missing after 20 minutes

[arnold]

hi there

for one reason or the other my car is missing after about 20 minutes (from cold to fully warmed up). I have been struggling for a real long time now and I fear I am stuck now. Please check my logs and my msq.

After about 20 minutes the car starts missing. I is as if something heats up, but I just don't know what to check. Please help

[904svo]

Check your MAT wiring It doesn't look right. Temp swing too small

[arnold]

Thx, yes I see now that it is very stable.... Although I do have a bypass valve and an intercooler it could very wel be that something is wrong here.... I am gonna check!

[arnold]

I checked the wiring, the sensor is working ok, but slow indeed. I swapped the sensor for an open one (Bosch). Is there anything else I can check. Could it be something with coolant related air density / EGO settings??

[arnold]

I did some more experimenting / changes:

- I installed an open cage IAT sensor (Bosch)
- I tested it and it works

I drove today for 20 minutes starting cold (24C), it runs great till about 20 minutes. The inlet temp slow raises to approx 40 C (this appears to be OK as I use an intercooler and a byepass valve). Then it slowly starts to miss and after 10 more minutes the car runs on 2 cyl most of the time

I tried;
- setting EGO authority on zero: NO result
- richer / leaner the fuel table as a hole: NO result
- more / less advance the spark table as hole: NO result (trim option)

I could hardly get home. Had to stop,, opened the bonnet, nothing to see. Checked for 5-10 minutes (things cooled off) then the car was driveable for a few minutes again.

At home I opened the MS, nothing hot.... I felt the coil not specially warm... Sooooo, what to do now????http://www.msextra.com/forums/posting.php?mode=reply&f=4&t=36838#

Dwell settings?? New coil?? I am more or less lost I fear

[904svo]

Did you use Easytherm and load the new values to your cpu? Also use a timing light when this starts and see if your getting spark on all
the cylinders. You may have a bad coil pack.

[turbo355]

Sounds like a component is over heating and shutting down, do you know if your loosing spark or fuel for those two cylinders?

[john.p.clegg]

Arnold

I had the same symptoms as you,had recently altered from resistors to PWM for the injectors,it didn't like it till I separated the PWM power leads from the sensor leads....(actually I sleeved all the leads with coax screening..earthed at one end)

John

[arnold]

Thanks

I had the same symptoms as you,had recently altered from resistors to PWM for the injectors,it didn't like it till I separated the PWM power leads from the sensor leads....(actually I sleeved all the leads with coax screening..earthed at one end)

I use high resistance injectors (4) all coming together in one manifold (wed) (16,3 Ohm)

Did you use Easytherm and load the new values to your cpu? Also use a timing light when this starts and see if your getting spark on all
the cylinders. You may have a bad coil pack.

No I had the resistors changed to 2.2 kOhm if I remember well when I assembled the MS

Sounds like a component is over heating and shutting down, do you know if your loosing spark or fuel for those two cylinders?

Yes that is what I think, quite certain it is spark or it could be one injector channel failing. Is there a way to test a coil?

No haven''t checked with a timing light but I am sure it is running on two / three cyl. I will check to see if I get a spark at all

Please any other suggestions????

[arnold]

I must add some information: the car has been running OK in the recent past. After using another laptop with a usb - serial adapter strange things occured (tables were modified). I took another laptop, with a serial port. No luck. I feared the code was corrupt so installed the newest (Y4).

Anyone??

1. Could the dwell setting cause these symptoms?

2. Could the wrong plug cause this?

3. Are my settings OK

4. What can I check / do the make sure the MS is working OK?? Can I / someone test it??

[jsmcortina]

Back to basics I guess.

Do attach a strobe to each plug lead and see if it tells you anything. Also, do the old test, pull off one plug lead at a time (using an insulated tool) and see if the misfire is specific to one cylinder.

Unfortunately there is no coil or injector test mode in MS1/Extra.

Have you tried tuning around it? i.e. what happens if you add say 10% more fuel? Does it smooth out or no difference?

James

[arnold]

Hi James

It is missing when you drive (accelerate) or rev, not when idle.... I think I will start swapping the coil.

Have you tried tuning around it? i.e. what happens if you add say 10% more fuel? Does it smooth out or no difference?

James

Yes Ii did, no effect

[stevemgbgt]

When this happened to me I did as James suggested and connected my timing light to each lead in turn when the poor running started and found that one side of the wasted spark coil was giving intermittent sparks.I moved the plug leads and changed over the spark A & B wires from the ecu and proved the fault moved with the spark output and not the coil position.A new VB921 cured it although the one I removed looked ok.Steve

[arnold]

Okay I did some more testing: I swapped the coil for another one (new) with the same specs (3,5 Ohm), drove for 15 minutes and it started missing again. I took my timing light and could see the missing as the lamp once in a while didn t light up while idling. This happened on all cylinders.

I turned off the engine and installed another coil (1,9 Ohm). In the begiining the car did well but soon (3-5 minutes) the missing could be felt again (while accelerating). I took the timing light again and could not see the missing anymore while idling. I inspected the plugs, notting expect a little bit of carbon. Mainly while accelerating (boost) it is as if the mixture cannot e ignited,

So, it appears that the lower imp coil has some effect and it seems to be a ign issue. To end, I use this setup :
http://msextra.com/doc/ms1extra/Dizzy_I ... ev2.2.htm/

and my running dwell was 4.0 (also tried 3.6 with no result)

What to do?? Could this be MS issue or do I have to focus on other hardware (other coil ign system?) Any help would be very much appreciated

[john.p.clegg]

Arnold
I know I've posted before but your symptoms are exactly the same as mine were,even to changing the VB921s,which seemed to help for a while,and can only think PWM "crosstalk" is spoiling something,maybe the ignition pulses,are you using resistive plugs?......I would try shielding the ignition wires,plug leads etc from the sensing leads...

Good luck
John
P.S. even sent my Ms back for a health check,and ordered a "spare" to try to locate the fault...all cured by shielding.

[arnold]

Arnold
I know I've posted before but your symptoms are exactly the same as mine were,even to changing the VB921s,which seemed to help for a while,and can only think PWM "crosstalk" is spoiling something,maybe the ignition pulses,are you using resistive plugs?......I would try shielding the ignition wires,plug leads etc from the sensing leads...

Good luck
John
P.S. even sent my Ms back for a health check,and ordered a "spare" to try to locate the fault...all cured by shielding.

Thnaks John, I do exactly understand what I should do. I do have resistive plug (NGK R), I use normal plugleads, I have shielded wires to and from the MS towards the ign module (Crane).

What should I do / check? Which other wires need shielding? The injectors wires?

I had the same symptoms as you,had recently altered from resistors to PWM for the injectors,it didn't like it till I separated the PWM power leads from the sensor leads....(actually I sleeved all the leads with coax screening..earthed at one end)

I do not fully understand this, sorry

[john.p.clegg]

Arnold
My story is,was running great with dropper resistors in-line with the low impedance injectors when decided to strap out the resistors and use PWM,all was fine for a little while then started missing,did the usual tracing,swapping plugs/leads/coils /SPk A/SPK B but eventually noticed one of the the spark LEDs was missing a beat when this happened,changed the VB921,solved the problem,for a while,but then the symptoms came back,sent the Ms back to Phil for check/test,came back ,no faults,eventually had a "clone" built to aid faulting by swapping,it was not the Ms....
My wiring loom is about 0ne metre of all wires wrapped together with cable ties,so I stripped the loom out and shielded each pair (or triple in the case of the throttle pot) with coax outer,all individual coaxes coming to the main earth at the MS...this solved it..

I also noticed it was more prevalent during warm-up while the ISCV was being used (again PWM)

Nothing showed up in the datalogs

All I can assume is that the more Puse Width Modulation one has the more likely it is to be induced into the other low voltage sensor wires and basically "muck things up" in the Ms

All I can suggest is to separate the PWM power wires (coil,ISCV maybe even the plug leads themselves) from the low voltage sensor wires and screen them electrically

I do believe Phil has a note about PWM Crosstalk...might be worth looking for it

Good Luck
John

[Peter Florance]

I have seen VB921 get intermittant. It is worth changing it.

[arnold]

I have seen VB921 get intermittant. It is worth changing it.

Hi Peter, I dont have VB921 as far as I know.... it is a MS1 with extra code / mod. Do you mean the Q9 or the U4???

My story is,was running great with dropper resistors in-line with the low impedance injectors when decided to strap out the resistors and use PWM,all was fine for a little while then started missing,did the usual tracing,swapping plugs/leads/coils /SPk A/SPK B but eventually noticed one of the the spark LEDs was missing a beat when this happened,changed the VB921,solved the problem,for a while,but then the symptoms came back,sent the Ms back to Phil for check/test,came back ,no faults,eventually had a "clone" built to aid faulting by swapping,it was not the Ms....
My wiring loom is about 0ne metre of all wires wrapped together with cable ties,so I stripped the loom out and shielded each pair (or triple in the case of the throttle pot) with coax outer,all individual coaxes coming to the main earth at the MS...this solved it..

Well I can take apart the wiring.... but I have the feeling the spark is nog strong enough....

[Peter Florance]

Oh sorry
Q9 may be intermittent.

Or MSD box could be failing; they do fail.