This is really helpful information. Thanks much.Originally Posted by Fast355
This is really helpful information. Thanks much.
I have the 350 Vortec running. Periodically at idle, the RPM starts to fall off then picks back up again. Comments please on this aspect.
I am wondering where the ECU gets its injector pulse width values when at idle in Open Loop mode? Is it that the engine must be warmed up, in Closed Loop Mode, and then capture the BLM History values in the on-idle table and then correct them near a value of 128. Once that is accomplished as well as correction of off-idle closed loop BLM values, then when the engine is cold at idle, it relies on the new on-idle BLM values? Is this true or is there some other MAJOR factors governing injector pulse width when on-idle, open-loop and cold coolant temp modes? Any thoughts on these aspects would be greatly appreciated. Please advise. Thanks.
Dave: In open-loop mode with the engine at idle, does the ECU use the VE values in the on-idle as the primary factor for setting injector pulse width values? Is there enrichment added by some other ECU factor when the engine coolant temp is relatively cool? Then when the engine goes closed loop it uses the on-idle VE values at lower RPMs and then transitions to the off-idle VE table values at the higher RPMs. Hope this thinking is somewhat correct. Your comments please. Please advise. Thanks.
I'm not 100% positive on all the subroutines the PCM does. It's my understanding that the PCM will enter a per-determined subroutine for engine warmup that uses the base VE tables values for open loop operation. It's my understanding that the "factory" assumes the VE table will provide BLM's of 128 +/- 5 during closed loop operation, therefore the open loop warmup operation will offset the injector pulse width based on temperatures.
I've noticed that once the VE table is correctly tuned, the engine warmup tends to work as expected.
There are two parameters that effect the transition from near idle to off idle, TPS % and MPH. Most .bin files will have off idle @ TPS % greater than 2.1% and MPH greater than 3 MPH.
dave w
Thanks again dave: That explains it.
Right now the fuel pressure regulator is set about 12 psi. The engine is running very good and AFR is approx 14.x when above idle in closed loop. Then communications was cut off with the PCM. TunerPro started acting funny in that when selecting communications with ALDL, the TunerPro app just quit. So, I deleted and reloaded TunerPro RT V5.x. Now it appears to be OK. The engine goes to lean condition, as witnessed by the Innovate LM-1, and then quits. Suspect blockage of fuel from the plumbed 5 gallon Jerry Can for the engine run-in stand. Need to inspect and clean as necessary. Then reload with 87 Octane, and run the 350 Vortec again. If it does not quit again, then I will transition to the binary file for the Export 350 Vortec with TBI injection and tune from that point on. Want to try as many aspects of TunerPro 5 as I can. Found that not any ADX file can be used. Grabbed a primarily transmission oriented ADX and wondered why so few engine parameters were displayed. Then when picking an appropriate ADX file, many other engine parameters are displayed. Getting more of the hang of things concerning TunerPro.
Dave: Need help. Ran the 350 Vortec again after cleaning the fuel filter. Again for the 4 or 5th time, it dies out at idle while going from 14.x AFR to 16, 17 and on etc. Also loosing communication through the ALDL to the Moates APU1 Autoprom through the USB cable to the computer running TunerPro V5.x. Check these cables and found they appear to be OK. All the time the SES light is lit. Stands to reason that only the TPS, IAC, CLT and distributor are hooked up. Likely there are some switches or parameters that need to be disabled in TunerPro to extinguish the SES light. Getting to my wits end with this lean cutoff at idle. If I advance the throttle before onset of the sometimes lean condition, then I can get the engine to rev up. Likely if I let it go back to idle, it will go to lean cutoff.
HELP PLEASE. Thanks. Please advise.
Maybe try pouring a small amount of gasoline (4oz ~ 6oz) into the intake manifold immediately after the lean cutoff, and see if the engine will immediately restart. This would lead to be think the injectors are not being pulsed by the computer.
I think I would:
1. Disconnect TunerPro and the APU1 and let the engine run like it normally does. Does the engine experience lean cutoff? If yes, go to option 2.
2. Maybe the injector driver or drivers are overheating and stop pulsing the injectors? Connecting a timing light like your going to set the timing on the engine. Instead of looking at the timing mark on the timing cover, strobe the injectors and closely observe the spray patterns. I'm thinking that just before the lean cutoff the spray pattern will change very noticeably as the injector driver or drivers begin to overheat. If it appears the injector driver or drivers are overheating, try option 3.
3. Try a different computer?
dave w
Dave: Will try the methods you have outlined. May just try another computer first to see if it does the same thing. If it does not, go on to step 2. Have previously disconnected the TunerPro, removed the laptop running it and the APU1 and it repeated the lean cutoff. That strobing the injector spray pattern with a timing light is a stroke of genius. My wager is on the computer being bad and like you say may be heating up internally and then failing and I have 2 other PCMs to try. Will try that tomorrow morning and let you know the results. As always, thanks ever so much for your expertise.
Dave W.: After much fumbling around and not getting the spare-2 16197427 PCM to work, finally able to get the 350 Vortec to run for an extended time period with spare-1. Found, with a timing light, that the timing was retarded nearly 10 degrees. Bumped it up to 10 degrees advance and now the engine runs at 1900 RPM with the throttle as far closed as possible. The TunerPro display says 10 degrees more advanced than the timing light on the graduated engine balancer. Yet the engine continues to run and stays running at high idle and approx 13-14 AFR. Cannot figure a way to get it to idle down. Will back off the advance by manually rotating the distributor in the retard direction till the timing light on the balancer says 0 degrees. The TunerPro display will read 10 degrees advanced.
Do not believe there is anything wrong with the injector drivers inside the PCM using Spare 1 16197427. Not certain about Spare-2 operation was not able to get it to work. Was able to cobble together a recording but have yet to verify it is of any value. Still new to TunerPro RT V5.x.
Did you set the timing with the ESC disconnected?
dave w
Yes sir I did set the timing with the ESC disconnected. Set it to zero degrees on the timing marks on the balancer. Reconnected the ESC disconnect and ran the engine. Right now the engine is idling about 1000 RPM closed loop. I recorded to log files but don't know which selection of the quick reply box to attach. I have a jpeg file of the binary, ADX and XDF files to attach. Hope it works. Here goes.
Attachment 8600
Files did not seem to attach. Use the "Go Advanced" option to upload files.
Did you clear the check engine light after setting the timing by disconnecting the battery for several minutes? Running the engine with the ESC disconnected will set a PCM fault, causing the check engine light or service engine soon light to come on.
dave w
Dave: For safety sake, I disconnect the battery which is on the run-in stand after each run. Every run, the check engine light has been on. Don't know what has to be done to extinguish the light. I have managed to upload the latest log file. Next time the engine is run, the time the engine has been running will be recorded as a reference.
In looking at the log recording, at idle the engine goes from a rich to a lean condition and back and forth as seen both by the pulse width and ego sensor. Don't yet understand what that is about. There is always a difference between the timing light and the TunerPro screen displaying ignition advance. Yet to figure out the relationship between these two factors.
Still trying to figure out the high idle situation. Maybe back off the ignition timing somewhat by loosening and rotating the distributor.
This going from rich to lean condition is very much cyclic. Just keeps going back and forth, rich then lean and repeat, repeat. Perhaps IAC is opening and closing at this cyclic rate. Need to modify constants to cancel the service engine soon (SES) light. The same action with the IAC to stop its operation as a trial. Have to monitor IAC commands also. Once the idle has been stabilized, try to retard the idle ignition timing in the PCM to get the idle RPM down to where it should be with a narrower injector pulse width for leaner idle.
Still learning how to tune the PCM. May just switch over to a more compatible export binary set up for the 350 Vortec and TBI. Then tune from that point on.
Appears the next course of action would be to disconnect the IAC valve to see if that stops the cyclic behavior with lean/rich injector pulse width and o2 on this 350 Vortec with 454 throttle body. Trying to achieve the objective of getting a good idle RPM and lean injector pulse. Maybe retarding the ignition timing will bring down the idle RPM. Yet the ignition timing seen on TunerPro and the actual with a timing light do not agree. Need to establish some kind of relationship between the two. Will disconnect the ESC and the IAC valve, set the distributor timing with the timing light, see what the PCM is commanding via TunerPro, then reconnect ESC with the engine running and see what happens with the timing light.
Need comments from the experts concerning this cyclic behavior. Maybe it is just an incompatibility of the binary with this particular engine?
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