Question about BMW Cars & Trucks

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I have what I consider a strange problem. I have blow back on my air intake from time to time. My car is a 1991 BMW 750iL 12 cylinder. The car has been in storage for about 5 years. Ran great before storage. To get the car started I had the old gas pumped out, change all the plugs and wires. Change oil put a new battery in the car bought new tires and it started. But the car drove poorly and I am experienced several problems listed below' 1.Bucking and jerking of the car while driving. 2. Idle surging of the car. 3. Sudden stalling of the car engine. 4. Hesitation while driving and trying to accelerate. 5. Sudden surge in car's speed while driving on both streets and highway. 6. The fuel economy of the car has drops drastically. To solve these problems I did the following work; I have installed 1. New Oxygen Sensors 2. New Mass Air Flow Sensors 3. New Idle Positioning Sensors 4. New Ignition Coils 5. Re-installed New Plugs The problems still exist. I thought I had an air leak so I brought it to a mechanic and he could not find any leaks. He did tell me that every once in a while there would be back flow at the engine air intake. Any one got an any ideas of what to do and how to fix this problem. What could cause a back air flow at the engine air intake. Any help would be appreciated.

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Valve stuck open from time to time
Lets keep in mind your talking a 1991
sitting for a few years or not.
Do a cylinder leak down test.
What was the reason the mechanic gave you ?

Posted on Aug 01, 2013


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SOURCE: 94 Firebird. Hesitates at 2K RPMs, surges at 3K. Low MPG, Rich.


Some other easy items to check. Remove and clean the MAF/MAP Sensor and the inlet to the thottle body with some brake cleaner/electronics cleaner. Also may want to try some Fuel Injector cleaner as well. The O2 Sensors usually require a special socket which you can buy at the local auto parts store, and you can also use a "Crowfoot" Wrench. Usually if the O2 Sensors are bad they will set off the Check Engine Light. Some other items to consider is a Rotor and Rotor Cap if you have a distributer instead of a coil.



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SOURCE: FORD F150 4.6 L Engine

Several thnigs to check there; review all informastion disponible to do it and solve this...

- Ignition Coil F Primary/Secondary Circuit Malfunction
The ignition signal from the Powertrain Control Module (PCM) or Electronic Control Module(ECM) is sent to and amplified by the power transistor. The power transistor turns ON and OFF the ignition coil primary circuit. This ON/OFF operation induces the proper high voltage in the coil secondary circuit.

- Engine Light ON (or Service Engine Soon Warning Light)
- Lack/Loss of Power
- The engine may be harder to start
- Engine hesitation

Possible Causes:
- Open or short in the ignition coil circuit
- Ignition coil circuit shorted to ground
- Ignition coil connector
- Damaged ignition coil
- Damaged PCM or ECM

Possible Solution:
- If damage, repair ignition coil circuit
- Replaced ignition coil
- Replaced PCM or ECM

P0152 - O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)
The heated oxygen sensor 1 is placed into the exhaust manifold. It detects the amount of oxygen in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. The heated oxygen sensor 1 signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.

- Engine Light ON (or Service Engine Soon Warning Light)
- High Fuel Consumption
- Excessive Smoke from Exhaust

Possible Causes:
- Harness or connectors (The heated oxygen sensor 1 heater circuit is open or shorted.)
- Front Heater oxygen sensor heater (Bank 2) may be faulty

Possible Solution:
Replacing the O2 Sensor 1 usually takes care of the problem

P0174 - Fuel Injection System Too Lean Bank 2
With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The ECM calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.

In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the MIL (2 trip detection logic).

- Engine Light ON (or Service Engine Soon Warning Light)
- Excessive Fuel Consumption

Possible Causes:
- Intake air leaks
- Front Heated oxygen sensor may be faulty
- Injectors may be faulty
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Mass air flow sensor may be faulty
- Incorrect PCV hose connection

Possible Solution:
Dirty air filter of faulty air flow sensor are common causes of the problem.

P2197 - DODGE - Sys Too Rich at Hier Load Bank1
Means that the O2 sensors on each bank are seeing WAY too much oxygen in the exhaust gas. In normal operation the signal from the O2 sensors should swing back and forth between rich and lean. Your sensors are locked on lean.

Those codes are the same as P0174 (and P0171). Sounds like you have a vacuum leak somewhere. Most common place is the PCV elbow where it connects to the throttle body adapter.

Hope this helps; keep in touch.

Posted on Dec 30, 2010

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