Lumpy Idle M30 B35 Engine

RonDwyer · Post by **RonDwyer** » Fri Jul 03, 2015 7:04 pm

Finally got the 530 project operational, got the custom exhaust worked out and getting ready to go see Mr smog referee here in Alameda. The engine seems to have a lumpy idle which was worse when the hose clamps were not tight enough, all new rubber hoses. Don't believe I have any hidden vacuum leaks...

I did not remove or test the injectors. They stayed on the intake while I rebuilt the head and the lower end. I'm wondering if I might have some clogging, or if the injector seals are bad. Seals are cheap enough.

Is there a reputable place to send the injectors for testing? I have seen rebuilding offered, but since they are swaged together, how does one honestly offer rebuilding? I'd believe high pressure cleaning with an appropriate solvent. Any suggestions if I am on the right track here?

Mike W. · Post by **Mike W.** » Sat Jul 04, 2015 10:42 am

What intake, which injectors and what engine management are you running?

RonDwyer · Post by **RonDwyer** » Sat Jul 04, 2015 11:44 am

Stock everything, 1988 735i donor car

I did overlook 2 vacuum ports under the manifold. I believe one goes to the fuel pressure regulator and the other is likely for the HVAC Vacuum controls?

There is one small hose off the crankcase vent line, not sure where to re-connect that. The vacuum on it is minimal at best because it is from before the throttle plate.

Mike W. · Post by **Mike W.** » Sun Jul 05, 2015 12:26 pm

RonDwyer wrote:Stock everything, 1988 735i donor car

I did overlook 2 vacuum ports under the manifold. I believe one goes to the fuel pressure regulator and the other is likely for the HVAC Vacuum controls?

There is one small hose off the crankcase vent line, not sure where to re-connect that. The vacuum on it is minimal at best because it is from before the throttle plate.

I believe that goes to one of the ports on the bottom of the manifold.

What does the O2 sensor say? Is it rich or lean or what?

pappentl · Post by **pappentl** » Sun Jul 05, 2015 5:23 pm

I'm having a similar problem. I installed an M30B34 non-cat euro engine running Motronic and the I can't get it to idle correctly. I've replaced everything (AFM, ECU, injectors, plugs wires, sensors), and I now believe my issue is the O2 sensor so I had to drop it at the local shop for diagnostics.

A diagram of the vacuum hoses is found at http://blog.bavauto.com/wp-content/uplo ... g-0061.jpg

RonDwyer · Post by **RonDwyer** » Sun Jul 05, 2015 5:39 pm

Hi Mike,

Voltage never made it above .023, I think a major problem has been identified. The net is telling me if it is below .45 it is a problem. Mine started negative and changed polarity as it warmed up.

Time to head over to the parts store to try to get a universal 4-wire. I hear they are pretty much all the same unless you buy them with end connectors.

I rigged in a check engine light because I heard one would be required to pass smog with this engine. After I pulled the plug on the temp sensor it stays on now but I decided a while back that I wouldn't need the test connector. If anyone has a diagram of that harness let me know.

CabbageFumes · Post by **CabbageFumes** » Mon Jul 06, 2015 12:50 pm

The O2 sensor isn't your idle problem culprit. It can run disconnected in open loop just fine, slightly rich. Look at making sure all vacuum ports are connected -crankcase recirculate hose, FPR are all you need to have connected. Any others get plugged. Check and clean the ICV and AFM. 1.3 naturally has a fairly smooth idle compared to most M30s, but not perfect.

RonDwyer · Post by **RonDwyer** » Tue Jul 07, 2015 4:15 pm

What does cleaning the ICV and the AFM involve? I have not had to do those procedures in the past. Just asking rather than just take a stab at it.

What about a faulty injector?

I think I've run it in enough to pull the plugs and do a compression test. All it got was a valve grind when I had it apart.

Pulling individual plug wires didn't seem to do anything a few days ago. Maybe I have a bum coil. Never replaced one of those in almost 40 years of working on cars.

Falkenberg · Post by **Falkenberg** » Wed Jul 08, 2015 1:43 am

RonDwyer wrote:Stock everything, 1988 735i donor car
I did overlook 2 vacuum ports under the manifold. I believe one goes to the fuel pressure regulator and the other is likely for the HVAC Vacuum controls?

E32 has no vacuum HVAC controls afaik. I does have a carbon canister which connects to a small vacuum port under the manifold, through a 'evaporative purge valve'. Just block it. The fuel pressure regulator needs also a vacuum connection, idle will be affected if not present - having it connected or not to the regulator should produce a noticeable change in idle.

Falkenberg · Post by **Falkenberg** » Wed Jul 08, 2015 1:47 am

RonDwyer wrote: Pulling individual plug wires didn't seem to do anything a few days ago. Maybe I have a bum coil.

If it runs, the coil should be ok. But do check HT order, HT rotor, dizzy cap. This is strange. Distrubution timing is set ok?

RonDwyer · Post by **RonDwyer** » Fri Jul 10, 2015 8:02 pm

There shouldn't be a timing issue, I'd have to rotate the head to change it n a motronic engine! (assuming the cap doesn't rotate)

I shall take the cap off tomorrow and look at it.

I shall run a re-assembly compression check. And replace the injector seals. Something about trusting a rubber that old...hmmm

The nice wiring trough might have to be re-considered, at least if I remove it i can pull the injector plug to see which cylinder is giving me trouble.

A 76 E12? That's a survivor. Last time I was in Kaiserslautern, DE. I realized the chances of seeing my favorite cars has passed to the era of car shows and collectors. Put up a few pictures if you can!

RonDwyer · Post by **RonDwyer** » Sat Jul 11, 2015 5:28 pm

Well, I put on a new 02 sensor, the old one was was bad anyway and got the exhaust pipes finished.

I expected it to still be lumpy, which it is.

Decided to do a compression test, but after I got the plugs out there were only 2 showing hot arcing, the rest were a bit blackened. Pulled the cap off and discovered the center brush on the rotor has disintegrated! The build date was 1997 and 1996 on the rotor. The rotor didn't look bad, but it is getting replaced.

Back to 002 on Monday to get a few more parts...I may just impulse buy the wires. BOSCH only. Good thing I don't need to finish this car on any schedule or something like that.

GripGreg · Post by **GripGreg** » Sat Jul 11, 2015 11:37 pm

Seems like you found the problem.
I would get a cap before the wires but, wires are a good idea.
Good luck,,,,Greg

Ps; You might want to either buy new plugs or at least clean & re-gap yours?
There will be a discussion concerning this but,
I use Bosch WR9L SILBERS in both my cars & everything has been sweet for at least five years.

PatinaBeforePolish · Post by **PatinaBeforePolish** » Tue Jul 14, 2015 7:51 pm

Glad to hear you found the issue. To your original question about injectors - I used this company for the injectors on my 225k e46. Made a difference in drivability and fuel economy went up 2 mpg. Fast turnaround, 17 bucks an injector, they provide before and after flow rates:

http://www.mrinjector.us/

Falkenberg · Post by **Falkenberg** » Thu Jul 16, 2015 9:42 am

My B35 had a '89 cap and rotor on it when I got it a couple of years ago. perhaps people forgot about their existence once the ignition timing went digital.

Firstfives.org

Lumpy Idle M30 B35 Engine

Lumpy Idle M30 B35 Engine

Bad idle and re-wiring the test connector