Crazy Random Shutoff- FIXED!!

[DaButt]

***UPDATED JUN 3RD*** SEE BOTTOM OF THIS POST***

Ok, R3V, I need your help.

Let me preface this with two disclaimers:
1. YES- I have searched extensively, and while there are an abundance of threads that outline possible causes, I've yet to find any with symptoms that exactly match mine.
2. I hereby swear, for the sake of future seekers, that I WILL update this thread when I've fixed the problem. Actually, if you're reading this months later and I haven't posted a fix, please PM me and I'll be sure to post it.

So settle in for my story, if you like:

Had my 84 eta for a little over a year, actually going on 18 months now. It's been troublesome, to say the least. Upon first purchasing, I changed all the operating fluids like a good e30 owner, plus made sure the timing belt/thermostat/water pump service was done. I've replaced coolant hoses, brake fluid, plugs, etc. You get the idea. The only thing I've yet to do is the distributor cap and rotor, and the O2 sensor.


I won't discuss upgrades in general since they likely have no bearing here, but one that might is the upgraded ECU from TMS. That being said I've run that nearly the entire time I've had the car with no issues- minus the week or so where I didn't realize I'd damaged my old ecu (it was a soldered board- it's a learning process, right?). Otherwise the motor is untouched.

The woes:

1. Blown Headgasket- fixed
2. Leaky/cracked oil pan- fixed

My most current woe: a crazy sputtering idle. Engine shakes and splutters and skips under load. It feels JUST like it did when I fried my DME. This started after I put a tank of 93 from Shell in it. Honest to God, after the oil pan job (shop job) I was enjoying the hell out of the car- it was revving freely, purring through corner, snarling on downshifts... ok it's an eta, so it doesn't do that much snarling- but you get it- the car was fine. So....

IMMEDIATELY after filling my tank the car started this monkey business. It would splutter and cough until it got hot. It would not overheat, mind you. But it would seem that there was almost a physical blockage or something that I had to blow through- again thinking a temperature-based thing. I drove it up to Road Atlanta for the weekend, where it performed admirably, though in the mornings I went through the same coughing spluttering fight. It mercifully made the trip up and back with no problems.

Which brings us to Monday, two days ago. When I parked the car sunday night, I assumed it would continue its pattern. Well, the next few times I tried it start it, on Monday, it would fire up to 2k RPM, then promptly die. It would either do that, or about every other try, would cough at normal (just shy of 1k) RPM for a few moments then die.

Searching yielded a few things to try.

I tried unplugging the AFM- no change. Tried unplugging the O2 sensor- no change. I tried multiple combinations of one plugged in, one disconnected- no change. So this morning I cleaned the ICV with carb cleaner. While doing so I decided to clean the intake butterfly while I was at it. While doing so I discovered a fairly sizable hole in the intake boot between the AFM and intake mani. I applied electrical tape to the intake boot, which covered the hole pretty well. Hopeful (but not very), I fired her up: and she maintained a weird rough idle. It sounded like it wanted to die, but then it would just barely sputter back to life. A spin around the block left me stalled mid-lane once and the engine choking a spluttering the rest of the way.

So- with the gas and the other stuff I've tried- tell me what to try next. If the general consensus is "smoke test" (looking at you Jim Levie), then that's what I'll do. But... I just can't get away from the facts: before tanking= fine; after tanking = horrible. Maybe try swapping fuel filter out before I do anything more expensive? You tell me.

I just want to say- I've been revived multiple times by this community. I've gone through some definite heartache and cash with this car. There have even been times where I've said "maybe I just got a lemon." I was perusing used-car ads last night in bed when my renewed vigor for e30 ownership came in this form: http://wheelmen.wordpress.com/

If you like vintage metal with a Bavarian soul, as I know you all do, you'll die over this stuff.


***UPDATE May 22nd 2013***

Had my car in shop for about 3 weeks now. Not happy about it. Here's what they've tried/found

1. Smoke Test/Intake Elbow cracked- easy fix
2. Injectors are getting fuel
3. Injectors are functioning properly
4. Spark is good
5. Crankshaft Position Sensors replaced- the guy realized that the tach wasn't registering any Revs despite the fact that he could hear the motor turning over. Led him to CPS
6. Replaced main relay

So before he did the CPS and Main Relay the car would sometimes maybe start, maybe not. Then after those two items were replaced it would start then operate smoothly for a few minutes before abruptly shutting off-

So I thought maybe my coolant temp sensor was bad. So I'm going to throw that part at it today, then report back.

*****UPDATE May 22nd #2*****

Shop threw the Coolant Temp Sensor on- no change whatsoever.

Should I try O2 Sensor, new CPS, new main relay, new Coolant Temp Sensor? Haven't messed with the O2 sensor...

********Update Jun 3rd- Car is Running Again!*********

Ok, so in an effort to keep my promise and increase the amount of usable data in the form of solutions on the site, I'm going to update and re-cap.

The symptoms- car was randomly skipping, stuttering, idling horribly, not starting or if it was starting, it would shut off after choking through a minute or two of running.

Initial Diagnosis- from a "old BMW guy" was that it was my valvetrain, which is VERY loud. It didn't end up being that, but I had the shop that adjusted my valves last doublecheck their work. So...

It was the two CPSs and the rotor.

The explanation- after initially doing smoke tests (they did several, they'd find leak, do it again, etc) and finding a minor intake leak in the intake elbow, the problem wasn't fixed. So the guy replaced the two Crankshaft Position Sensors. Unbeknownst to him at the time, one of the two CPSs came from the OEM parts dealer already fried. Don't ask me how he discovered it, but it "seemed" to fix part of the problem. So he swapped both CPSs and fired the car back up, it was running, but it was still skipping. So he went back to double-check the spark. Upon doing so he realized that the spark was intermittent, so it led him to the distributor/coil/cap area. Well, he knew the coil was working so he started at the rotor- it was fried. Simple fix, 50 dollar part and two CPSs later, the eta is purring smoothly along. As preventive maintenance I'll be installing a new distributor cap and ignition wires this week. All better!

[jlevie]

Replace the intake boot and since the O2 sensor is probably past it's scheduled maintenance interval (100k) replace it. The work from the top to the bottom of what follows.


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

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.

[dnguyen1963]

Whenever you discovered an intake leak and fixed it, you need to disconnect the negative cable from the battery to reset the ECU then drive around a bit for the ECU to learn the new environment. It will have rough idle for awhile until the ECU adapts.

[DaButt]

Whenever you discovered an intake leak and fixed it, you need to disconnect the negative cable from the battery to reset the ECU then drive around a bit for the ECU to learn the new environment. It will have rough idle for awhile until the ECU adapts.

Jim- you are authoritative as always, sir.

I'll look into things tonight. Didn't know about that 'resetting the ecu' thing, though.

Now I know the standard answer is to get a shop to do it, but are there any preliminary DIY-hobo-at-home methods of smoke testing? I know a lot of guys blow cigar smoke in them or something... is that it- just blow smoke in the intake?

[dnguyen1963]

Search the internet for DIY smokers. The key thing is that you need to keep the pressure at 2-4 psi in order to find all the leaks. That means plugging up the air intake and the exhaust. For larger leaks, blowing cigar smoke into the vacuum port on the intake manifold connecting to the FPR is okay.

[Victor_PR]

Jim- you are authoritative as always, sir.

I'll look into things tonight. Didn't know about that 'resetting the ecu' thing, though.

Now I know the standard answer is to get a shop to do it, but are there any preliminary DIY-hobo-at-home methods of smoke testing? I know a lot of guys blow cigar smoke in them or something... is that it- just blow smoke in the intake?

This is the approach I will be taking. Just need to buy the 6 ft. of vacuum hose and put her to the test.

http://www.r3vlimited.com/board/showthread.php?p=3530331

HTH.
Victor

[DaButt]

Haven't gotten around to the DIY smoke test. Am not thrilled by the prospect of spending a bunch of money on stuff to do it myself, honestly. I think I'm selling the car.

[DaButt]

Bump. Updated first post. Now car won't stay running- it does start with the new CPSs in, tried putting a new Coolant Temp Sensor in- no dice. Still dies at random.

[dnguyen1963]

Do a SMOKE TEST! Eliminating vacuum leaks can solve many of the E30 problems. It does not pay to do anything else until you know for sure that you have no vacuum leaks.

[DaButt]

Do a SMOKE TEST! Eliminating vacuum leaks can solve many of the E30 problems. It does not pay to do anything else until you know for sure that you have no vacuum leaks.

#1 item in my update- smoke test completed by the shop. It was the intake elbow. New part is in the mail. BUT- the shop "quick fixed" the elbow by liberally applying duct tape.

[jlevie]

Did the shop retest after taping up the boot?

[DaButt]

Good question. I'll ask.

[dnguyen1963]

#1 item in my update- smoke test completed by the shop. It was the intake elbow. New part is in the mail. BUT- the shop "quick fixed" the elbow by liberally applying duct tape.

That is precisely the reason that I ask for a smoke test. Once you eliminate one leak you have to do the test again. You go from big leak down to medium then small. Also, did the shop plug the intake and exhaust when they performed the test? E30 is very sensitive to vacuum leaks. My '97 Camry had a 1 in crack in the intake boot, but did not give me any problem. I discovered the crack when I changed the air filter. My E30 had a small leak in the elbows connecting the the throttle body. That took awhile to find because the damn elbows could move in and out slightly...sometimes there were leaks and other times there were none.

[DaButt]

That is precisely the reason that I ask for a smoke test. Once you eliminate one leak you have to do the test again. You go from big leak down to medium then small. Also, did the shop plug the intake and exhaust when they performed the test? E30 is very sensitive to vacuum leaks. My '97 Camry had a 1 in crack in the intake boot, but did not give me any problem. I discovered the crack when I changed the air filter. My E30 had a small leak in the elbows connecting the the throttle body. That took awhile to find because the damn elbows could move in and out slightly...sometimes there were leaks and other times there were none.

But would it really be that drastic? I mean, the car is starting just fine with new CPSs- then it will just randomly cut off. What is it about the intake that's so crucial it would make it randomly die after idling normally for a few minutes? I ask not out of flippancy, but rather a lack of knowledge... For real, I'm going to keep trying, but if I'm ever going to be able to do this stuff myself I want to understand the theory behind it... Thanks for the advice, though.

[PNWDan]

Test the gas? Maybe you got bad gas or it has water in it. Just an idea since it started after you filled up.

Another thing to check is something that happened to me. When my car got up to temp, coolant would leak out of the overflow hose and worked its way down a plug wire into the distributor cap and short out that cylinder. It was a tiny tiny leak and took me a bit to figure it out.