clove86

Help.

I have a 1991 L98, rebuilt with miniram, comp cam 08-503-08, ported heads with upgraded springs and valves.
I am tuning. The car feels great, but on acceleration the blm drop from 128 to 80, and work there way back to average 128.
I am being told this is not normal and I need to fix the motor.
Other than that I don't know how to fix the motor.
Is this a vacuum issue? Fuel pressure regulator issue?
I need some ideas or pointers.
I have the latest datalog if you want to review it.

Thanks

clove86

Ok I believe the FPR is tee off vacuum with another line. I'm going to reroute it tomorrow for more direct vacuum.

stew86MCSS396

Not sure what to tell you. If the engine is not mechanically sound then that needs to be addressed. Before you start tuning, I'd start with key on engine off sensor data to make sure everything is within spec. From there, you dive into tuning the engine. Since you have a datalog, 1 can assume you have the means to acquire the data. Do you have a means to alter the tune on the PROM??? I believe you can attach your datalog preferred as a csv file.

clove86

i found some faulty vacuum hose connections.
im diving into full replacements first and closing the system in. i suspect vacuum leaks can cause the strange numbers.
i can view the numbers. im continuing to narrow the issue down.

im using tunerpro, i dont know exactly how to save a csv file format.

stew86MCSS396

clove86

easy enough.
attached.

thank you

stew86MCSS396

I see code 25 and 42 that need to be fixed before you progress. IAC at idle could be taken down some from 60 to 30 but this in turn will bring up TPS volts that will need to be lowered within spec ~.54v. The BLMs are all over the place in some areas and VE can be adjusted accordingly. Ironically, I have no means of making the data look more sensible when it's in a csv format except scrolling through the mind numbing data. I wonder if you took the xdl change the extension to csv and posted that, then I can change back so I can peak at it with TPRT.

clove86

Thanks for picking through it.
Like I said before, I found a fairly egregious vacuum leak in a broken hose. I ordered a new one.
I've tried adjusting the tps volt readings. But its a 91 speed density motor, and I don't believe it makes a big difference. Since it can be tuned.
I suspect the idle air numbers could be high due to the vacuum leak.
Code 25. Manifold air temp low. I relocated the temp sensor to the air filter hosing because miniram does not have a hole for it.

Code 42 is set when the engine is running at > 600 rpm and there is no pulse on the white wire from the ECM to the ignition module (CKT423) for more than 200 milliseconds
I had a bad set of injectors. Code 42 may have triggered when I had them. I'll reset it.

I'll see what I can do about getting the file loaded on here.
Thanks for your time

clove86

attached as requested

stew86MCSS396

That seemed to have worked. I can't seem to get the histogram to populate, come to think of it, I've never been able to get it to work on a 1227727 ECM. Which adx are you using and does it populate the histograms??? Anyhoo...what I'm seeing is the integrator does take a dive after you get out of PE. I'm thinking that's just a response to switching from a targeted afr of ~11-12 to 14.7. I would clean up the VEs so the BLMs are closer to 128 + 3. Almost forgot to mention, a vacuum leak would make your IAC drive to close=less air bypassing.

clove86

Copy that.
Thanks.
I'll fix the motor issue and record an updated log.

clove86

ok attached is a log i just finished with.
attached the same as the one before
i forgot to clear the codes before i went. but it looked like a much more stable numbers after i repaired the vacuum leak.
let me know your thoughts

clove86

I found some bad rotten vacuum lines.
I belive this is the cause for all the issues.
Thanks for looking at it for me.