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Way off topic 1993 caravan transmission


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Lot of old time mopar lovers here, wonder if any have a clue about my current issue. Or junked the car because of it  :D 

The van has about 185k miles on it, Transmission was sent to a shop and rebuilt at 150K miles.

The speed sensor was bad from the start and gave a hard shift (sometimes) into 2nd gear. Finally went out and was stuck in limp mode.

We took it to a shop 4 years ago, put it on a obd1 scanner and told us what they thought ... they did not want to touch it.  :D

I replaced the sensor and it worked perfect for 4 years and then it went out again.

I replaced it and worked fine, first drive out of town and 3rd sensor quit working.

I find that the fluid level affects this. When it reaches the add line, it goes into limp mode. I added a slight bit to much fluid.  (1" from a quart bottle) It was in the hot level when only warm, then when it did get hot from driving it showed overfull and back into limp mode.

I spent 2 days fixing my leak and get fluid level exactly right.

 

Now, if I start it up and start driving right away it is stuck in limp mode. If I let it warm up for a few min, transmission 4spd overdrive works perfect.

Hard to trust it and drive it out of town.

Going to order a 4th sensor and try it, keep a spare in the glove box .... is this just a symptom of cheap overseas junk? Anyone else run into something like this?

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Wondering if its a bad wire in the harness? Have you tried unplugging and plugging the harness back in without replacing sensor?  
also, any debris stuck to the sensor when you remove it. 
 

it wouldnt suprise me that the quality of the replacement part is poor. 
been a while since i had anything to do with one that old, is the transmission part of the ecm or is it a seperate unit? 

Edited by Tooljunkie
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You might want to take a look at the transmission temp sensor instead of the speed sensor.  It's hard to believe a low fluid level sensor would also read overfilled and and send into limp but a temp sensor could be sensitive to both.   Unless that shop was OBD 1 capable on their scanner, they were guessing on the codes.

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2 hours ago, Tooljunkie said:

Wondering if its a bad wire in the harness?

I was thinking this myself. The original harness looks fine and shows no damage. unplugging - plugging it back in does not help. Next step would be to loosen the harness and pull the cover off and check the 2 wires.

Yesterday I started it up, let it run for 30 seconds then drove off ... was 65 degrees outside. It was stuck in limp mode (35 mph) I drove 6 blocks to the store and when I came back out and started it, it drove perfect again.

 

Other day I took off in limp mode again, drove to my neighbors house and let it run while got his shopping list ... drove it 35 miles one way on the freeway to walmart and back with no problems.

 

4 hours ago, Tooljunkie said:

is the transmission part of the ecm or is it a seperate unit? 

There is a transmission control module that rockauto sells for $175 + $50 core charge ... Just not convinced this would fix it ... there is no other electrical parts sold for it.

 

41 minutes ago, Dave72dt said:

You might want to take a look at the transmission temp sensor instead of the speed sensor.  It's hard to believe a low fluid level sensor would also read overfilled and and send into limp but a temp sensor could be sensitive to both.   Unless that shop was OBD 1 capable on their scanner, they were guessing on the codes.

I agree ... I have rubber trans lines on it the fatherinlaw installed when he had transmission rebuilt, 1 line loosened up and dripped a little oil, 1 quart in 6-8 months before I found leak and fixed it. I really thought it was a axle seal and putting it off.

That's how I found  out when it gets to the add line it goes into limp mode, and to be fair it went in limp mode 2-3 times over the months. The 4th time it never came out of limp mode. So I added another splash of fluid thinking it wont hurt but may be too much. Did not help.

 

I changed the shift sensor, it road tested fine. Next morning taking wife to DR and 10 miles from town at 75 mph it went into limp mode. We drove home and let it sit, I tried a few hours later and it worked fine.

Drove it around town some and was fine, then one day drove it enough times to get trans up to hot working temp and went out again ... let it cool off and fine.

So I went ahead and drained some fluid, got the level just perfect. Now you can drive it long distance without going into limp mode.

Just strange when you start it that sometimes it is limp mode till you run it a few min and sometimes not.

 

Thinking out loud here, sorry for long post but going over it gives me a new idea.

I want to compare the sensor to a electrical safety switch like a breaker in your home. If you overload it too many times, it will trip but eventually will burn out and wont reset and need replaced.

Because of the fluid leak and last sensor went into limp mode a few times then failed ... could be my fault.

The new sensor has already went into limp mode 2 times because of over filled .... I know debatable but lowering fluid did help. Now sensor acts odd or 'laggy'

While the sensor still works kinda sorta, going to replace it, keep it for a spare in the glove box. They cost $12 at rockauto or $20 local. Takes 2 min and pliers to change.

Then I am going to do a lot of driving this week & hope it is fixed. Just to test it.

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What were the codes that it generated and was read the first time?  You stated that they used an ODB1 reader so they should have the codes.  Without those we're all just guessing. 

 

Shift solenoids seem to be the source of most of the limp mode issues.

Edited by kencombs
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39 minutes ago, JerseyHarold said:

Just a WAG, but try disconnecting the battery for a half hour , then reconnect and go for a ride.  The trans may have to reprogram itself.

I had a 93 Chrysler Town & Country (until the rust demon ate it up), and I had some issue with the transmission once, and took it in to a transmission shop.  (Or I thought there was a problem. The mechanic said there was nothing wrong.)  He took it for a drive (with me along), and in the course of our conversation he told me that that transmission was one of the most technologically advanced designs of any auto maker, specifically mentioning it's ability to 'learn' when to shift, depending on your driving habits.  So it might well help to make it start over.

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Some very interesting comments, I cant say I have disconnected the  battery for some time. Well worth a try.

Tomorrow it is like a spa day, it is getting a oil change, new speed sensor, vacuum of the carpets and interior wipe down.  Would not hurt to disco the battery while doing this.

 

I really appreciate the ideas, this one has me puzzled. Either works perfect, or not at all.

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Bought a 91 pt cruiser that a transmission shop diagnosed as a bad transmission. I scanned it and it called for an output speed sensor. I replaced it, then it wanted an input speed sensor,and after that one it wanted some pressure sensor. Wtf? Ordered a factory manual and discovered it had a seperate trans controller. In the fender ahead of front wheel. 
road salt corroded it and controller was full of wet salty sand. Had a huge hole in it. 
$40 for a used one and it ran until my daughter crashed it. 

had a later model caravan that wires were broken in the harness,right ahead of transmission, where it was tied into body.the wire retainer caused wires to break in the bundle. That one created range selector issues. 

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9 hours ago, Tooljunkie said:

had a later model caravan that wires were broken in the harness,right ahead of transmission, where it was tied into body.the wire retainer caused wires to break in the bundle. That one created range selector issues. 

I think for peace of mind, I will open up that harness today while working on the car. In my internet search for a solution, I have heard of a few others have a issue with broken wire in that harness.

The harness is dry, clean original and not messed with. But if it is a factory retainer causing the issue, then that could also be my problem.

 

Would be nice to open it up and see a damaged wire, so you know you found the problem.

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Just thought would share progress. Put it on jack stands yesterday, was all prepared to open the wiring harness .... "You cant get there from here" comes to mind.

I will have to access the harness from the top, remove the battery, possibly the battery tray if I can & then some other items I do not know what they are. Just not going to be a simple task.

 

I changed the motor oil and the shift sensor and called it a day. I test drove it and worked fine.  Of course it was warmed up and checking the oil level etc ....

This morning started it up let it run 30 seconds and took off. Shifted ok. A guy can tell the difference in the way it shifts. @JerseyHarold suggested it may be the transmission re-learning to program itself .... could be whats going on right now. I admit I did not disco the battery.

 

What I mean is, the last sensor was real smooth and could barely tell when it shifted ... except when it stopped shifting.

This one is real active. it shifts when it should, you slow down and can feel it down shifting.  Not a rough shift ... just seems to be doing what it should be doing.

 

I really am starting to suspect poor quality over seas parts.

#1 was shifting bad out of the box til it failed.

#2 lasted 4 years and many miles.

#3 kinda works sometimes but not always.

#4 I am hoping gives me 4 more years  :D  Too early to tell.

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Something I read about years ago was how the O2 sensor would be in a vehicle's maintenance schedule every 60k or so.  That sensor can wear out, as it is in the exhaust stream and subjected to heat + moisture from continued use...but also, the O2 sensor can become "lazy" as it ages, especially on vehicles not driven daily or only for short distances.  The various sensor metals build corrosion that makes O2 sensor response sluggish, which adversely affects engine performance.  I bought a Century Wagon and a Dakota longbed years apart, both garage-kept low miles specimens that were around 10 yrs old.  They ran OK but weren't quite right...new O2 sensors really brought them engines alive, the Buick especially as it no longer had trouble climbing steep hills, both idled smoother on cool humid mornings.  So I keep this in mind whenever I am dealing with anything that has older sensors on them, as the sensor may be sending erroneous data to the controller.  This came up 5 yrs ago when Mom's Equinox spit out a code and smelled like an electrical fire one summer afternoon near its 7th yr...I cleared the code, inspected the buggy for damage, test drove with no problems...Mom complained for weeks afterwards that the buggy had no power on hills, I figured that the responsible sensors were right at the threshold of failure...a few weeks later, Dad swapped that chevy for a Journey and she drove that for years...

 

Disconnecting the battery should be a harmless exercise that could reset the controller to default settings and allow for re-learn for optimum performance.  Suspecting faulty imported parts is not a stretch to do these days.

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On 3/4/2021 at 11:28 PM, JBNeal said:

Something I read about years ago was how the O2 sensor would be in a vehicle's maintenance schedule every 60k or so.  That sensor can wear out, as it is in the exhaust stream and subjected to heat + moisture from continued use...but also, the O2 sensor can become "lazy" as it ages, especially on vehicles not driven daily or only for short distances.  The various sensor metals build corrosion that makes O2 sensor response sluggish, which adversely affects engine performance. 

You make a very good point there. This was the mother in-laws car, Father gave it to daughter when mother passed away.

It does not have a cel when you start it, when you drive on the freeway about 20 miles the cel comes on.  Stop for gas and light goes out, need to drive aprox 20 miles for it to come on ... or just drive around town and does not come on.

Father claims it is the 02 sensors need to be replaced. I think he is right. I cant think of any good excuse for why I have not replaced them yet. Not sure if it has 1 or 2.

 

While it has only been a few days, so far the shift sensor is working good .... crosses fingers.

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16 hours ago, Los_Control said:

You make a very good point there. This was the mother in-laws car, Father gave it to daughter when mother passed away.

It does not have a cel when you start it, when you drive on the freeway about 20 miles the cel comes on.  Stop for gas and light goes out, need to drive aprox 20 miles for it to come on ... or just drive around town and does not come on.

Father claims it is the 02 sensors need to be replaced. I think he is right. I cant think of any good excuse for why I have not replaced them yet. Not sure if it has 1 or 2.

 

While it has only been a few days, so far the shift sensor is working good .... crosses fingers.

The 20 mile cel is likely egr issue. Sustained highway speed and all parameters arent met then you get a light. Then when stopped it resets. 
had an older chevy do that. 

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Good with the bad .... Just thought would throw it out there.

Yesterday the car went into limp mode while driving around town. Not fixed yet. I will be tearing into the wiring harness.

 

Guessing it has to be wiring or possible the transmission control unit ... I hate guessing games and OBD1 is just not accurate enough  :(

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Yup obd1 leaves a lot to be desired. My 92 gmc is running lean. And goes into open loop even when its warm. 
think the egr is leaking. 
 

have a poor running 93 toyota hilux in the shop,no codes and it requires a different adapter to get live readings. So not sure what in going to do with it. 

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  • 3 weeks later...

Turned out with mine was a fuel pressure regulator. 11 psi is on low side but acceptable. 
i decided to pull the throttle body and check the regulator.

i was suprised it ran at all.found a good spring in another tbi. Runs way better now.

0A552A96-1816-4A37-8598-F424E4407C95.jpeg

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I had a conversation with some relatives just after my grandmother's recent passing about her '88 camry, as it has some problems and her thrifty nature meant that car was not properly maintained.  A few non-mechanic relatives believe it'd be good basic transportation with a little TLC, I countered with the difficulties of dealing with OBD1, which left everyone in the conversation all deer-in-headlights, and recommended calling the local pick-n-pull to come get it since it hasn't started in years.  If that car had been maintained, I would not hesitate to tinker with it, but I would rather not waste time and $$$ on a lost cause decades-old economy car...in this case, it might need a starter, catalytic converter, O2 sensors + spark plugs, a set of tires, and a transmission 🤬

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Long term lack of maintenance will add up. Some prefer driving the older cars and vans. 
so if body is solid, to some thats a win and the rest is just nuts and bolts. My gmc is real long in the tooth,and im on the fence about fixing it or putting it to rest. I like the truck, but its getting pretty ugly.  
 

 

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Does that caravan have an underhood fuse panel/ power distribution centre? 
you might want to open it up and take a look. I recall some issues with corrosion, causing various problems. But only if the transmission is powered through it. The newer obd11 ones had a rash of trouble with the fuse boxes. 

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On 4/2/2021 at 1:45 PM, Tooljunkie said:

was suprised it ran at all.found a good spring in another tbi. Runs way better now.

Glad you found that. The gasoline today really sucks if you have a car that sits a lot. I rebuilt a carb for my uncle, looked almost exactly like that except it was gray goo.

 

1 hour ago, Tooljunkie said:

Does that caravan have an underhood fuse panel/ power distribution centre? 

I do not think so, will have to pull the battery & try to pull the tray to get better access to the harness. Might find a distribution box hidden away but doubt it.

I had the van in front of garage to work on, then my chebby truck developed a hot no crank issue. I had to fix it first.

Then it was going to rain and parked the pilothouse back in the spot, then spring hit and had to plant the garden, spring cleaning, etc...

I got a pile of crap in the back yard and no outside garden shed ... painted 16' of fence yesterday and need to plant some post today. Just tired of looking at the mess.

 

On 4/1/2021 at 9:51 PM, JBNeal said:

Sticky EGR valves and broken thermostats do weird things on OBD1

I think this statement has made up my mind ... I have to change my attitude, I know the 02 sensors go out at ~80k typically reading old post on forums for these vans. I may get better mpg if I replaced them ... buuuuttt \o/ it seems to run fine as is soooo. I know the IAC valve is a little gummy and needs cleaned, gives a little idle issue when running the AC. Would not hurt to change the egr. Would really  be just catching up on overdue maintenance. Possibly eliminate random issues caused by older obd1 computer.

Then after checking the wiring best I can, there is a electronic transmission controller that is a good possibility of being the problem. Rock auto sells a rebuilt for $157 + $50 core. That is cheap, if it would fix it ... kinda spendy if you just guessing.

 

The van is a decent little van, A school teacher bought it new, that era had paint peeling issues and the van was re-painted and issue fixed. Maintained regularly.

Transmission rebuilt at 150K, along with new axles, brakes, fuel pump.  I went through it and gave it a complete tuneup, greased the rear wheel bearings, shocks, tires, all new belts, hoses, water pump ... car has never seen road salt and has no rust.

We keep driving it around town, and works fine 98% of the time. Once in awhile 2 times in the past few weeks it drops into limp mode and can not go over 35mph.

Speed limit in town is 35 anyways and only 6 blocks from home. Then go home unload grocery, next time you drive it works perfect .... just totally random.

I swear going to get all over it like stink on poop, soon as my garden center is up  :D

 

 

0404211005a.jpg

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I thought would share a photo of it ... was a freak ice storm in Texas a few years ago. While we were house shopping was held up in a motel for a week because of the storm.

Not perfect, just old ... I am not ashamed to drive it.

IMG_20180221_174124413.jpg

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The last few years of the K-car platform minivans were good ones, with the refined ride + V6, good all-around visibility, ease of entry, and utility with the rear seat(s) removed.  Keeping one in good running condition is worthwhile for its utility alone, with the load height lower than a full size pickup, it can haul a lot of stuff and easier to load and unload, especially if you're not going off-road.

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