It's alive!!! But...

#1

Car idles real rough. Stumbles a little on revving.

Hooked up vacuum gauge to pressure regulator vacuum line - vacuum is smooth and constant with no needle bounce.

Earlier trouble shooting revealed the vacuum connection to the underside of the throttle body that leads to the charcoal canister was split - replaced with a piece of hose.

Found a couple minor H2O leaks (fixed) around the T-body but nothing to really cause the rough idle and revving.

I’m about of the opinion that I just need to put around the neighborhood to let the ECU learn.

Oh yeah, I haven’t checked to see what idle rpm is supposed to be, but I’m shooting for about 800.

Thoughts, additional opinions, miracle answers? :smiley:

Thanks,

KB

#2

While other causes are possible, what you describe sounds most like an intake leak. The definitive diagnostic for intake leaks is to have a smoke test run on the intake. Visual inspection and spraying carb cleaner around can locate some leaks, but that doesn’t work for all of the possible locations. And since several small leaks add up to a major leak, you really need a smoke test. 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 hose and valve
Fuel pressure regulator & hose
Injector seals
Valve cover gaskets & bungs
Oil filler cap
Dip stick o-rings
Oil return tube o-rings

#3

Smoke test? Like smoke a cigarette and blow smoke around to see if I can spot suck in areas?

#4

If your rubber intake elbow is fairly old like mine was. It could have cracks in it that only open up when you rev it. I ordered a new one, and my idle returned to rock solid once warm.

#5

mine completely ripped in half when I changed the air filter!

#6

Intake boot
Throttle body gasket - new
ICV hoses & connections - new
Brake booster, hoses, and connections
Crank case breather hose - new
Evaporative control hose and valve - found 1 leak, will look closer
Fuel pressure regulator & hose - new hose
Injector seals - new
Valve cover gaskets & bungs - new
Oil filler cap
Dip stick o-rings
Oil return tube o-rings - frome the oil cooler? - new hoses, did have one o-ring split, replaced, others ok.

That leaves

Intake boot - Checked, looks like new.

Brake booster, hoses, and connections - One looked cracked up a little, am going to rebuild. Brake booster is great, you could hear a strong vacuum seal break when you pulled out the hose fitting.

Evaporative control hose and valve (hose to canister is original)

Oil filler cap
Dip stick o-rings

No signs of oil or coolant leaks.

#7

When I checked the vacuum, it was steady but low, ~ 10-13 psi (should be 17-20).

When I took the trouble to actually read the gauge face, it said the vacuum level indicated retarded timing. Hah!

Since I can be retarded :slight_smile: I decided to check my timing and valve settings. I was satisfied with my findings. When routing the wires back around the front of the timing belt cover, I decided to look closer at the timing pickup wire at the sensor.

Bet ya can’t guess what I found? Yup, broken wire going down into the timing sensor.

You can’t set the timing on these motors right? Everything is controlled by the ECU, correct? While reading the BMW service manual, I saw something about earlier distributor version motors that had a wire you unhooked to set the timing and that it would retard the timing 10*.

What I found on my car kind of makes sense I think. Because the ECU isn’t picking up the timing sensor, it’s in a retarded timing mode.

Guess it’s time to pony up for a new sensor.

#8

Smoke Test = Find a mechanic with a cool little smoke making device. Splice it into a vacuum line and let it run forcing smoke into the engine. The only place smoke should exit the engine is via the air filter intake. If it exits any place else you have a vacuum leak.

I found two or three small leaks on my car when we ran this test. Its invaluable on these older cars.

#9

Can’t solder the crank pos sensor wire? Could save you almost $100.

#10

I decided to start the car Sunday afternoon without the Crank Sensor…no go.

While futzing with the old crappy Crank Sensor on Saturday, I broke the other lead on it. Sunday’s failed attempt made me suspicious that I had really gained no progress in trouble shooting the poorly running motor and that I had only succeeded in breaking something else. :slight_smile:

Got a new Crank Sensor left for me on the front porch today and…yup, you guessed it, the car still runs crappy. Tried to pull it out in the street to see how bad it was and it barely made enough power to move around in the drive way. So now I’m back to trouble shooting.

As previously stated, vacuum is steady, but low. Timing Belt and Valves are correctly set.

All the vacuum related circuits have been gone over and freshened: valve cover, fuel pressure regulator, brake booster.

I sprayed starter fluid all around the intake related components with no change in the engine’s idleing.

Question: Does the '87 Oil Cooler have a specific flow? The deal is that I could not install the new Oil Cooler Lines as indicated in Real OEM. One was short enough to prevent installing per the diagram (provided it is accurate). After getting the engine and crank case hot, the oil cooler lines and oil cooler were still cold. (ambient)

I need to overcome this hurdle pretty soon as I am to drive the car at VIR with FSR PCA next weekend. Arrgghh!

After more poking around, Rob Keehner helped me find a hiss when you lay your ear down to the throttle body. The faint hiss was in the area of the throttle body side towards the front of the car. This is where the crank case breather tube dumps into the throttle body. It’s also where all the idle control valve plumbing is located. Tomorrow I’ll check those connections and redo them till they have no audible. Might stop by Harbor Freight on the way home to get a stethoscope with a probe.

#11

How are the fuel injectors? We recently traced a similar problem to a few bad injectors.
Ed

#12

I think the Fuel Injectors are ok. I did send them out to be cleaned, rebuilt and calibrated.

Last night we pulled the plugs. Found the #3 plug on a brand new wire set from Turner to be bad. The #3 plug has not fired once. We’re feeling cautiously optimistic that a new wire set will fix everything.

I’m using the original accordian intake boot and idle control valve boot that came with the motor. While they appear good externally and internally, I’m concerned about how well they seal around the christmas tree ridges on the idle control valve. I’ll probably get Turner to send me a new set with the replacement wires.

#13

Well this is gettin’ effin’ silly.

New plug wires came in, still no run properly.

How many inches of Hg should I be pulling at idle? I got 15. I can’t find it in the @#$#Y# manual.

Next step is to check fuel pressure, injectors, TPS and ICV.

I need a win!

…10 minutes later… well I’ll be dipped in $*^)! I can only hear injectors 2,4 & 5 clicking. This could definitely explain no power and poor revving. Sigh… 3 of the plugs are fuzzy with carbon fouling. Unfortunately I can’t really associate which is associated with what cylinder because they didn’t get put back in their original cylinders the other night when #3 was found to be not firing.

Another 10 minutes later…ohmed out the injectors. Specs call for 15 - 17.5 ohms. I get 166 ohms. WTF!!! Alright, assuming the injectors are ok, that means I got harness or ECU issues. That, or I got stealth injectors :).

#14

Understand that the injectors are organized as two banks of three. The injectors for cylinders 1,3,5 are bank 1 and those for cylinders 2,4,5 are bank two. Power for all of the injectors is common and each bank is grounded by the DME to fire. So if one bank is firing, but the other isn’t the problem will be a wiring fault or a failure in the DME.

A commonly encountered problem on M20B25s built after 9/87 is corrosion of the C191 connector (located under the throttle body) from past leaks in the throttle body heater. The correct fix for that is to splice in one or both parts of that connector. The ghetto fix is to hard wire in place of the connector. But that means that replacement of the fuel rail or separation of the harness from the engine requires removal of the intake. If you have C191 and it is the problem, fix it the right way.

#15

My motor is a 12/86 build - no C191.

I’ve ohmed out the ICV - ok.

I’m trying to set the TPS at present. It wasn’t ohming out fully closed. I think I finally got it.

It seems from what you said Jim, that only one bank of injectors is firing. Where can I find a pin out of the ECU connector? I guess I’d like to confirm that my injector harness wiring is good.

I can get an '87 ECU in Durham tomorrow for $75. Think I should go for a ride?

#16

Alrighty then. Went to Durham and picked up another DME & AFM.

Checked the wiring to the injectors - all ok

Fuel pressure is about 42 psi nom, jumps up to about 50 when revving the engine and drops to about 38 after sudden release of the throttle and then levels out to nom.

Compression ranges from 173-183.

Changing DMEs matters not.

All injectors ohmed out ok. Injectors 2, 4 & 5 have audible clicking with a screw driver to the ear. 1, 3 & 6 make no sound. This isn’t a bank fire issue. Bank fire is 1, 3, 5 & 2, 4, 6.

At this point I’m suspicious that the fuel injector guy did something to make 3 of the injectors hang open. Rob Keehner is helping me get in touch with a guy locally and we’re hoping we can get him to test the injectors tomorrow. If we can get some proof the fuel injector guy screwed them up I’ll try to get my money back. If I’m lucky we can fix the 3 silent ones and double check the ones that appear to be working, which means I won’t have to order another set of injectors.

FSR PCA at VIR starts Friday. Errgh.

#17

Sorry this has been so frustrating!

Simpleton questions:

Have you swapped the working injectors into the non-working harness plugs?
IIRC you have been doing some engine bay painting–are the ground locations free of paint? (OK, that’s a SWAG, but it happened to me when restoring my 240Z, so I thought I’d throw it out there.)

BTW, where in Durham did you get the parts?

#18

Pull the fuel rail and injectors and point them into a towel and crank over the engine with the coil disconnected. If one or more injectors aren’t firing it will be obvious. And it will be easy to swap injectors around to see if the problem follows the injector or connector.

Since you have an early harness, be aware that there is are splices in the engine harness that are known to be somewhat problematical and could explain what you are seeing.

#19

Steve - Wagners. However, I was unable to get a 173 DME, I had to settle for a 153 from an '87 325ic. Luter gave me a 252 when I bought everything last year. They have a 154 DME still available, again from another '87 convertible.

I masked off the ground areas when I painted, also scotch brited afterwards. I’ll give 'em a lick and a promise again just to make sure. Grounds I know of: Crank Case to side of Chassis in Engine Bay, Valve Cover to Ground on Battery Shelf in Engine Bay, also 2 ring terminals from Harness to same Battery Shelf Ground. Of course the Battery Ground in the trunk were the battery really is. I don’t think I’ve missed a ground, but some body pipe up if I have.

Jim - You nailed exactly what Fuel Injector Buddy here in G’ville told us to do! It’s gonna be a PITA digging all that out of the Intake Manifold, but kinda fun once I get it rigged up.

I know what you’re saying about the splice between the relay and the individual injectors. I ohmed all that out earlier today. Also ohmed out the circuits between the DME connector and the injectors. All were good.

#20

Ok!

Pulled the injectors and fuel rail. Put the injectors in like they came out. #'s 2, 4 & 5 were the only ones spraying fuel. Nothing from 1, 3 & 6.

Swapped injectors as follows: 2 & 6, 1 & 4, 3 & 5.

#'s 1, 3 & 6 were the only ones spraying fuel. Nothing from 2, 4 & 5.

So now I’ve proven (the hard way :slight_smile: ) that I do indeed have 3 bad injectors.

I checked with the local Advance Auto and they couldn’t get me a set of injectors in sooner than the 20th. No Way. I have to have a set here between tomorrow and Tuesday.

What’s my best resource?

update - I can get BWG (Borg Warner?) injectors from O’Reileys by Tuesday. $37 ea