need help interpreting PowerLogger data

at7we2

Member
thanks for reading this post. I've been trying to diagnose and eliminate a problem with my GN for a LOOONG time now. I have a very irratic popping and misfire under boost. Sometimes I can go WOT and it runs flawlessly but most of the time, it starts popping and misfiring as the boost starts to build (usually starts between 5-10 psi). I also register a lot of KR - usually 10 degrees or more when this happens. Over the course of about 3 years I've replaced all the fuel system compnents *except* the injectors and all of the ignition components *except* the alternator (if you consider that part if the ignition system). I've also gone through and checked, replaced, added grounds, swapped MAF's, swapped numerous chips, swapped ECM's, and of course the coilpack, coil module etc. Nothing has eliminated the problem. I also have removed the Translator and put the stock MAF back on and it didn't make any difference.

I finally bought a Power Logger and logged some data when the problem was occuring. Can someone take a look at the attached Power Logger dat file and see if you see anything that might indicate whats going on? I'm no tuning guru, but one thing I've noticed in the attached data file is that when the "event" occurs, the MAF reading pegs out at 512 and the injector pulse width maxes out also. Am I going lean???? The O2 mV don't look particularly low to me, (could be wrong) and I've got plenty of fuel pressure (data logged that with a Snap-On data logger). The only thing I can think of is maybe I have a bad injector??? I've checked plugs and they look fine and all of them appear very close to the same color. One import note, the car runs absolutely *perfectly* under normal driving conditions. This is the third turbo Buick I've owned since '96 and this one runs the best under normal conditions.

The attached data file has three seperate occurances of the popping misfire event. The first occurance begins at about 25 seconds into the file. There are two more occurances, but I don't remmeber what time they begin at.

Any input is greatly appreciated.

Info:

- '87 GN
- stock long block
- TE-44
- MSD 50 lb inj.
- Walbro 340 pump
- Accufab fp reg.
- Power plate
- Big Mouth CAI
- Trans. + w/extender chip and 3" MAF
- 10" non-l/u stalling at about 3k

TIA!!
 

Attachments

what chip is in the car for this datalog? It does not appear to be an extender.
In which case your MAF is pinning 255, not 512.

Are you running the stock MAF in this file?

The RPM spikes worry me. I wonder if you have a crank sensor issue. The crank sensor feeds into the ignition module where is is amplified and sent to the ECM. So wiring along the way, a bad module, or grounding issues could affect the RPM signal.

Do you have any more datalogs?

Bob
 
Interesting data display I only saw 3 very short throttle blips each with a huge corresponding amount of knock retard. Oddly enough when I told PL that there was an extender, I noticed that on the maf display that it was pegged out (not good) What are the switch settings in your T+?
Your O2 trace also looks as if it never goes out of closed loop. The closed loop flag never turns off. Your O2 trace should smooth out with that much throttle.

MAF trace odd
O2 trace odd.

T+ settings?
 
wow! that was quick! thanks guys.

I didn't drive the GN today so I'll have to check/ verify all the information you guys asked about.

TurboBob -
- I hadn't noticed the rpm spikes.
- the crank sensor is a new GM part, installed as part of my throwing parts at it to "diagnose" efforts.
- The MAF is a GM 3" LT1 type. (will verify 3" or 3 1/2" and will verify T+ switch setting)
- I believe the chip is an Extender, although I might have swapped in my TurboTweak chip the last time I messed with the car. (will verify) Both chips were burned for this combo.
- no other data logs yet, that was from yesterday morning, will try to get more this weekend

TurboDave -
- will verify and post T+ settings this weekend
- had not noticed it was staying in closed loop. I dont' have a thorough understanding of how the system works in closed versus open loop so I don't really understand what that means or what might cause it - can you elaborate?

And I forgot to mention, I have the spark control on the T+ disabled (pigtail installed). I did that a while back in an effort to eliminate the Translator as part of the problem. It hasn't made a difference that I can tell either way. Sorry I forgot to mention that in my original post.

Thanks again guys. I'm glad I bought the PowerLogger. I've used data loggers here at work so I know how powerful a tool they can be. It was really amazing to be able to playback what was going on with my Buick. Now, with some help, hopefully I can interpret the data and figure out what the problem is! :) I've been chasing this problem WAAAY to long.
 
update...

finally had a chance to hook up the laptop and log more data after checking the MAF sensor, Translator settings and ECM chip.

verified the MAF is a 3" LT1 type sensor - however....:redface: I will nominate myself for idiot of the year because the "BASE" setting on the T+ was set for a 3.5" sensor DOH!! not sure how long that's been set that way. anyway corrected that problem. :redface:

checked the chip and I was wrong there too, it's the TurboTweak chip I had burned a while back. not sure what I did with my Extender chip for this combo, I think I may have loaned it out and never got it back. since I verified I have the TurboTweak chip installed, I also checked and verified that I *DO* have the "Limiter" dip swith in the "ON" position in the Trans.+ and I also changed the MAF display in the PowerLogger console to the 255 grams setting.

in my defense, :p I've been working on diagnosing this problem for a long time and sometimes it's months before I check/change settings, etc. Obviously, I forgot some of what I did the last time I messed with it.

I have uploaded 4 more data files. the last data file is just sitting in the garage in Park, with the engine idling some and me raising the RPM some and holding stead for a few seconds. It was not running well tonight, not sure why - maybe has something to do with the MAF setting in the Trans+?? it ran better when the setting was wrong :confused:

Going to work on aquiring another Extender chip. I had one before and the car still had this problem. Like I mentioned in my original post, I've tried numerous chips and the problem has been present with all of them.

data files...
 

Attachments

All you have to do is tap into the MAP wire and get a 3 bar MAP.

I'm not having any boost issues so I haven't been concerned with logging boost. The turbo spools fine and I never have any kind of boost spikes. I suppose it would at least give some addtional data to correspond with the misfire events. ok, you talked me into it :p I'll get the PowerLogger setup to log boost. I also have an AutoMeter elctric fuel press. gauge that I believe will allow me to log fuel press. as well, but I just haven't had an opportunity to install it yet.

Anyone have any comments on the last few data files I posted?

Thanks again for reading these posts and offering help.

Rob
 
thanks for reading this post. I've been trying to diagnose and eliminate a problem with my GN for a LOOONG time now. I have a very irratic popping and misfire under boost. Sometimes I can go WOT and it runs flawlessly but most of the time, it starts popping and misfiring as the boost starts to build (usually starts between 5-10 psi). I also register a lot of KR - usually 10 degrees or more when this happens.


I know you feel you aren't having any boost issues but your first post reads different. I'm glad you've decided to log boost as it's critical,especially since your problem is under boosted conditions.


And yes, you can log FP with the autometer transducer. You'll have to monkey with the voltage offsets to get it right.
 
I know you feel you aren't having any boost issues but your first post reads different. I'm glad you've decided to log boost as it's critical,especially since your problem is under boosted conditions.


And yes, you can log FP with the autometer transducer. You'll have to monkey with the voltage offsets to get it right.

Thanks for the input WS6. gotta find time to set install the 3 bar MAP sensor and electric FP gauge.

Thanks,
Rob
 
got the 3 bar map and electric fuel pressure gauge installed, but havne't hooked them up to the PowerLogger yet.

I seem to have lost my original Extender chip. I've torn apart the garage and the car looking for it but can't find it :mad:

Does anyone have an Extender chip for 50 lb. injectors they would sell me?

Thanks,
Rob
 
Ok, I'm back at this again...

purchased a 3-bar MAP sensor from Alky Control, got that installed *and* connected to the PowerLogger.

got my Autometer electric FP gauge installed *and* connected that to the PowerLogger so I am now logging both boost and fuel pressure

I logged some data this morning, made some WOT bursts and did a little cruising around. I'm still learning how to read the data so any help is GREATLY appreciated. One of the first things I noticed is the MAP values look WAAAY high to me with peak values topping 200! :eek: I originally thought it would display the data in PSI, but obviously that's not reading in PSI. So, my first question is, what units does the PowerLogger display MAP values in?

I have attached a ZIP file containing 5 PowerLogger DAT files from this morning. Can anyone look at these files and possibly shed some light on the popping and misfire I'm getting?

Thanks!
 

Attachments

Ok, I'm back at this again...

purchased a 3-bar MAP sensor from Alky Control, got that installed *and* connected to the PowerLogger.

got my Autometer electric FP gauge installed *and* connected that to the PowerLogger so I am now logging both boost and fuel pressure

I logged some data this morning, made some WOT bursts and did a little cruising around. I'm still learning how to read the data so any help is GREATLY appreciated. One of the first things I noticed is the MAP values look WAAAY high to me with peak values topping 200! :eek: I originally thought it would display the data in PSI, but obviously that's not reading in PSI. So, my first question is, what units does the PowerLogger display MAP values in?

I have attached a ZIP file containing 5 PowerLogger DAT files from this morning. Can anyone look at these files and possibly shed some light on the popping and misfire I'm getting?

Thanks!


If your're looking at the data page, you can see boost displayed as boost, and also a MAP display. Boost is displayed in PSI, and MAP values are displayed in KPa
If you're looking at the graph page and one of the graphs is MAP, you can right click that graph and choose BOOST instead.
 
ah ha! got it now. I've got my boost set to 15 psi so the 200 value I was seeing on the MAP graph is about right when converted from kPa to psi and after subtracting 14.7 psi for atmospheric pressure.

Thanks for the explanation on that. Any ideas what might be causing my car to pop and misfire under boost?

Thanks,
Rob
 
I have to agree with Bob. It looks like some type of ignition problem.

How did you set the crank sensor up?

Did you gap it to something or just center it up.

Did you turn the crank and check the gap on all three blades?
 
I have to agree with Bob. It looks like some type of ignition problem.

How did you set the crank sensor up?

Did you gap it to something or just center it up.

Did you turn the crank and check the gap on all three blades?

I didn't setup the crank sensor myelf. The crank sensor was replaced by our local turbo Buick guru. I purchased a brand new Delco crank sensor and asked him to install it while he was doing some other diagnostic testing. I know this guy and his abilities very well so I have complete faith that he installed the crank sensor corrctly. The car was popping before the sensor was replaced and still doing it after.

I just checked the cam sensor Sat. night (it was dead-on). I'll go ahead and re-check the crank sensor the first chance I get this week.

Thanks,
Rob
 
file 032909.dat

What happened to injector Duty cycle on frame 658-659? on .dat file 032909. It's at the peak of KR?
 
The crank sensor was replaced by our local turbo Buick guru. I purchased a brand new Delco crank sensor and asked him to install it while he was doing some other diagnostic testing. I know this guy and his abilities very well so I have complete faith that he installed the crank sensor corrctly. The car was popping before the sensor was replaced and still doing it after.

Alrighty then. How about the coil pack & module itself. Have you tried a swap from another car? Make sure the ignition is bolted tight to the motor. Has to get a good ground. Also check grounds on the back of the motor (passenger head). Make sure there tight.
 
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