Satan causes intermittent power loss/bucking?

[jrichker]

Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.
The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel.

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.

Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer.

Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them

The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

Code 67 - clutch not depressed (5 speed) or car not in neutral or park (auto) or A/C in On position when codes where dumped. Possible neutral safety switch or wiring problem. This code may prevent you from running the Key On Engine On tests. You can generally ignore this code, since it has no effect on engine performance.

 

[jmitchell38925]

Sounds like the exact problem i had with my module.......it tested fine at autozone, but my mechanic told me those tests have a tendency to be inacurate....anyway i replaced it with another from autozone(LLT warranty ) still the same prob.....went to the ford place and bought a genuine (though waaaaay more expensive) ford module.....hasn't missed a lick since.....just a thought anyway

 

[Nutzy19]

Im having the same problem as you and I also work at AutoZone... maybe thats where the problem lies....
Lopey like a cam... however I just replced my o2s about a month ago soo I m watching this one closely

 

[Darkwriter77]

Well, I can see the ignition module tests as being "inaccurate" if you don't do them repeatedly to get the thing warmed up, being that a lot of problems with 'em happen only when you get up to operating temperature. That's why when I test modules, I'll cycle it through almost ten times to make sure it still passes, as it tends to heat up while you're running current through it. Mine passed with flying colors ... and I finally got some use out of that little special TFI module tool I bought a year ago.

It's been three days now since it's had a hiccup. It occurred to me that it only seems to do this sorta thing, anymore, when it's really humid/rainy outside, so perhaps it's a matter of my O2 sensors getting wet and/or something else affected by the weather?

PM incoming for darthcual...

 

[MustangShane76]

Okay here's something else to throw out there. Have you looked at the ground and wire going to the computer itself. Seeing as your car as so many miles it could be part of the problem. The PVC fix that you experienced may have just been luck. Its alot cheaper than some of the fixes I've read.

 

[Darkwriter77]

I've already cleaned all the grounds I could locate - both battery ground cables (one to the quad shock mount, one to the body), the braided one off the back of the intake against the firewall, and those two small grounds on both sides near the bumper stops for the hood near the radiator supports. Sanded the contacts and the contact points down to bare, shiny metal and coated 'em with dielectric grease. What other ones did I miss?

I was interested to find that there's no ground strap going from the rear section of the tranny to the frame, though I have one on my '90 Town Car. Maybe it got removed during the prior owner's AOD - T-5 swap and never was replaced?

 

[Mikey1968]

Perhaps I have your Holy Water....

Say this out loud....PIP sensor!

If you have the original distributor in the beast, it's time for a rebuilt one. The PIP sensor can do all sorts of weird intermittent things. Oil vapor can travel up the dist. shaft to the sensor wires and affect the insulation. You could just replace the sensor but I would do the whole dist.

I have an 86 Capri that around 200K miles would just randomly cut on and off real quick. Then run fine a few weeks, then do it again. Then cut out and make me pull over. Cool down a bit then start like nothing happened, then same thing but took longer to cool. After swapping all things ignition in flavor, I swapped the whoe dist. with new TFI module. Halos appeared and the darn car felt like I put in NOS or something. WOW! When I compared the old with new dist., you could spin the new and feel the magnetic pull on each pole but almost nothing on the old.

Also had this problem with a UnilLite dist. on my 68 Cougar. I know, different car and system but same damn problem. Fixed it with a Crane Fireball set up in the dist. Sounds like a viable option as you changed everything else, huh?
Good luck!
Mikey

 

[Euphoric306]

at least now you've got somewhat of a condition that it happens under

and im glad the fallen angel has finally shown some much-deserved mercy

 

[Darkwriter77]

Perhaps I spoke too soon. It's being crappy again, bone-dry weather for the past three days. Satan rears his ugly head once more. Bah!

PIP sensor? Picture-in-Picture? Periodically It's Poopy? Pain in the Pants? Never considered that one, but I'll add that to my list of suspects. True enough, with about 200k or so on the (presumably) original distributor/TFI module (how's THAT for durability!), it's entirely likely that my dist's guts are finally beginning to give up the ghost. Heck, the TFI is still the factory Motorcraft unit, but it still checks out just fine.

Changing the distributor out sounds like a mighty pricey/time-consuming option, but at this point I'm definitely running out of options. If I do go through that expense, might as well go the extra mile and put on a nice MSD unit. As much stuff as I've replaced/tested/cleaned, it's almost like I'm making payments on a brand-new motor, as it practically will be, by the time I get this resolved...

Ever since swapping out the cone and putting back the stock airbox n' paper setup, the severity of the surging has diminished considerably, but it's still there (still intermittently, too). Still running rich, chugging gas (more than usual), and being all wimpy from time to time.

This may be a bone-headed thought, but do the 89 models have an IAT anywhere? I know that the 94-95 5.0's had them, and there's all this talk about an IAT relocation mod and whatnot. I've had the top intake manifold off of the car two times in the past couple of months (first doing O-rings and then replacing all 8 injectors) and I saw no such sensor anywhere in or around there. Just figured that there might be a chance that it could be a possibility, as the IAT sensor on the '00 Chevy S-10 delivery truck we had at work was causing vaguely similar symptoms until we changed it out ($15 part, 5 mins of work, two weeks of headaches trying to figure it out). Btw, yes, I've checked and double-checked the torque on the intake manifold after re-installing it, as one of my first thoughts was that I'd either left something loose, it had un-torqued itself through heat cycling, or I'd pinched something between the manifold and gasket during reassembly. If only it could be something as simple as that ... *sigh*

 

[jrichker]

Intake Air Temp sensor is screwed into the #5 intake runner on stock manifolds.

A faulty sensor will usually set code 24.

Code 24 - Intake Air Temperature (ACT) sensor out of range. Bad sensor, bad wiring. The ACT for Mustangs built before 95 is in the #5 intake runner. It measures the air temperature in the intake to help computer the proper air/fuel ratio.

Note that that if the outside air temp is below 50 degrees F that the test for the ACT can be in error.

ACT & ECT test data:

The ACT & ECT have the same thermistor, so the table values are the same

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer. Here's the table :

68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61

Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms

 

[Darkwriter77]

Oh! Jeez. The thing was staring right at me the whole time. I never had to pull the lower half of the manifold, so I never had to disconnect it and, hence, never thought twice about it. I had assumed it to be a coolant temp sensor, since it's so close to the gauge temp sending unit. They're only around $25, so it wouldn't necessarily be an expensive risk, but I haven't been getting a trouble code for it (yet). Might it be reasonably possible that it could be failing without tripping a code? Thanks for the info (and also on the O2 sensor cause/effect).

Seems that Beelzebub is not content to settle for merely causing misery through surging, popping, and power loss. Oh no, no, no! NOW his latest meddling involves my idle. When coming to a stop, right after I push in the clutch, take it out of gear, and let it sit in neutral (with my foot then off the clutch), the RPM's will do a small roller coaster ride that first dips low (around 500 RPM), then high (about 1200 RPM), and low again, but not as much. It flattens out to a nice, smooth purring after about five seconds, but it's that initial time of putting it into neutral that's filled with demonic activity. What's worse, it has progressed to the point of stalling out (had it twice now), and it will sometimes almost stall out when I put it back into 1st and release the clutch to take off. As always, this doesn't happen all the time, only when it's randomly choosing to be fussy.

I've already previously replaced the IAC at the same time as the EGR valve and MAP/BAP. I've read that aftermarket IAC's sometimes work oddly, and that some folks have reversed theirs as a means of solving their idle issues. I flipped mine awhile ago, and all that netted me was a sticky idle that wouldn't drop below 1000 RPM and would hang at 1300 RPM for five to seven seconds after disengaging the clutch. I flipped it back to normal mounting and it's back to its "normal" steady idle at about 650 RPM. (Seems low to me, but it's still quite smooth.)

Dunno if this is a separate issue arising, or if this is a worsening symptom of the same mysterious plague that's been curising my ride throughout this semi-dramatic saga, but I figured it warranted a mention...

 

[Darkwriter77]

The stalling is becoming more frequent. If this keeps progressing, I'm going to wind up with an undriveable 'Stang.

Okay, time to update the list. (Hopefully I can remember everything.) Items which I have cleaned and/or replaced and thereby ruled out include:
- Mass Air Flow Sensor
- MAP/BAP sensor
- IAC valve
- All vacuum tubing (I've replaced just about every last inch)
- Fuel injectors
- Fuel Filter
- Air Filter/Airbox
- EGR Valve
- PCV Valve and screen
- Distributor cap/rotor (twice)
- Spark plugs and wires
- 10-pin connectors (Salt & Pepper shakers - cleaned, spread pins, and re-greased)
- Ground wires at rear intake, battery, and two front radiator support locations

Items that I have checked and which SEEM to be in good working order (tests might not always reveal faulty parts?):
- TFI module
- TPS
- Distributor (shaft does not wiggle loosely at all)
- Alternator (although I still desperately want a 3g upgrade)
- Battery (load tests good)

Again, the only codes I'm getting are 91 and 41, which specify that it's reading a lean condition at the O2's (even though it's running rich). I have yet to change out the O2 sensors, but I'm still not entirely sure they could be causing these kinds of drivability issues (particularly the stalling). My current list of suspects (may be more than one) include:
- O2 sensors
- Fuel Pressure Regulator
- Fuel Pump (gawd, I hope not!)
- TFI module (tests good, but with almost 200k on it, it can't last forever, right?)
- PIP sensor (which would entail replacing the whole distributor ... ouch)

I'm going to try renting a fuel pressure gauge to see exactly what I'm getting at the rails, which may/may not tell me anything about the FPR, but at least will give me some info on the fuel pump. The O2's are on the replacement list, either way. I'm gonna go ahead and throw on a new TFI module and keep the current one for a spare. And, finally, if none of the above fixes it, I'm going to ... um ... seek the help of the Pope, or something...

If y'all see anything I've left off the above list, lemme' know. I tremendously appreciate the suggestions/info you've all given me thus far. I'll update the results (if there are any to be had) after I go through the above tasks today (got two days off in a row to fight this demon). Wish me luck!

 

[Euphoric306]

i dunno who is familiar with OTC manuals, but basically my dad brought htem home from work and they have all the codes you can pull out of the computer and, using usually only a DVOM or DMM (digital multimeter) you can test circuits to see exactly which part is faulty

it's telling me that both code 41 and code 91 are the EGO sensor codes (41 being the right EGO and 91 being the left EGO)

are those still the only codes you're getting after this surge/stall situation has arised?? im having exactly the same problem with my idle and it turned out to be by canister purge solenoid, which was tripping code 85 in my computer

 

[darthcual]

When you get it figured out you can do a Jim Carrey from Ace Ventura a like so, "YES YES YES, CAN YOU FEEL THAT BUDDY, HUH!" "I have excorsized the demon, this house (car) is clear."

 

[Darkwriter77]

Oh, I can assure you, there will be much jubilant celebration when I have definitely nailed down the source of my problems and thereby cured it. At this very moment, I'm waiting for the beast to cool down so I don't burn the bejesus out of myself trying to fiddle with today's tasks: yanking the distributor (again ... *sigh*), replacing the TFI, adjusting the timing (might as well bump it to 12 or 13* instead of 10*), and sucking down a Coors Light or two to "reward" myself.

If this new TFI and the O2's don't do the trick, I'm pretty much screwed. I'll be doing this crap... ... back n' forth to work until I can save up for a new fuel pump, AFPR, fuel rail gauge, and fuel level sending unit (might as well replace that worthless turd while I've got the tank dropped - I hate using my trip odometer to guess my remaining fuel level). That's only going to amount to, oh, about $300 ... all of which I had hoped to instead put towards a 3g swap or an aluminum driveshaft. But hey, the upside is that at least I'll have all of that taken care of for the next few thousand miles ... until Satan chooses to revisit my car once more...

Would you believe nobody around town (parts store-wise) seems to carry a new distributor mounting gasket for a 5.0L? Like it's some kind of unheard of ancient Egyptian mystery part, or something. I've been re-using the current one without problems thus far, but still ... that's just so . It's just a little friggin' paper O-ring, fer cryin' out loud. Might as well make my own...

And, just in driving to/from my old parts store (Checker) and my new employer (AutoZone), the thing died on me no less than three times. Same thing, idle dropping down too far when I push in the clutch. Either the air/fuel mix is worsening, or I got a crappy IAC when I replaced that the other week, as it's never done this stalling crap until just recently.

 

[Darkwriter77]

Okay, the last time I pulled the distributor, I just marked where things were at TDC, yanked the bugger, ran my TFI module over to the shop and tested it (passed with flying colors), poked it all back together, and it ran just dandy. Timing was sitting at 10* then.

So, I decided I should check the timing again before yanking the distributor. I checked the timing with the spout in, and it's jumping all over the place. I pull the spout, and it's sitting steady right at 0*. WTF?!? I cranked it back up to 10* with the spout out, I shut it off and re-connect the spout, and when I start it up it's sitting around 17*, and idling steady at about 900 RPM (instead of the previous 650 RPM). This kinda strikes me as being a little odd, to say the least.

Only thing I can figure to explain this might be the TFI module. The jumping-around timing was probably a matter of me happening to catch it during one of its moments of Satanic possession, as it was dead steady with the spout out or in after I re-adjusted it. I just can't figure how the heck it could have gone from 10* to 0* on its own without the distributor moving the slightest bit away from the marks I made last time.

Gonna take it out for a test drive, just to see if anything's changed, and then I'm changing out the TFI module, anyway - no sense in leaving it up to chance when I've got the part sitting on my kitchen counter. More to come...

 

[darthcual]

Sounds like your having a hard time nailing the problem for two reasons.
1. The computer is making adjustments on the fly to compensate.
2. You still have not put the holy water in your radiator.
A.Side note/ Holy water was used in the 1986 game Castlevania to destroy the very evil Frankenstein and his evil monkeys (I cant make this stuff up)
B.Maybe Frankenstein and his evil monkeys inhabit your engine bay?
C.Holy water would take care of either Satan or Frankenstein but if it Dracula your gonna need a stake.
D.Better to be safe than sorry, Carry a gun w/ a silver bullet.
E.I hope you find the culprit, did you say you did replace the fuel relay. 8 bucks at Your P.O.E.

Good Luck

 

[Darkwriter77]

Interesting theory. After all, Frankenstein did have bolts on his neck that looked an awful lot like those on my battery...

Not so sure the fuel relay would be involved. The pump's switching on and running quite nicely. At this point, I'm more inclined to say it's an ignition issue that's causing the fuel problem.

I didn't get around to swapping out the TFI today, since it's been ungodly hot outside (110* plus sticky Monsoon humidity), and I was cruising around, testing out different timing settings (12* seems to make it right perky with 89 octane without pinging). Advancing the timing made a HUGE difference in performance - the car's never felt this fast and torquey as long as I've owned it - and I couldn't get it to replicate the surging, but the power loss did come and go twice and the roller coaster idle eventually emerged. Similar to what others have been mentioning in other threads, I've been noticing that turning off the car for a minute or two (long enough to grab a soda at the local QT) and restarting seems to make the problems go away for awhile. I toyed with this for awhile, stopping at places, shutting off, restarting, cruising, repeating, and at least that part seems consistent. This leads me to lean further toward an ignition/sensor part as the culprit, and all but scratches off the fuel pressure regulator. (Doesn't entirely rule out the fuel pump, though.)

Just so long as I don't have a problem re-stabbing and re-timing the distributor tomorrow, I should have the module changed out in the morning, and I can hopefully verify whether or not that solved anything. All this newfound power from adjusting the timing (yeah, I'm a lazy bum, never bothered to tamper with it 'till now) has created only one new problem: no traction in 1st gear.

NOTE: Another problem, my OEM-replacement clutch isn't as grabby between gears now. I can stand on it in 5th and it doesn't slip, it's just not sticky enough to shift as quickly/hard as I'd like. More power than stock + 4.10 gears + stocker clutch =

 

[Euphoric306]

HAHA darkwriter i just noticed ur extra feature in ur signature... nice

sorry dude im as clueless as you are about your timing adjustment

but still have you checked your codes after your stalling problem arose?

 

[Darkwriter77]

Haven't checked 'em yet. Gonna wait until I get the new module on, and I'll reset the ECM, in case it needs to re-learn anything from the bad lessons the previous TFI module might've been teaching it. Curious to see if it'll make the lean readings go away, or not.

As a precaution, I'm warranty swapping out my IAC. Never had the funky roller coaster idle/stalling problem until a couple o' days after bolting that bugger on. Only got 3 months' warranty to mess with, might as well make use of it...