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Hesitation/Missing
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MikeDanger  



Joined: 21 Nov 2002
Posts: 636
Location: Denver

PostPosted: Mon Mar 15, 2021 6:48 am    Post subject: Reply with quote

Mike9311 wrote:
I've read most of what you've posted but I don't think I have seen you check your plugs?

Run the car with the miss and turn it off. Then check your plugs. Do they all look the same or is any single one different?

I always start at the plugs because they tell a story and it really is the easiest thing to do unless you are tmic'd of course


Will, do however we are currently having a blizzard so I wont be able to run the engine for the next 24-48hrs. But last time I started it I ran it till it started to miss, think thats good enough or should I pull the plugs right after shut down?
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Mike9311  



Joined: 14 Dec 2004
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Location: Chicago-ish

PostPosted: Mon Mar 15, 2021 10:36 am    Post subject: Reply with quote

Probably good enough if its still consistently missing

Just curious if one cylinder is off color from the others
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MikeDanger  



Joined: 21 Nov 2002
Posts: 636
Location: Denver

PostPosted: Mon Mar 15, 2021 12:44 pm    Post subject: Reply with quote

heres a pic, back to front order:
the #3 was slightly wet as there was some left over soapy water from my testing.

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Mike9311  



Joined: 14 Dec 2004
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PostPosted: Mon Mar 15, 2021 10:58 pm    Post subject: Reply with quote

Ignoring 3 and looking at 4, its a lot more carbon fouled, but still firing at least at times, than 1 and 2

Did you do a compression check? something isn't consistent over the 4 cylinders

I would probably put in a new set of plugs, run it, and try again to read. Plus that compression check

Also concerned if you found the one injector had an issue how are the others?
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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morghen  



Joined: 21 Jan 2005
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Location: Romania

PostPosted: Mon Mar 15, 2021 11:49 pm    Post subject: Reply with quote

The one on the right has some small shiny bits stuck to its electrode, what material are those little stuff made of?
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safe  



Joined: 18 Mar 2017
Posts: 261
Location: Sweden

PostPosted: Tue Mar 16, 2021 1:17 am    Post subject: Reply with quote

Get new plugs or at least burn them clean with a propane tourch (heat until electrode is cherry red, brush off).
Run them untill it hessitate, shut down (on the side of the road), pull them out immediatly and check how they look.
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Mike9311  



Joined: 14 Dec 2004
Posts: 1102
Location: Chicago-ish

PostPosted: Tue Mar 16, 2021 2:03 am    Post subject: Reply with quote

safe wrote:
Get new plugs or at least burn them clean with a propane tourch (heat until electrode is cherry red, brush off).
Run them untill it hessitate, shut down (on the side of the road), pull them out immediatly and check how they look.


+1

Didn't know that trick but I was going to say buy new plugs
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1979 924 NA M650 Herausnehmbares Dach
1982 931 Red Resurrection - 951 IC
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1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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safe  



Joined: 18 Mar 2017
Posts: 261
Location: Sweden

PostPosted: Tue Mar 16, 2021 2:10 am    Post subject: Reply with quote

Mike9311 wrote:
safe wrote:
Get new plugs or at least burn them clean with a propane tourch (heat until electrode is cherry red, brush off).
Run them untill it hessitate, shut down (on the side of the road), pull them out immediatly and check how they look.


+1

Didn't know that trick but I was going to say buy new plugs


Not sure if its good in the long run, but it works in a pinch. The result is that they look like they been running in a perfectly tuned engine, sort of.

But new plugs are cheep so that would be my first choice. (NGK)
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Fasteddie313  



Joined: 29 Sep 2013
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PostPosted: Tue Mar 16, 2021 2:57 am    Post subject: Reply with quote

If your screwing around near det limits I’d ditch the projected tips and go with br8es or maybe even 9s..

9s have been fine in my car and I think crsr runs even colder plugs..
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safe  



Joined: 18 Mar 2017
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PostPosted: Tue Mar 16, 2021 3:18 am    Post subject: Reply with quote

Judging by how the plugs look I would go with hotter....
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Carrera RSR  



Joined: 08 Jan 2010
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Location: Somerset, UK

PostPosted: Tue Mar 16, 2021 6:00 am    Post subject: Reply with quote

Fasteddie313 wrote:
If your screwing around near det limits I’d ditch the projected tips and go with br8es or maybe even 9s..

9s have been fine in my car and I think crsr runs even colder plugs..


I'm running colder because mine has been running right and can keep its plugs clean with nice golden brown tips ..... its back on the dyno tomorrow for another health and power check
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MikeDanger  



Joined: 21 Nov 2002
Posts: 636
Location: Denver

PostPosted: Tue Mar 16, 2021 6:19 am    Post subject: Reply with quote

Mike9311 wrote:
Ignoring 3 and looking at 4, its a lot more carbon fouled, but still firing at least at times, than 1 and 2

Did you do a compression check? something isn't consistent over the 4 cylinders

I would probably put in a new set of plugs, run it, and try again to read. Plus that compression check

Also concerned if you found the one injector had an issue how are the others?


The other injectors are ok I added some sealant to the threads and tested with Starting fluid/propane.

As for plug 4 I think its the side of the plug, I noticed one side of the plugs has more carbon than the other, heres a pic with 4 flipped over. I think they all look close enough that they don't account for the missing/hesistation at idle, at least not enough to have NO power off the line.

But also if there was a leak at#4 it would be leaner not richer right?


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Last edited by MikeDanger on Tue Mar 16, 2021 6:26 am; edited 1 time in total
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MikeDanger  



Joined: 21 Nov 2002
Posts: 636
Location: Denver

PostPosted: Tue Mar 16, 2021 6:24 am    Post subject: Reply with quote

safe wrote:
Judging by how the plugs look I would go with hotter....


I was thinking about going colder since I will eventually turn up the boost, but its the stock 6psi for now.

I think they look a bit black because it was running way rich for a time, and it always starts rich. I've never had a chance to do any high way stretches, all my driving has been around the neighborhood, most steady speed driving I did was less than 2 min. basically stop sign to stopsign (or stoplight) with a few WOT tests.
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Rasta Monsta  



Joined: 12 Jul 2006
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PostPosted: Tue Mar 16, 2021 6:29 am    Post subject: Reply with quote

I don't suppose your CSV is leaking.
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MikeDanger  



Joined: 21 Nov 2002
Posts: 636
Location: Denver

PostPosted: Tue Mar 16, 2021 7:04 am    Post subject: Reply with quote

Heres my current train of thought.

Something "blew" while the car was running (and I was almost Good on the AF tuning) (im quite certain the TB wasn't the issue)

What ever it is that went bad, isn't affect when the engine is Cold/or the first few minutes of running.

#1 the AAV, that changes in the first few minutes, but could that "Blow" after the car is warmed up and running ok?

#2 the O2 sensor (it was new) Obviously that changes when the car warms up right?

#3 The WUR (SORT OF), so as I start the car, I see the cold Control start around 20 then slowly raise to 45psi. Now could what ever "blew" Not be affected by the lower initial pressure, but as the pressure rises during the warming period it affects that failure?

#4 the Frequency Valve: when I reinstalled the TB I forgot to reconect the ground for the FV and it didnt work, I started the car and had to really lean it out, until I realized, "hey I dont hear the FV working". I didn't realize the FV would have that much of an effect on the Mixture.
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