WAYNE88N/A

I've been troubleshooting this little "mini hesitation" problem for a while now, and it's getting progressively worse, which is why I'm posting- maybe this has happened before to someone. The basics:

It started out as a mini-hesitation, maybe a 1/10 sec kind of thing, about 2 or 3 times over the 50 mile trip to work (and back). No bucking feeling, just a slight loss of power, like an injector wasn't firing, or a spark plug, for just a split second, then everything's back to normal. Now, 98% of the time it happens, the car has just hit some form of bump in the road. Not a big pothole, more like the unlevel freeway sections type of thing, or a "shallow" hole.

I've got the code LEDS in the cabin, and have never gotten a code to flash during these "episodes"- except tonight, at a stop light, the idle fell (and recovered) and a single short LED flash ensued (CAS)...

I've watched the meter on every item from the ECU that might have something to do with this over the course of several weeks now, and the only thing remotely considered a "twitch" during a bump came from the TPS, but that bad boy is so sensitive it could have been my foot shifting positions slightly as I hit the "bump". The TPS checks out beautifully otherwise, full sweep, hot or cold, nary a twitch...

The AFM also checks out great over all of the bumps. There are only a couple of components on the car I would consider "shock sensitive"- AFM, TPS, and perhaps CAS, so now we're on the CAS, which inputs signals much too rapidly to be caught on an analog meter (and I'm not driving around with an o-scope, Mark, lol).

I'm changing the fuel filter tomorrow, just in case, but I doubt that's it- I can romp off the line and keep her romped until 5th gear with no hesitations at all, and can do 90+ down the freeway for extended periods (as long as it's smooth) with no problems...It's just the blasted bumps, lol...

I've also checked all visible wiring for chaffing, and found none...

So, the question after all of this rambling is: How many guys have had the CAS go bad on them, or have had anything resembling my "bump moments" before the CAS went out?

And before you say grounds, they're good

Mx6-Rx7 Addict

I really don't know.. But like you said.. the AFM would be my first guess.. Have you thought about your fuel pump?? I really don't understand why it would do that.. just a random guess though.. Are you able to read your AFR's??

Justin

WAYNE88N/A

Yes, I've thought about the pump, and about a hundred other things (I have a list going of things it could be, by any stretch of the imagination). I'm not the type to throw parts at something, as some of you well know. I want to troubleshoot this bitch down to the only thing it could be & nail it!

BlaCkPlaGUE

Yea thats weird. Check your fuel lines too, any kinking of them at high speeds like that will cause slight hesitations. But yea the MAF connections may be loose or weak too, cause when its disconnected the engine just dies, if its loose it will only disconnect for a second and could cause what your saying. Just check the harness and make sure the plugs are nice and solid, nothing 'wiggly'.

I have a feeling its something electrical, something your test setup on the ECU is not seeing... maybe becuase it hapens for just a fraction of a second, it doesn't show up on your test setup to the ecu..


this is weird, im trying to think of anything that could be shock sensitive on the 13b.. sleep on it wayne, you'll probably figure it out tomorrow and say "OH YEAAAAAA, thats gotta be it", you'll remember some kind of work you did on the car, or something that you forgot to do during a job that will just all click.

best of luck, hope i've given you some insight

DerangedHermit

Wayne doesn't know something...?

WAYNE88N/A

AFM plugs are "solid", as you say. AFM reads out with a meter beautifully, even on the bumps, as stated earlier.

It almost can't be anything fuel delivery-related (filter, kinked lines), because like I said, I can do 90 for a couple of minutes straight with no problems.

If it's a loss of signal, it happens long enough to see a meter needle twitch, and I see none. Plus the fact no codes are thrown (except that CAS tonight) rules out most of the sensors and their wiring...

I've been "sleeping on it" for weeks now, lol, it's your turn

WAYNE88N/A

Lol, impress me Hermit, and shout out something I haven't thought of yet

DerangedHermit

Lol, I never said I knew anything . I'm a newb and randomly spout out answers that sound good in my mind, but upon re-reading (30 minutes later after someone calls me an idiot) I realize that I was completely wrong.

Ex.

Q: "Why is my car running like crap?"

A: Check the gas tank for a small dead llama.

White_FC

Would be very strange for a CAS to 'go bad'.
They're very simple devices, so unless its the plug and/or wiring to the CAS then I doubt its the CAS.

But... since the ECU said it was the CAS, i'd be checking the plug first.
And there is also another plug somewhere up behind the trailing coil. Check that, and make sure the metal sheath is grounded.

WAYNE88N/A

Hey, FC, what's up? Already looked at the connectors & wiring- it all looks solid...My theory here (if it is the CAS) is that after 193,000 miles, she's just getting worn out, the rotating shaft part anyway, and that's causing the shaft to "wobble" a bit, screwing with the gaps between the magnets & the pickup coils.

I'm going to pull the cover tomorrow morn, and see what kind of side-to-side play she has...

White_FC

hmm thats a possibility...

If theres alot of oil in there or leaking out of it already then you might have 'wobbling' issues.

haha you'd have to have a pretty shagged bearing for that to happen though.

RETed

Never had a CAS go bad unless the mag sensors get loose inside.
We have had LOTS of headaches with the CAS plug!
The plugs get dirty and contacts go bad.
Try and pull the contacts out, clean, rebend the pins for better contact, and replace...


-Ted

HAILERS

So why don't you put the meter leads on the output wires of each coil at the ECU, and massage the wiring b/t the cas and the ECU while looking for *opens*? Never seen a bad CAS myself.

WAYNE88N/A

It doesn't appear to be the CAS. The wiring is nice and tight in the connectors, the plugs and contacts are clean. The shaft has absolutely no side play, the only play being about 1/2 mil up & down, which doesn't affect the pickup gaps at all. Speaking of gaps, Mazda only has maybe a .010 to .015" gap (eyeballed it, but I'm good at these things, lol). Very, very close tolerances, considering you could get a perfectly fine mag pickup in a coil from .060" away & more...Everything's nice & clean inside, no oil, no chaffing wiring, etc...

I'll play further with the CAS outputs later, Hailers, today I'm eyeballing the O2 sensor output on the way to work, figuring if the pump's kicking out I'll see it there. Just looking for a twitch...

WAYNE88N/A

Oh, forgot to mention, the shielding for the CAS wiring starts at the plug near the unit, but for the life of me I can't tell where the hell they grounded it. I don't see it at the plug under the trailing coil, and there's really no where else along the harness between the two points to ground it. Figuring that if it's not grounded, and I'm picking up plug wire interference, I moved the plug wires further away from the CAS wiring, just to see if that helps (picture the much-too-long NGK plug wire "falling" a bit during a bump, and inducing a voltage in the CAS wiring...I'm all for long shots, here, lol)

SonicRaT

iTrader: (6)

Have you checked the sock on your pump? Maybe it's not holding gas and the bumps are just making it breathe air instead (as the gas is placed elsewhere from the bump?) Normally you only notice then under severe cornering and the car will stall, but who knows.

DerangedHermit

Sure it's not a small dead llama in the gas tank?

WAYNE88N/A

Welp, I thought I nailed the bastard...

Hooked up the O2 sensor to the meter at the ECU for the drive to work- the freakin' thing was going haywire. Got to cruising speed in 5th (mini-hesitations happening lots now), she's reading damn near 0v, running WAY lean, put her in neutral while rolling, back up to the .8v idle I'm used to seeing. Put her back in gear, bam, back to 0v...

Got it- "it's the fuel pump" I think to myself, as I turn the car around to go back home & call in for a vacation day. Let her idle, checked the pump voltage at the strut connector- 13v...Gotta be the pump...

Got a new one (new aftermarket pump from the auto parts place), put her in, went for a "spirited" drive. Feels much better now, even the O2 sensor is bouncing around .5v like it should, and I'm running rich while romping. Nailed it...But wait...Couple of minutes into the drive, you guessed it, "mini" hesitation. Then a couple of more before I got her back home...And by looking at the O2 sensor inputs, it doesn't show to be lack of fuel, but you never know since that sucker takes a split second to register the A/F...Son of a biatch...

I'm gonna jack her up & look at the tranny wiring next...Slowly scratching things off the list

WAYNE88N/A

Oh, BTW Hermit- the tank is immaculate, nice premix-colored gas, with no debris...No dead llamas, sorry to say

New sock on the pump now, Rat...But I often wonder if these socks were made strictly for gasoline, not a gas/premix blend???

RETed

It's grounded at the ECU end.


-Ted

DerangedHermit

Well, I've exhausted my knowledge in that case. Good luck!

WAYNE88N/A

But it doesn't "jump" across the plug under the trailing coil, Ted...That means that the shield section between the CAS plug & that connector under the coil HAS to be grounded somewhere, or it's not acting like a shield...

Even so, there's a shield "pigtail" sticking out near the CAS plug, that I could ground myself if I wanted to. I moved the spark plug wires out of the way of any part of that CAS wiring run, just in case, but since I'm still having my "mini" problems, I doubt that was it anyway...

Tranny wiring looks good, the only questionable item I found under the car was the connector for the oil thermo switch (which was removed during the rebuild), its wire was rubbing on the AN fitting for the aft oil cooler hose, so I took care of that.

RETed

Yes, you are correct.
The wiring on the CAS side is not shielded.


-Ted

WAYNE88N/A

You sure about that? Sure as heck looks like the end of a shield sticking out near that CAS plug, the same type of shielding I've been working with for 20 years now...Braided steel cloth-looking stuff...

Why would Mazda run a shield through the harness there and not ground it? Doesn't make sense...

White_FC

Well mine was definatly grounded somewhere near there.

Believe me, I just rewired that whole section of my car