1992 E36 318is m42 issues [FIXED]

[agmishka]

 After getting the car and some TLC the car ran like a champ. Recently we had some heavy rain, and after a windy/stormy night these new problems appeared (it was completely fine the night before and through other rainy days/nights).

What's weird is that the car runs completely fine from a cold start, but if you let it warm up, or drive a few blocks the issues show. So far I've noticed:
-Sputter between 1-3k rpm (almost sounds like a motorcycle)
-During the sputter the shifter shakes
-Sometimes it feels like a depressurizing "pop" before it loses power
-I was going up a hill in 3rd gear and no matter how hard I pushed the gas it was capped at 2k
-After driving for a while, or during warm start it dips the idle to almost death but brings it up again
-No CEL, just 1444(no problem)


I had a the car serviced a few months ago, basic tune up (plugs, etc.)
From what I gather around the forums it could be: ICV, Vacuum leak, Injectors, Plugs, Plug wires, Coils, O2, Any and every sensor..

I've swapped the O2 sensor 20mi ago with no changes. I got a set of new Ignition Coils, but weirdly enough when I swapped them the problem multiplied (horrible idle, car shakes) so I just threw the old coils back in. Tested the old coils with a meter and they all read 0.6ohm which I know is within range.

Unfortunately I don't have much space or time to work on the car as it is my daily, and I hate to give it to a shop and get raped on prices for such an easy-to-work on car.

 heres a little video of how it runs https://youtu.be/8eus_QulHfQ



DO YOUR BASIC TUNE UP. COP, New plugs, all working coils.

[keflaman]

A coil normally displays the symptoms you describe after it gets warm. The fact that things got worse after replacing the coils is puzzling. When you tested the original coils were they cold or warm/hot?

Were the replacement coils "new" to you, or were they actually brand new?

Here's a suggestion that may sound crazy, but drive the car until it starts to shake and sputter, then pull the coils and throw them in the freezer. Re-install before the rest of the car loses its "heat soak" to see if that makes a difference.

You could also heat the coils up with a hair dryer or heat gun before starting the car while it's cold and see how it runs.

I'm not sure if the plug wires could break down after getting warm, but I always checked them at night with the hood open. One time I found a bad plug wire just by passing my arm in close proximity...I wasn't actually checking for spark at the time, but it sure shortened the troubleshooting process.

Welcome to the forum!

[agmishka]

The coils are new new, but they are Bosch (maybe the car is being super picky). I've done the ohm reading when the car was both cold and hot. The reading jumped around a little, but I think that was just user error of me trying to keep the prongs still, the reading settled down to about 0.7.

I'll try the freezer/heat gun method. I do have a CoP kit coming in soon, so hopefully I can eliminate the wire issue entirely.

I'm just trying to figure what a night of heavy rain could've done to cause this to happen.

[DesktopDave]

Check the passenger cowl drain and be sure the DME didn't get flooded. If that little drain hose plugs up, rainwater will overflow into the DME and possibly damage a coil driver. It might be totally OK too, once it's dried out.

You'll have to pull the cover off to dry out the DME and inspect the coil driver transistors. I wouldn't recommend installing new coils until you've determined that the drivers are OK; you damage a coil.

Pull the plugs too, see if they look OK. If the DME and coils are OK, I'd recommend a compression test to see if the motor is healthy and a fuel pressure test to be sure the pump is still optimal.

[agmishka]

The DME was the first thing I actually looked at, although I didn't crack it open, the compartment and the module seemed completely dry. Maybe i'll take a second look, what does a coil driver look like.. or what should I be looking out for?

[DesktopDave]

The coil drivers look like small black boxes sitting above the DME circuit board. They're a set of large capacitors under some clipped-on heat sinks. I'll take some pics of what you should be looking for, and update this thread later on today.

After you've removed the cover (unscrew the four hex-head screws on the cover, and bend the crimped tabs back). I've already removed the steel spring and plastic insulator from the coil drivers on the left side. You'll see this:
 

Closeups:
It's hard to see, but the left-hand driver in the first pic is burned-out. The singed plastic insulator definitely indicates that it overheated.


Replacing them is difficult unless you're handy with a high-wattage iron and a solder sucker. Solder joints have to be nearly perfect, since they switch a large amount of current at a high frequency. I was planning on salvaging good coil drivers from some cheap E36 EWS DMEs to replace them instead of researching a more expensive modern replacement. They're a high-current/high-temperature MOSFET Darlington transistor. Bosch does offer an updated part, popular in MegaSquirt installs, called a BIP373. Unfortunately it's not a direct fit, and I'm not sure it's even pin-compatible.

So we're stuck with an obsolete, non-standard, high-current transistor. Bosch never bothered to publish specifications; even an obsolete 30 year old part is part of their precious intellectual property.

[agmishka]

So I opened up the DME and... it seems perfect. The module might not be original.

I didn't take the cover off the little black boxes with "30014" lettering, but they have absolutely no marks. Although the pins do have a little wear. Here's an album of the photos I took, if you wanna give it a glance. http://imgur.com/a/U9bJS/all

[DesktopDave]

That does look clean; I'd guess that the unit is OK. I've never seen a sticker like that on the heat sink clip...I wonder if it's been rebuilt? I've only opened 3-4 of them myself. The original DME on our cars should have a sticker with a partial VIN on the case somewhere.

Transistors can fail and still look good. I've never found an easy way to test them. Some common tests (like continuity and resistance) can instantly destroy them.

[agmishka]

So I found something interesting today.. I guess when I changed my belts I didn't properly tighten the power steering belt because I could hear some squeeking when I turned the wheel alllll the way to each side, but whatever it wasn't a big deal to me as I never turn that far anyway, and when I do whatever it's a squeak...

Edit: I guess it can also be low PS Fluid levels.

Well, when parking, I was turning my wheels to get ready to leave and noticed that the idle dropped everytime I turned the wheel to the squeaky zone... So a loose belt can cause all these issues!? I'm gonna be really mad at myself if that's the case.


nvm.

[agmishka]

So i decided to re-start from the beginning, basic tune up.

Oil - Was kind of low, and when changing it was really black.

Plugs - Not sure if i damaged them or they were the cause of the problem but, when i pulled the first plug there was visible water and gunky  corrosion mess, the inside of the rubber tube has watery gunk in it too.


This is the 1st plug, it had some oil on the thread and gunk on the top, but otherwise looks ok(?)

#2


Plugs 3 and 4 looked good, pretty much spotless.  Since this happened after a storm, im assuming water made it's way into the 1st and 2nd plug area and made a mess of everything?

[Delta]

Very possible! Id clean everything out and get new plugs and wires. Can definitely cause problems or missing under load.

[agmishka]

So i decided to install the COP plate, eliminating the wires out of the equation. Of course one of the new coils i got was 0.3 ohms -_-.

COP, New plugs, all working coils. Problem hasn't come up on my 15 min drive.