Need help from the Ford guru's!

[Whysohigh]

Hello Gents! I've been researching all day with no prevail as to exactly what to do, so I have turned to the pro's for advise... So my 15 yr old son was just givin his first vehicle (94 FS Bronco, auto, 5.8l) from grandma. Truck is in mint stock condition with 132k on the clock. Truck was sputtering and stalling again, so grandpa put it in a local shop again, they claimed they couldn't read the codes and just threw parts at it! Ended up with a ne MAP sensor and Control Module... After around 50+ miles, it stalled out again while driving, yeah, son's first test drive, bummer.... I limped it home, cel was coming on and off, would just lose power and stall. I could restart in neutral while rolling and put back in gear, bucking/surging, no power, had to feather the gas to keep it going. Today, I did my research to check the codes by using jumper wire and reading cel, came up with 126(MAP), then stored memory was 212 and 126. When warming the engine for the KOER part, truck fired right up, idled great for about a minute, then died, fired again ran for a couple minutes, went to die, pushed the peddle and picked up...then died a minute or so later. Then fired it again and stayed running long enough to get temp up. After hooking jumper wire and firing back up, it did not give 4 flashes to start brake, steering, OD steps, just started giving codes, 998 and 126, so the 998 explains the surging situation (limp mode) and the 126 is MAP. The MAP was just replaced by mechanic with oreilly part, control module from azone (I know, boooo). Odd that grandpa replaced the MAP last year also, when first started acting up, along with a few other sensors. I really don't want to throw any more parts at it without having a good idea of the actual problem. I read to not test the MAP with a regular volt meter, then what kind do I need? What could cause it to keep throwing the code if it isn't bad? I checked for vacuum leaks and can't see any, sprayed base of intake with brake cleaner (all I had ) ... What are yalls thought? Any help will be GREATLY APPRICIATED by my son and I, I know very little about Fords, but do driveway mechanic work on Jeeps all the time

 

[miesk5]

yo W,

WELCOME!

Here is what I have;

See if another shop has a DVOM or a parts store will "loan" you one and a hand-held vacuum pump for a refundable deposit.

See Probst's info below, incl other possible issues in Chapter 12, page 296

Also, have you checked for HVAC sys vac leaks in cab and Under hood?

See my vac line test @ http://broncozone.com/topic/23994-90-58l-getting-continuous-code-33-and-running-code-44/ Post #20

========

DTC 126-129, P0235-P0237; "...Manifold Absolute Pressure (MAP) Sensor Gasoline Engines:

Description: On gasoline engines, the manifold absolute pressure (MAP) sensor senses atmospheric pressure to produce an electrical signal. The frequency of this signal varies with intake manifold pressure. The powertrain control module monitors this signal to determine altitude. The PCM then adjusts the E4OD shift schedule and EPC pressure for altitude.

On diesel engines, the MAP sensor measures boost pressure. The PCM monitors this signal and adjusts EPC pressure.

Symptoms: Firm shift feel, late shifts at altitude.

Diagnostic Trouble Codes: 126-129, P0235-P0237.

..."

Source: by Ford via Steve http://www.supermotors.net/registry/media/704885

Testing, Symptoms & Overview; "...a multimeter that can read frequency is normally required to check the sensor’s output. But you can also use an ordinary tachometer because a tach can display a frequency signal. Here’s the procedure: Connect the two jumper cables the same as before, (see diagram in site) attaching each end terminal on the sensor to its respective wire in the wiring connector. If you want to measure engine vacuum so you can correlate it to a specific frequency reading, connect a vacuum gauge to a source of manifold vacuum on the engine, or tee the gauge into the MAP sensor hose. Turn the ignition ON and note the initial reading. The reading on the tachometer should be about 454 to 464 at sea level, which corresponds to a frequency output of 152 to 155 Hz. Start the engine and check the reading again. If the MAP sensor is functioning properly, the reading should drop to about 290 to 330 on the tachometer, which corresponds to a frequency output of about 93 to 98 Hz. No change would indicate a defective sensor or leaky or plugged vacuum hose..." a vacuum gauge to a source of manifold vacuum on the engine, or tee the gauge into the MAP sensor hose.

Testing w/DVOM & Overview; "...The first job of the MAP/BP sensor is the measurement of the barometric pressure. Whenever you turn the key past the run position as you start the engine or if you turn the ignition switch to the "run" position without starting the engine, there obviously is no piston action yet and the only reading sent to the computer is the barometric pressure signal. The ECA also updates the barometric reading when the throttle approaches the wide open position (High Load = High manifold Absolute Pressure) which helps the performance of a car as altitude changes. Second, it measures the absolute pressure in the intake manifold. Absolute pressure is barometric pressure minus the vacuum created by the pistons. So, if the barometer is reading 30 inches of Mercury ("Hg) at sea level and the manifold vacuum (gauge) is 20"Hg at idle, the manifold absolute pressure would be 10"Hg. All MAP sensors work this way. As with most MAP sensors, this one has a three wire circuit. The first is the 5 volt reference. The second is the sensor ground (through the ECA). The third is the sensor's output to the ECA. Now, most other MAP sensors send a variable voltage to the ECA ranging from around 1 to 1.5 volts at idle to around 4 to 5 volts at wide open throttle and during key on engine off. Ford sensors differ in this respect. This sensor sends out frequency variations instead of voltage variations. If you were to read voltage on the output wire, you would see a reading of around 1.5 to 3.5 volts. This reading varies slightly with altitude and does not tell you if the output is correct or not. It is merely an indication that the sensor is operating. The frequency range of the Ford MAP/BP sensor is 92 to 162 Hertz (Hz). An engine idling at sea level may create 17"Hg to 21"Hg. At this vacuum, the absolute pressure is 13"Hg to 9"Hg. (Remember, absolute pressure is calculated by subtracting manifold vacuum from barometric pressure. The output frequency at idle should be 100 Hz. to 109 Hz. This signal varies as the manifold pressure varies. The frequency range of the Ford MAP/BP sensor is 92 to 162 Hertz (Hz). An engine idling at sea level may create 17"Hg to 21"Hg. At this vacuum, the absolute pressure is 13"Hg to 9"Hg. (Remember, absolute pressure is calculated by subtracting manifold vacuum from barometric pressure. The output frequency at idle should be 100 Hz. to 109 Hz. This signal varies as the manifold pressure varies. The most accurate way to test this sensor is to measure output using a DVOM (digital volt-ohm meter). In this case the meter must have a frequency measuring ability. The figure below shows how to hook up a DVOM to check the Ford MAP/BP circuit. Remember to select "DC volts" to measure the 5 volt reference and ground wires. Then select "Hz" to measure sensor output frequency. You might want to use a vacuum pump to create different vacuum signals to test the full range of the sensor. Note: Vacuum gauge testing and DVOM tests should be used to verify scanner readings and engine manifold vacuum..." see diagram

Source: by kemparts.com

http://web.archive.org/web/20090207214824/http://www.kemparts.com/TechTalk/tt11.asp

=============

Testing & Servicing, Chapter 11, from Ford Fuel Injection and Electronic Engine Control: How to Understand, Service and Modify, 1988-1993 BUT NEEDS FORD MAP Sensor TESTER

Source: by Charles O. Probst via http://www.yunost.ru/docs/Ford-injectors-book/Part11/Part11.pdf

Testing & Diagnostic Trouble Codes (DTC), Chapter 12, from Ford Fuel Injection and Electronic Engine Control: How to Understand, Service and Modify, 1988-1993

Source: by Charles O. Probst via http://www.yunost.ru/docs/Ford-injectors-book/Part12/Part12-1/Part12-1.pdf

Page 296







===============

Waveform in Bad Condition; MAP sensors are only used in Speed Density systems; "...This bad ford digital map sensor was captured using the digital MAF/MAP autometer. This vehicle was experiencing an extreme rough running condition as well as stalling out at times. Notice the autometer shows the current frequency reading plus the minimum and maximum reading recorded, a histograph of the frequency, and a labscope display of the waveform..."

Source: by omitec.com

Waveform in Good Condition; MAP sensors are only used in Speed Density systems; "...MAP sensors measure engine load and provide a barometric pressure value to many PCMs when the ignition is first switched on, before the engine is started. MAP sensors detect changes in engine load by measuring the amount of pressure inside the intake manifold. Manifold pressure is relatively low at idle and increases during acceleration. MAP sensor voltage or frequency (Ford) also increases as load increases. DonÕt confuse manifold vacuum with manifold pressure. Compare MAP voltage to vacuum in the chart below. Mirror images aren't they?..." Slide# 2 shows 90 Lincoln Town Car Reading

Source: by wrenchead.ca

http://web.archive.org/web/20081211081735/http://www.omitec.com/en/support/waveforms/

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I'll get back w more info on other codes later; I can't stay on-line long.

Also, have you checked for HVAC sys vac leaks in cab and Under hood?

See my vac line test @ http://broncozone.com/topic/23994-90-58l-getting-continuous-code-33-and-running-code-44/ Post #20

 

[Whysohigh]

Thanks miesk5! Did not know to check for vac leaks in cab, I will need to do this... Today I started with the obvious 126 code by contacting oreilly and swapping out the MAP with another since it had already been paid for, cleared codes and put about 20 miles on it, no cel yet... I just ordered a dy1077 since I moticed it bas a grey one on it that is probably stock... This should take care of the 212 code, correct? I also will be checking the plug wires to ensure 1&3 and 5&6 are not touching, since the wires were replaced a couple years ago by a mechanic. I think the problem is not fixed, just waiting for the reset on the computer to throw a code again. The 5.8 is very sluggish, and I swear I could feel a very slight surge in power when pulling a hill today, like power, no power, power, no power back and forth for just a couple seconds of each threwout the entire hill we we driving up (at lower speed, in town on city streets). I could feel it with my neck analyzer, head back the forward, then back then forward, lol, ever so slight tho. Truck idled and ran good tho, although when in park only, the rpm would fluxuate between 800-1000, drop slowly to 7-800ish then jump back to 1000 and slowly drop again... Almost seamed as tho I felt that surge under load, but stopped in gear, rpm held steady around 750... Will check plug wires tomorrow and look for vacuum lines under the dash... Should get new ICM in a couple days, Rockauto, $58 + shipping thanks for any additional thoughts,

 

[miesk5]

yo,

YW!

Yes, DY1077 (BLACK ICM) is correct for 94.

Check Spark Plug Wire Routing with TSB 94-04-10

94-96 5.0 & all 5.8 - engine miss, spark knock, buck/***** surge and other driveability concerns; MIESK5 NOTE; & The firing order for 1994 5.0Ls & all 5.8Ls is 1-3-7-2-6-5-4-8. On these vehicles the #1 and #3, or #5 and #6 spark plug wires must be separated to eliminate the possibility of an induction crossfire. To eliminate the possibility of the coil wire becoming disconnected, route the coil wire under the spark plug wires at the distributor cap.

http://www.supermotors.net/clubs/superford/registry/5180/32495



and

Vacuum; I see that you have researched a lot! See my Vac Test for other vac leaks such as @ Master Brake Booster, Vac Tee atop intake, etc.

94