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Hesitating and sputtering lower RPM (datalog)
1 Attachment(s)
New lifters, resurfaced heads, put back together over weekend and the car is hesitating and sputtering through the lower RPM range. Acting as if there is a vacuum leak. Sprayed brake cleaner around the intake and vacuum fittings while running and nothing changed.
Data log is attached. The O2 sensor readings are different. Any ideas on what I need to address? Thanks in advance. |
Re: Hesitating and sputtering lower RPM (datalog)
The O2 sensor readings are different. In closed loop each bank of the engine operates individually so the O2 readings are seldom in synch. Since there is only a small amount of closed loop operation (~31 seconds) it can be hard to pick up any patterns in the differences. I'll poke around, but not expecting much. I'll review it in more depth tomorrow. |
Re: Hesitating and sputtering lower RPM (datalog)
Originally Posted by Injuneer
(Post 7001658)
In open loop the O2 sensors are operating in a very lean range, because the AIR pump is running. They are not very accurate at conditions that lean, and the temperature difference can account for variations from side-to-side. The left side is varying up and down a bit, compared to the right side. That could be caused by variations in the AIR pump flow on that side, or maybe some sort of injector irregularities on that side. Not real significant all by itself. Almost all of the log (3025 records, 470 seconds) is open loop. There are a couple of unusual places where the PCM shuts off the AIR pump, then turns it back on. The O2 sensors pick up the changes from lean to rich and back to lean.
In closed loop each bank of the engine operates individually so the O2 readings are seldom in synch. Since there is only a small amount of closed loop operation (~31 seconds) it can be hard to pick up any patterns in the differences. I'll poke around, but not expecting much. I'll review it in more depth tomorrow. |
Re: Hesitating and sputtering lower RPM (datalog)
I think I screwed up the number of seconds in open loop, I check tomorrow. I'm on an iPad right now and can’t access my marked up file. Won’t change anything, but as I recall, it went into closed loop at 206 seconds, exactly what the stock timer is set at.
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Re: Hesitating and sputtering lower RPM (datalog)
Correction, went into closed loop at 206 seconds, then idled in closed loop for 32 seconds. See below for cause of confusion.
Exactly when is the engine "hesitating and sputtering through the lower RPM range"? The data log only shows an engine running under no load. It was never driven. Does it run rough under load, or only when it's idling, or when it's sitting still and you are revving the engine up to ~3,000 RPM under no load? Then, after about 3 minutes from initial startup,. the engine shut down for 85 seconds.... did you shut it down, or did it stall on it's own. RPM is steady so it doesn't look like it stalled. Why did you shut it down? |
Re: Hesitating and sputtering lower RPM (datalog)
I did not know how long to run it. Later today, weather permitting, I will hook up the computer and do a fresh cold start, warm up drive, and a few WOT runs before shutting it down. Anything else I should do during that run?
Thanks again.....Bob |
Re: Hesitating and sputtering lower RPM (datalog)
Start it cold, let it idle and warm up for at least 4 minutes. That should get it into closed loop. Don’t rev it while it’s warming up, just leave it alone. Then just drive it moderately for a few minutes, then try a full throttle pull, but say no more than 4,000 RPM max. Just be able to describe how it started, how it idled, how it reacted under low to moderate loads, and how it felt during the full throttle pull. |
Re: Hesitating and sputtering lower RPM (datalog)
1 Attachment(s)
Read your last post after I did the last run. New data log is attached. Feels like it is missing during moderate acceleration. Could not go full WOT since the roads are wet and I kept breaking loose. I hope this new log helps shed some light on my issue.
Thank you for your help. . |
Re: Hesitating and sputtering lower RPM (datalog)
Downloaded. Hope to get to it later today.
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Re: Hesitating and sputtering lower RPM (datalog)
Thank you Fred.
Bob |
Re: Hesitating and sputtering lower RPM (datalog)
While I was looking through this data log, I thought I remembered going through something similar for you a while back. I found I had another data log from you back in March 2014. In reviewing the new one, there are some similarities and some changes to my comments.
These are the comments from my March 2014 post, with new info in bold: The following data looks OK: -idle is stable at programmed RPM (800) - still OK -IAC is in acceptable range at idle (38), and opens up with RPM as it should - still OK, counts down to 29, but no problem -Coolant temp appears normal (194) - still OK, at 190-deg due to cooler weather -Intake air temp appears normal (85 while driving, 94 at idle) - still OK, down to 75-deg due to cooler weather -System voltage is good, always above 13V - still OK -Closed throttle TPS is in the acceptable rang (0.75V) and WOT as well (4.53V) - still OK, except you never went over 90% throttle, probably due to traction issues -MAF readings at idle are a little high... might be due to the tune/cam. Used to looking at 6 grams/sec, and you are running 10+ G/Sec. Could also be the result of mods to the MAF calibration table, or a problem with the MAF. The excess air flow at idle corresponds roughly with the PCM's efforts to reduce fuel. - better. MAF at idle is down to ~8.0 grams/second. That reduces the fuel supplied, and may have contributed to a reduction of the excess fuel at low loads. 8 gps is not out of line for the cam -MAP slightly high at 46kPa, but not out of line with the cam specs. - still OK -Spark advance at idle, and even under load looks to be on the high side. The increased advance at idle may be the tuner's method of compensating for the cam. - still looks high to me, at 29-deg at idle. Did you ask the tuner about this? -As noted, you have a lot of knock retard, but the worst incidents (6/7*) are experienced on lifting throttle. Any chance something is banging on the chassis when you let off the throttle? - much worse. Any throttle application, even gentle, produces up to 12-deg of knock retard. Appears the tuner may have reduced the max allowable retard from stock 15-deg to 12-deg. I suspect this is the cause of what you sense as "hesitation" Wouldn't cause "sputtering", but you may be getting additional knock after the system maxes out at 12-deg. -At idle, the PCM is pulling out 15% fuel on both sides, and another 15% using the short term fuel corrections on the left bank, for a total fuel reduction of 30%. The right side isn't quite as bad, but the long term corrections are bottomed out on both sides. - better. At low loads the PCM is pulling out about 10% fuel using the LTFT's, but no additional with the STFT's. Did you discuss with tuner? As noted above, the big problem is the high excess fuel at idle, and continuing on into the low load cells. By the time you get to the high load/high RPM cells, the problem has virtually disappeared. In PE mode, defaulting to Cell 15 and LTFT's of 128, your O2 readings are not unreasonably high. Right side is generally just under 900mV, and the left side is generally just above 900mV, although it does reach 945mV on a couple of the WOT pulls. Read cautions above on the accuracy of narrow-band O2 sensors in PE mode. - in high load cells, its adding a small amount of fuel to the left side only, but within normal tolerances. In PE mode, the average O2 readings have dropped a bit below 900 mV, still not lean enough to cause all that knock retard. But - the same old caution, the narrow-band O2 sensors are not accurate at WOT . Could possibly be a bit lean and promoting knock, although a lot of your accel was so gentle it didn't get into PE mode very often (which is even worse, because the PCM is not shifting fro the stoichiometric 14.7:1 to the richer target A/F ratios used in PR mode I'd provide these comments to your tuner and see if he can think of reasons it would be running extremely rich at idle and in low load cells. - the big question.... 5 years ago, did you provide this analysis to the tuner, to ask for advice? |
Re: Hesitating and sputtering lower RPM (datalog)
Injuneer, At the time, my tuner was not responding to me so I reached out to Solomon at LT1 PCM Tuning. He reworked my tune and the car ran great for the last 4.5 years. It wasn't until this last top-end tear down and rebuild that the missing problem started. I checked my emails, and it looks like I did not share those notes with Solomon back in 2014. I will reach out to him again.
Thank you......Bob |
Re: Hesitating and sputtering lower RPM (datalog)
Show him your latest log, and mention concern about the knock retard. I looked at everything, and I don't see the signs of the hesitation and stuttering. In the main event of knock retard (starting at scan time 585.89 seconds) you are coming off a light decel at 11% throttle, and rolling into the throttle up to 17%. the left bank is lean. Knock counts increase and knock retard appears. Left bank stays lean and retard jumps to 10,5-degrees,
You relax the throttle to 9%, and knock retard decays, You gradually increase throttle to 22% then hold it there, and the knock counts increase rapidly, and knock retard jumps to 12.00-degrees and stays there. The left bank O2 sensor averages 0.176 volts (lean), and the right bank 0.336 volts when all this is going on. You continue to hold the throttle steady at 22%, and the retard starts to decay, very slowly. During the steady state throttle, the MAF and MAP readings hold very stable. No sign of an actual misfire. Refresh my memory - do you have the EVAP system intact? During this extended period of knock, and seemingly lean condition, the EVAP duty cycle is increasing from 57% to 86%. Possibly a vacuum leak in the EVAP system? Solenoid opens, and instead of sucking in a rich mix of air and fuel vapor, it sucking in all air???? But the next time there is a 12-degree knock retard event, the EVAP DC is only 16% to 29%. Grasping at straws here.... no smoking gun! |
Re: Hesitating and sputtering lower RPM (datalog)
Originally Posted by Injuneer
(Post 7001769)
Show him your latest log, and mention concern about the knock retard. I looked at everything, and I don't see the signs of the hesitation and stuttering. In the main event of knock retard (starting at scan time 585.89 seconds) you are coming off a light decel at 11% throttle, and rolling into the throttle up to 17%. the left bank is lean. Knock counts increase and knock retard appears. Left bank stays lean and retard jumps to 10,5-degrees,
You relax the throttle to 9%, and knock retard decays, You gradually increase throttle to 22% then hold it there, and the knock counts increase rapidly, and knock retard jumps to 12.00-degrees and stays there. The left bank O2 sensor averages 0.176 volts (lean), and the right bank 0.336 volts when all this is going on. You continue to hold the throttle steady at 22%, and the retard starts to decay, very slowly. During the steady state throttle, the MAF and MAP readings hold very stable. No sign of an actual misfire. Refresh my memory - do you have the EVAP system intact? During this extended period of knock, and seemingly lean condition, the EVAP duty cycle is increasing from 57% to 86%. Possibly a vacuum leak in the EVAP system? Solenoid opens, and instead of sucking in a rich mix of air and fuel vapor, it sucking in all air???? But the next time there is a 12-degree knock retard event, the EVAP DC is only 16% to 29%. Grasping at straws here.... no smoking gun! |
Re: Hesitating and sputtering lower RPM (datalog)
I replaced spark plugs last night and car runs 90% better. I was cheap when I put the top end back together and reused the set that only had 1000 miles on them. Don't know if it was the plugs or if I had a loose spark plug wire but now she runs strong.
Thank you Injuneer for comparing a log from 2014 to my last one. I will run a scan using EEHack tonight to share with my tuner and share with him your analysis. Thanks again......Bob |
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