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My car misses like crazy Pages: 12

Kolbergk on Sat April 21, 2007 3:22 PM User is offline

Year: 1993
Make: Ford
Model: Taurus
Engine Size: 3.0
Country of Origin: United States

It started a few months ago. And it keeps getting worse. I've tried all the obvious things. Spark plug, rotor, distributor cap, fuel filter, (fuel pressure is at 34 and 38 psi, engine on and off), run a couple bottle of injector cleaner though, checked vacuum (18.5"), checked for vacuum leaks, and the check-engine light is not on. (yes the light works when you put the key in) I put a reader on it anyway. The only code that comes up is 634, 'Manual Level Position (MLP) sensor - signal voltage higher or lower than expected.'
It's an automatic and that sound like a shifter thing. It doesn't run too bad at idle, gets real bad with the A/C on. I've listened to the injectors and they sound OK but again that at idle. Does anyone have an idea what I should look at next? I've had this car since the day I drove it off the dealers lot back in Oct of '92. It's in great condition, well except for this!! Thanks, Ken

NickD on Sat April 21, 2007 4:37 PM User is offline

I had the same problem with my 89 Continental, no codes, terrible miss, idled okay, was the MAP sensor, manual doesn't tell crap about it, but learned it was suppose to output a 95-155 Hz frequency with 12 V applied when varying the vacuum input from 0-20"Hg. This thing was all over the place kicking out 20 Hz then 200 Hz driving the ECA and me nuts. Suggest taking a look at that. If you have a MAS, that can act the same way.

Kolbergk on Sat April 21, 2007 6:50 PM User is offline

I will certainly look into those. Thanks for the reply!

bohica2xo on Sat April 21, 2007 7:51 PM User is offline

With the key off, pull the electrical connector off of the MAP sensor.

Start the car, and go for a drive in "limp home" mode. See how it runs. The default for limp home is usually a bit rich.

.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Kolbergk on Sat April 21, 2007 11:44 PM User is offline

Ok, and if it runs better than it indicates the MAP sensor? (as bad)

NickD on Sun April 22, 2007 6:36 AM User is offline

Without test equipment, you are guessing, can also be in the MAP connector, the ECA side, wiring, like a broken conductor within the insulation, cold solder joint in the ECA, or within the MAP sensor module itself. Forgot about Bohica's suggestion just to unplug it and put your vehicle in the limp mode to see if it cures your misfire, won't run as strong, but at least will tell you if it's in the MAP circuit, try unplugging it and let us know. Disconnecting the battery for about a minute and reconnecting it resets the computer putting your computer in the learn mode, will also run rough for about ten miles until it relearns.

Can tell you, if every connection is perfect and every sensor and module is tuned to the center of it's specification, the computer doesn't have anything to learn so the engine will run perfectly after disconnecting the battery, this includes proper initial timing.

Your car is also 14 years old and according to statistics, is at the end of it's life, Ford uses a lot of unplated electrical connectors that tend to corrode over time that contribute to strange electrical problems.

bohica2xo on Sun April 22, 2007 2:34 PM User is offline

Nick:

On the web, it is hard to know the level of equipment / training available on the other end - I try to provide a path for the LCD...

Yes, disconnecting the MAP will not tell you if the problem is the sensor itself, or a wiring issue - but it will quickly narrow your search, without any test equipment.


Kolbergk:

Disconnecting the MAP is obviously the first step. Depending on where you live, contact corrosion may be a big issue. If you find that the 'miss' disappears, then it is related to the MAP sensor & circuit. While you have the connector removed, carefully inspect the connector halves for corrosion on the contacts. Look at the back end of the harness connector for loose wires, or corrosion. If you find any corrosion, correct the connector problems. Once you are sure the connections are good, reconnect & road test again. If the connector is clean, you can "substitute a known good part" (that is right out of the service manual) if you have one.

If you have good test equipment, Nick can walk you through the test procedures.


B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Kolbergk on Sun April 22, 2007 3:30 PM User is offline

Gentlemen, I've come to the conclusion that this engine doesn't have a MAP sensor. Is that possible? I have a subscription to All Data auto repair for this vehicle. I can't find a reference to a MAP sensor there. I then went to two different part stores (NAPA first-he looked at two different engines and found no MAP sensor listed for this car. Next was Advanced Auto and they were happy to sell me one but couldn't figure were it would go). I didn't buy the $54 part. (rockauto.com sells it for $7.68) Go figure.

I did disconnect the battery for a few minutes. Interestingly the car is running better, but still not right.

There is a vacuum line routing diagram under the hood and it doesn't show a MAP sensor either. Still lost, KEN

bohica2xo on Sun April 22, 2007 10:21 PM User is offline

You are correct, in 1993 the MAP sensor became the BARO sensor as the system switched over to Mass Air from Speed/Density on the Taurus.

Since you have a mass air vehicle, the usual suspect is the AMM - but that usually shows a code for the problem. I never had much to do with the Taurus in those years, and many other vehicles were still S/D in 1993.

My books show sensor voltage data for hot wire type (MAF) , vane type (VAF) & MC-VAF air flow sensors, as well as Flex Fuel sensors, MAP sensors, BARO sensors, DPFE sensors, ACT & ECT sensors, TP sensors, TOT sensors, and the MLP sensor you have a code for. Obviously a change over year.

Lots to test, and you will need an oscilliscope for some of it. Things like the BARO sensor have a test value of 122.4Hz to 164.4Hz across a range of 17.1 in Hg to 31.0 in Hg.

Does your alldata info include the voltage range charts / pin voltage charts?


B.

Edited to add:

How many miles on the vehicle? You say it misses, does it lack power at highway speeds too?

.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Edited: Sun April 22, 2007 at 10:26 PM by bohica2xo

NickD on Mon April 23, 2007 11:24 AM User is offline

Suppose we should do homework first, too many vehicles, too many changes, believe the last year for the MAP sensor was 1992. A worth while device for telling the computer exactly what the absolute pressure is in the intake manifold the mainly controls engine timing to retard it when hitting the gas. Also an implicit method of obtaining this value by the throttle position sensor, engine speed sensor, and data from the mass air flow sensor, you still have these. Logic is, while not as good as taking a direct measurement, software is a hell of a lot cheaper than hardware and Ford can still get the same price if not more for the car. A barometric sensor was also previously used to compensate for altitude, but that was made history before the demise of the MAP.

Half working on a 95 Escort 1.9L that also lacks the MAP, but still has the MAF, runs great on the highway, starts instantly, but if allowed to idle more than 30 seconds in or out of gear, has an AT, engine instantly goes clunk and dies, hit the starter and it's running again, the instant the starter is hit. Does not kill when the engine is cold.

First step was to check out the ignition, this car was always maintained by a Ford dealer, new Motorcraft plugs, two were gapped at 0.020 the other two at 0.10", yeah that far off, cleaned and regapped the plugs, have a spark plug tester, checked the sparkplugs, and spark gap, all okay. Engine still dies at idle.

Checked the IAC, very badly carboned up, cleaned it with no improvement and even wasted 67 bucks with a new one as the valve was still jamming, no improvement.

Checked the EGR, lots of carbon, cleaned the lines and checked for a good seal when closed, then checked the EGR vacuum valve, kind of crazy, doesn't switch vacuum to the valve, but bypasses it, either draws vacuum from a then dirty filter or from the EGR valve, it was badly carboned up as well and leaked like crazy. If anything, the EGR was not coming in at all, but has a PFE that is working and was not generating any codes, matter of fact, no codes period, and fuel pump pressure is good. After this, still dies at idle.

The TB is loaded with carbon, that is my next step to clean that, oh, and I did clean and check out the MAF sensor, didn't find any problems there, but above an engine speed of 1K rpm, it runs great. I did drop in a can of Slick injector cleaner, well wasn't Slick, but like it, the kind that is suppose to clean all the carbon off the intake valves., After driving the car for about 150 miles, noticing an improvement, this time the idle drops to about 500, engine shaking like crazy, but if I put a little pressure on the gas pedal to bring it back to 900 rpm, it runs fine, even in gear.

Well the problem with this car is carbon, and lots of it, will see what happens after I clean the TB when I get to it, not really being an earth day kid, would still not mind if they took the carbon out of gas, a PITA. Fords are notorious for carbon in the TB as the PVC returns to the air cleaner inlet, other cars return this crap line to the base of the TB that leaves it clean, but both still put plenty of deposits on the injectors. You normally get an O2 error code when they plug enough or a misfire code, but apparently this car isn't quite that bad yet. May have to pull the injectors and clean those, always find a lot of crude that really affects the spray pattern, gas more like drips out.

As an engine wears, a lot more crap comes back from the PVC that really augments the carbon build up problem, does help to decarbonized the engine as the piston rings are also carboned up, you should try to remove these rings from a badly carboned engine. But we are driving very limited life consumer grade products that are designed more and more to be thrown away and with some of these older cars, that is becoming very tempting.

Sometimes we like to find one simple problem, but it is a series of a bunch of minor problems, some were lucky claiming replacing the MAF solved all their problems with that kind of misfire, but I wasn't there to observe if it really made that much of an improvement.

mk378 on Mon April 23, 2007 7:05 PM User is offline

Nobody mentioned the spark plug wires. They've been the source of most of my missing problems. They can look perfect but still not work. I don't really advocate "shotgun" replacement of parts, but it may be worth considering.

See if you can isolate the miss to one cylinder by disconnecting the spark plugs one at a time. If it isn't clearly one cylinder then it may be a computer related problem rather than just ignition.

The other classic cause is air or vacuum leaks. Especially if the car has an air flow sensor of some type, and air is getting into the engine without going thru the sensor, it won't idle well, if at all.

Edited: Mon April 23, 2007 at 7:07 PM by mk378

NickD on Tue April 24, 2007 9:25 AM User is offline

With a misfire, lots of oxygen pours out the engine that the O2 sensor can't deal with kicking out a code, no codes. Got the opinion that idle was okay and a misfire is worse at idle, but plug wires can be a problem. Ford takes the center carbon string conductor and folds it under the plug connector that over time bakes that joint causing high resistance. Should measure about 2,000 ohms per foot. To save a couple of bucks, spread the connector, strip off another 1/2", also jam a piece of bare plated 20AWG wire for extra conductivity, recrimp, and get the normal resistance. Clean the insulation with solvent, make sure the holders are in good condition, after all the best insulation is distance to any metal surface, and good to go.

Just like an electrical appliance they tell you to unplug it by pulling on the plug, not the line cord, but pulling the boots off is one of the worse part of changing plugs. I did purchase a boot puller but a piece of crap, works like a pliers making it just that more difficult to pull off a baked on boot, why don't they put on some silicone grease in these things. If some guy did pull on the wire, it will stretch and break that inner carbon string and that wire is history. I took a piece of 5/8" flat steel, bent it at a 90* angle with a notch to get under the boot with a pair of vise grips to pull the boot off, works much better as that expands the boot.

Can recall spending hours trying to get the #1 plug out of the 3.8L Ford, what a PITA that was, even called my Ford dealer for recommendations, told me his mechanics hate that job, and will only do it based on an unknown time at 75 bucks per hour. I finally removed the tension pulley, a couple of easy bolts and was able to reach that plug from the front of the engine, Ford put those plugs in with the engine on the subframe before they jammed it in the car, their job was easy. Also prayed just the plug would come out and on the threads of that aluminum head, sucker was welded in and PB Blaster is only so good.

Course then, if Kolbergk is not getting any codes, everything is okay, and that miss is his imagination, what many times have you heard that story?

Kolbergk on Wed April 25, 2007 9:01 PM User is offline

Hi All, I never thought it could be the plug wires because I bought them with a lifetime warrantee years ago. But someone suggested it so I looked a night, in a dark garage, and I could see lights were the wires passed near metal. Damn. So today I when back to the place I bought them and they said "too bad, we changed names and don't have to honor the warrantee". Anyway, with a new set, the misfires are gone! Just like that. Live and learn. Thanks for all the replies. You guys are great! Keep up the good fight.
Ken Kolberg

NickD on Thu April 26, 2007 4:59 AM User is offline

Learned to avoid anything with a lifetime warranty, somehow, assumed OE spark plug wires of the correct length and routing, surprised you were not getting an O2 code with excessive oxygen, but would be concerned about the status of your catalytic converter, that guy was running red hot with that misfire. Stick with OE stuff.

mk378 on Thu April 26, 2007 11:01 AM User is offline

Sweet. I really don't like just replacing parts without confirming they're bad, but with wires it's just hard to tell. I've found that the cap, rotor, and plugs will outlast even a decent set. So they've become my "go to" part in case of misfiring especially misfiring under load, which points to weak sparks.

Long ago, the discount stores started selling brake pads with a lifetime warranty. There was of course nothing magic about those pads, they were going to wear out the same as any other pad would. It was just a come-on to raise the price, and develop some loyalty to that store.

HECAT on Thu April 26, 2007 4:27 PM User is offline

Ken,

Glad you found the problem, don't you just hate it when it turn out to be something that simple. Trust me, we have all been there. The night time check of the plug wires has always been a neat trick to diagnose direct shorts.

Some interesting comments about lifetime warranty came up that I would like to explore. We would all like to believe that purchasing an item with a lifetime warranty means it is of better quality. Unfortunately, I know when I worked out of my tool box we sold crappy mufflers, shocks, brakes, wipers, and a ton of other stuff all with lifetime warranty. It was not about inflating the price but rather about creating customer loyalty and returning visits. Nick says never buy anything with a lifetime warranty. I find myself more wary of the extended warranties offered for a price.

I offer a lifetime warranty on certain models of the equipment/tools we manufacture. I do this because of the history and proven longevity of the product. It's not an inflated price but rather a marketing promo and risk I am willing to take to promote the durability and long service life.

My question is: Do you think this enhances or detracts interest in the tools? It has worked for Craftsman, Snap-On, etc. Please share your thoughts.



-------------------------



HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

NickD on Thu April 26, 2007 4:55 PM User is offline

You just had to mention Craftsman to make a liar out of me, recently returned twenty some odd screwdrivers, some 40 years old, some I used for a pry bar, others just flat worn out, for all brand new ones. If they didn't have the same model, would give one of a higher quality. No charge, no tax, no shipping, even trade. But if you lose the tool, warranty doesn't apply. Torque wrenches are not covered in the hand tool line, so have to take good care of that kind of tool and find something else to smash down an old brick wall with.

Guess I was thinking about mufflers and brakes that I had purchased with a lifetime warranty, not that it was the reason why I purchased them, same story, we don't carry that brand anymore, have to go back directly to the manufacturer, if you can find him.

powerflite on Thu April 26, 2007 5:59 PM User is offline

My last experience with liftime brake linings? When I returned them I was told that it does not cover normal wear and tear! What?? Lesson learned, just get what you want and forget the hype. You will be happier.

mk378 on Thu April 26, 2007 7:06 PM User is offline

I think the "lifetime" brake pads truly started with good intentions. Brake pads are basically very inexpensive to begin with, and if giving some away will keep people coming into the store to buy other stuff, it seemed worth it. In the early days, few questions were asked. The store's attitude was "make the guy happy." Even if someone brought in what were obviously the OEM pads that came with the car, they'd get free new ones.

Of course whenever a "system" is established, it is incumbent on everyone to "game" it as much as possible. This ranged from outright lying to just buying the rotors somewhere else because they're a dollar cheaper. The stores were no better, rather than stop selling "lifetime pads" yet honor the "lifetime" commitment to old customers, they come up with loopholes. And they continue the practice which is now outright decpetive, of promising "lifetime replacement" which will never happen.

NickD on Fri April 27, 2007 6:53 AM User is offline

I miss my brake store of the 50's ran by a couple of old guys, bring in your drum and two shoes per wheel would turn and clean the drum, strip the linings off the shoes, clean, some kind of an epoxy coating, and bond new linings to them, then arch the linings to the drum. Price was two bucks per wheel. Did this while you were waiting with interesting conversation, didn't believe in rivets as they used over half the thickness of the lining and would grind the drum when the linings were less than half worn, so the brakes effectively lasted over twice as long. But no lifetime warranty. They were good brakes.

Miss the old hardware stores too with a guy that knows everything and knows where everything is, grab a handful of screws, bolts, or nails and drop them in a paper sack, weighs and charged around a dime a pound. Today, have to pay a buck for a bubble pack with 2 or 3 screws in it and takes a half an hour to open that pack and sometimes slip after the tenth pack and cut my finger trying to get the damned things out. Other bolts come with a permanent bar code pasted on with a use safety glasses warning, takes another half an hour trying to remove that label before you can use it. If you ask for help from a clerk, if you don't see it on the shelve, we ain't got it.

Auto parts counter guys will never change, swear their phones have grown into their ears and are a permanent part of their heads. Last time took my cell phone with me. Hi, I am the guy standing right in front of you will a cell phone in my hand, wait, do not hang up! Would you please check me out? That works.

bohica2xo on Fri April 27, 2007 2:16 PM User is offline

Huh.

I have never had a problem with the lifetime warranty on pads. I just take them back to the store, and they smile and hand me a new set. I realize that most customers do not keep a vehicle long enough for them to see the pads come back, so they make it on the volume.

I had a Bronco that was hard on U-joints. AutoZone replaced at least 6 of them under the lifetime warranty, and replaced the con-vel joint once as well. Never an issue.


Good call on the plug wires, Mk378. I usually replace the wires / cap / rotor as an assembly, and missed the fact that he did not replace the wires.


B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

boatmoter on Thu July 05, 2007 10:04 PM User is offline

coil paks are notorious for going bad on those.. get a spray bottle filled with water,get up to engine temp. spray light mist on the coil pak. watch for a difference in idle..

-------------------------
Glenn //

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