Strange problem, possible bad MAF

Ok I'll start at the beginning but give the quick version. Recently i was on the highway cruising along and the truck lost power. U pimped the gas pedal on it came back, but after about 2 seconds it lost power again. This continued in this fashion down the road for several miles. It would have power for a few seconds and I could preemptively lift my foot and reapply it to keep moving. If I stayed in the gas for more than about 3 seconds though it would loose power. It did not change the time that it would keep going if I went to WOT or just eased into it. It was late and there was no traffic so I thought I would turn off the truck and fire it up again to try to fix the issue. this caused me to have no power upon starting the truck and I had to pull over.

that this point I tried to start it for about 10 minutes off and on. It would sometimes start Ok but as soon as I tried to give it gas it would seem to go really rich and die. I was on the verge of having it towed when it started up and ran fine. I got on the road and made it to where I was going.

Several days later I was on the my way home and the same thing happened, maybe 10 minutes into the trip. Again I pulled over and after a couple of minutes in which I did not even attempt to do other than start the car it was fixed and I made it 60 miles home.

Sice then it has been getting worse but usually I can drive the truck for several miles before anything bad happens, and I can usually turn the car off, restart it while giving it gas, and the problem will go away for a bit. Sometimes I can pump the gas and keep it moving and other times it is jst dead, wont do anything but adle at about 550 RPM for a while before it dies.

I went to Autozone to have the codes checked, the check engine will come on sporadically when this happens, but they were clueless down there. So I went home and looked up from here how to check them myself.

I got a KOEO code of 159, MAF sensor is/was out of range.

So I picked up a new MAF, put it in in the parking lot and thought I was done, I got almost home before I got the same problem again. Same code is thrown.

so now I wonder if it is a ECM problem. I check the voltage going to the maf and it is battery voltage. I thought it would be a 5v sensor but I guess not. Also it is not regulated, it is straight battery voltage, I am not sure if this is normal.

So what now. Do you figure i got a bad replacement MAF, it has happened to me with alternators fro there so I am considering it a possibility, or is it something else and is masking itself as a MAF problem.

Could the fact that it seems to happen once the car has warmed up point to a O2 sensor issue? Also I reset the codes and the KOEO kept throwing the 159 code. does it read that code anew every time or is it possible that it's a saved code that did not reset.

Sorry for the long post but I am lost. I am hoping that someone will recognize the symptoms and tell me what the problem is.

A KOEO code is read anew each time you pull codes. CM codes (the second set output during the KOEO test) are the stored codes.

Because KOEO codes are set with the engine off, they almost have to be electrical in nature, which means it probably isn't the O2 sensor.

Remember that codes point to problems in circuits, not sensors. The battery power supplied to the MAF is just an "excitation" voltage kind of thing. (To get really technical, if an automotive MAF is like other industrial MAF's tha I work with, it is wired as a wheatstone bridge, with the two elements that are in the air stream as two legs of the bridge. Battery voltage is the source voltage to the bridge, and the other two wires going to the computer are measuring the voltage drop across the bridge.) Just because the MAF is seeing battery voltage doesn't mean the correct "MAF signal" getting back to the computer.

PCM's don't go bad very often. The usual procedure for diagnosing a bad PCM is to eliminate every other possible cause for the code. If everything else is functional, then the PCM must be bad by process of elimination. I would suggest checking the continuity of all the wires between the MAF and the PCM.

If it helps, you might go to the library and see if you can get a good manual (Mitchell or Motor Engine performance, diagnosis, and troubleshooting or something like that). From there you can get a copy of the "circuit pinpoint test" for a KOEO 159 which can help organize your diagnosis to follow the proper diagnostic tree.

Ok, here's an update and another question.

First of all I tried to track down any possible bad wiring or other electronic problems for a few days and when I could find nothing I decided to replace my ECU. I have had similar problems in other cars and it turned out to be bad capacitors in the ECU in those cases. So I called the junkyard and they found me an ECU. The 4 character code did not match my NAP2 but he said it would work. The Serial on the ECU was close to mine which is F37F-12A650-TC but the one he gave me ended in -BC

Well this turned out to be a problem, I believe the one i got is set up for an auto tranny and not my 5 speed. The truck runs with it in but not well, like the fuel curves are way out of whack. But it runs bad consistently, none of the problem I was having before. So he has been trying to get me a replacement but not having any luck with it. So I called up an ECU repair place and that guy told me this is a common problem with my particular ECU so they are hard to get. He said that he recently replaced one for a guy where some component went bad a burned a hole in the board. So I popped my apart and found all 3 caps are definitely bad. They are leaking and overheating. Luckily I know someone that does ECU repair on other cars and he is going to take a look and make the repairs for me. He doesn't usually work on fords but it is a simple fix, he does cap replacement all the time.

Ok for the question part. Does anyone have a good source for capacitors in small quantities? Mouser sells the ones I need but in lots of 1000. Newark has a 2000 minimum. In case anyone else finds this problem here are the specs for the caps you will need.

You will need 2 of the following:
47µF 16V 105ºC Made by Nichicon part #A9244 (not in current catalog)

And 1 of the following:
10µF 63V 105ºC Made by Nichicon part #A9209 (not in current catalog)

Update on the problem:

I got the caps replaced and it seems that all the problems are fixed. I would suggest that anyone having strange electrical problems take a few minutes and check their ECM. While checking around trying to find one i found that a lot of people have had similar problems in one case getting so bad that it burned a hole in the board.

If you want to check for this problem open up the ECM by taking out the 2 T-20 torx screws in the side. then the two half can be lifted off and you can see the board. The caps look like little barrels and are probably blue. If they are really going bad like mine were you will be able to see black spots on the board under then where they have leaked and are overheating and melting the protective coating off of the board. They can be bad and not look like that, one sign that they could be going bad is a bulge in the cylinder. If these go bad your truck will not run well and it can throw all kinds of strange code and be very hard to diagnose.

If you are really good with electronics and want to try to replace them yourself go for it but be careful. the big problem may be getting the caps for it. I found a store locally that sells that kind of thing but if you look online you can find exactly what you need but it's hard to get less than 1000 at a time. I ended up taking my ECM to a local business Jestr Tuning, that works on performance ECU's and dyno tuning. I've had john from Jestr do all my DSM electronic work for many years and I have never had any problems with him so I figured I would see what they could do. They had never done a ranger ECM that I am aware of but they did a great job of fixing mine. If anyone is having an ECM problem I would recommend them. You can email John at jestr@jestrtuning.com

Ok well that's it. I am back on the road. I hope this update helps someone someday.

Nichicon is just one of many vendors that make radial electrolytic capacitors. There are a lot of others that would work as long as you use the same capacitance and the same voltage (or greater). As a further note, observe the polarity of the cap before you remove it from the PWB.

It's amazing that Ford is still using electrolytic capacitors in their ECM electronics, as electrolytics only have a designed service life of 5 years, anything after that is a gift. Tantalums have a better service life and may work fine in these circuits also (but are more expensive, and thus not used in the factory units). There are also some new generation ceramics that would work well but they are surface mount and would take a bit of work to retrofit.

Nice post Talon.

Excelent INFORMATION

Dear Friend,
I've just fixed my explorer XLT 94 using your clues or hints hier found, changing those 3 capacitors 2x47mf 16V and one 10mf 63v or 50v that I took from used computer board to subistitute. The car after a week being reserched, I gone through all sensors and this was really the point, the capacitors was leacking and corroaded in the base, I just cuted them with a sissors thakeing care not to overheat the components below, once this is a double circuit board and resoldering them in correct polarity back.
The car work marvelous later, of couse I did full revisions in spark plugs, MAF, TP, AIC, WT, AT, filters, fuel pump, CKS and O2 but I only found problems in your EEC-IV capacitors.
Thank you very much
I'm at your disposition, cheers from Rio, Brazil.
Ricardo Carlos von Montfort

Where is the ecu?

On my '92, it's behind the kick panel, just in front of the passenger door, below the glove box.

Thanks man, I hope its not cooked.

Hey Talon, did you have a ground problem at all?

Here was my situation:

1994 E250 Van
Stalling and rough idle
Pinging in overdrive
Maintenance up to date
No codes
236,000 miles
5.8l engine, automatic

Then I found a few threads like this about replacing electrolytic capacitors in pcms. When I pulled my pcm, an easy task, I found a 1/8" puddle of black oil underneath the 10mf 63v capacitor. I replaced the capacitor, available at Torrance Electronics in south Los Angeles, and my problems disappeared. I used only a pencil soldering iron and a desoldering pump from RadioShack. I struggled for a couple hours with removing the old solder. I was being careful not to overheat the gold foil on the circuit board. A desoldering iron would have been more suitable, I imagine. This would be an easy job for a tv tech who is used to more intricate soldering. He would just need to remove the rtv protectant.
I think I have saved myself at least half the cost of pcm repair and programming.

TalonG32 said:

Ok well that's it. I am back on the road. I hope this update helps someone someday.

Click to expand...

It did. Post #4 fixed me up with my Ranger. My ECM had the same issue. Kept giving a bad MAF reading. Replaced the scorched ECM with another unit and problems are gone!

See kids, searching does work!

I've been lurking here for a while -mostly when I had a problem with my 93 Explorer - but I decided to register after using the info in this thread.
The suv has about 90K on it. I've owned it since new.
It started running poorly -spark knocking, no power, poor(er) gas mileage and finally the check engine light came on. Pulled the code 159, MAF out of range.
So I replaced the MAF with a rebuilt one. Same thing happens. Disconnect the MAF and it runs better but not good. Checked the wiring from MAF to PCM -all good - has to be the PCM, right?
Then I found this thread. Took out the PCM, opened it up and found black puddles under two of the three capacitors. Ordered replacement caps fro Jameco Electronics
I just finished replacing the caps and reinstalling PCM. Took the car out for a test drive and it purred like a kitten. FIXED for less than twenty bucks!
Thanks, everyone!
Jack

Thanks!

I checked my ecm today after three weeks of headache (93 ranger) sure enough, bad capacitors!one was completely poped another leaking.

Information like this is the reason Forums were made; and people like you, who actually follow through and post your fix are the key to everyone's sucess.

Thanks for sharing the information,
Brian

1994 4.0 V-6 Ford Ranger manual 5 speed. PCM located on firewall behind fender well on drivers side. Whats the easiest way to remove it. Is it to remove the fender well. It will run great after 30-35 mph but before that it acts like its starving for fuel. Idle only reads 330, then vehicle shuts off.