keefe
Level 3
Level 3
Posts: 250
Joined: Sat Sep 02, 2006 1:13 pm

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

Post by john keefe » Sun Aug 12, 2018 9:40 pm

Took your advice and cleaned the TB again... no difference. Although I did waste a good hour trying to find that damn retaining spring which locks the TPS connector onto the TPS. I guess that's why they call them springs.

So, I did find the following: KOER codes 31 and 41, which basically have to do with the PFE sensor (pressure feedback) bolted onto the air cleaner, and the EGR solenoid, which is next to the purge canister below the battery. Both referenced a bad EGR valve, but also from what I was reading, I need to test each sensor to eliminate them.

Curiously, when I disconnected the vacuum line to the fuel pressure regulator to test it, exposing the vacuum line seemed to fix everything. RPM's went up slightly, smoothed the engine, and turned off the IAC (I had the intake hoses off). I don't get it... the vacuum line is less than 1/4 the diameter of the bypass valve port, yet it supplied enough extra air to make the engine run fine, and shut off the much larger bypass valve. Happened with both valves.

Any idea? Does that eliminate the EGR as the problem.

Ed Lijewski
Level 8
Posts: 7153
Joined: Thu Sep 04, 2003 5:53 pm
Location: The Belly of The Beast

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

Post by Ed Lijewski » Mon Aug 13, 2018 6:57 am

Kinda guessing here...

The PFE code would indicate either the solenoid is erratic (at least clean electrical connections to it) or the EGR valve is not moving (or enough) when the ECU commands the solenoid to open/close, or the PFE sensor is faulty. My first guess is to suspect the EGR given the tough environment it operates in.

On the FPR, I can only note that when I installed a new FPR I found that the mounting base had become distorted and so the new FPR leaked, until I straightened the base on the fuel rail.
20141123_141945.jpg
20141123_141945.jpg (184.36 KiB) Viewed 2889 times
.

YMMV
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!

User avatar
Bob Weir
Membership Coordinator
Posts: 953
Joined: Tue Oct 14, 2003 6:49 pm
Location: Allentown PA

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

Post by Bob Weir » Mon Aug 13, 2018 7:39 pm

Use a vac source with gauge and manually pull vac on the EGR. Test eng off and running, I think manual tells correct psi.

brokencase
Level 4
Level 4
Posts: 383
Joined: Sun Dec 06, 2015 12:18 pm
Location: PA

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

Post by brokencase » Mon Aug 13, 2018 9:26 pm

I'm gonna wager it is engine coolant temperature sensor...or wiring/connector thereto...
The reason I think that is it - is because I have experienced a broken coolant temp sensor on two occasions in the past.
Hard start and rough idle is the symptom....and you usually don't get a diag code from the EECIV when it happens.

john keefe
Level 3
Level 3
Posts: 250
Joined: Sat Sep 02, 2006 1:13 pm

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

Post by john keefe » Tue Aug 14, 2018 2:19 am

Hey Bob, I've only pulled vaccum to 17psi both engine on and off. Didn't want higher vac than that. No difference. On the other hand I don't know if that means the EGR is stuck open. I'll have to take it apart to test actual flow...

Brokencase, I kinda' expected that might be a culprit, but didn't know the symptoms, and hadn't yet found direct references to the ECT sensor in the manual. Though I recall seeing more than a few discussions on here in the past about upgrading it. Is there an actual, better "upgrade" sensor? Is that the same as the XR's? Got plenty of those laying around.

Ed Lijewski
Level 8
Posts: 7153
Joined: Thu Sep 04, 2003 5:53 pm
Location: The Belly of The Beast

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

Post by Ed Lijewski » Tue Aug 14, 2018 9:07 am

Motorcraft ECT FTW.

Re trans shift issues, could the modulator shift rod be installed off center? It's easy to not get it aligned dead center on the trans valve given the very tight working space. (I learned this through experience...) Might be worth verifying. And then trying adjusting the modulator diaphragm pressure via the hex screw on its top.

YMMV
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!

User avatar
Bob Weir
Membership Coordinator
Posts: 953
Joined: Tue Oct 14, 2003 6:49 pm
Location: Allentown PA

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

Post by Bob Weir » Tue Aug 14, 2018 9:24 am

John
You mention cleaning the TB. Are you sure the connection of EGR pipe to TB is not leaking? I've also had a very thin crack in the small vac hose that connects to the EGR.

Post Reply