Lean condition--FAST

[Ricky Trussell]

N/A engine 383 with fast b2b wb02 and timing control. This is a street car. Starting after 1750rpm the engine starts leaning out. this last through the next cell (2100) then clears up. This is at 56kpa and above. At 2450 which is the next cell it clears up.

At 1750 rpm my cell values are high 60's, at 2150rpm I can go as high as 95 and still have a lean reading. This is also true at 56kpa, 62kpa, actually all the way up the kpa scale at 2150rpm, but as soon as it leaves that cell the lean condition is gone.

I have;
turned off wb02 correction
changed plugs
changed wires
checked timing
I thought this could be a miss which would make 02 read lean.

I am dead on with target a/f on both sides of the 2150rpm cells and all over as far as that goes.

Also with the car out of gear and holding steady rpm at 2000 the engine runs lean enough to hunt around. If I change the cell value to 110 it clears up.

I have a accel ignition box and new distributor which is all that is left to change but I'm getting tired of throwing new parts at this problem.


I am lost and my forehead is getting bigger!!!!!!

 

[55Belair]

Ricky, did you get the email I sent you?
Wondering if it helped any.

 

[Ricky Trussell]

I changed the VE table by interloping then drove the car without any other changes. The engine ran fine until 2000rpm then started getting lean and stuttering around until it got in the next cell then cleared up.
I got on the interstate and held the engine at 200rpm and the engine was doing the same thing. I would have to open the throttle more than normal to get it out of the 2000 rpm cells, as I pushed the throttle the kpa reading was going up and the engine would really stumble then gain enough rpm to get into the 2400 cells and pick up and the engine would really come on then.

No matter how I get in the 2000rpm cells at 56kpa or above the engine starts leaning out until I accelarate out of it, even after the trans shifts and the rpm settle back to 2000rpm it leans out.

I have raised the ae vs map pretty steep and still no change. I unhooked the IAC today and turned the wb02 off. I still have to have 95 and above in the 2000rpm cells for the engine to half way run right.
I know 13.0a/f should be enough in that area, I just can't understand why it takes 95's to get there and the problem is only better not corrected.

There is something other than AE fuel problems here because I have run steady at 2000 and get the same thing.

Any more ideas, I have the time but my patience is getting a little thin.

 

[CSJTA]

Ricky have you tried changing or checking timing when this happens? Just throwin out a idea here, those numbers in your fuel map seem mighty big for that area of the map.

 

[Ricky Trussell]

I have checked timing but as far as changing it in that area yes. I have ran at a steady 200rpm and moved the timing up and dowwn 10* with no change in the lean condition. I have 35* total in there AT 2000RPM with 32* at idle. I am going out now to try some more logs.

Does anyone change the AE map parameters?

 

[540Malibu]

what are your head and cam specs, i had this same problem with the small block in my malibu, 1900-2200 just plain leans out.

 

[T66Typhoon]

I have the EXACT same problem on my Typhoon.. I have added so much fuel that when it gets past 2000 it goes to 10 .. it swings from 15.94 to pig rich... I have had to take a break from dealing with it... frustrating.

 

[Ricky Trussell]

My engine spec are:

383
10.5 to 1
Air flow Research 190 heads
519 lift 219 duration cam 112 lobe plus 1.6 rockers
Accel intake
1200 cfm accel throttle body
42lb. injectors
I am running a small cap hei with timing controlled by the ecu.

I ran more logs today, still don't see what the problem is.
If it did it only on acceleration then I would put more AE fuel in, but it also does it at a steady 2000rpm. As the engine eases into the 2000rpm cells the A/F is good and into the cell is goes lean like the fuel is cut back even with high ve numbers, then out of the 2000rpm cell to the 2400 it clears up real fast with ve numbers 30 less.

I am also wondering about my throttle follower settings. I have it set at 10 at my idle IAC then slight taper to the 40 IAC on the end of the graph.

 

[T66Typhoon]

Ricky...

Where is your Open Loop/Closed Loop transition set? I let mine idle in Open Loop and then have it set so Closed loop high is 1500 and low is 1300.

Just anothing thing for you to try to correlate it to.

Also, have you tried putting a stock TB back on it? Just an idea.

Well my Throttle follower setting is higher than yours... you may have just pointed me at my problem....

Just reference mine setup is:
265 CID
4.3L V6
8.4:1
Vortec Ported Heads
83# injectors
Stock TB
T66, P trim Turbo
544 lift, 281 Duration with 1.6 rocker

 

[Chuck Leeper]

Lean at 2K?

What is the TPS % at 2000?? On my setup, I am at a start point of 31 and then 35, then58, ten on up to 87 at 44%.. end of graph.
shoot! mine may be further off than yours, but you might try it???

 

[Ricky Trussell]

I have closed lop set at 700 high and 600 low to control idle A/F.

My tps setting at idle is 23, at that point I have my throttle follower set at 10 then a slight taper to 50 at the end of the graph.
I am not satisfied with my IAC. I set it then drive the car for awhile,when I stop at a light then IAC might be opening and closing making the engine jump around.

I am wondering about IAC settings and my tb idle settings.

I will check tomorrow for vacumm leaks and and exhaust leaks on the 02 side.

I drove the car today trying to find the problem but still end up with very high VE numbers in the 56-72 kpa 2000rpm areas and no where else.

Keep throwing Ideas out and I will try them.

 

[Chuck Leeper]

IDLE and TPS??

My car idles real well at 850 RPM, hot. At that point the TPS % is 4.

 

[T66Typhoon]

Well this is my understanding... again, I want to qualify, I am not an expert with this.. I am learning same as a lot of people here.

A vacuum leak will be irrelevant... the car is seeing ACTUAL Map pressure and reacting to it... should not matter on a speed density system if there are some minute leaks.

On the Ty, the GN's or your application is probably the same from the factory. The factory ECU can tell when the car is in park or a gear, the FAST cannot. On my Ty, as a friend of mine did on his Sy, I run the truck in open loop at idle. I set the A/F a bit rich, about 13.6:1 and then when it gets the lean spike when you pull it into gear, turn on the air, etc, it will not make it stumble. Just a suggestion.. try running it in open loop down low. Not that this will cure your 2000 RPM miss.. just a suggestion.

Also with your IAC.. since the FAST cannot see when you put it in gear, etc... it is necessary to open your throttle plates a bit at idle, about 3/4 of a turn did it for me. Basically look in all of your maps that deal with the IAC and crack your throttle plates open a bit until the IAC setting matched the actual. This will give your IAC a range to work in... if there is no range for it to work in, when it is expected to open to make up air, it cannot open any more because it is at the top of its range trying to just keep the car running.

What will these item do to help your stumble..maybe nothing.

But you can also try running it in open loop low and see if the stumble is still happening in open loop. Anothing thing I was told is that the computer is pretty slow.. the more calculations it has to make the more chance of a stumble,etc. So I was told to be sure that there are not huge gaps in the numbers... say a 52 right next to a 75, etc... I think I was told about 6 was all you wanted them to be apart.

I would try running it in open loop, maybe set the high to 2500 and the low to 2300 and drive it... it is not going to hurt it will the kind of RPM, etc you are running. That would be my next step.. I am not sure what that will tell you ... but another idea.

Hope something here helps.. it is 11:15 in Knoxville, I am starting to ramble... had you noticed...


4% at idle? did you move your sensor? I did not think that was possible.. does your sensor get past 50% at open throttle?

 

[Chuck Leeper]

4% at idle??

Nick asked?
4% at idle? did you move your sensor? I did not think that was possible.. does your sensor get past 50% at open throttle?

I went back and looked at the latest logs. I found: TPS at idle was 4% and the max was 95%.
As I remember, we had the tps set by volts on the Tb when the engine was controlled by the OEM computer. I don't think it's been moved since.
BTW, the TB is a 70MM Hemco.

Back under my rock....

 

[55Belair]

Ricky,
Just for kicks, have you tried to use my complete GCT file in place of yours to see if you get the same results. Our engines seem to be pretty comparable. 383, I am running dart 215's, etc.
Just remember to save your file as your base before you try it just in case it doesn't like it at all.

 

[Ricky Trussell]

I should have done that already. All I have done is made a few changes to my Map vs AE and changed my start IAC settings. I am having a tank made with an internal baffle so after tonight I will be out of service for a few days. I will let you know when I do.

 

[Ricky Trussell]

Okay guys I drove the car today and maybe have some info that will help.

Running steady 2000rpm in overdrive and push the pedal down some the engine acts like a plug misfiring and spits back out the throttlebody. I can actually push the pedal a pretty good bit and the miss last for 4 or 5 seconds before it moves to the 2400 cell and smooths out. (Plugs are new set at .035.)

Spitting out through the tb I thought was a timing issue??? (Timing is at 34-35* at 2000)

I say a miss but it really acts like a dead cylinder or a plug that breaks down under load, but watching my 02 correct it is putting alot of fuel in to keep the 13.0 a/f ratio with the ve table set at 95 to 105 in the 2000rpm cells from 56kpa all the way up to 85 kpa then it pops over to the 2400 cells with the 72 ve setting and is fine. Again running steady 2000 rpm the 02 adds 15-20% to get the 13.0 a/f ratio.

Chris, I will try your setting on the way home from work in the morning. I was at a car show and drove the car to work because of time.

 

[CSJTA]

Spitting thru thur TB could also mean a lean condition. So Ricky, are you saying while crusing at 2000 you are getting a 15 to 20 percent o2 correction?

 

[Ricky Trussell]

Yes, I had my 02 limits set at +10 but the 02 was maxing out and the engine was still acting lean so I bumped the correction limits to +20 to see what the engine wanted.

The problem I have with this is the VE table settings are way out of whack only on the 2000rpm cells with the 95 - 110 settings and the engine still does not run right in the 2000rpm cells. That is a 25 to 30 number difference from the cells on either side of 2000rpm and they are dead on as for as A/F ratio and have VE settings of 68 - 72.

I have changed the A/F ratio from a 12.2 to a 13.8 trying to get the engine to smooth out with no luck.

 

[Rickerbucks]

I have a VERY similar problem to Ricky's.

I'm quite happy with the AFR at idle and under load up to WOT but from time to time I get a 'fart' out the TB when I tip-in. I have a log but it is impossible to tell what happens first to cause the problem.

The MAP, timing, afr etc. all seem to spike at the same time not really giving me a clue as to what caused it.

Is this timing or fuel? Why does it happen sometimes? Should I be using the "AE vs TPS rate of change" to add fuel at tip-in (I have already increased that curve a bit)? I notice that when I tip-in it spikes to 15.94 on the AFR but I do not always get the fart?