Rough Idle & Ultimate Shimmy Guide

[shogun]

The following is courtesy of Steve Wilson
and refers mainly to E32

Rough Idle & Shimmy – the Ultimate Guide!

(Including information about Catalytic Converters)
Thanks to Johan for examples/pictures on his website – to follow the link click here
http://bmwe32.masscom.net/

1) Spark plugs, plug wires, rotor & ignition coils - Clean and inspect.
2) Check compression – poor cylinder head compression is common for an older car. Big job to fix this.
3) Use a good fuel-injector cleaning treatment into the tank – take it for a good run.
4) Change fuel filter.
5) Remove and clean injectors – might need to replace injectors.
6) Hose to fuel pressure regulator – might be cracked/worn (buy a new one)
7) Rubber hose between Airflow Meter and throttle – cracked?
8) Mass Airflow meter/sensor – if dirty clean it up. Bad Air Flow Meter will cause flat spots in acceleration or erratic spots in the throttle depending on the opening of the airflow meter not usually a complete lack of power.
9) Hose to air filter – cracked?
10) Air filter – replace if dirty, check seals.
11) Distributor cap – if eroded and worn - changed to new one
12) Check fuel pressure - Replace the Fuel Pressure Regulator. Might need to replace Fuel Pump.
13) Check and Adjust valves - throttle valves, PCV valve behind intake runner, Idle Control Valve (ICV).
• ICV Idle Control Valve. Remove and clean it with brake parts cleaner. This regulates the air coming in to your intake manifold when the throttle body is closed and it tends to get dirty, sticky and the motor inside could not turn the valve properly.
• Idle control valve sometime sticks open – causes issues when in Idle
14) Throttle Body - Clean it out and replace the gasket (can use gasket material cut to size).
15) Check all Vacuum lines.
16) Conduct a ‘leak down test’ on all exhaust valves.
17) Check for Oxygen (O2) sensor function tests.
18) Check the wide-open throttle switch under the gas pedal.
19) Check throttle position switch on the throttle body.
20) Make sure connections on battery (under back seat) are very clean. Use wire brush.
21) Check rubber boot between the Mass Air Flow and the DKM.
22) Check for intake manifold gasket leak
23) Have the transmission checked for correct functioning – (by mechanic).
24) Make sure there are no other sources of drag in the driveline.
25) Checked coolant sensor.

Try the RESET Procedure before all of above.
Notes:
The reset procedure is billed as a ‘cheap fix’. It does often give good immediate results, however if there is something wrong with your car (any number of issues as listed above) then over a 2-8 week period the car will likely return to its original state.
The reset procedure removes all mean values stored by your onboard computer that control engine timing, fuel use etc. As you continue to drive the car, the stored values ‘average out’ to best suit the engine condition.
If your car has for example a leaking intake manifold gasket or broken O2 sensors, the readings are quickly going to become ‘corrupted’ with incorrect information. This can lead to the engine running too rich or too lean (check your sparks for evidence). Within a short period of time the car will return to rough idle as the underlying problem has not been fixed. That said – the reset procedure can reset values that are no longer applicable. You may have replaced something on the car (e.g. Catalytic Converters) thus causing a sudden change in normal engine running. The readings stored over 10-20 years will suddenly not suit you recently modified car. The car will however read new values in and average out over time. The Reset procedure simply speeds that process up.
The long and short of it is that this procedure can sometimes fix rough idle and transmission timing and seems to improve the cars performance. However with existing underlying issues as outlined above – it won’t be long before the problems return. Perhaps this procedure could be used if you’re trying to sell your E32 ;-)
Procedure:
1. Disconnect battery cables, first negative, then positive.
2. Cover and protect the battery posts! Leave no potential of a battery short circuit.
3. Turn ignition to position II.
4. Connect both battery cables ("SHORT") for at least 10 minutes. This step drains a capacitor in the ECU/TCU. (Covered the battery with a thick, dry shop towel to prevent actually shorting the battery! – careful of arc welding in my back seat! As the battery was in place, and the cables aren't that long, you could use a very long Craftsman screwdriver and two small vice-grips to actually clamp the negative and positive cables to the metal shank of the screwdriver.
5. Wait 10 minutes - then ignition off, key out.
6. Reconnect battery positive, then negative.
7. OBC says "PPPP", reset time. Start and idle the engine for 5 minutes, then off for five, then out for a drive.
8. Now, with the car in lowest gear (one or two depending on your make), accelerate until at least 5000 rpm is reached. Allow the car to slow to idle, and then repeat two more times. Let the car idle for 5 minutes. All Done!
9. Idle should smooth out over 10-12 miles; shifts should be immediately smoother.

SHIMMY @ 80mph – likely culprits
Check the following in this order:
1) Wheel alignment by a recommended mechanic (dynamic balancing)
2) Check your brake pads!
3) Check thrust arm bushings. (Some call them upper control arms). Bushing can go after several thousand km’s
4) Replace/check tie-rod center, and Left & Right tie-rods
5) Check Struts / Shock absorbers while your there.
6) Sometimes (rarely) disks are warped – replace them (machining is just as expensive if not more).
Details about the Catalytic converter:
The catalytic converter is our main line of defense against air pollution, so it's important to make sure it is functioning efficiently and passing exhaust without creating undue restrictions that might reduce performance, fuel economy or emissions. That's one of the reasons for periodic vehicle emissions testing. If the converter isn't working, you won't pass the test.
If the converter is plugged, it will create a restriction in your exhaust system. The buildup of backpressure will cause a drastic drop in engine performance and fuel economy, and may even cause the engine to stall after it starts if the blockage is severe.
The easiest test for converter plugging is done with a vacuum gauge. Connect the gauge to a source of intake vacuum on the intake manifold, carburetor or throttle body. Note the reading at idle, then raise and hold engine speed at 2,500. The needle will drop when you first open the throttle, but should then rise and stabilize. If the vacuum reading starts to drop, pressure may be backing up in the exhaust system.
You can also try to measure backpressure directly. If your engine has air injection, disconnect the check valve from the distribution manifold, and connect a low pressure gauge. Or, remove the oxygen sensor and take your reading at its hole in the manifold or headpipe. Refer to the backpressure specs for the application. Generally speaking, more than 1.25 psi of backpressure at idle, or more than 3 psi at 2,000 rpm tells you there's an exhaust restriction.
If there appears to be an exhaust restriction, disconnect the exhaust pipe just aft of the converter to relieve pressure and recheck the readings. CAUTION: The pipes will be hot so wait awhile for things to cool down. If vacuum goes up and/or backpressure drops, the problem isn't not a plugged converter but a plugged muffler or collapsed pipe. If there's little or no change in readings, the converter is plugged.
Just because a converter is passing gas doesn't mean it is okay. If the catalyst inside is contaminated or worn out, high carbon monoxide (CO) and/or hydrocarbon (HC) readings will be present in the exhaust. If you have access to a high temperature digital pyrometer (or an oven thermometer will do), check the converter's temperature fore and aft. A good converter will usually run 100 degrees F hotter at its outlet than its inlet. Little or no temperature change would indicate low efficiency, or a problem with the converter's air supply. Converters need supplemental oxygen in the exhaust to reburn pollutants, so if the air injection system or aspirator valve isn't doing its job the converter can't do its job either.
Check the air injection pump, belt and check valve. If you suspect that the check valve is allowing exhaust to flow backwards, remove it and blow through both ends. It should let air pass in one direction, but not in the other. Examine the air injection manifold, too, because it tends to rust out and leak air. Check the diverter valve to make sure it is working correctly, too. It should be routing air to the converter when the engine is at normal temperature.
On engines with aspirator valves instead of air pumps, you should hear and/or feel the fluttering of the internal flapper as the engine is idling.
CAUSES OF CONVERTER FAILURES
Fouling, clogging, melt-down and breakage of the ceramic substrate inside a converter are common conditions that can cause problems. Plugging is usually the end result of a melt-down, which occurs because the converter gets too hot. This happens because the engine is dumping unburned fuel into the exhaust. The excess fuel lights off inside the converter and sends temperatures soaring. If it gets hot enough, the ceramic substrate that carries the catalyst melts.
The unburned fuel may be getting into the exhaust because of a bad spark plug or valve, but an overly rich air/fuel mixture is another possibility. In older carbureted engines, a heavy or misadjusted carburetor float may be the underlying cause. But on newer engines with "feedback" carburetion or electronic fuel injection, the engine may not be going into "closed loop" (the normal mode where the computer regulates the air/fuel mixture to minimize emissions).
A bad oxygen sensor or coolant sensor may be giving the computer bogus information. A sluggish or dead O2 sensor will make the computer think the exhaust is running lean, so the computer will try to compensate by making the fuel mixture rich. A coolant sensor that always indicates a cold engine will also keep the system in open loop, which means a steady diet of excess fuel. But it might not be the sensor's fault. A thermostat that's stuck open or is too cold for the application can prevent the engine from reaching its normal operating temperature. So if your converter has failed and needs to be replaced, the engine should be diagnosed for any underlying problems before the new converter is installed.
Another cause of converter clogging and contamination is excessive oil consumption. Worn valve guides or seals can allow oil to be sucked into the engine's combustion chambers. The same goes for worn or damaged rings or cylinders. Oil can form a great deal of carbon, and metals present in the oil can contaminate the catalyst. A compression check or leak-down test will tell you if the rings are leaking, while a fluttering vacuum gauge needle will help you identify worn valve guides.

[shogun]

One of the most common glitches on the BMW E30 3 Series is an erratic engine idle. Have you noticed that the idle seems to surge constantly? Does it constantly move between 800 and 1800 RPM? Does the idle stay steady at 1800 RPM? In this tech article I will go over the steps involved with checking the idle system and vacuum hoses. This article is intended for you to learn a little something about your car, and at the same time, point you in the right direction towards fixing that erratic idle. Keep in mind that this article is specific to the 1987 through 1991 E30 6 cylinder cars, however the basics apply to nearly all BMW’s.

First off, most modern BMW’s from 1986 and on use the Bosch Motronic fuel injection system. The Motronic system is probably one of the most reliable fuel systems on the market, and is still widely used in most European cars. While the system normally requires no adjustments, over time, heat and age will start to take it’s toll on the various vacuum hoses on the engine. When vacuum hoses age, they dry out and crack. The result is vacuum leaks. A vacuum leak will usually cause the car to idle higher. The reason is simple. You are introducing more air into the engine. If you look at the throttle body or carburetor of any car, it is essentially a valve or a series of valves. When you begin to open the valve, air is able to flow into the engine, increasing the engine speed. With a vacuum leak you are getting the exact same result. In some cases, even a leaking valve cover gasket or oil filler cap can cause this leak, so make sure your valve cover is properly sealed.

To begin to diagnose the idle problem, we will need to first need to look at the vacuum hoses. In this case, I have decided to replace all the hoses just for extra insurance. Vacuum hose is cheap, so you might as well replace all the hoses. Now look at the passenger side of the engine at the top of the valve cover. Loosen the hose clamp on the hose coming out of the top of the valve cover. Now, follow the hose to the other connection on the throttle body. Loosen the hose clamp and remove the hose. This is the breather hose. It is an important part of the vehicle’s emission system. It is used to recalculate oil vapor back into the engine to be burned again, rather than venting it out into the atmosphere. I found that the breather hose from the valve cover to the throttle body has an interesting size. One end is 14mm and it sizes up to 22mm on the other. You’ll also notice that this hose is formed in such a way that it will clear a bend on the intake manifold. Rather than trying to splice together two different size hoses and snake them around the intake manifold, I simply ordered the OEM hose from BMW to save time. (Pelican carries this hose for $6.30) Now snake the new hose into position under the valve cover and slip it on to the valve cover and tighten the hose clamp holding it in place. Do not connect it to the throttle body at this time.

Now look above the valve cover on the intake manifold. You will see two small 3.5mm vacuum hoses. On the left side, the hose is plugged up, on the right side; the hose connects to the fuel pressure regulator. This hose is used to help control the fuel pressure on the car using engine vacuum. Just remove the hose clamps on either end, and pull the old hoses off. Now cut the new hose to the same length as the old ones, push them on and tighten the hose clamps.

With those hoses installed, now look at the driver’s side of the engine down by the air cleaner. You will see the Air Mass Sensor bolted to the air box. One the other end of the sensor, there is a hose clamp that holds the intake air boot to the sensor. Loosen the hose clamp and carefully pull the air boot off the sensor. (Note: you may find it easier to remove the boot by taking out the air box completely. Unplug the air sensor, and just remove the two 10mm nuts holding to the bracket and pull it out.) Now look at the top of the air boot. You will see two fittings looking form the top. On the left side is the fitting for the idle control valve. On the right side is the vacuum attachment for the power brakes. Start out on the right side and loosen the hose clamp holding the brake fitting into the intake air boot. Now, on the right side, disconnect the electrical connector from the idle control valve, and remove the rubber strap holding the valve to the bracket. Now look at the other vacuum hose off the valve. We will simultaneously have to pull the valve out of both hoses. You may need to use a bit of force, however it will just pop out. If it hasn’t already come off, remove the vacuum hose going from the control valve onto the throttle body fitting.

With all the fittings out of the intake air boot, now loosen the hose clamp holding the boot to the throttle body. Now take the boot off. Before you continue, inspect the intake air boot for cracks. This is a common location for vacuum leaks. If you see any cracks or holes in the boot, replace it with a new one. Pelican carries these boots for $12.67. Now, look down under the throttle body. You will notice a vacuum hose attached to the throttle body, this is part of the emission control system. You should be able to just pull this hose off. Cut a section of new hose to the same length as the old one, and using hose clamps, attach it to the throttle body and the valve below.

Now before we begin to re-install the boot and other items, we will need to check the throttle switch on the bottom of the throttle body. This switch is used to control the idle control valve. If this switch has a fault, it will cause the idle control valve to operate incorrectly. In order to test the switch, first remove the electrical connector from the switch. Just push down on the metal wire, and pull it off. Inside you will see three terminals. From the left, they are numbered 2 then 18 then 3. First, connect a digital multimeter between terminals 2 and 18. Now open the throttle halfway and slowly let it close. When it is between 0.20 and 0.60mm from it’s stop, check for continuity between the terminals. Now, connect the multimeter between terminals 3 and 18. Now open the throttle slowly. Check for continuity when the throttle switch is within 10 degrees of being fully open. If you don’t see continuity while testing the terminals, loosen the screws on the bottom of the switch, and adjust the switch until it comes within these values. If you still do not have continuity, this means that the switch is bad and must be replaced. Pelican can provide you with this switch if needed. If the switch is good, re-connect the connector onto the switch.

Once you have tested the throttle switch, the next step is to test the idle control valve.

The idle control valve controls the amount of air that bypasses the throttle butterfly and keeps the engine idling. The throttle switch is used to control the idle control valve. Essentially, when the throttle is fully closed, the throttle switch sends a voltage to the idle control valve. This voltage opens the valve and allows air to pass, increasing idle speed. Now, connect the multimeter between the two outer terminals on the valve and check for resistance. There should be around 40 Ohms of resistance. Now check the center terminal and each of the two outer terminals. There should be roughly 20 Ohms of resistance between them. If you do not get these values, the switch has gone bad and must be replaced.

Now, we will continue re-installing the various components of the intake system. First, take the new breather hose from the valve cover, and push it onto the port on the side of the throttle body and tighten the hose clamp. Next, re-install the intake air boot, and tighten the hose clamp that holds it on to the throttle body. Re-install the fitting for the brake booster and tighten the hose clamp. Now re-install the idle control valve into the intake air boot and into the fitting on the side of the throttle body. Re-connect the electrical connector and rubber strap onto the valve.

The last step is to re-connect the mass airflow sensor into the intake air boot and tighten the hose clamp. Re-connect the electrical connection to the sensor. Now start the car and listen to your idle. If everything in within spec, you should have a smooth idle between 700 and 900 RPM.

Well, there you have it - it's really not too difficult at all. If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. Your continued support directly affects the expansion and existence of this site and technical articles like this one. As always, if you have any questions or comments about this helpful article, please drop us a line.
source and original article:
http://www.pelicanparts.com/bmw/tech...leshooting.htm

[shogun]

Q: I got a 91 750il where bank two is down with no eml light on. Both fuel pumps runs. Fuel is flowing to both regulators ok. Checked the spark on bank 2 and all wires have ok spark. A fault code is stored saying that there's a problem with the ignition on bank 2. Viewed the fuel injector pulsewidth and it's at .4 ms and shows the load being at 0 on bank 2. other side has normal readings. Also the scan tool says the the ignition fault would cut off fuel injector pulse width. Tried swapping coils, dme and maf, nothing's changed. Any ideas?

A: ask here http://www.bimmerboard.com/forums/e32/
there are the experts for the E32. Add the complete production month and year as your signature there so that you get more answers from people in the know which look into wiring diagrams then.

One trial you can make before: switch the MOTRONIC modules in the E-Box from one side to the other to see if the fault goes to the other side.
Test the CPS for both sides. test data I have posted on Bimmerboard, search with "CPS shogun" there.
--------------------
A: found that the spark plug on # 12 was fouled causing the cylinder identification 2(bank 2)signal to be skewed because it runs off of cyl. number 12 spark plug wire for info to the DME. It thought that it had a dead cylinder and the engine management would cut off fuel pulsewidth to that bank.
---------------------------------------------------------------------

The check the crankshaft position sensors
read this http://www.bimmerboard.com/forums/posts/595336/
http://www.bimmerboard.com/forums/posts/524868/

[shogun]

my collection
http://www.bimmerboard.com/forums/posts/244840

[shogun]

In case plug lead 6 or 12 (the ones with the inductive pickup donuts on them) are disconnected or short, a protection circuit embedded within the Motronic will severely clip the duty cycle of the injectors for that side to protect the catalysts from being drenched in raw, unburned fuel.


Catalytic converter protection function
Ignition circuit monitoring

The ignition circuit is monitored by the cylinder detection sender (pin 16) on ignition line 6 (or 12). If it detects no ignition signal on ignition line 6 (or 12) , the fuel supply to to the relevant cylinder bank is cut out by shortening the injection signal. The sender monitors the entire primary side of ignition, and cylinder 6 or 12 on the secondary side.
The inductive sensor is outlined in red above.

http://www.fibersonde.com/e31/images...catprotect.jpg

[shogun]

The above was from roadfly E31 board, and the MOTRONIC was 1.7 M70.

Now we just tried:

results of test (simple)



Shogun's 1988/89 750iL (11/88, MOTRONIC version 1.2)

well we disconnected the passenger side cylinder ID plug at front of engine.
key to position 2, EML light comes on, after a few seconds off.
engine start, runs on only 6 cylinders and rough -- NO EML or other warning!
Accelerator used, still no warning.
Reconnected and restart -- all 12 running, no warning.

Disconnected both cylinder ID plugs.
same result -- engine runs but only 6.

Used Peake Fault Code reader and found no fault codes related to engine --ummm

Reconnected and runs like a champ. Still no warnings.

I thought the engine would stop with both disconnected but no true.

Over to you guys

[shogun]

answer by Timm from the U.K.:
The sensors on ignition leads 6 and 12 are not there to disrupt the injector duration, they are there to identify the camshaft position and are a direct forerunner of the camshaft sensor. The sensors are called 'cylinder identification sensors' and detect when cylinders 6 or 12 fire, they do not measure the primary circuit, how could they, they are stuck on the ignition leads! This is not part of the EML system, any failure will not light the EML indicator. It is a basic ECU input that is found on straight-6's that do not have EML as well as EML variants of both the M30 and M70.

Without the cylinder identification sensors, the ECU's do not know which of the two unique revolutions the crankshaft is on. This does not matter to the ignition as the spark is directed to the correct cylinder by the distributor. It does matter to the injection circuits which should fire every two crankshaft revolutions or every one camshaft revolution.

During cranking the only reference signal is the crankshaft sensor and 'double injection' is maintained until the ignition from cylinders 6 and 12 are detected. From this point on the ECU is aware of the correct camshaft position and can fire the injectors every two crankshaft revolutions. If the cylinder identification sensors fail to detect ignition pulses then the injectors continue to fire every crankshaft revolution but the injector duration is reduced to prevent damage to the catalytic converters.