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Hesitation/Missing
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MikeDanger  



Joined: 21 Nov 2002
Posts: 636
Location: Denver

PostPosted: Tue Mar 16, 2021 7:06 am    Post subject: Reply with quote

Rasta Monsta wrote:
I don't suppose your CSV is leaking.


It's possible.
I think Im going to pull it, and pull the AAV, since those are easy enough to check out
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Fasteddie313  



Joined: 29 Sep 2013
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Location: MI

PostPosted: Tue Mar 16, 2021 8:48 am    Post subject: Reply with quote

Frequency valve will have a huge effect.. It needs to be running..

My thoughts on the cold plugs are that you are playing with your AFR while not having an IC.. danger danger

Colder plugs that don’t project would add a bit more safety while you are experimenting..
Plugs aren’t even $10 a set.. Try a bunch, keep the old ones for the bikes and sleds to use..
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MikeDanger  



Joined: 21 Nov 2002
Posts: 636
Location: Denver

PostPosted: Tue Mar 16, 2021 10:11 am    Post subject: Reply with quote

CSV is not leaking
heres a pic of the AAV at 55deg, (car not started for a few days)

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MikeDanger  



Joined: 21 Nov 2002
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PostPosted: Tue Mar 16, 2021 10:52 am    Post subject: Reply with quote

Just tested the AAV, it works
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MikeDanger  



Joined: 21 Nov 2002
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PostPosted: Tue Mar 16, 2021 5:21 pm    Post subject: Reply with quote

I came across this statement: "The frequency valve is always adjusting the mixture. When the O2 sensor is not providing a signal, it uses a pre-set duty cycle based on throttle position, coolant temperature, and engine speed."

AND this: "The range is typically from 0mV to 900mV. The voltage rises as mixture gets richer. The "funny" thing is the voltage leaps from, say, 250mV to 650mV very rapidly at air/fuel ratio 1. It's not the best for fuel economy nor performance, but it's the range where cat-equipped cars try to keep the mixture. So, you'll most likely to operate just "rich" or "lean".


because thats sort of what its doing, with the AF quickly going up and down.
So what would happen if the o2 sensor/wiring was bad? and as it relates to Not having a problem On Cold start?

Im starting to lean towards the things that control the Frequency valve
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Rasta Monsta  



Joined: 12 Jul 2006
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PostPosted: Tue Mar 16, 2021 11:42 pm    Post subject: Reply with quote

Another dumb question but are control and system pressures in spec? On my 931, while cruising, you could watch the AFR bounce slightly around stoich (.1 above, then. 1 below).

I'm not sure the FV is capable of causing the broad swings you're seeing.
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MikeDanger  



Joined: 21 Nov 2002
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Location: Denver

PostPosted: Wed Mar 17, 2021 6:23 am    Post subject: Reply with quote

Rasta Monsta wrote:
Another dumb question but are control and system pressures in spec? On my 931, while cruising, you could watch the AFR bounce slightly around stoich (.1 above, then. 1 below).

I'm not sure the FV is capable of causing the broad swings you're seeing.


System is 85psi, Control I can set, this whole time I have been adjusting the Control pressure to get the A/F where I liked, but its around 55-60, however until I had this current problem, unless it was really lean or rich, It didn't act like this, and the AFRs didnt swing so much.

So that was leading me towards one cyclinder with and issue or the "computer" getting a bad reading and trying to adjust.
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Rasta Monsta  



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PostPosted: Wed Mar 17, 2021 6:36 am    Post subject: Reply with quote

I really don't think the lambda system can effectuate the drastic AFR swings you are seeing.

I also think the only utility in an adjustable WUR is changing boost enrichment. The actual load/fuel relationship is determined by the (carefully developed) shape of the bowl in the AFM, and is obviously static.

For that reason, the thing will never run right if you are tinkering with the base control pressure across the board.

IMO.
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MikeDanger  



Joined: 21 Nov 2002
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Location: Denver

PostPosted: Wed Mar 17, 2021 6:58 am    Post subject: Reply with quote

Rasta Monsta wrote:
I really don't think the lambda system can effectuate the drastic AFR swings you are seeing.

I also think the only utility in an adjustable WUR is changing boost enrichment. The actual load/fuel relationship is determined by the (carefully developed) shape of the bowl in the AFM, and is obviously static.

For that reason, the thing will never run right if you are tinkering with the base control pressure across the board.

IMO.


Yeah, but it was running pretty decent before while testing the WUR adjustments trying to dial it in. Something changed/broke in the middle of driving
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safe  



Joined: 18 Mar 2017
Posts: 256
Location: Sweden

PostPosted: Wed Mar 17, 2021 7:02 am    Post subject: Reply with quote

MikeDanger wrote:
Rasta Monsta wrote:
I really don't think the lambda system can effectuate the drastic AFR swings you are seeing.

I also think the only utility in an adjustable WUR is changing boost enrichment. The actual load/fuel relationship is determined by the (carefully developed) shape of the bowl in the AFM, and is obviously static.

For that reason, the thing will never run right if you are tinkering with the base control pressure across the board.

IMO.


Yeah, but it was running pretty decent before while testing the WUR adjustments trying to dial it in. Something changed/broke in the middle of driving


Changed the plugs yet?
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MikeDanger  



Joined: 21 Nov 2002
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PostPosted: Wed Mar 17, 2021 7:24 am    Post subject: Reply with quote

well this page was somewhat informative, although for the 911
https://jimsbasementworkshop.com/CIS/pages/descr_lambda.html#:~:text=In%201980%2C%20the%20US%20CIS,also%20called%20the%20Lambda%20system.&text=If%20the%20O2%20sensor%20determines,it%20increases%20the%20duty%20cycle.
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MikeDanger  



Joined: 21 Nov 2002
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PostPosted: Wed Mar 17, 2021 7:26 am    Post subject: Reply with quote

safe wrote:


Changed the plugs yet?


Not yet they didn't have them in stock locally and I don't have a Daily Driver right now.
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MikeDanger  



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PostPosted: Wed Mar 17, 2021 10:46 am    Post subject: Reply with quote

Ok I Pulled the plug off for the O2 there was some oil on it, but im not sure that would affect the contact. Either way once I put the plugs in (on order) we will see what difference that makes.

I know im burning a little bit of oil, as evidence of fresh oil on the tip of the injectors, but it can't be that much as i don't see any smoke out of the tail pipe. So I don't think its enough to Kill the new o2 sensor I put in less than 100mi ago
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MikeDanger  



Joined: 21 Nov 2002
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PostPosted: Sat Mar 20, 2021 3:56 pm    Post subject: Reply with quote

Damn, still can't figure it out.
I cleaned the plugs I had and put them back in (I got some new colder plugs but didnt want to foul them, I figured the current ones were good enough after i cleaned them, until I get it running right)

So I unplugged the O2 and started it: Again, ran ok at first, then after about 5-6 minutes I could hear it start to miss slowly, However the hesitation from initial throttle was a little better but still there. Let it run for another 5 min, adjusting the WUR and mixture slightly made no difference, The miss persisted regardless of the setting. And the AFR swung quickly but not as much only between 13-14ish

Also I unplugged the air temp sensor and the RPMs dropped (assume that works) same with disconnecting the Overboost sensor.

I let it rest for somewhere between 5-10 minutes, started it again, with the miss still, but the miss started to double its timing.


I feel like one cylinder is missing. which is why the AFR swings, 1-2-3 are good then 4 is lean, But why??

Can a Headgasket be "just barely bad" to cause this? (but then i don't see or smell any exahust/oil in the coolant and same for the Oil.

My other thought was Maybe an injector is going bad? Heres my possible theory: When the engine is cold, the Control pressure is low (therefore MORE fuel pressure is going to the injectors), so that bad injector is getting enough pressure to counter its lack of flow, until the WUR starts raising the Control pressure (I.E. reducing the pressure to the injector)....??? (but would an injector go bad that quickly?)
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safe  



Joined: 18 Mar 2017
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Location: Sweden

PostPosted: Sat Mar 20, 2021 5:24 pm    Post subject: Reply with quote

If your injectors are original they are probably all bad... One might be worse than others.

Pull the injectors put them into jars. Check spray pattern and amount at part throttle, half throttle, full throttle. They should be pretty spot on! If uneven move around injectors to se if the issue follows.
Don't bother cleaning injectors, buy new ones...
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