buckin bronco

[tdub]

I'm not quite sure what the problem is. I was driving home from a friends house when all of a sudden I hear this weird noise as i'm taking off from the stop sign. It sounds like something is stuck between the break pads and the rotor. I give is a little gas and it's instantly gone. I come up to the next stop sign and it starts again before I get stopped. Then when I take off again it hesitates and shakes a little. Then stops kicks into second and starts the process all over again. I had a mechanic look at it when I bought it a month and a half ago. I guess something could have developed since then, but this was all of a sudden. It's totally fine when I'm cruisin at 45.

I put it in four wheel drive, moved forward a bit, then took it out and moved backward a bit. I thought something in the transfer case might be stuck, I dont know. I finally pulled up to the house and backup again for good measure and then pulled into the drive way. When I was pulling in it was lunging/bucking. ?!?!?!?!?!?!

any ideas?

 

[Broncobill78]

any ideas?

Yup, sounds like the Mass Air Flow Sensor. There's a TSB out on this, it gets dirty/contaminated and one of the symptoms is bucking/jerking & hesitation/surge on acceleration. I'll see if I can find a copy of the TSB

Here, just found it. TSB 98-23-10

Article No.

98-23-10 MASS AIR FLOW (MAF) - SENSOR CONTAMINATION - SERVICE TIP

Publication Date: NOVEMBER 10, 1998

FORD: 1990-97 THUNDERBIRD

1990-99 MUSTANG, TAURUS SHO

1991-99 CROWN VICTORIA, ******, TAURUS

1992-94 TEMPO

1993-97 PROBE

1995-99 CONTOUR

LINCOLN-MERCURY: 1990-97 COUGAR

1991-99 CONTINENTAL, GRAND MARQUIS, SABLE, TOWN CAR, TRACER

1992-94 TOPAZ

1993-98 MARK VIII

1995-99 MYSTIQUE

LIGHT TRUCK: 1990 BRONCO II

1990-97 AEROSTAR

1990-99 RANGER

1991-99 EXPLORER

1994-96 BRONCO

1994-97 F SUPER DUTY, F-250 HD

1994-99 ECONOLINE, F-150, F-250 LD, F-350

1995-99 WINDSTAR

1997-99 EXPEDITION, MOUNTAINEER

1998-99 NAVIGATOR

1999 F-250 HD, SUPER DUTY F SERIES

ISSUE:

This TSB article is a diagnostic procedure to address vehicles that exhibit lean driveability symptoms and may or may not have any Diagnostic Trouble Codes (DTCs) stored in memory.

ACTION:

Follow the diagnostic procedures described in the following Service Tip. The revised diagnostic procedure is a more accurate means of diagnosing the symptoms.

SERVICE TIP

MASS AIR FLOW (MAF) DISCUSSION

MAF sensors can get contaminated from a variety of sources: dirt, oil, silicon, spider webs, potting compound from the sensor itself, etc. When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over-estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows.

If vehicle is driven at Wide Open Throttle (WOT) or high loads, the fuel system normally goes open loop rich to provide maximum power. If the MAF sensor is contaminated, the fuel system will actually be lean because of under-estimated air flow. During open loop fuel operation, the vehicle applies Long Term Fuel Trim corrections that have been learned during closed loop operation. These corrections are often lean corrections learned at lower air flows. This combination of under-estimated air flow and lean fuel trim corrections can result in spark knock/detonation and lack of power concerns at WOT and high loads.

One of the indicators for diagnosing this condition is barometric pressure. Barometric pressure (BARO) is inferred by the Powertrain Control Module (PCM) software at part throttle and WOT (there is no actual BARO sensor on MAF-equipped vehicles, except for the 3.8L Supercharged engine). At high air flows, a contaminated MAF sensor will under-estimate air flow coming into the engine, hence the PCM infers that the vehicle is operating at a higher altitude. The BARO reading is stored in Keep Alive Memory (KAM) after it is updated. Other indicators are Long Term Fuel Trim and MAF voltage at idle.

NOTE: THE FOLLOWING PROCEDURE MAY ALSO BE USED TO DIAGNOSE VEHICLES THAT DO NOT HAVE FUEL SYSTEM/HO2S SENSOR DTCs.

Symptoms

Lack of Power

Spark Knock/Detonation

Buck/****

Hesitation/Surge on Acceleration

Malfunction Indicator Lamp (MIL) Illuminated - DTCs P0171, P0172, P0174, P0175 may be stored in memory

OBDII DTCs

P0171, P0174 (Fuel system lean, Bank 1 or 2)

P0172, P0175 (Fuel system rich, Bank 1 or 2)

P1130, P1131, P1132, (HO2S11 lack of switching, Bank 1)

P1150, P1151, P1152, (HO2S21 lack of switching, Bank 2)

OBDI DTCs

181, 189 (Fuel system lean, Bank 1 or 2)

179, 188 (Fuel system rich, Bank 1 or 2)

171, 172, 173 (HO2S11 lack of switching, Bank 1)

175, 176, 177 (HO2S21 lack of switching, Bank 2)

184, 185 (MAF higher/lower than expected)

186, 187 (Injector pulse width higher/lower than expected)

NOTE: DO NOT DISCONNECT THE BATTERY. IT WILL ERASE KEEP ALIVE MEMORY AND RESET LONG TERM FUEL TRIM AND BARO TO THEIR STARTING/BASE VALUES. THE BARO PARAMETER IDENTIFICATION DISPLAY (PID) IS USED FOR THIS DIAGNOSTIC PROCEDURE. ALL OBDII APPLICATIONS HAVE THIS PID AVAILABLE. THERE ARE SOME OBDI VEHICLES THAT DO NOT HAVE THE BARO PID, FOR THESE VEHICLES OMIT THE BARO CHECK AND REFER ONLY TO STEPS 2, 3, AND 4 IN THE DIAGNOSTIC PROCEDURE.

Look at the BARO PID. Refer to the Barometric Pressure Reference Chart in this article. At sea level, BARO should read about 159 Hz (29.91 in. Hg). As a reference, Denver, Colorado at 1524 meters (5000 ft.) altitude should be about 144 Hz (24.88 in. Hg.). Normal learned BARO variability is up to

 

[bidibronco]

Well, if you just kept your foot on the gas instead of "feathing" it, it'll stop.... sorry... couldn't resist!

 

[ford_zilla]

i have the same problem it sounds like in my 87, but i also herd it could be my tranny kick down not set properly. its a new rebuild on it with a shift kit

 

[mbtech2003]

i have the same problem it sounds like in my 87, but i also herd it could be my tranny kick down not set properly. its a new rebuild on it with a shift kit

yes for u no for the 95 bronco as it uses the throttle positition sensor for transmission shift control. i would agree with the air mass meter, because u live in calif. you will have one unlike the rest of the country lol. some times they can get crap on them. use a can of ele. cleaner from your local parts store and clean it off. also if u just installed a new K&N air filter check and make sure it doesnt have too much oil on it as it will be sucked up and go on th sensor >-

 

[tdub]

I think I described the situation wrong. I had a similar situation in my 94 explorer (with the push button 4x4). It sounds like the transfer case is trying to engage, but only because some sound is coming from the area where the drive shaft meets the front diff. My explorer was stuck between 4x4 and regular. I took it to the shop and the mechanic told me the transfer case was filling up from the fluid in the tranny. But that means the tranny was low. I put 2 quarts in the tranny after the mechanic cleared the beast a couple of months ago.

Anyhow, the mechanic said there's a seal between the transfer case and the tranny that might have gone bad causing something to ***** up in the transfer case, he sent me to a tranny specialist. The tranny guy got in the car drove it with me in it, said, "that's weird i've never heard that sound before" basically the same thing the mechanic said about the sound. Needless to say I felt better in my inability to relay the sounds to you all. But i'm still stuck...

So here is a really odd question, if the transmission is pushing fluid into the transfer case, is there anyway that the 4x4 could be trying to engage because of some pressure? I know that sounds like a dumb question, I just am baffled.