Hesitation "Stumble" at various throttle positions

[darkryd]

Hi everyone. I had my BGN inspected for an exhaust leak which was fixed but drivability/hesitation issue ensued. I had the Powerlogger installed about 3 days ago. I’ll start with the lead up to the Powerlogger files attached.

May-June 2016 - Exhaust Leak: Exhaust Leak coming from the front. I did notice rough idle until warmed up & periodic stall at stoplight after 15 minutes of driving

• Diagnosis and Resolution:.
  • Exhaust leak fixed by resealing manifold and turbo
  • Drive test observed hesitation impacted drivability severely

July/August 2016 - Hesitation: Significant hesitation when throttle down. Occurred at any speed

• Completed the following:
  • New NTK O2 Sensor 21002
  • New SMP Regulator PR3 (due to 80 psi)
  • New NGK spark plugs 6630 v-power
  • New Map Sensor
  • New vacuum lines (replaced all, some were cracked badly)
  • Verified working properly: turbo, MAP, IAT sensor, spark strength
  • Reset idle speed, TPS
  • Improper secondary waveform led to install of new ignition module and coils. Didn’t change the issue. Removed new ignition/coils.

At this point the garage and I decided to install the Powerlogger. Once we installed the Powerlogger and recorded, the hesitation or “stumble” wasn’t as apparent. Go figure. The first file running in park with Throttle depressed did result in a hesitation. We then recorded a short drive and then another instance in park. Please find attached 3 Powerlogger .dat files:

• File 1: 001_2016.08.10_DARKRYD_HESITATE_PARKED_Frame692.dat: starting at Frame 692 there are three quick hesitations. This was recorded while in park with variable throttle
• File 2: 002_2016.08.10_DARKRYD_HESITATE_DRIVING.dat: mechanic took for a quick spin. He said there wasn’t any hesitation/stumble. I looked at the file and didn’t see anything like what he had seen in File 1.
• File 3: 003_2016.08.10_DARKRYD_HESITATE_PARKED.dat: just another recording while in park. I didn’t see anything erratic but maybe someone will see something in the file.

I really appreciate the support in advance. Please let me know if you’d like me to re-record files. This was my first time recording with Powerlogger.

 

[SCOOBY DOO]

TPS stays constant in the first file...but it appears the 02's drop out at the 3 hesitation points. I've had 2 TR's do this. The first was a broken wire making intermittent contact at the TPS...and the other was a bad 02 sensor. You've installed a new 02 sensor...and it's odd the TPS isn't dropping out at the hesitation points. Check the TPS wires very closely anyway.

Jogging my memory I had a 3rd instance of this...and it was the ECM...but it was constant. With key on...but engine not running...make a PL file. Slowly depress the gas pedal to the floor a couple times. Let's see if the TPS is smooth...or erratic.

Mike, the original injectors and KB chip should be updated.

 

[TurboBuRick]

A worn cam sensor will cause issues like you describe.

Start the engine, unplug the cam sensor, leave it disconnected and go for a ride.

 

[darkryd]

TPS stays constant in the first file...but it appears the 02's drop out at the 3 hesitation points. I've had 2 TR's do this. The first was a broken wire making intermittent contact at the TPS...and the other was a bad 02 sensor. You've installed a new 02 sensor...and it's odd the TPS isn't dropping out at the hesitation points. Check the TPS wires very closely anyway.

Jogging my memory I had a 3rd instance of this...and it was the ECM...but it was constant. With key on...but engine not running...make a PL file. Slowly depress the gas pedal to the floor a couple times. Let's see if the TPS is smooth...or erratic.

Mike, the original injectors and KB chip should be updated.

Hi Scooby Doo. Thanks for the quick reply. Based on your recommendations I’ll do the following:

1. Check the TPS wire closely
2. With key on...but engine not running...make a PL file. Slowly depress the gas pedal to the floor a couple times. Let's see if the TPS is smooth...or erratic

The shop who’s helping me with this also thought it might be the ECM. With respect to the chip and injectors, do you have any recommendations? I’ll try to get the above completed today and upload some new logs.

Thanks!

 

[darkryd]

A worn cam sensor will cause issues like you describe.

Start the engine, unplug the cam sensor, leave it disconnected and go for a ride.

Hi TuboBuiRick. Thanks for directing me to this forum and for your quick replies. After I complete steps 1 and 2 recommended by Scooby Do, I’ll unplug the cam sensor and go for a ride. I should be able to upload some new logs later today.

Cheers!

 

[SCOOBY DOO]

Eric at Turbotweak sells injectors and his chip as a combo.

 

[darkryd]

TPS Sweep: Scooby Doo, all looked good from what we could tell. There is a .dat file attached “004_2016.08.12_DARKRYD_HESITATE_TPSsweep.dat”

Cam Sensor: TurboBuRick, we started the engine, removed the Cam Sensor and we still had the same problem. Unfortunately, we didn’t get a Powerlogger .dat file for this. Do you want one?

Hesitation: We recorded 9 files of the Hesitation (“Glitch”). They are attached. The hesitation got worse with more throttle and more time. When “glitching”, injector pulse spikes and black smoke from exhaust as we’re dumping fuel.

The mechanic wanted me to post this additional information that I didn't capture in my previous post:

• Injectors: checked the pulse and all 6 checked out ok
• Checked for ground 5v ref and signal. Functional and within range at the junction behind the dash. Check with a scope.
• IAC: minimum air rate: reset procedure completed and then reset the TPS to it
• EGR system is functional and the ecm is in control.
• Wastegate confirmed functional. Opened and still there.
• MAF: Unplugged the MAF and still having the same issues.
• MAP Sensor: how does the ECM get the map data? Does it go to the IP? We can't see map data on powerlogger. We can see the map data on the Snapon Brick. The mechanic said it looked good. It was changed anyway.

 

[SCOOBY DOO]

TPS file looks fine. Gonna download the others and have a boo at them. This is when I start swapping in known good parts...one at a time. Mike...are the CC's and 02's moving at a good pace at idle in Park with the engine at operating temperature...or do they seem sluggish?

 

[SCOOBY DOO]

Mike. Have your mechanic look at the MAF reading on each file.

 

[darkryd]

TPS file looks fine. Gonna download the others and have a boo at them. This is when I start swapping in known good parts...one at a time. Mike...are the CC's and 02's moving at a good pace at idle in Park with the engine at operating temperature...or do they seem sluggish?

Hey Scooby Doo. Thanks for taking a boo at the files.

In terms of CC's, if one were to base an assessment on the following source, http://www.vortexbuicks-etc.com/basics.htm, where "a good sensor will increment counts at least 8-12 (as a minimum) per ScanMaster frame. That would be about 30 frames on the PowerLogger time wise", then it would seem the CC's are sluggish in park. In most cases the O2 is pegged above halfway point so it doesn't go back and forth to increment the counts.

• File 005 does't start incrementing until frame 330, mind you the operating temp may not have been met Coolant @ 130F.
• File 006 is at 188F and CC's hardly increment at all the entire file. Note: the ECM I/O shows Rad. Fan instead of Park/Neut
• File 007 is at 182F, still showing "Rad. Fan", CC's increment at frame 160. Once they do, looks like 5-10 per second. (would really like to put this into Excel and look at the average CC per second or something like that, no .CSV export option it seems, tried importing .dat file... hmm is that machine language?)
• File 008, temp looks good i think 190. But, doesn't look like an "in park" file as there was vehicle speed in this file. CC's do increment at certain points in the file and resets back to 0 from 255 at frame 281.
• File 009-013, same characteristics as 008. All non-park files.

I'm not sure what that means. Should we do another park/neutral runs? Should I be concerned that the ECM I/O is not showing in Park/neutral sometimes and is showing Rad. Fan? The mechanic also said the O2 sensor was replaced. Are we at a point where we might think of swapping in a different o2 sensor?

 

[darkryd]

Mike. Have your mechanic look at the MAF reading on each file.

Hi Scooby Doo, the mechanic said that he unplugged the MAF and we still had the same problems. Are you seeing something in the MAF readings? I do see a lot of spikes that seem to correlate with LV8, IPW and IDC.

Thanks again for taking a look at the files.

 

[darkryd]

TPS stays constant in the first file...but it appears the 02's drop out at the 3 hesitation points. I've had 2 TR's do this. The first was a broken wire making intermittent contact at the TPS...and the other was a bad 02 sensor. You've installed a new 02 sensor...and it's odd the TPS isn't dropping out at the hesitation points. Check the TPS wires very closely anyway.

Jogging my memory I had a 3rd instance of this...and it was the ECM...but it was constant. With key on...but engine not running...make a PL file. Slowly depress the gas pedal to the floor a couple times. Let's see if the TPS is smooth...or erratic.

Mike, the original injectors and KB chip should be updated.

Hey Scooby Doo. Another quick question. Do you know how I can find out if the original KB chip is open or closed loop? Reason I ask is most of the time O2 at idle is around .800mv. When i was responding to your question about O2 sluggishness, I perceived the O2 pegged at .800 as sluggish. But if its open loop, isn't it supposed to be there at idle? "If you have a chip that provides an Open Loop idle, it will probably show zero cross counts at idle and this is normal. Check the cross counts at cruise. Also, do not expect cross counts at wide open throttle." - http://www.vortexbuicks-etc.com/Scantool_Readings.htm

Learning as I go... It's fun

Thanks

 

[darkryd]

See attached spreadsheet for my worksheet. The ACTIONS tab lists out my next steps. This list is based on multiple sources of research on turbobuick.com, vortexbuicks-etc.com, buickturboregal.com. I in no way created this by myself and wouldn't dare take any credit for it. I tried to tailor the list based on my symptoms and PL readings and the information provided in this thread thus far. My guess so far leads to something electrical, either wiring or the ECM. I'm also intrigued by the mystery of the MAF. Its readings are higher than normal (but not by much). As well, the MAF was unplugged and the symptoms persisted. Here's my list of next steps:

A001: Check Electrical Given that the hesitation started after the exhaust leak was fixed, at the manifold and the turbo, and the symptoms are "glitchy" without a glaring trigger, the issue appears to be electrical in nature, either wiring or a module that is electrical (ie. ECM):
1. ELECTRICAL: ground cable to the turbo support bracket is firmly bolted down. this is a likely culprit given that one of the things that changed before this started was resealing the turbo due to the exhaust leak
2. ELECTRICAL: small ground cable off the negative battery post is attached to the inner fender sheet metal as it should be
3. ELECTRICAL: the coil/module is bolted down firmly against the mounting bracket and the bracket is bolted firmly to the intake/plenum
4. ELECTRICAL: check the grounds on the back of the passenger head to make sure none are broken or loose. These have to be well connected or you will have problems. Many of us relocate them to the firewall with a kit, or pull them up and put them on an intake stud.
5. ELECTRICAL: Make sure the positive battery cable from the battery to the starter is firmly attached to the starter bolt and that neither the cable or the fusible link bundle that attaches to the starter post is touching, or can touch the headers or anything else that could short out the positive feed
6. ELECTRICAL: Put your volt meter on AC and read the voltage across the battery when the car is idling. It should be less than 0.5 v AC
7. ELECTRICAL: pull all the spark plugs and see if they all look like they are firing properly and none of them appear to be wet or seem to have not been firing. I would replace them with a new set of properly gapped plugs no matter how they looked.
8. ELECTRICAL: Measure the resistance between the spark plug terminals on each coil pack (engine not running, of course) and see if the resistance falls between 11,000-13,000 ohms on each pack
A002: O2 Sensor (& ECM) Confirm O2 sensor should be around .770 to .800 at idle. Is the chip (Kenne-Belle KB9007PR) open loop? (asked in this thread). If so, then this makes sense. Would also explain why Cross Counts are 0 when at idle as the O2 sensor stays around .800 and doesn't cross .441v median to invoke a cross count.
As well, getting trouble code 45. O2 sensor running rich. see TC.45 tab. Perform trouble code 45 diagnostic tree:
1. Run warm engine (75-95 DegC) @ 1200 RPM
2. Does Scan tool display O2 above 750mv?
3. If yes, Disconnect O2 sensor and jumper harness CKT 412 to ground
4. Scan should display O2 below 350mv
5. If yes, refer to Diagnostic Aids
6. If no, faulty ECM, the mechanic and Scooby Doo both thought this could be the culprit. This step might help to confirm it.
Additionally: to confirm ECM faulty, follow HL Troubleshooting tab and if arrive at Chart 1, then may arrive at Faulty ECM or grounds.
A003: ECM Depending on A002, the outcome may be to replace the ECM
A004: MAF Appears to be running higher than normal (006: 7.9 - 9 gr/sec at idle vs 4-6). Forums suggest looking at the MAF readings in all files. Replied back to forum that MAF was unplugged and still getting same symptoms. Have not heard back if there are other reasons to look at MAF readings.
MAF could be at 7 idle if idle RPM programmed at 850RMP. However, it looks like its programmed for 650. How to tell what the RPMs have been programmed to? At idle, RPM dips to 450 when glitches.
A005: Ignition Voltage 006 file. Drops to 12.1 when glitches. Anything below 13 should be investigated. Not sure what would need to be done to improve voltage consistency. Seems to be a symptom of another problem, ie ECM, electrical (grounds?)
A006: Checklist Review "Not Started" checklist items.
A007: Chip/Injectors As per Scooby Doo's recommendation, upgrade Chip/Injectors. See Turbotweak.com
A008: Wires Spark Plug Wires
A009: Wires Injector Wires
A010: Injectors Clogged injectors?
A011: Crank Sensor
A012: HL Troubleshooting Follow HL Troubleshooting tab

 

[SCOOBY DOO]

Info on that KB chip will likely be scarce...as it's out dated. When I get to a point like this, I swap out KNOWN good components. The stock MAF's crap out regularly...and the aftermarket units are calibrated incorrectly. If it were me...then I'd swap out the 02 sensor with a Denso unit. If that had no effect...then I'd go with a KNOWN good MAF...and then move on to a KNOWN good ECM.

 

[darkryd]

Info on that KB chip will likely be scarce...as it's out dated. When I get to a point like this, I swap out KNOWN good components. The stock MAF's crap out regularly...and the aftermarket units are calibrated incorrectly. If it were me...then I'd swap out the 02 sensor with a Denso unit. If that had no effect...then I'd go with a KNOWN good MAF...and then move on to a KNOWN good ECM.

Thanks for the direction. Agree to start with the 02 sensor. I think the tricky part is the MAF and ECM and finding a KNOWN good. I'll post up on the parts wanted forum.

i'm meeting with my mechanic tomorrow to talk about this and my previous post. will provide an update afterwards.

 

[darkryd]

Found a known good original MAF and ECM (thanks to Dank GN and Turbo Keith). Actually, I'll have two MAFs and one ECM. Expect parts to be shipped soon. I'm in Canada so the parts might take a while. Will post an update once we get the parts and install. We're also getting the Denso O2 so we can rule that one out as well. Turbo Keith stated that he upgraded to the LT1 and translator and its been a huge improvement, especially at idle. Once we exercise this demon we'll look to upgrade injectors, chip and MAF.

 

[SCOOBY DOO]

I'm in Ontario. What province and town are you in?

 

[darkryd]

Hey Scooby Doo. No kidding. I'm in Ottawa. Where are you?


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[SCOOBY DOO]

Cobourg...3 hours west of you on the 401.

 

[darkryd]

Howdy neighbour. Leafs fan?


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