Engine stutter, need help interpreting data log

Doug · 07-13-2008, 11:11 PM

So I used ecuExplorer to capture these logs because recently I started having some stutter/bucking starting at around 3000 rpm (described here).

I'm using the latest Cobb stage 2 93 4EAT map w/Helix DP & Prodrive axleback. No CELs to date.

Here is a 5 second portion of a log that shows an example of what I'm talking about. This isn't at WOT, but under moderate acceleration. Notice the car gradually accelerating but the rpm falling off in the highlighted sections. I am NOT lifting off the throttle during these spikes; there is always constant, increasing pressure on the accelerator:

Here is another one. Again I've highlighted where the engine speed either trends downward or flattens out despite constant input on the accelerator from my foot:

If it would help I can upload the entire csv files for each of these pulls, but this is really my area of concern. I'm brand new to data logging, so if there are other parameters I should be looking at then let me know. I've been advised to look for cylinder roughness, but I can't do that on ecuExplorer and I've been unable to get my ECU to connect to RomRaider so far, but will keep trying.

I've been through several tanks of gas since I originally noticed this problem and suspected bad gas, including a bottle of Techron and a couple bottles of Heet w/isopropyl alcohol for good measure in case it was water that was the culprit. I think the symptoms have gotten better over the last two weeks, but the problem remains.

If anyone can venture a guess that might help me with my stuh stuh stutter, I'd appreciate it.

Doug

EDIT: .csv files now attached, if anyone's interested

thefoos · 07-14-2008, 08:34 AM

I have the same problem, but only when the motor is cold. I thought it was a boost control issue, but I don't think it is anymore. Then I thought tip-in enrichment, but I realized it mainly happens well after a throttle position change.

Quite a few of us have been experiencing this after going stg 2.

I have also suspected the timing belt. They stretch over time with load, I'm at 77k miles, I wonder if it has stretched a bit or skipped a tooth or something. After a reflash, it runs like crap for a couple of minutes. Someone else on the board experienced that and when they did the timing belt, it had skipped a tooth or two.

I'm looking for ideas too!

fourortwowheels · 07-14-2008, 11:40 AM

both of my fsxts did it stock and still did it after i flashed to stg1. a protune is the only solution..

Doug · 07-14-2008, 11:50 AM

I'm not sure it's good to hear that this may be a problem others are experiencing with the Cobb maps... I'd love to get a protune but resources around me are scarce...

However, I should mention that I've been running this map for more than six months and haven't noticed this problem before now. Kind of weird for it to appear now, IMO.

And Scott, you're right, it does seem more prevalent when the engine is cold.

Oh, and I've got 43,000 miles on my FXT. Seems a little early for timing belt issues. I'm still suspicious of the fuel filter/pump though.

thefoos · 07-14-2008, 04:37 PM

Quote:

Originally Posted by fourortwowheels

both of my fsxts did it stock and still did it after i flashed to stg1. a protune is the only solution..

What are the protuners tweaking that smooth it out? Is it sawtooth timing strategies or something else?

beantown · 07-15-2008, 06:29 AM

I have the same and i'm using a greddy piggyback unit. My car has only 8k for mileage.

thefoos · 07-16-2008, 09:16 AM

my bucking/stuttering/hesitation issue was a unclean MAF. I'm a dumbass. I thought I knew how to clean it, and I was only half right. I've only been cleaning the IAT sensor.

fourortwowheels · 07-16-2008, 02:58 PM

Quote:

Originally Posted by thefoos

What are the protuners tweaking that smooth it out? Is it sawtooth timing strategies or something else?

im not sure on that so i dont wanna answer that question. your local tuner should be more knowledgable on the subject. however i do know that it can be tuned out and its not cobbs fault. its in the stock ecu.

both my fsxt did this stock, stg1, and stg2. it is more prevalent in the 07+ canbus models. SOA really did a ****ty job on there stock tune.

after seeing the afrs and tq curve, i believe cobb leaves a lot of stuff alone and just tweaks some boost, fuel and timing here and there and leave it alone. it is desgined to be a base map and work on multiple vehicles. every car is different, you get where im going w/ this.

a protune should be the first mod after scoring an ap to truly benefit from it. IMHO the ol/cl delay associated w/ the 07-08 canbus cars is very scary. stock cars are blowing up, let alone modded.

the second my tbe comes in my car will be getting protuned. i cant wait....

thefoos · 07-16-2008, 05:32 PM

Quote:

Originally Posted by fourortwowheels

im not sure on that so i dont wanna answer that question. your local tuner should be more knowledgable on the subject. however i do know that it can be tuned out and its not cobbs fault. its in the stock ecu.

both my fsxt did this stock, stg1, and stg2. it is more prevalent in the 07+ canbus models. SOA really did a ****ty job on there stock tune.

after seeing the afrs and tq curve, i believe cobb leaves a lot of stuff alone and just tweaks some boost, fuel and timing here and there and leave it alone. it is desgined to be a base map and work on multiple vehicles. every car is different, you get where im going w/ this.

a protune should be the first mod after scoring an ap to truly benefit from it. IMHO the ol/cl delay associated w/ the 07-08 canbus cars is very scary. stock cars are blowing up, let alone modded.

the second my tbe comes in my car will be getting protuned. i cant wait....

I understand why Subaru tuned as they have. Sure the AFR's are way to rich, and they have to run way too much timing to compensate. But that is a safe strategy. Their control systems are very adept at pulling timing. That is their strategy for margin.

I can't speak to the malfunctions with the ol/cl strategies on the 07/08's. If only tuned 02-04 cars.

I certainly do agree with the protune statement though. The canned / off-the-shelf maps suck (I don't care who you go to for them). I've reviewed many of them and I haven't seen one that was worth a damn. But, I suppose that since I'm a semi-protuner with open source (I have people bugging me to tune their car, but no one seems to want to pay for it), I'm a bit biased.

twg · 07-16-2008, 09:58 PM

Did cleaning the MAF fix your bucking problem while the car is cold issue ?

I have the same issue, bucking while cold, but fine when warm...

Quote:

Originally Posted by thefoos

my bucking/stuttering/hesitation issue was a unclean MAF. I'm a dumbass. I thought I knew how to clean it, and I was only half right. I've only been cleaning the IAT sensor.

thefoos · 07-17-2008, 04:59 AM

Quote:

Originally Posted by twg

Did cleaning the MAF fix your bucking problem while the car is cold issue ?

I have the same issue, bucking while cold, but fine when warm...

It cleared it up for the most part. Still not perfect and smooth, but not as bad.

twg · 07-17-2008, 08:00 AM

interesting... what did you use to clean your MAF ?

thefoos · 07-17-2008, 10:13 AM

I just used some carb cleaner. I'm sure thats not the best choice. I know there are better options (electronic cleaners, maf cleaners).

thefoos · 07-26-2008, 07:41 PM

^^Update. After a couple days, after cleaning my MAF with carb cleaner, the stumble came back. I recleaned with CRC MAF cleaner. It works better. Highly recommend using it instead of carb cleaner.

Also, I have seen others on NASIOC with DBW 2.5L's complain about stumbling as well. Some have blamed the TPS. They may be on to something. Before I had this issue, my TPS always read 100% at WOT. Now, it reads low 99% (like 99.12%) at WOT. The calibration slipped. I can't confirm that this has anything to do with the stumbling issue, but I will find out. Food for thought.

07-14-2008, 08:34 AM	#2 (permalink)
thefoos Join Date: Jan 2007 Location: Granger, IN Posts: 684 Gallery: 0 iTrader: 6 / 100%	I have the same problem, but only when the motor is cold. I thought it was a boost control issue, but I don't think it is anymore. Then I thought tip-in enrichment, but I realized it mainly happens well after a throttle position change. Quite a few of us have been experiencing this after going stg 2. I have also suspected the timing belt. They stretch over time with load, I'm at 77k miles, I wonder if it has stretched a bit or skipped a tooth or something. After a reflash, it runs like crap for a couple of minutes. Someone else on the board experienced that and when they did the timing belt, it had skipped a tooth or two. I'm looking for ideas too! __________________ Scott 04 MT FXT STG 2 5 spd 02 WRX STG 2 5 spd

07-14-2008, 11:50 AM	#4 (permalink)
Doug Join Date: Jan 2006 Location: Arkansas Posts: 992 Gallery: 0 iTrader: 1 / 100%	I'm not sure it's good to hear that this may be a problem others are experiencing with the Cobb maps... I'd love to get a protune but resources around me are scarce... However, I should mention that I've been running this map for more than six months and haven't noticed this problem before now. Kind of weird for it to appear now, IMO. And Scott, you're right, it does seem more prevalent when the engine is cold. Oh, and I've got 43,000 miles on my FXT. Seems a little early for timing belt issues. I'm still suspicious of the fuel filter/pump though. __________________ MY06 XT 4EAT

07-16-2008, 09:16 AM	#7 (permalink)
thefoos Join Date: Jan 2007 Location: Granger, IN Posts: 684 Gallery: 0 iTrader: 6 / 100%	my bucking/stuttering/hesitation issue was a unclean MAF. I'm a dumbass. I thought I knew how to clean it, and I was only half right. I've only been cleaning the IAT sensor. __________________ Scott 04 MT FXT STG 2 5 spd 02 WRX STG 2 5 spd

07-17-2008, 08:00 AM	#12 (permalink)
twg Join Date: Jan 2006 Location: Toronto, Ontario Posts: 809 Gallery: 0 iTrader: 0 / 0%	interesting... what did you use to clean your MAF ? __________________ 2004 FXT

07-17-2008, 10:13 AM	#13 (permalink)
thefoos Join Date: Jan 2007 Location: Granger, IN Posts: 684 Gallery: 0 iTrader: 6 / 100%	I just used some carb cleaner. I'm sure thats not the best choice. I know there are better options (electronic cleaners, maf cleaners). __________________ Scott 04 MT FXT STG 2 5 spd 02 WRX STG 2 5 spd

07-14-2008, 11:40 AM	#3 (permalink)
fourortwowheels Join Date: Apr 2007 Location: Long Island, NY - 2008 FSXT Posts: 1,099 Gallery: 0 iTrader: 9 / 100%	both of my fsxts did it stock and still did it after i flashed to stg1. a protune is the only solution..

07-15-2008, 06:29 AM	#6 (permalink)
beantown Join Date: Feb 2007 Location: braintree, ma Posts: 59 Gallery: 0 iTrader: 4 / 100%	I have the same and i'm using a greddy piggyback unit. My car has only 8k for mileage.

07-26-2008, 07:41 PM	#14 (permalink)
thefoos Join Date: Jan 2007 Location: Granger, IN Posts: 684 Gallery: 0 iTrader: 6 / 100%	^^Update. After a couple days, after cleaning my MAF with carb cleaner, the stumble came back. I recleaned with CRC MAF cleaner. It works better. Highly recommend using it instead of carb cleaner. Also, I have seen others on NASIOC with DBW 2.5L's complain about stumbling as well. Some have blamed the TPS. They may be on to something. Before I had this issue, my TPS always read 100% at WOT. Now, it reads low 99% (like 99.12%) at WOT. The calibration slipped. I can't confirm that this has anything to do with the stumbling issue, but I will find out. Food for thought. __________________ Scott 04 MT FXT STG 2 5 spd 02 WRX STG 2 5 spd

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