93 Camry dtc 12 shifing at high rpms when engine cold, and wandering idle FIXED.
 

93 Camry LE, 2.2l 4cylinder, auto trans, no anti lock brakes, or traction control, non California emissions car.

I bought the car back in Jan. The car only has 95k miles, and I changed the trans fluid, trans filter, timing belt, etc about a week after getting it home.

The engine always had a slight wandering idle like maybe 500 rpm, up, and down at idle. This got much worse over time, and the tach needle would fluctuate, at idle, from 1000 to 1200 rpms

A few weeks ago the transmission started shifting funny when the engine was cold. I did get a check engine light, it turned out to be a code 12.

I gambled a new coolant temp sending unit, as from what I read this was the usual issue with a strange shifting trans before warm up, and it didn't help.

Today, after installing the temp sender, I took the car out for a test drive.

It shifts from 1st to 2nd, at 3500 rpms [outside temp today is around 93 degs], and from 2nd to 3rd at 3500 rpms.

After driving the car for approx ten minutes it shifts fine.

I was thinking about pulling the pan, and the shift solenoids, and cleaning them with carb cleaner, just in case some debris worked its way into something.

The car looks to be in immaculate condition for its age with the original paint/interior.

Also, I have rebuilt several transmissions, but I don't think the internals of the transmission are at fault here.

Update: I found out how to get the obd1 codes, and was able to pull codes 12, and 41.

Code 12 deals with the distributor, and 41 with the tps sensor.

I tested the tps sensor, and passed all of the tests so that is not the problem.

I pulled the neg battery cable, and left it off for about 5 minutes, then reconnected it.

Now the engine light is staying on [it used to be intermittent], and all I'm getting is code 12. The engine will hesitate when cold from a stop.

I'm guessing the hesitation, and transmission shifting issue are hand in hand, as in the hesitation of the engine is causing the transmission to shift late. Also it don't explain why the engine runs just fine after its fully warmed up.

From what I've been reading the coils on these cars go bad, but it would seem that the engine wouldn't run at all were this the case.

Code 12 is an issue with one of the pickup coils in the distributor, the air gap for the coils or ECM.

Pickup coil will change with distributor temperature. Perhaps a coil is out of spec when cold and in spec when hot.

Does the distributor have built in ign coil or external?

I'm pretty sure its internal.

What is the air gap specs for the coils. I will check tomorrow...........thanks.

What you're saying does make sense as its definitely temp related.

Internal coil distributor cap has only 4 high voltage connections and these are for the plugs (no 5th wire for the external coil).

Air gap 0.008–0.016 inch.

Pickup coil resistance.
Between terminals G+ and G- of distributor plug
Cold 185-275 ohm
Hot 240-325 ohm

Between NE+ and NE-
Cold 370-550 ohm
Hot 475-650 ohm

Hot is 122 to 212F

When facing the distributor/plug outlet from the drivers side and looking towards passengers side. Terminals from top to bottom are NE+, NE-, G-, G+.

Check ign coil resistance.

Primary connection
Cold 0.36–0.55 ohm
Hot 0.45–0.65 ohm

Secondary
Cold 9.0–15.4 Kohm
Hot 11.4–18.1 Kohm

Check coil body for cracks and signs of arcing.

Make all resistance readings are stable and don't start to climb or drop with continued taking of a reading.

Ok, I'll give it a checking out this afternoon.........thanks.

Yep, it was the coil that was bad.

I had a fun time trying to get those four screws holding the coil to the dizzy housing as they were all on the bottom of the housing facing the transmission.

It would have been easy if the dist wasn't locked up [it wouldn't budge so I couldn't turn it]. I did spray some penetrating where the dist meets the head so maybe I can free it up for future, possible issues.

The old coil had a crack in the epoxy, and was arching on the metal tab of the coil.

I took a drive down the road, and the engine ran much better. I was amazed it made so much difference.

Today the NGK plug wires came in, and I installed them, and here is where the problems started.

The car would bog on gear change at the same exact place it always did just down from my house.

I tried pressing the plug wires more firmly on their connectors, but nothing seem to work. I also received my new fuel filter so I thought maybe its a fuel issue so I install it, and yep, same problem with the bog from a stop, and wandering idle.

Great job! Thanks for posting back with the fix.

Well, it did the same thing again this morning. I had to drive my wife to town for some errands so I took the Camry just to make sure all was well.

I was telling my wife what a great mechanic I was for fixing the car, and as soon as we hit the same spot in the road the problem happened again.

Its always at a stop sign about a 1/4 mile from my drive. We turn right, and go up a very small grade [maybe 10% grade, or less].

After the trans shifts from first to second there is a bog. I can floor the throttle, and the engine won't respond. Then very gradually the car will pick up speed until its going all out.

Only does this when its cold. After its warmed up there is no problem.

I checked the idle sensor [I think that is what its called] under the throttle body, and took it all apart about a week ago, and cleaned all of the carbon off the little barrel looking part { I filled it up with carb cleaner, and let it sit for about two hours]. I also moved said part left to right until it was moving very freely, then reinstalled it.

Like I said the plugs tested good [hot, and cold], the old coil was bad, and replaced with NGK coil, new dist/rotor, and now new NGK plug wires.

Oh, and the temp sending unit was replaced last week.

I'm still getting a code 12 even after clearing all of the old codes.

Might be something I have to just live with. The only thing left to change is the dist pickup, and the ignitor.

Did you replace the distributor?

When engine is hot, any bog issues when just revving the throttle when car stationary?

No, I haven't replace the distributor. The car only has 95k miles, but of course its 25 years old.

I did some reading, and from what I read the egr valve can be an issue when the engine is cold so I took it off, and let it soak with some automotive paint thinner.[ not the diaphragm, just the egr body]

I'll do a test drive down the road, and report back.

Also, the engine don't bog under no load, only on the that 1st to 2nd gear change.

Starting out in 1st gear its fine, then second gear is fine [I live at the top of a small hill so when I start out of the driveway its down hill on both sides of my driveway].

Its just when I get to that stop sign, and start up that low grade that I get the bog.

Like I said, it may be something that I have to either live with, or wait for it to get worse so I can better find the cause. Its strange as the old coil was cracked in the epoxy so we KNOW it was part of the problem.

Well, I took yet another test drive today after cleaning, and reinstalling the egr valve, and there is a very slight hesitation, but no more bog.

I did notice that the vacuum line going to the bottom of the egr valve had some carbon in it. So that may have been a source of the bogging when the engine was cold.

Anyway, I'm done for now, and am happy with the car as it, IMO, beats the new cars hands down for simplicity, reliability, and cost of replacement parts.

A bit of an update.

The trans still shifts late when cold [like not driven overnight]. It shifts from 1-2 at around 2900 rpms, and 2-3 at around 3200 rpms, and it takes forever to shift into overdrive [way higher than 3300 rpms.

Anyway, today I pulled the valve body, and took it all apart, oh, and there is NO DIAGRAMS on the valve body check valve so I will post them. Everything was clean, and moved freely, no dirt, or metal shavings, etc.

The shift solenoids were cleaned in automotive paint thinner [as was the valve body parts] as that is what we used when I ran a trans shop waaaay back in the '90s. [just don't leave anything with rubber in the thinner too long, just to be safe].

I tested the solenoids with a battery, and they worked fine. I put everything back together, with all new fluid, [I changed the fluid/filter when I first bought the car this past Jan so it was still good, even reused the gasket].

Still shifting late when cold. I'm stumped, as were it an internal problem with the transmission it would still shift late even after everything warmed up, but it don't, it shifts fine after about ten minutes of driving.

I've been playing with the adjustment of the kickdown cable, but one thing I don't know, hence my question. After adjusting the kick down cable, does the computer need to relearn the shift points?

Here are the pictures of the valve body, and fluid lines { I had to print out a picture of the fluid lines to get them back on correctly].

This is for a 93 Camry with an A140F. Here is the little filter.
Attachment 4947

This trans have four plastic/rubber.
Attachment 4948

Attachment 4949

Also, there is a very small valve that might pop out, and leave you guessing where it came from. Here is a picture of where it goes. The valve is at the bottom left corner of the pic, right beside a hole in the corner of the valve body.
Attachment 4950

There are two more steel check valves in the separate, upper part of the valve body. I was pressed for time so I didn't get a shot of them. When you remove the upper section, make sure you have all of the hold down bolts off, then flip the whole valve body over, and while holding the top part of the valve body in your hand pull it off the main valve body. That way the check valves "should" stay in place, as well as the little rod you see in one of the pictures [it took a while to figure out where it went], and a tiny clip that goes on the kick down valve. Take pictures of the check balls, clip, and tiny rod locations just in case they get moved. You can spay that part of the vb with carb cleaning spray, which may not disturb the balls, clip, etc.

When you're ready to put things back together, grab a jar of Vaseline. Put a big gob of Vaseline on the check balls, cover them with it. Same thing with the clip as this will keep them from falling out when you flip it over to reinstall it. Do the same the check balls in the main valve body as it will keep them in place during re-installation.

The trans shifts OK (hot or cold) after 10 minutes of driving?

The trans computer functions solely by a programmed map. Much later Toyota started to have the "learn" ability.

Yep, it shifts just fine after about 10minutes of driving. My thoughts were, that when the trans is completely cool the fluid is thicker, and that there might be either trash, or sludge keeping the fluid from moving like it should. After everything warmed up, the fluid was thinner, and better able to move though the valves, etc., which is why there isn't a problem when the car is warmed up.

But, today, taking pretty much everything apart, I couldn't find even a hint of sludge, or trash. I also thought that changing fluid might help just a bit with any trash, but its still high rpm shifts before the trans is fully warmed up.

I even blocked off the EGR valve since its function dependent on engine temp, but to no avail.

I've tried adjusting, and readjusting the kick down cable, but again there is no change.

The only one little change today was that I've got the accelerator cable turned almost all the way in [its supposed to increase line pressure, and I've been driving the car this way for a few days just to see if it had an effect].

Well, after getting everything back together, and taking a test drive that seemed to make things even worse. The trans didn't want to even shift out of second gear until around 4k rpm. At that point I slowly drove to the church parking lot, and adjusted the kick down cable more towards the factory setting [but not quite]. This helped a bunch, and the car started shifting correctly, but everything had warmed up by then.

I waited until the car had cooled off just a bit, about an hour, and took another test drive. It worked better than before shifting 1-2 at 2900 rpms, and 2-3 at around 3k rpm. So I adjusted it even more to the factory settings, waited another hour, and no change at all this time.

Do you think its the ecm having issues? I've heard these things rarely go bad, and with the cars relatively low miles, I wouldn't think it would be having problems, but there again its 25 years old.

With my 05 Nissan I went though Hell trying to get a used ECM. Nissan no longer makes the damned thing so Ebay was my only hope which helped since I at least could sent it back if the unit was bad [vs a junkyard with no returns]. Problem was, with every used computer I bought I had to take it to the dealer****s, and pay $150 to "find out" if the used ECM was good, or not. When all was said, and done I had paid $600 to the dealer****s, not counting the money I spent on used ECM's.

So the question is, first, does anyone in the aftermarket make a good replacement ECM for a 93 Camry? Also, where I to buy used, I'm assuming the numbers of the used ECM have to match the numbers on my factory ECM.............thanks.

Suggest adjusting the kick down cable per the manual and calling this good for the cable.

How was the trans oil filter and its connection pipe to the trains, any possibility of leaks? Ditto for the valve body mating surfaces.

Can you check line pressure? Perhaps the system pressure changes too much, warm versus cold.

ECU typically work or they don't. But sometimes replacing them can cure engine problems and false check light issues. Can you try using a hair dryer to heat the ECU to simulate a warm condition. Might also try this with the TPS.

Try Ebay for used ECU's, which at times some can be very reasonable. Get the exact part number or if applicable its superseded number.

Everything was fine in the trans when I looked.

We drove it to town, and its the same thing, drives us nuts until it starts shifting normal.

The only other thing it could be would be the temp sending unit which I replaced.

I may have to try another computer from Ebay, as from what I've read on the shop manual I can't think of anything else. At least I won't have to take it to the dealership after installation.

Keep us informed!

OK, will do.

Well, the parts came in today, and I've installed them with no change in the shift points for the trans, nor getting rid of the code 12.

What I received was a new dist cap, and rotor [Standard Ignition]. I had just bought a new cap/rotor a few weeks ago, but it looked like the rotor was hitting the metal prongs inside the cap.

So, I figured this was where the code 12 was originating, but its obviously not.

From more reading, and digging on code 12, I have pretty much changed out all of the problem parts except for the ignition pickup inside the distributor. For some reason, there is NOBODY making these parts, and Toyota no longer sells them.

I also pulled the distributor, and found its an aftermarket so it would seem that someone else had a problem with the ignition.

I decided to check everything on the dist again, and all tested just fine [ignition pickup, and coil] The only things that were out of specs were the air gaps on the pickups. I reset them to .006. No shaft side to side play [which one would expect with a re manufactured dist.].

I will reinstall the dist tomorrow, and see if there is any change, or not.

No change at all so I decided to check for spark.

I started the engine with number one plug pulled, and guess what, there was no change in the way the engine ran. I plugged number one back in, and pulled plug wire number two.

This time, the engine didn't start at all. So I plugged number 2 back in, and still the damned engine won't start.

Left the battery unplugged for a while, reconnected it, and still no start.

Checked the pickups, and it looks like I blew one of the damned pickups [ohms isn't registering [bottom two], so I will have to buy another distributor. Any guess's on why leaving the plug wire off while the engine was running would kill the damned pickup? I've done this many times with other cars with no issues.

The distributor coils go to the ECU and are very low voltage.

Any wiring issues?

No wiring issues. This car must have been owned by an older couple as there are no stains on the upholstery, nor any hacked up wiring.

Also, it looks like everything on the car is bone stock even down to the exhaust.

I've been doing quite a bit of reading on this subject "code 12", as you might expect, and from what I've gathered is that it does seem to be an issue with the magnetic pickups inside the dist [for which I cannot understand why these aren't for sale in the aftermarket, nor OEM for that matter].

The pickups seem to loose their magnetization, which sends the ecu the wrong info on what rpms the engine is turning. This would be something you really couldn't test for as all of the ohms tests could be good, but the magnets are going bad.

This would also be hard to figure out, as in my case I tested everything on the dist, and it all tested good. So you assume the dist is good, and move on to look for something else while its the dist the whole time.

I ordered a Spectra dist from Rockauto today, as I'm not about to pay over $1000 for an OEM dist when it too may go out with less than 100k miles. I think the problem with the dist [if in fact that is the problem] has everything else out of wack including the transmission, and wandering idle.

Here is a video of someone else with a code 12, with the exact idle problem I'm having.

Thanks for all of the help. I WILL be back to let you know the problem as, again, it may help someone else some day. Oh, and Toyomoho, PM sent.

Finally an update, its fixed.

I ordered a new distributor from Rock Auto for $100 shipped. The dist was made by Spectra so I will try to update this thread when this dist dies, be it a few weeks, or a few years.

Now the engine starts, and runs, but the high rpm shifts when engine/trans isn't warmed up still persists. Also the engine still has the fluctuating rpms, just like in the video above.

I've already changed out the IAC valve because in most threads the IAC is the problem In my case it wasn't the problem.

So in my frustration [I still haven't made a smoke kit to find vacuum leaks, and I've NEVER had any luck using propane, carb cleaner, or water to find vac leaks], so in my frustration I decided to check the vacuum of the engine at idle, and wadda you know, the vacuum was low. According to my vac gauge it w as either late valve timing, or a vac leak in the intake manifold.

Well, on my car someone had already made the timing marks highly visible so when I changed the timing belt I went by the marks. Today I went by the timing marks on the pulleys, and block, to make SURE it was in time, and yep it was perfect.

So I plugged every single vacuum port in the intake, and it was still reading low vac on the gauge. This narrowed it down to the intake gasket itself.

Let me tell you its a real pain in the a$$ to pull that intake, more so than I initially thought. You see the intake is one long runner C shaped piece. Its not a two piece like later intakes [which would have made this job a breeze].

Anyway, after much blood was lost, and many sore neck/shoulder muscles I was able to get everything back together. At this point I would advise anyone to have a helper to help you verify each vacuum line goes to the correct place as I found one that was wrong. The mis-connected vac line was on the vac switch behind the block. What I did was have a friend pull on the vac line from the top of the engine bay, while I pulled the correct line from below so that we could find the right line. The vac lines are all in a tube so you can't see from which they originate, or end, which is why you need someone to pull them on top of the engine bay while you lay under the car, with the vac diagram.

After getting it all back together the car runs great, no more bogs/hesitation when accelerating from a stop. No more wandering idle, no more super high rpm shifts when trans is cold [NOT THE AMBIENT TEMP,! Rather the temp of the transmission before its fully warmed up].

So, if you start having a small fluctuation of rpms at idle [it starts out small, and gradually gets worse] be sure to get your vacuum gauge, or borrow/buy one, and test the vacuum FIRST before spending money.

Also for the code 12, the new distributor fixed all of that.

One more thing, which I think is important for your distributor, if you're getting a code 12. Make SURE you have the dist cap gasket/o-ring as this o-ring spaced the cap away from the rotor quite a bit which might explain a code 12 when the engine appears to run fine. However if the gasket is not installed it will eventually kill the dist cap, and rotor, as the clearance between the rotor, and the prongs in the cap will be off. This gasket is easy to loose, and I would bet many people would forget to reinstall it, or think it had little to do with anything as most distributors I've worked with over nearly 40s don't have a gasket between the cap, and dist body which is why I wasn't aware it was missing.

Hope this helps someone down the road...........good luck.

Also a big thanks to toyomoho for all of his help, and support.

Another update.

The trans didn't start shifting normal like I thought it was, again only does it when engine, and trans haven't been run for a while, like overnight.

So I found my old transmission pressure gauge, and tested the pressure according to the shop manual.

I tested pressure at idle, in park, then reverse, and last in the drive position. With the cable adjusted all the way out [as tight as the adjustment would let me] I would get the lowest acceptable pressure listed in the shop manual.

The cable had stretched too far over the years, BUT I didn't want to gamble even more money that I've already spent on a new cable. So I bought this cable end, and installed it about an inch shorter than the factory end, and now the trans shifts correctly when cold [not cold as in ambient outside temp, but rather cold as in not ran for several hours].

Here is the ends, and if you need to do this, make sure you get the exact same size as I did, which is 3/16" very tiny.

https://www.ebay.com/itm/SHERCO-MOTO...72.m2749.l2649

I'm going to drive the car all this week, and make sure that the cable stretch was the issue, and then I will eventually buy a new cable. If you buy the ends you can save nearly $100 to make SURE the shifting problem you're having is in fact a stretched kickdown cable, and not something else.

Also, the cable WILL FRAY when you cut it, which kinda freaked me out as I didn't think there was any way to get the cable into the tiny hole in the barrel end fitting. But, I was able to get the cable through the hole by twisting the cable, and twisting the barrel end while pushing the cable into the hole. Next, when you get the cable where you want it, just tighten down the hold down screw on the barrel fitting, and grind off the excess cable from the fitting. I thought I would be able to keep the extra cable length on the fitting so I could adjust it if needed, but there is just no way to get the cable end to fit into the throttle linkage until you've trimmed the excess cable flush with the exit hole in the fitting.

Thanks for the update and great info!