Hard Start rough run/idle, stall hair puller BMW E30

[sierra9260]

Hello all,

Thanks for having me on these forums.

I have had my 1988 BMW e30 320i for around 2 years now and it has never run perfect from the first day I brought it. I wasn't very mechanically minded back then nor am I now and I have been wrestling with thing for a long time.

It hard starts, often have to get pressing on gas pedal to get it to finally start. The idle is rough, gas mileage is pretty poor. It dies/stalls when at a stop light. last time I drove it which was some time ago whenever the gas pedal was pressed it would stutter and want to die. All this seems to get worse once the engine is warm.

I haven't touched the car for a long time and it has been parked up until now. I used to be into swapping parts and generally being pretty newbish when it came to fixing this thing and have since taken a different approach. I have tried fuel pump, ICV, TPS, MAF Sensor, Vaccum leaks (seem pretty tight now) cleaned out intake a bit and icv as it was all oily which brings me to another point that I had to let like 2L of oil out as it was over filled when I got it. It also when to an auto electricians who wasted my time and money and put a few zip ties here and there and whacked a blue temp sensor on. i also replaced the exhaust manifold gasket and the car runs a little worse now if I'm honest but no more fumes are leaking. Recently I have taken all the injectors out and cleaned them and am making some big head way on this thing and I would like it to be fixed once and for all. I took some pictures of the spark plugs and removed the distributor cap and found some hefty corrosion on the contacts.

Any help with this would be greatly appreciated, thanks guys.

[sierra9260]

Another note is that the oil in the sump smells of gasoline and the thing seems to be running pretty rich, I was lead onto the C 191 plug for the injectors but that looks to be in really good condition. I've narrowed it down to either being Fuel, Ignition or the o2 sensor but some guidance here would be great. Also I know I should probably check the integrity of the engine and do a compression test but finding that distributor head like that leads me into thinking maybe could be something as simple as that. Anyway i will get on to replacing that with a good non corroded one in the next few days.

[jlevie]

Start at the top and work to the bottom without skipping any steps and your will find/fix the problems.

Idle or hard starting problems are most commonly caused by intake leaks and/or
a sticky or defective Idle Control Valve (ICV). The only reliable method of
locating intake leaks is to have a smoke test run on the intake and crank case
and to test the brake booster with a gage and vacuum pump. The complete list
of possible causes of an intake leak is:

Intake boot
Throttle body gasket
ICV hoses & connections
Brake booster, hoses, and connections
Crank case breather hose
Evaporative control hoses, valve, and expansion tank
Fuel pressure regulator & hose
Injector seals
Valve cover gaskets & bungs
Oil filler cap
Dip stick o-rings
Oil return tube o-rings
Pann gasket or oil level sensor gasket

While leaks in some of those can be found by inspection or by spraying carb
cleaner on suspect areas, not finding leaks that way doesn't eliminate the
possibility. Only a smoke test will really work.

Once the possibility of intake leaks is eliminated, the ICV needs to be
removed and cleaned with carb cleaner until the vane inside moves freely. When
the ignition is switched on you should be able to feel vibration from the
ICV. If no vibration the ICV is bad, there's a problem with its wiring or
connector, there's a problem with the TPS, or the DME (or Idle Control Module
(ICM) on an ETA car) is faulty.

For the DME (or ICM) to control idle, the idle switch in the TPS must work
correctly. The switch should close when the throttle stop is 0.030-0.060" off
the idle stop screw. Hearing a click doesn't mean the TPS is working. Check
with a meter or test light.

The fuel system should be tested via the suite of tests in the Bentley manual
as invalid rail pressure can be a contributor to idle and starting problems. A
simple injector check is to pull the injectors, jumper the fuel relay to run
the pump, and see if the injectors are leaking. You can also point the
injectors into a towel, remove the coil wire, and crank the engine to see if
all of the injectors appear to be spraying in a similar fashion. The best
approach to possible injector problems is to have the injectors cleaned and
flow tested. Since raw fuel can or will be released in these tests, have a
fire extinguisher handy.

While a bad check valve in the high pressure pump can result in longer than
normal cranking, if the fuel system is working as it is supposed to the rail
will reach normal pressure in a few turns of the engine. A weak pump, clogged
filter or leaking FPR in conjunction with a failed check valve can result in
longer cranking and/or idle poroblems.

The O2 sensor can be a contributor to idle problems. The O2 sensor is a
scheduled maintenance item with a useful life of no more than 100k. If the
sensor has that mileage or more (or is of unknown age), replace it.

The AFM can be a contributor. If the vane doesn't move freely or the
resistance track is worn the DME may be receiving invalid data from the
AFM. And if someone has fiddled with the bypass air adjustment the DME may be
unable to stabilize idle. The bypass air adjustment should only be adjusted
per the procedure in the Bentley and with an exhaust gas analyzer. And even
then everything else associated with engine management has to first be
operating properly. If the AFM becomes a suspect, replacement with a good used
unit is the best approach.

Improperly adjusted or malfunctioning valves will affect idle and starting. As
can compression issues from ring or cylinder wear. A valve adjustment is
called for every 15k. A useful diagnostic is to run compression (dry and wet)
and leak down tests on the engine. Aged ignition wires, plugs, distributor
cap, or rotor can cause problems. Insulation does break down with time and
heat. And since the youngest E30 is going on 20 years old, if the ignition
system is original or the plugs are old replacement is indicated.

Although not usually a problem, a bad DME temp sensor is a possibility. That
generally won't cause an unstable idle, but can cause hard cold or hard hot
starts and/or a rough idle. As can problems with the timing reference
sensors. Although not commonly encountered, a bad harmonic balancer on an
M20B25 or M30 engine will cause problems.

When all other possibilities have been eliminated and idle or starting
problems persist, replacement of the DME, or if applicable the ICM, is
indicated.

In many cases the cause of problems will be a combination of factors. So it is
important to test and repair all of the possible causes.

[sierra9260]

Appreciate the definitive reply, some food for thought. Will tidy some things up and report back.

[DigginMyE30]

Any progress/update?