Ford Mustang Forum banner

Open Loop issues- which sensors

27K views 195 replies 7 participants last post by  145566 
#1 ·
Are there any particular sensors to look at when trying to diagnose a problem once it’s in open loop? Especially when it comes to not wanting to idle unless I give it gas. It idles real well in closed loop, and it will drive in open, it just doesn’t want to idle.
For example, what would be more suspect, the o2’s or the MAF? Or both and it’s a crap shoot? It seems in the past when I had a bad MAF or o2 (different vehicles) it would run real bad like it was missing, and it would hardly idle warm or cold.
Anything else y’all can think of?
 
#3 ·
#11 ·
No MAP sensor on the mass air mustangs. Mine doesn’t have the rotten egg smell. It’s more gassy. It runs like a lawnmower engine with the choke on. Good when warming up but I think “the choke” is still on after it’s warm and it’s flooding it out. When I open the throttle I think enough air gets in to keep it running.
 
#13 ·
If you do decide to purchase a maf sensor from pmas,I would call the company directly to order,so you can talk to the tech dept first to make 100% sure you get the correct sensor for your application.
Dont you run 24lb inj,an Anderson Power Pipe & a conical filter now or no?? I know the filter setup is important when they do the calibration to the sensor electronics, so its information they need to know when they're recommending which maf you need.
That link you posted is a 80mm maf
w/19lb calibration w/stock airbox for a Ford thats currently running a 80mm maf.
So you might need a maf with a cai or conical filter calibration,but they're the experts that can tell you that.
There are several other mafs listed specifically for 94-95 models.The only ones I listed below are the black finish mafs.

MH80FB-24
80mm/24lb/stock airbox/with a flanged 70mm maf installed currently/94-95 Mustang


MH80FB-24CA
80mm/24lb/cold air intake/with a flanged 70mm maf installed currently/94-95 Mustang


MH80FB-19CA
80mm/19lb/cold air intake/with a unflanged 55mm maf installed currently/94-95 Mustang


MH80-FB-19
80mm/19lb/stock airbox/with a flanged 80mm maf installed currently/Fords
**The description for the maf above stated to use part number MH80-19 if you are running a conical filter,but that number maf isnt shown at all on the site.
Numbers like MH80A-19/MH80B-19/ MH80FA-19/MH80FB-19 are shown,but no MH80-19**

I would definitely call them.
 
#14 · (Edited)
I actually emailed them earlier today.
I’m using Vortech’s induction setup and 19#’’ers. The filter attaches to the MAF w a clamp and there’s a collar that slides over that attaches to the stock maf’s flange.
I’m assuming I want their cone filter style maf. I guess/hope the flange the where it bolts up is the same size as the stock one.
I wonder if the difference in calibrations between the air box style and cai type are in the electronics or the housing? I hope their “19# calibrations” aren’t too far off from stock to where it causes tuning issues. Seems like the maf’s should be/would be pretty much stock like. I didn’t see a 75mm, I think that size would be better suited for my asthmatic top-end. The stock maf is 70mm and the opening on the intake manifold is 60mm or less. BBK and others have 75mm I know, but I’m not paying $250+ for a maf. What makes the Pmas look attractive is the price. It’s $109, a new Duralast is $85, and a reman is $65. I’m not really expecting any more power out of the deal. But surely it’d be of better quality than the parts store stuff. I just hope the whole calibration thing works out right since it’s been dyno tuned.
I see that the one for a cai is unflanged. I need a flange, I think? Or maybe it’ll work if I don’t use the collar the flange goes to.
*Edit*
I’m going to call them, but I think this is the one I might need. It’s the 80mm for 19’s and cai. The description says it doesn’t have a flange but the one in the picture has one. I think I’ll be able to use one with or w/out one though. I’m going to wait and I get any cold hard cash for X-mas this year before making a purchase.
http://www.pmas-maf.com/product/mh8...19lb-stock-injectors-w-cold-air-intake-black/
 

Attachments

#15 ·
One thing I found odd was that they listed the MH80FB-19CA for a 94-95 Mustang, but yet its supposed to replace a unflanged 55mm maf,which is the size of the maf that came on the 89-93 Mustang.
I would have thought their maf thats made for a 94-95 model would have been
listed as replacing a 70mm maf,not a 55mm,so thats a little odd.Another one was the part number you originally listed thats supposed to replace the 80mm maf
on Fords already using that size.Why would someone replace their maf with the same size maf,but I guess someone could use it as a direct replacement if something happened to their stock maf.It would allow them to buy a new maf to replace their stock maf instead of buying a reman unit.
It looks like one calibration is for use with a stock airbox & one is for a cai and/or conical filter?? Its a good point you bring up about whether the calibration is in the electronics or housing.I don't think youll have an issue with a new maf since you're still running 19lbers.On a na setup,its usually a good idea to size the air intake components to where it funnels the air
into the intake (i.e.- going from slightly larger pipe down to smaller/identical size pipe as the throttle body/egr spacer,so that airflow can build up speed and make a smooth transition into the intake. However on a boosted setup,since you're forcing that air into the engine,artificially speeding it up,pipe size might not be as important?? The main thing is to not have the air hit an obstruction,like using a 75mm tb when the intake opening is only 60mm or having 60mm pipe size meeting a 75mm tb.It creates turbulence.
 
#16 ·
I noticed that too about the 55mm unfanged end and found it odd. It said 94-95 it was for a 94/95. I think I saw another one with the same description and specs but they had it listed for ‘89-‘93. I guess I’m going to have to call them.
 
#19 ·
Pmass

I finally talked to Pmass. At first I received an email and it was vague. It said I wanted the “regular” type if I don’t have a cai, or the cai type if I do. I of course told them my setup when I emailed them. I called to get a little clarity. They said if you don’t have an air box you want the “cold air calibration” because it recognizes more air coming in than if one was using an air box.
Meh sounds like a mess to me. I’m going to steer clear. I mean after all, isn’t it the ecu that does the work and the MAF just reports what it sees? Wouldn’t a “non calibrated” MAF be able to report what it “sees” as well? No room for trickery in my application or wallet.
 
#21 ·
The O2s are fully responsible for closed-loop operation but only after the PCM gets the "OK" from the Engine Coolant Temperature (ECT) Sensor. Prior to that, the engine fuel/air mix is governed by the programmed "look-up" tables used by the PCM. IOW, during open-loop operation emissions are basically disregarded, a fact so disliked by the bureaucrats at EPA, that O2s were given heaters which internally begin heating them up as soon as the key is turned "ON".

The fuel/air mix is controlled by injector opening time, PCM using the various inputs like air quantity, eng. speed, eng. load, air pressure, etc. to open them based on programmed "look-up" tables covering all those variables. Those numbers change often and quite a bit....the O2s take over in closed-loop by "fine-tuning" the mix above and below the look-up values. IOW, the O2s control the engine basically. In some models, Wide Open Throttle (WOT) cancels closed-loop temporarily to allow maximum power output.
 
#23 ·
An exhaust leak prior to the O2 could cause an o2 malfunction right? The easiest way I know how to find one is to run Seafoam through the intake. I know my muffler is leaking but I’m not sure about in front of the o2. Maybe I’ll Seafoam it, jack it up and take a look underneath with it running to see if smoke is coming out where it shouldn’t.
I’ve seen guys stick shop vacs up the tailpipe w/ the motor off, but I’ll prob lose all my air out of the rusted muffler.
 
#24 ·
I don't think it causes the sensor itself to malfunction, does it? Rather, the sensor senses the extra air, which the PCM interprets it as a lean condition, and tries to correct it with extra fuel.
 
#28 ·
I let it idle today to see if it would die once it was warmed up. I heard the rpms drop like it does once in closed loop. It kept idling but there were a couple of times that it would stumble but it would “correct itself” and keep idling. I took it for a drive and it ran great and it idled at stops. When I pulled into my driveway the idle stumbled and it died...
The exhaust is still pungent whether it’s hot or cold.
When I replaced the injectors not long ago I looked at the vac line on the fuel pressure reg and I didn’t notice any fuel in it or on it.
On a side note, it always has trouble passing smog due to high hc’s. It has a laundry list of new sensors on it. Except for the MAF, and it did suck up some water in a flash flood once. MAF is near the ground.
 
#33 ·
Plan of Attack

Alrighty, well I ordered the new (not reman) Duralast MAF from Autozone and they say it’ll be here tomorrow. Since I have to peel back the inner fender to replace the MAF, I’m going to try amd look at the charcoal can lines while I’m under there.
Throwing parts at problems stinks, but due to the whammy 511 error code and the location of the MAF, it is what it is at this point. Process of elimination. If the new MAF doesn’t fix the problem at least it’ll be clean. I’ll just chalk it up to “restoration” along with all the other new sensors I guess.
I took a screen shot of a post that I read on another forum regarding the maf’s role during open and closed loop. It might be false hope, but for now it’s hope. I’m gonna mess with it this weekend prior to riding the Polar Express.
Also, here’s a plane I saw flying over ahead
 

Attachments

#34 ·
The EVAP purge solenoid was on backwards so the vapors were running the wrong direction. I’m not sure how long it was like that, awhile I’m guessing. I put it the right way but it didn’t make any difference. I drove it for about 20 miles and it ran great on the open road. But once it was warm it didn’t want to idle and when it died it didn’t fire up right away. I think it’s flooding out at idle. I’m pretty certain it’s not ignition related. The pip went out already. It wouldn’t cruise down the road when it went bad.
Arg..
 
#36 ·
I disconnected the MAF and then started the engine. It fired right up and idled well like it always does when the motor is cold. I only let it idle for a second but it didn’t act like it was trying to die.
I took the MAF off and autozone is supposed to have a new one for me tomorrow. It seems like in the past if I was to disconnect a MAF the motor wouldn’t run or at very least it’d stumble pretty bad.
I hope maybe I’m on to something.
 
#37 ·
The new MAF helped the exhaust smell and it ran a lot stronger and it idled better for longer. No more flooding.
However, I have a charging system issue. When I first started it up the stock volt gauge was reading on the M on NORMAL. I noticed that everytime the fan would come one the engine would try to die. After driving it around it idled at nearly ever stop. But the longer I drove it the worse it did and the voltage gauge read lower and lower. At one point it tried to die when I turned the vent fan on. After running awhile the alt is scorching hot. Hotter than the supercharger head unit and the intake manifold. It is a brand new PA performance 130 amp alt. The alternator that it replaced was doing the same thing. What’s the deal?
 

Attachments

#39 ·
Did you ever check the fuses for the alternator?? There are also two fusible links on the black/orange wire.There is 1 alt fuse in the fusebox under the dash #18 20amp & 1 alt fuse in the underhood fusebox 20amp.Did you ever notice if the charge indicator lamp is coming on when the key is turned on?? If it doesn't light up,
#18 fuse is blown,the charge indicator lamp bulb and possibly the resistor that runs parallel is blown or the wire is damaged.There are also 2 fusible links on the 2 gray wires coming off the starter relay/solenoid,where they meet the black/orange alternator wire,that should be checked.The diagram below should help.If the fuses/links are good,but the charge indicator lamp isnt coming on,youll wanna trouble shoot that circuits bulb,resistor and wire.Theyre shown in the diagram too.Check your 3 main grounds too.The alternator case mounting ear and bolt need clean contact with the bracket also,so make sure paint isnt present at these areas since the alternator being grounded properly at its mounting point + the intake/cylinder head to firewall ground strap is what grounds the alternator. A additional 4ga ground cable should also be ran from the eec ground location to the block ground location where the neg battery cable is already attached.This is needed anytime a 3g is in place.
 

Attachments

#40 · (Edited)
This morning before I went to work I turned the key on in the ole stang and the battery light comes on.
If the fuses were blown would the alternator work at all? I haven’t looked at them yet. When I had the dud reman alt in there the volt gauge on the dash didn’t work and the battery died. The old alt that it replaced acts like the new PA performance alt. It charges until the alt overheats.
It’s a 3g unit from the factory and I’m assuming if the factory wires are up to par, which they very well might be old and fried. Would the wiring be the next logical step if the alternator works until it overheats? Or would it half-azz work if it has a blown fuse? The non working reman I got didn’t even try to charge the battery.
When the alt gets too hot the and tries to die volt meter will rise and fall with the tach needle. If give it a quick rev the volt meter will go towards the charging side and the idle will steady out for a little few seconds. If I don’t give it a rev it will die. It takes about 20-30 min of driving for this to occur. It’s all good the first 20-30 min. It’ll fire right up and go.
 
#41 ·
It doesn’t look like anyone makes aftermarket oem type battery cables for the 94/95. I’ve found foxbody, 96+, and universal. The universals don’t appear to be quite right. It appears on oem there are smaller wires (possibly grounds) coming off of the main wire. The universals don’t seem to have those.
Any ideas? Just a couples lengths of 2 or 4 ga wires?

*Edit*
I read UPR’s instructions for their bat relocation kit. It didn’t mention anything about the little wires with the fused links. Are those tied into the battery cable or just running along side it?
 
#42 ·
I see cables available for '95 V6 models... trying to think of why they might be different, since they're not coming up as an option for our V8s.

The starter cable would probably (?) be of similar length, but an image search tells me that the V6's alternator is much closer to the battery than it is on the V8, so that's probably the main difference as far as the positive cable is concerned. I bet the alternator cable is too short.

As for the negative cable, I'm not 100% sure, but I think the grounding points might be close enough on V6 and V8 models to work. Maybe.
 
#45 ·
Yeah, parts store is showing 130 amp stock replacements for V6 models. Wire gauge should be the same then.

The negative cable I saw is STANDARD MOTOR PRODUCTS A744TC. Comparing the V8 and V6 diagrams below, they appear to be identical, except that the V6 has an extra ground line that eventually leads straight to the Data Link Connector. (I guess OBDII connectors get their own dedicated ground)

G104 is the same ground point right next to the battery, and G105 is on the engine. Not sure where C113 is, but the new cable has a butt connector on it, suggesting that you're expected to cut the old wire somewhere in there and crimp the new one on. That leaves you with one extra ground wire that our cars don't need (but maybe you can find a use for anyway).
 

Attachments

#48 ·
Actually, the V6 positive cable that I found doesn't go to the alternator. It just has one run going to the starter, and another going to the fuse box. I guess the fuse links for the alternator are considered a separate piece.

Huh. So maybe it would fit V8 models after all? STANDARD MOTOR PRODUCTS A544TB, if you're interested.
 

Attachments

#49 ·
Ah good find. Thank you much.
I was thinking, which can be dangerous.. But several years back the pigtail to the alternator with the single plug shorted out. It was staying hot with the key off and it killed the alternator. The alt was hot to the touch when the motor had not been running. After replacing the pigtail and the alternator it was up and running. So now I’m thinking that the wire the pigtail is connected to might be a good place to start inspecting. I need to peel the plastic wrap back but it looks like it runs from the alternator to over to the fuse box area and possibly into the firewall.
*edit*
I see on the drawing it goes from the alt to the fuse box in the car. Wonder why it got fried that one time?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top