2.3 with ocasional WOT stall and hard 1-2 shift

[spoiled2.3]

98 2.3 - When cruising along at say 40% throttle and then flooring it, car occasionally stalls for 1sec throwing me foward in my seat, and then takes off full power. Also I have a hard 1-2 shift which I suspect is related. I thought it was a misfire but don't have any codes or cel.

I have been having this issue since I bought the car a year ago The stealership hasn't been of any help except to tell me to sell the car while it's still running good. Infact, that's where the car is now. I asked them if they could check the coils and precats and they said no problem. So when I got back to them I asked if they checked em and they said no cause there's no codes indicating a problem. I realize most mechanics including dealerships know very little of maintaining the Millenia S and really don't want to work on it.

Here's the work I've done so far, and the problem has been there since I bought the car a year ago and still persist
Replaced Valve cover gaskets - were leaking bad
Replaced a vacuum T
Replaced Plugs - cleaned coils and boots (Installed E3.48 plugs, was this a mistake or should i have sticked with OE?) Think it had the original plugs still.
Replaced In-tank fuel filter
Replaced Fuel pressure regulator - was leaking
Replaced all intercooler and intake manifold gaskets
Transmission service - transmission guy said it looked like normal wear, very little metal

The dealer did mention that there were some engine solenoids that could be checked but threatened me with a open ended hefty bill if I want to go that route. He still hasn't gotten me an estimate on those yet, I am waiting. Right now he's doing bigb's cabin filter mod for me.

I'm leaning toward the injectors now as I've read a lot about those here. Is there a simple way to test them all easily like yel-low did here on the 2.5?How to diagnose a bad injector – (KL Engine only)
Also I did not replace the fuel injector crush washers when I had the rails out as I only learned about those recently.

Another idea I had was maybe the timing belt is off by one notch. The dealer replaced it just before I bought this car. Maybe it slipped cause the oil leaking from the valve covers got on it. I did visually see some of the belt and it didn't look like there was any oil on it now.

Any ideas what could cause this stall and hard shift? Any help is greatly appreciated

[keninn]

the ONLY like situation i get with BOTH of our cars(2 99s') is when the cars start out then shift to second, then floor it, and it downshifts. then it does exactly as you describe. i have switched to valvoline himileage dex/merc, which is a full synthetic, and this, plus the hard upshift, has greatly improved. i also use the lubegard additive, as i have for all our automatic transmissions. i also flush trans fluid yearly. on the freeway, at cruise speeds, flooring it is always seamless, the downshifts are very smooth, and pickup is really nice. i really doubt it is injectors. and dont ask the dealer anything, they dont know this car, and are just guessing, like a LOT of shops. perhaps resetting the ecu might help. also, the transmission is controlled by a separate control unit, perhaps changing to another, or just reconnecting it might help. there might be corrosion on the leads. another possibility is your map sensor

on a similar note, our black car, which we have owned since new, is a different animal from our white car, which we got used, with 65k on it. the black car has way better shift points; for instance, when turning, then accelerating, it will automatically downshift, and then when accelerating, it always seems to be in the correct gear. the white car likes to stay in whatever gear, then downshift only when accelerating. the black car has way better power steering, much more feedback, and it feels a lot tighter. the white car steering is way too much assist for me. even the suspension on the black car feels a lot stiffer, and the car seems to handle a lot better, and i have put a rear sway bar on the white car, too. i have often thought about swapping tcu's to see if the shift points change with the tcu. maybe i go get the tcu from the parts car in ft worth, and swap them, just to see.

[Saint_]

I would say old tranny fluid as well but you are saying ATF has been changed. Maybe the filter is clogged?

Why dont you try pushing hold and flooring it. Then the tranny wont shift and you can tell if its tranny related or not.

I agree with ken about quality consistency of Millenia. My car is at 160k. My interior is rock solid, nothing squeaks. I drove a 50k 2002 S. Its interior was falling apart. I dont think the girl did anything special to the dashboard which has 5 mm play. Its just a bad batch IMO.

[spoiled2.3]

Originally Posted by keninn

the ONLY like situation i get with BOTH of our cars(2 99s') is when the cars start out then shift to second, then floor it, and it downshifts. then it does exactly as you describe. i have switched to valvoline himileage dex/merc, which is a full synthetic, and this, plus the hard upshift, has greatly improved. i also use the lubegard additive, as i have for all our automatic transmissions. i also flush trans fluid yearly. on the freeway, at cruise speeds, flooring it is always seamless, the downshifts are very smooth, and pickup is really nice. i really doubt it is injectors. and dont ask the dealer anything, they dont know this car, and are just guessing, like a LOT of shops. perhaps resetting the ecu might help. also, the transmission is controlled by a separate control unit, perhaps changing to another, or just reconnecting it might help. there might be corrosion on the leads. another possibility is your map sensor

on a similar note, our black car, which we have owned since new, is a different animal from our white car, which we got used, with 65k on it. the black car has way better shift points; for instance, when turning, then accelerating, it will automatically downshift, and then when accelerating, it always seems to be in the correct gear. the white car likes to stay in whatever gear, then downshift only when accelerating. the black car has way better power steering, much more feedback, and it feels a lot tighter. the white car steering is way too much assist for me. even the suspension on the black car feels a lot stiffer, and the car seems to handle a lot better, and i have put a rear sway bar on the white car, too. i have often thought about swapping tcu's to see if the shift points change with the tcu. maybe i go get the tcu from the parts car in ft worth, and swap them, just to see.

The stall is exactly as you describe, only happens around town at slower speeds, never happens on the freeway, usually happens if it shifts to first from second or third. If this also happens on your 2 different Millenia then that makes me feel better that nothing is wrong and it is just a quirk that is characteristic of these engines. It would be nice to know what the results are from switching the TCUs from your two vehicles to see if it is a controller issue, let me know if you ever do it. I will check the connectors and clean them to make sure that's not the problem. As for the hard shift, it isn't too bad and doesn't always happen. I will try the additive and let you know if it helps. I will also look for the synthetic oil you described. My 98 is in great shape inside and out and the engine is clean, 135k miles on it. Love the way it zips through mountain passes on the freeway and really holds those long high speed winding turns. It's a great car for trips.
Thanks for your input.

Originally Posted by Saint_

I would say old tranny fluid as well but you are saying ATF has been changed. Maybe the filter is clogged?

Why dont you try pushing hold and flooring it. Then the tranny wont shift and you can tell if its tranny related or not.

I agree with ken about quality consistency of Millenia. My car is at 160k. My interior is rock solid, nothing squeaks. I drove a 50k 2002 S. Its interior was falling apart. I dont think the girl did anything special to the dashboard which has 5 mm play. Its just a bad batch IMO.

I have have tried the hold button test and the stall never occurs in this situation as it only happens if the tranny shifts to first at WOT. Think it may just be normal operation of my Millenia because kennin also has this occur on both of his Millenia. Does your Millenia ever stall breifly when going to full throttle? I will check with my transmission guy and see if he inspected or changed the filter. Thanks for your help :-)

[Saint_]

I dont have bucking during a downshift. But it sometimes takes time to shift which is normal for an AT.

It may also depends on how you generally drive. They say TCU adapts itself to your driving. I didnt notice any difference after a battery reset though.

[bigb]

You may want to check the CAC bypass actuator. at low RPM it is supposed to be open so that the intercoolers are bypassed not being used. if it is closed the intercoolers are being used all the time and heat up quite quickly at low speed / city driving.

that might be why you only feel it in the city. at highway speeds you are going fast enough to cool the intercoolers even if they are in use all the time.

open the observation port and have a look to see if the butterfly valve is gummed up. also backtrack the vacuum lines from this valve and make sure everything checks out.

That is the only thing from the engine side that could cause what you are seeing. other than that, it is what was described above as a transmission "quirk"

[spoiled2.3]

Originally Posted by bigb

You may want to check the CAC bypass actuator. at low RPM it is supposed to be open so that the intercoolers are bypassed not being used. if it is closed the intercoolers are being used all the time and heat up quite quickly at low speed / city driving.

that might be why you only feel it in the city. at highway speeds you are going fast enough to cool the intercoolers even if they are in use all the time.

open the observation port and have a look to see if the butterfly valve is gummed up. also backtrack the vacuum lines from this valve and make sure everything checks out.

That is the only thing from the engine side that could cause what you are seeing. other than that, it is what was described above as a transmission "quirk"

Thanks bigb, the CAC sounds like it could definitely cause the symptoms that I have. I will check it as soon as I get the car back from the dealer. I found this Youtube of the CAC with a very good description of how it works.
Charged-Air Cooler Bypass - Mazda Miller Cycle - YouTube

[bigb]

I'm not saying it is the cause, but if it had to be something on the 2.3, this would be the area to look. here or the abv valve since that basically bypasses the supercharger all together.

[Saint_]

My CAC solenoid is dead. I dont have that problem.

[spoiled2.3]

Okay seriously, my Millenia is still at the dealer, getting bigb's cabin filter mod done, shoulda done it myself, I'm a little worried, I know they broke some clips in the glove box when they dismantled it and were trying to locate parts. Wondering if they destroyed my filter box too and cut it all wrong...? I'm still gonna look at everything discussed here and I'll let you know if anything helps.