Very lean at idle RPM/MAP problem

[WicketMike]

How can B3617 be the cause? If the car is at idle I don't see how a PE table can effect it. I too have the same problem and I notice a trend here... All three of us have 30# SVO's... Coincidence..

i have stock injectors

[bink]

Injector offset table????

[jfpilla]

How can B3617 be the cause? If the car is at idle I don't see how a PE table can effect it. I too have the same problem and I notice a trend here... All three of us have 30# SVO's... Coincidence..

I don't know what the cause is but I'm curious. Not concerned, just curious.
Doesn't the car use PE for some time after startup? If it doesn't then B4901 gets the change to within 1 point or so short or another table could be involved or my extrapolation could be bad. B4901 seems to be involved since the AFR does richen as g/s increases.

I don't think the injectors are the issue in SD at startup.
However, if they don't flow as advertised, it may be one reason for commanded and actual AFR not matching up in WOT PE.

[Blacky]

Try changing your injector timing at cold start temperatures to the same timing value at normal operating temperature.

I have no reason to believe that will solve anything, other than it causes a difference at different operating temperatures, which is the only clue that is available.

Just thowing ideas into the ring.

[jfpilla]

Injector offset table????

Hey Joel,
The offset table does not reference temperature in HPT or EFI but I think it does in Edit. The injector timing tables do reference temperature, so they could be involved.

Someone let me know if B3617 is or isn't involved in open loop when not
WOT.

[WicketMike]

Try changing your injector timing at cold start temperatures to the same timing value at normal operating temperature.

I have no reason to believe that will solve anything, other than it causes a difference at different operating temperatures, which is the only clue that is available.

Just thowing ideas into the ring.

that could be it B3702, because at 176f (80c) is when that table reaches its highest setting. which is the tempature i am seeing where it richens back up to where its suppose to be.

[Black02SS]

that could be it B3702, because at 176f (80c) is when that table reaches its highest setting. which is the tempature i am seeing where it richens back up to where its suppose to be.

jnorris point this out to me as we were discussing this the past few days and I agree that I "think" it may help the issue. I won't be able to test my theory until Monday.

Hey Paul/Ross - Is the car in PE at all upon startup?

[jnorris]

Here is what I have tried last night and today and the results.

• Changed the OLAF table idle AFR at low ECT temps. back to the 13.3 values which were 11.2 to offset the lean condition.
• Put the stock IAC Effective area table.
• Used the 2002 B3702 and B3703 tables

Although the commanded AFR at low ECT did not match my WB the AFR was not 17 – 18:1 lean but was in the 15.8:1 range. As the ECT increases the gap between the command AFR and WB AFR narrowed. This was a cold start.

Today I saw jfpilla’s post about B4901 and B3617. I zeroed out the B3617 table and flashed the PCM. When I started (ETC =21c cool start) the car the AFR was still a little leaner than the commanded AFR. In the 1st min the commanded AFR avg was 12.49 and the WB average was 14.3. Within 2 min of the startup (ECT = 50c) the commanded AFR and the WB AFR were within .3 points of each other.

I think that with some tuning of the OLAF table in the cool ECT at idle MAP this lean startup problem can be solved.

So overall I had good success with resolving my lean start problems. Tomorrow morning will be the real test.

John

[jnorris]

My take on B3702 Injection Timing and B3703 Injection Timing Trim tables.

By the description of these tables it seems that they are values that the PCM uses to open the injectors earlier in the piston cycle based on ECT. The IPW stays the same.
At 6000 RPM 2.5 – 5.5ms is not significant. These tables will have the most affect on fueling at low RPMs.
In looking over stock flash files the 99-02 F-body (A4 and M6) cars are the same, only the 98s are different. The few Corvette files I looked are different than the F-body cars.

On the 98 A4 Vette the Injection Timing Trim table is the same and the Injection Timing table is about .2 higher.

Are the difference in these values from 98 and 99-02 PCM driven?

John

[Black02SS]

I have already zero'd out B3617 on my tune but still see it. I need to check to see if I can't find the post you are refering to.

Here is what I have tried last night and today and the results.

• Changed the OLAF table idle AFR at low ECT temps. back to the 13.3 values which were 11.2 to offset the lean condition.
• Put the stock IAC Effective area table.
• Used the 2002 B3702 and B3703 tables

Although the commanded AFR at low ECT did not match my WB the AFR was not 17 – 18:1 lean but was in the 15.8:1 range. As the ECT increases the gap between the command AFR and WB AFR narrowed. This was a cold start.

Today I saw jfpilla’s post about B4901 and B3617. I zeroed out the B3617 table and flashed the PCM. When I started (ETC =21c cool start) the car the AFR was still a little leaner than the commanded AFR. In the 1st min the commanded AFR avg was 12.49 and the WB average was 14.3. Within 2 min of the startup (ECT = 50c) the commanded AFR and the WB AFR were within .3 points of each other.

I think that with some tuning of the OLAF table in the cool ECT at idle MAP this lean startup problem can be solved.

So overall I had good success with resolving my lean start problems. Tomorrow morning will be the real test.

John