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sbiggi
10-07-2005, 09:32 AM
I am posting this for my brother since I am bored.

His car has been having missfires for a while now. It idles fine but once the boost comes up it start missing and hesitating badly.

Usually a brand new set of plugs will clean it up for a while.

We thought it was some bad/weak coils, so he bought COP from Buschur, but it is still missing.

He cleaned up the mount point for the transistor, and at first seemed to help but now its missing again.

Things we still need to try are a different transistor, I have one but it may not be much better as mine blows spark out as it is.

What else to check?

The tuning for WOT should be dead nuts, as the timing is conservative and the fuel was around 11.5 - 11.0 : 1 last time we checked with the wideband.

JamesonGST
10-07-2005, 10:04 AM
Seems like I am having the same issue with our 95 TSI, plugs fix for it for a little bit than back to hesitating under boost. Would really like to figure out this problem also :D

sbiggi
10-07-2005, 10:26 AM
Seems like I am having the same issue with our 95 TSI, plugs fix for it for a little bit than back to hesitating under boost. Would really like to figure out this problem also :D


Well i can guarantee that its not the coils on ours.

I think its a bad transistor/ignitor thing.

We will try swapping mine in to his car and see what happens, but I dont know if that will help. My car blows the spark out at 22 psi+ in at least one cylinder, where his does it at alot less airflow and boost.

-Seth

Hal
10-07-2005, 10:47 AM
When the ignitor pukes you use 2 cylinders or 4, not just one.

The loss of one is the spark going someplace other than the electrode on the plug.

Blown wires, spark leakage at the coil towers, etc.

I've seen towers arc to strut bars when wire boots don't seal properly.

COPS's don't have wires, but they DO have "boots"

Those boots are usually too long. Some places trim the boot length.

Hal

sbiggi
10-07-2005, 10:53 AM
When the ignitor pukes you use 2 cylinders or 4, not just one.

The loss of one is the spark going someplace other than the electrode on the plug.

Blown wires, spark leakage at the coil towers, etc.

I've seen towers arc to strut bars when wire boots don't seal properly.

COPS's don't have wires, but they DO have "boots"

Those boots are usually too long. Some places trim the boot length.

Hal

Does the ignitor directly effect the intesity of the spark?

Hal
10-07-2005, 10:59 AM
I'm not sure if it does or not.

If it does, it would be related to "dwell time".

If the dwell was to short, the coil would not be fully charged, resulting in a weak coil.

All failing PFETS I've seen are pretty obvious. An immediate loss of spark (even while cruising at steady speeds).

Hal

sbiggi
10-07-2005, 02:34 PM
Well... searching the Nabar archives I found some other things to try.

Rewiring the b+ to the coils and the ground to the ignitor.
That might fix my misfires but I dont think that will help my brothers, but its worth a try and its cheap.

Hal
10-08-2005, 06:14 PM
If the COP boots are full length, I'd cut them back about .5" to .75"

What spark plugs are you running?

sbiggi
10-08-2005, 06:57 PM
If the COP boots are full length, I'd cut them back about .5" to .75"

What spark plugs are you running?


They were already cut from Buschur, and it has bpr7es. Stock gap.

We tried a different ignitor and also tried running new power wire (10 guage) right off the battery.

It still cuts out at 3500rpm with anything more then 1/2 throttle.

Also the car knocks and even pops sometimes when it does this. Plus this all started at the Import drags.

I think maybe the CAS crapped out, but I dont have any other 91+ cas to try.

Hal
10-08-2005, 07:09 PM
It still cuts out at 3500rpm with anything more then 1/2 throttle.

Check the MAS air sensor, that's typical of a large air leak or failed sensor.

JamesonGST
10-08-2005, 07:49 PM
boostedTSI, when this hesitation occurs on your car do you get any weird smells? When ours does this hesitation I can smell something really strange, not exhaust, belt or fuel, really hard to describe. Was just wondering if you have this symtom also?

sbiggi
10-08-2005, 08:00 PM
boostedTSI, when this hesitation occurs on your car do you get any weird smells? When ours does this hesitation I can smell something really strange, not exhaust, belt or fuel, really hard to describe. Was just wondering if you have this symtom also?

Well its my brothers car... and I havent rode in it lately, but he never mentioned anything about that.

sbiggi
10-09-2005, 06:22 PM
Does anyone have a 1g CAS that we could borrow?

-Seth

sbiggi
10-11-2005, 05:22 PM
Finally got my brother the boost leak tester.... had a bad injector seal.

Then his turbo went out about an hour later :rolleyes:

92laserawd
10-12-2005, 04:49 PM
boostedTSI, when this hesitation occurs on your car do you get any weird smells? When ours does this hesitation I can smell something really strange, not exhaust, belt or fuel, really hard to describe. Was just wondering if you have this symtom also?
I think that smell you are smelling is from the CAT. Is the smell like a match? I had that same smell occationally from the Laser that I just sold. From what I understand when a cylinder missfires, it dumps raw fuel into the exhaust and then burns in the catalitic(sp) converter. Nasty smell though, that's all I can say.

JamesonGST
10-13-2005, 09:07 AM
I think that smell you are smelling is from the CAT. Is the smell like a match? I had that same smell occationally from the Laser that I just sold. From what I understand when a cylinder missfires, it dumps raw fuel into the exhaust and then burns in the catalitic(sp) converter. Nasty smell though, that's all I can say.

That would be about the closest thing I could compare the smell to is a match. I will try switching out the coils and see if that fixes it, keeping my fingers crossed :D If that doesn't fix the problem what would you guys say would be the next best thing to check?

boostedTSI, glad to hear you found the root of your problem, but sucks the turbo went out.

sbiggi
10-13-2005, 12:16 PM
That would be about the closest thing I could compare the smell to is a match. I will try switching out the coils and see if that fixes it, keeping my fingers crossed :D If that doesn't fix the problem what would you guys say would be the next best thing to check?

boostedTSI, glad to hear you found the root of your problem, but sucks the turbo went out.

He was about to upgrade anyways, this just sped things up.

sbiggi
10-17-2005, 09:00 AM
Fixed my own misfire under boost.

Hooked up a freinds oscilliscope. Cylinder one was requiring 6x more energy to fire.

Tried swapping plug wire on 1 and 4, made no difference. Put new wires in, made no difference. Replaced the spark plug, but was still getting blow out.

Through my brother COP in. Now I can run stock gap of .028 with out any problems. My coils are done.