6MTGirl

iTrader: (7)

Hi guys,

I need help resolving a mysterious issue with the idle stumbling at a stop sometimes and other weird car behavior. Can anyone look at the attached datalogs and tell me if anything pops out at you?

Some background on the car and symptoms: original 6-port engine with 74K miles. Compression was tested by Mazda last year and was good. Running OEM coils and plugs and Magnecor wires with 5K miles on them. No starting issues, hot or cold. Only relevant mods are an RB airbox, 3" midpipe with HJC cat and MM tune.

After an auto-x event a few months ago I threw a misfire CEL, accompanied by an idle stumble almost everytime I came to a stop and LTFT at idle in the neighborhood of -15%. Because of the misfire, I decided to replace the 2 trailing coils with old ones I had lying around. LTFT returned to normal and the car ran fine for ~400 miles.

Soon afterwards, LTFT at idle dropped again to -8% or so and the idle issues started again. The idle dips and then comes back up when stopped, either just once or repeatedly, but without stalling. Even when the idle is stable, you can feel the engine 'missing' every few seconds. No misfire codes. At some point, LTFT went from -8% to +6/+8% without me making any changes to the car. At this point I took some datalogs at WOT as someone suggested to me and noticed my AFR was in the 13.5-14 range past 7500 RPMs. It had never run so lean on this tune, so I immediately switched back to the MM base map because I was afraid of leaning out the car. Now it's not running lean anymore with the base map, but the idle problem persists and trims are still in the +5/+8% range (see attached datalogs).

I took the car to Mazda for diagnostics and they couldn't find an issue. They didn't see any misfires or vacuum leaks and they said the trims are 'normal' and the idle may be due to the 'old age' of the car. :p That still doesn't explain why it's happening, or why the car decided to run lean at WOT with the MM tune, or why the fuel trims at idle have been all over the place. I'm honestly stumped... Any help and suggestions would be highly appreciated!

yomomspimp06

did you ask them to do another compression test? I would replace the plugs with a completely fresh set(all 4)
do you have a way to check fuel pressure? maybe the pump is failing? I'm just brain storming here. I can see the hiccup in the logs but its tough to say what exactly is causing it.

wcs

iTrader: (2)

First thing and not at the OP but at me ... **** I just hit the back button and lost everything I was writting!!! gggrrrrrr

Ok sorry I'm better know.

I had a whole list of simple easy free things to check.
AutoX car is going to have more wear and tear.
Do all the easy stuff
- clean and reset maf
- check motor mounts
- check air filter
- clean maf
- check/replace all spark plugs
- check coils and leads using HEI Coil tester
- Check battery and terminals


Idle logs:
Positive LTFT not aways but can indicate a vacuum leak.
Actually the LTFT on the stumble log is better than the Normal log.
However the Normal idle log has a higher G/S and a better AFR, with the stumble log is leaner and a lower g/s value ... vacuum leak showing its presence? maybe

How far apart in time where these logs taken?
Where they both from the MM tune?

Same question with the WOT logs, both MM tunes?

Why did you ever switch from the MM tune in the first place?
What was this other tune you were using?
Did you and MM discuss that the car would be AutoX'd as I think he does run a bit more fuel up top with cars that are going to be run hard but I'm not sure what that AFR would be?

The WOT Logs you're running pretty rich for a NA "street car" (see above question)
Your reporting 12 and 11 AFR (LTFT is adding 3.74%) fuel at about 5700 rpm and up on both 2nd and 3rd WOT's
That could be causing your misfire.
I also noticed a weird blimp with the Throttle position in the WOT log at row 239 .. did you let off the throttle?

Something must have changed to cause all this ... I would be checking for vac leaks.

DarthRX8

I would check your MAF (clean it). I recently had the same issue after taking my 8 in for an oil change at the dealership.

They over filled my oil and I ended up getting some oil in my AEM intake tubing... I had the same symptoms (higher LTFT and slight shudder at idle; never stalling but it was noticable).

After cleaning my MAF and the intake tubing everything went back to normal.

TANKERG

Does it idle the same wether or not the clutch is depressed?

Ricky SE3P

iTrader: (10)

any other ideas? (just a friend bumping the post for her)

wcs

iTrader: (2)

How about some answers and updates to what's already been posted

6MTGirl

iTrader: (7)

Happens! Thanks for re-writing it all so thoroughly.

I haven't been able to work on the car due to a recent surgery, but I'm picking up the spark tester tomorrow and hoping to check out the usual suspects with the help of a friend. All these things have been replaced/done in the past year and/or 5K miles, but you never know.

All of the logs were taken after switching back to the base tune. The Idle (Stumble) one was taken 2 weeks prior to the rest, during which time the car was driven minimally.

MM Base map.

I was using an MM custom calibration tune. After a few hundred miles of no fuel trim issues, LTFT went negative, then positive. I took a WOT log in 1st and 2nd gear just to see if it would be safe to auto-x the car in that state, and AFR hit 14 at WOT (log attached at the bottom of this post). I don't know the reason why it started running lean all of a sudden, but I didn't want to lean out the car so I switched to the MM Base map. All the logs in the first post were taken after I installed the Base map.

Yup, he's aware. He's not overly concerned about the idle 'stumble', but he doesn't know what caused the AFR/LTFT to change either. He thought it could be the weather, but it's been warm all along here.

Since that WOT log was taken with the Base map (not with a custom one), MM said that my car seemed leaner than typical for the Base map. And to clarify, the misfire CEL happened with the custom tune. I think I truly had a bad coil because at the time my car picked up a ton of negative trim (-14%) and after I swapped out the trailing coils, it was fine for a long while.

Perhaps. I don't remember consciously doing it, but I got pretty paranoid about the speed I was getting up to on that particular road.

I'm with you on that. The dealer checked for vacuum leaks -supposedly- but just because they didn't find any doesn't explain what's been happening.

Same, the clutch has no effect.

Going to do that, even though I did it not too long ago. Glad it worked for you!

Mazurfer

I'd clean the ESS for the hell of it as well........it's free!!!!!

wcs

iTrader: (2)

lol beat me too it ... actually I typo'd in my original post

I put clean and reset Maf ... ooops my bad I meant ESS

But yeah what he said.

wcs

iTrader: (2)

Jeff`s a pretty smart guy ... mmmmm
It`s not just the temperature that can effect the trims but the Barometric pressure as well.
Generally +-3% LTFT is acceptable.

I don`t want to work against what you and Jeff have talked about.
Does he know you`ve switched back to the base map?
I`ve seen some of the Base Maps and they run super rich and are not intended to be used long term.
Because you are now back to a base map the LTFT is no longer relative, well relative in the sense that we can`t tell if we have corrected the initial problem.

You see when Jeff scales the Maf table, that's what removes the LTFT (all things being equal and mechanically sound) that is why on his custom tune you saw no trim for a long time.
Something happened and you started getting some trim, for example the failed coils. After fixing the coils, I would have just reset the ecu with the same custom tune and waited to see if I gained some trim again.

The base map you are running likely does not have a corrected or scaled maf table suited to your unique car.
So any trim values gained here could be because of the Maf table or something else.

Have you tried going back to the custom tune and putting a few drive cycles on it?

The trim values in the latest log are way better than the first post (which came from the custom tune so this makes sense).
Again I don`t have to mix up what you Jeff have decided on but I would go back to the Custom Tune. Drive around for a day or two and see what the trim looks like.

And just so we are on the same playing field ... what AFR range are you looking for at WOT?

edit:
Just reviewing that log in your latest post again. On row 21 I see the spike to 14.11 at 7395 rpm which is right after the VDI opens. Yeah that does seem lean but look at the Calc Load is only at 89% that must be the first gear pull. Things happen so fast in first gear.
The rest of the log looks fine at low to mid 13's

Also try turning off some of the logging parameters in the Cobb AP this will give us a higher logging resolution.
For example we don't need the knock or ignition timing stuff, Throttle Position and MOP

Ricky SE3P

iTrader: (10)

Well today 6mtgirl and I met up not for another car shoot, but to help figure this issue out.

Used the starter fluid method for vac leaks as well as checked all the hoses and fittings; nothing

Motor mounts good

Air filter good

Battery and terminals good

Cleaned the throttle body even though it was already clean

Cleaned the crank sensor even though it was already clean

Intake tube has some residue in the bottom, possibly "cough up" from the oil pan. Advised for catch can as I have and will be looking into if a catch can is legal for STX class Auto-X..

Cleaned MAF (cant really tell if it was dirty or not, cleaned anyways especially with accordion residue..)

Checked for spark from coils; All seemed to spark very well with the exception of the front trailing coil. Front trailing seemed a little on the weak side, will get that addressed as soon as possible. If finances permit will get BHR setup, if not OEM for now..

Pulled plugs to check them, took pictures of my findings. Basically from looking at the photos it appears that the front trailing plug isnt firing very well. We believe this to be due to that coil not firing very strong.

Our current perspective on the situation is her front trailing coil is on its way out and her MAF is getting slightly dirty (especially after hard running autox events) from oil pan gunk coming up into the intake since she doesn't have a catch can. Couldn't find anything else that could be to blame. The ONLY other thing I believe it could be that we didn't discuss is the possibility of also there being an issue with the front O2 sensor not reading consistently.

wcs

iTrader: (2)

Great pics! Thanks

Yes, I hadn't thought about the front O2 sensor ... what year is the car?

The log data doesn't show a crazy afr reading, when my front O2 sensor died it bottomed out and wouldn't move.
I've also had a Maf sensor go as well.

Let's not get ahead of our selves here, those first two pictures of the spark plugs don't look normal. Well the first leading plug isn't bad but that trailing plug is fouled.

Do you have a timing light available?
Hook that up to the front trailing plug wire and rev the engine a bit. If the timing light stops flashing you've found at least one problem.

edit:
Hate to say it, any chance you can get a compression check on that front rotor?
We know the trailing plug is bad, why? Coil, Lead or Plug .. replace all dunno what your budget or time is like
What are your thoughts on the ECU Map? Have you switched back to the custom tune?
Did you remember to do the 20 brake stomp after cleaning the ESS?

There are different break points across the Maf table for the LTFT ... what are we getting at idle right now? Don't need a log file for this

TeamRX8

iTrader: (25)

The only reason to need a catch can is if the engine is bad, good engines don't spit up oil into the intake

An HEI spark load tester tool is the only proper way to test the coil.


.

Ricky SE3P

iTrader: (10)

As far as the can; its more vapors and a beige colored residue that builds up in the intake which I have concern about, but I see what you're saying.

We did test them using that tool, which is also why I said front leading coil seems to be firing on the weak side.

The car is a 04 or 05 if I remember correctly.

Trailing plug definitely fouled and likely not firing..

Didn't have one available, no.. but if need be we can get our hands on one.

She plans to test compression right before warranty is up, but should be okay..

Could be her coil and from using tester I believe it is at least part of the problem. wires are also rather difficult to get on plugs which also leads me to believe at one point possibly someone put the boots on the plugs but it wasn't properly connected to them, just something to look out for after changing coil and plug.

I have a rather open schedule and I'm sure 6mtgirl would be fine letting me work on her 8 to get it back on its feet again running strong. However budget is rather tight for her due to recent events...

It is reset, and after doing all the work on the car we let it idle and the LTFT started off at -3% and slowly worked up to 0%. That however was before going on the drives to go eat and stuff so the current LTFT is unknown to me.

6MTGirl

iTrader: (7)

No pictures after Armor-Alling the tires?


Yes, I sent him my latest datalogs that are in the original post.


That's what I did. Car started running rough and threw a 'cyl 1' misfire code back in October. I *thought* I had a failing coil, replaced both trailing coils with old ones I had (which I think could be what fouled the front trailing plug). While changing the coils, I saw the accordion tube was oily on the bottom so I cleaned it and trims and idle were OK for 400 miles on that same MM tune. Then after the November event we picked up negative trim and started with the idle issues again. Then the negative trim turned into 6-8% positive and the car started running lean with the MM tune. So I switched to the base tune and made this thread.


Just got a new one from Jeff based on the MM Base tune datalogs, and we worked on the car yesterday and cleaned the intake tube. So far after only ~15 miles of driving, LTFT at idle is at -2% and it idles OK. Only time will tell.


According to what Team has told me, low to mid 13s, higher than that would be hard on the apex seals over time.

Gotcha. It was leaner than previous logs I had done with this same tune, and I got scared when I saw 14's.


K. I turned everything on in case it's useful information. It's all Greek to me. :D


2005.


I really think that me replacing both trailing coils in October with old ones of unknown mileage might have something to do with this. We tested the front trailing one twice with the HEI tester. First time no spark, second time very weak.


Excuse my ignorance, but what does a timing light tell that the HEI tester already didn't?


I might have to take the car back to Mazda and pay for yet another compression test since my engine warranty is about to expire. Sigh! As for that trailing plug, as I said above I really think the old coil I put in is the culprit. I'm not sure I had a bad coil to begin with or if the residue in the intake tube has been causing my issues all along (hard to believe, but...). Unfortunately I don't know anything about how or where to get all the coils tested. I've been told a multimeter doesn't work on our coils.


I'm at -2% at idle right now with the tune I got from MM last week. Like I said, only ~15 miles on it, though.


That's how we tested the coils with the help of your DIY. I'm thinking of re-installing the two 5K-mile coils I took out of the trailing positions back in October and testing those as well with the HEI tester. At least one of them I'm sure is good and for now it would be a good idea to replace the weak front trailing one. I'm going to replace the plugs and wires as part of my annual maintenance once I can work on the car again.

What concerns me now is the oil, vapor residue or whatever it is on on the intake tube - and enough of it to cause idle issues within a month of cleaning it. I haven't overfilled the oil and I always use a long neck funnel.

wcs

iTrader: (2)

^^^ I only suggested the Timing light if you didn't have a HEI tester.

TeamRX8

iTrader: (25)

Overfilling the oil sump is likely not the issue because it has to be 2+ qt.s over. All you can do is clean it and see if it comes back.

A timing light is a poor way to check coils. Even if it catches a weak spark (and theres a good chance you won't since its not load-based) how do you figure out if its the coil, wire, etc.? The tester is $15 at most parts stores.

Idle is heavily dependent on the trailing coils. If you think one is weak that would be a good place to start.

dmazda

For 3 years I had the rough idle problem My 04 has 104,000 miles on it now. the original motor. Finally 2 weeks ago the Idle got to the point where it would stall in traffic. I have been working a lot and have not been the DIY guy I use to be but I did some quick work. I changed the RB in take replaced the warped air filter and air flow control pipe. The car ran better but still was stalling. I broke down and brought it to the dealer. They found 2 motor mounts were bad and replaced them. The cars idle was smooth but it still was dipping and stalling in traffic. I brought it back to the dealer. They found that the throttle body was bad. Once they changed that the car runs as smooth as glass. I did do the coils and changed the plugs a year ago. I might check the coils again since I still feel a little lose of power. My cat is bad so that's next item on my list. My advice is check the throttle body. I believe this was the cause of my rough idle all along.

Mazurfer

^...................wonder if the TB was truly bad, or just needed a good cleaning?
As stated in some other thread, I have put that one on my general maintenance list.
My car will act as you describe.........starts to act up in neutral coming to a stop and idle. Once I feel the RPM's start to move much below 750ish, it's time to clean it.

Ricky SE3P

iTrader: (10)

TB is fine, i checked it... Just spent a weekend with 6mtgirl in Sebring for some AutoX.. Even rode in the car with her to watch for changes. Everything was fine up until post AutoX when LTFT starting going positive again. Checked the intake accordion and there was oil residue. I'm very confident that its blow-by and other gunk coming up from the oil pan. Advising a catch can, however unsure if that is STX legal...
Waiting for 6mtgirl to chime in..

6MTGirl

iTrader: (7)

I took my car in for another compression test and to have the oil blowback checked out, since my engine warranty expires in a few days. The shop foreman told my SA that the oil in the intake tube could be caused by engine braking (supposedly a lot more vacuum is created when you get off the gas and the rpms drop than when you're actually on the gas). 'Splain that?

Also the shop foreman told my SA after driving the car that "this car doesn't need a new engine, it's got plenty of power, we replace engines on a weekly basis and I'd be afraid to put a new engine in it because it may end up with less power than it already has". And "we can do a compression test, but it would be a waste of money".

I had them do a test last year (3,500 miles ago) and the results were: front 8.24/8.67/8.67 and rear 7.46/7.46/7.46 normalized for 250rpm. That's more than a 1 kgf/cm2 difference between rotors, but the baro test was within spec and Mazda said no way are we replacing this engine.

The question is, with those numbers should I insist on another compression test and possibly a new engine?

TeamRX8

iTrader: (25)

since the tube connects both before and after the throttle body my assumption is that a catch can on it would not technically be legal for STX. That particular hose is also shown as part of the emission system rather than the intake system so it seems to fail the test all around.

however, the avg competitor probably care less though it would be a possible way to lose money or points

and tell the genius mechanic that the tube bleed point is ahead of the throttle body and won't see vacuum there regardless. It simply gives combustion gases seeping into the oil sump an emissions-compliant place to flow to rather than accumulate in the sump and build up pressure or dumped out into the air as pollution.


.

6MTGirl

iTrader: (7)

I will tell him tomorrow when I go to pick up my car.

Dixie is looking like the only big event I'll be able to take the car to this year. But I can always remove the catch can for national events and keep an eye on the intake tube. Of course, I'll make sure my local competition is okay with me having it. Ruggles especially.

wcs

iTrader: (2)

Thanks for keeping us updated.