BMW Turbo Discussion  - BMW 745i and BMW Turbo Project Forums
User Name:
Password:
Save Password
Forgot your Password?
Home | Active Topics (0) | Members | Online Users | Statistics | File Library | Search | Avatar Legend
 All Forums
 The e23 745i and Turbocharged BMW Motor Topics
 BMW M106/M102/M30 Turbo Topics
 engine jerks - short cutoffs problem
Next Page
 New Topic |  Reply to Topic |  Bookmark Topic |  Printer Friendly
Author Previous Topic Topic Next Topic
Page: of 7

Ondra_m
Garage Guru

Status: offline

119 Posts

Posted - May 12 2004 :  04:38:06  Show Profile  Visit Ondra_m's Homepage  Reply with Quote
I have problem with short cutoffs and i dont known what with it now.

Configuration
M106 (3.4i) motronic
converted to 5speed

Situation:
On neutral, on stoped car - when i press accelerator and slowly increase rpm, then around 3800 it always have small cutoff, rpm always drop about 200 down and still again (i have acc. pedal in same possition), when i press the pedal little more, then engine with same cutoff increases rpm to 6250 with ca.3 cutoffs.

When car is moving:
When i accelerate hard on 1-2 gear i didnt have that problem, but...
When i accelerate (not depend on boost/noboost, hard or slowly) on 3-5gears (rpms not increase very fast like on 1-2gear) then i get cutoffs from 3000 rpms to cca 5000rpms.

Cutoffs are very short i think about 1/3sec.
Some times on heavy accelaration situation it have longer cutoff up to 1sec, and after engine back to run, i hear very heavy explosion in my exhaust.

I have friend with absoutely same configuration of this engine and 5speed. His car works normally.

I tryed to change following (but it is still same :-()
1) Coil
2) air flow meter
3) main Motronic unit
4) boost unit
5) temp sensor (blue)
6) spark cables
7) sparks
8) distributor
9) rotor in distributor
10) rpm sensors on flywheel
11) TPS adjusted to 0.22v diference
12) more ground connection beetween engine and chassis

tryed to drive with disconected conector to:
1) ping sensors
2) altitude sensor
3) reference rpm sensor (disconected after start)
4) temp. sensor
5) tryed to drive with disconected one to one injectors (drive on 5-3 pistons only :-))
6) tps

I cannot found any airleak.
It not depend on temperature.
Wastegate operating normally.
When im in not cutoff situation then it have full power.
Fuel pressure 2.1Bar on -0.8Bar (idle)
Fuel pressure 2.5Bar on 0Bar (in acc.)
Fuel pressure 3.4Bar on 0.6Bar (boost).

When i build engine to my chassis it works fine, but after cca 1000km it have thats cutoffs.


Any idea? I dont known.....[9]

Test procedures welcome..

:-)

tihuovin
Over 745 Posts!

Status: offline


956 Posts

Posted - May 12 2004 :  06:30:28  Show Profile  Reply with Quote
Hi Ondra,

Again the same question, do you have the chip where the boost limit has been eliminated?

It all sounds like motronic based problem and one cause can be the chip, if its original 745 chip. The motronic contains preset program, all the fuel maps and ignition maps. Depending on the load and on the rpm, it controls the fuel injection and ignition and it's timing. Small gear, small load, no cut off's. Large gear, larger load, cut off's. That's how I see it (without seeing the car and its engine).

You have tested it with another motronic unit. Was the chip installed to that or not? If not, are you absolutely sure that the setup in your friends car is OK (wastegate, ping computer, etc.).

BR,
Timo
Go To Top Of Page

Ondra_m
Garage Guru

Status: offline

119 Posts

Posted - May 12 2004 :  07:10:40  Show Profile  Visit Ondra_m's Homepage  Reply with Quote
I have chip from Jarmo, my friend too.
There is no real difference beetween my and friend car. Only in intercooler piping. But, i tryed (only for test) use hose directly from airflow meter to TPS (without turbo on intake) - still same.
And, i have lighten flywheel... :-)

Problem looks like no Load dependent, only on rpm depends.
Ping computer: i tryed it - no change.


:-)

Edited by - Ondra_m on May 12 2004 07:11:13
Go To Top Of Page

RDAvena
Gas-fueled God

Status: offline


338 Posts

Posted - May 12 2004 :  09:25:31   View RDAvena's Photo Gallery  Show Profile  Send RDAvena an AOL message  Reply with Quote
Ondra, is your transmission side of the motronic connected? Some have said that their cars run without needing the interconnect from engine ECU to transmission ECU. But some others have needed this connection. Might be worth a try.

Duh! what am I thinking youwere the one that reccomended the interconnect. Sorry I will be more useful next time.

Edited by - RDAvena on May 12 2004 09:27:34
Go To Top Of Page

patric
Grease Monkey

Status: offline


70 Posts

Posted - May 12 2004 :  09:25:31  Show Profile  Reply with Quote
Hey ondra, you already checked everything I could think of.
Well Once I had a problem with the DME relay which released contact and den DME was shut down and after some millieseconds
the Relay closed again and everything went on as usual, these cut offs felt very heavy.
Did you already check the fuel pump?

Ah yeah, once a Audi S2 with ABY engine (from a friend) had similiar symptoms, he told me
he solved it cleaning the electrical contacts very well of all the sensors and actors, (corrosion).

Well I don't really believe in my tips since they don't explain the regular amount of cut offs, but
I think every tip is welcome ;)..

Go To Top Of Page

Ondra_m
Garage Guru

Status: offline

119 Posts

Posted - May 12 2004 :  13:27:57  Show Profile  Visit Ondra_m's Homepage  Reply with Quote
Patric: Good tips thanks, i will try to interchange relay.
Connections looks like very clean.

RDAvea: :-) Yes its me, i did discover that interconnection for my friend, and for me :-)
When you dont have that interconnection then symptoms is different.

Every tip are welcome.

Today i got tip from my friend from BMW service about some guy with osciloscopes and another electrical machines for eletrical problem detetection. I will try him :)

:-)
Go To Top Of Page

greg_mazur
Over 745 Posts!

Status: offline


1234 Posts

Posted - May 12 2004 :  17:43:08   View greg_mazur's Photo Gallery  Show Profile  Reply with Quote
Sounds like you have done a lot! grasping for ideas now... how about main relay.on passenger side cowl panel,
bridge sockets 30 to 87 with small wire and push relay back into socket. this will in effect cause relay contacts to be closed regardless. You may need to rig up considerable test equipment, taped to your windshield in order to determine just what you are loosing to cause this cut-out.
Go To Top Of Page

marc79euro635
Garage Guru

Status: offline


179 Posts

Posted - May 12 2004 :  20:24:12  Show Profile  Reply with Quote
sounds like your loosing spark somehow? the explosion in the exhaust should indicate injectors continueing to work during cutoffs
good luck
marc

Go To Top Of Page

tihuovin
Over 745 Posts!

Status: offline


956 Posts

Posted - May 13 2004 :  01:53:42  Show Profile  Reply with Quote
Hi Ondra,

As everyone has said, you have worked really hard in order to find the cause. I can only imagine how long time it has taken.

It still sounds like a electrical problem. However, I do not think that the fuel supply is the cause, hence the cut off's. If fuel related, it might die slowly.

If the oscilloscope does not give any enlightening new ideas, start to check the wiring and attached components. Main relay (bad contact, cold soldering inside etc.), bad grounding, bad connector/joint (cracked, dirty, corroded), cracked wiring insulator (signal grounded due to viration) ... which start to haunt your car when rpm's reach certain point. Pay attention especially places where the wiring loom has through holes in the chassis or via intake manifold.

Needles to say, that at least I am confused. It seems that you have checked everything I can think of.

One thing which might help, slight possibility but at least one. Take a pictures of the engine room and the set up (turbo, magnetic valve, ...). Also the picture of motronic unit when cable and wires connected could help a bit. Somebody might see something which might cause it.

BR,
Timo
Go To Top Of Page

Timmo6
Master Technician

Status: offline


268 Posts

Posted - May 13 2004 :  05:02:24  Show Profile  Reply with Quote
Hi Ondra,
This seems to be like those cutoffs I've got when i made those interconnections. I think the DME should be reprogrammed for manual use or we have to build an own DME(like megasquirt)to overcome those problems. When I drove my car without those connections but with manual boost control(0,7bar)the engine went great but then the timingrange is not as it should because I think the DME is working in safeprogram and retarding the timing constantly, so this is also not the way to go.
Either I will go the new DME or I will put the L-Jet system on it.
Tim
Go To Top Of Page

Jon 86 745 MS
Over 745 Posts!

Status: offline


1423 Posts

Posted - May 13 2004 :  08:59:29  Show Profile  Reply with Quote
Ondra, I have been doing some reading in the Porche 944 turbo manuel. Seems this can be a problem if the flywheel sensors are too far away from the teeth or the secondary TDC indicator. Spec is .8 mm .1 on each sensor. You might want to check it and see if all is within spec.

Jon Jacobs
85 Korman 745i (AKA Das Borg) R.I.P.
86 745i (Die Rakete)(no mas :(
1.2 bar + Boost with
Team WWW.745i.com Performance Parts
Go To Top Of Page
Page: of 7 Previous Topic Topic Next Topic  
 New Topic |  Reply to Topic |  Bookmark Topic |  Printer Friendly
Next Page
Jump To:

Please consider donating to help keep BMW Turbos! online.
Donate now using the link below. Thank you for helping keep the M102/M106 discussion forum alive!

BMW Turbo Discussion - BMW 745i and BMW Turbo Project Forums © Scottie Sharpe Go To Top Of Page
BMW TURBOS! generated this page in 1.05 secs. Snitz Forums 2000