Way off topic 1993 caravan transmission

[Dave72dt]

Maybe take a look at the plugs once more now that you have some miles on it.  Your first statement back in September mentioned key codes and TPS out of range.  Out of range can be an indication of a poor ground.  Chrysler had a habit of tying multiple sensors together with a single ground as well as having multiple ground locations.  Check them once again for any indications of that green corrosion on the terminals.  Fresh, bright copper wire with a fresh terminal on it.

[Los_Control]

21 hours ago, Dave72dt said:

Maybe take a look at the plugs once more now that you have some miles on it.  Your first statement back in September mentioned key codes and TPS out of range.  Out of range can be an indication of a poor ground.  Chrysler had a habit of tying multiple sensors together with a single ground as well as having multiple ground locations.  Check them once again for any indications of that green corrosion on the terminals.  Fresh, bright copper wire with a fresh terminal on it.

That's good advice there Dave .... I pulled a plug to take a peek. ... almost 1500 miles on them.

 

I think my next plan, after the Holidays ... Is to pull the plenum.

Both vacuum and electrical run under it and I will get a chance to spend time and make sure I did not miss something when I installed it.

All the main harness plugs I cleaned and used dielectric grease on them .... except the ones I missed

 

Doing the engine swap, I may have got in a hurry and missed something when connecting those items and installing the plenum .... double check my work.

 

Also this plenum I noticed has a lot of oil in it from when the engine blew up ... I have been moving the plenum and all the sensors/TB over to the new engine .... The old dried oil is 3 years old now and I doubt it would be a issue ... I have 2 clean plenums so will swap it out.

 

I also have the modified fuel rail that is working fine and the injectors have 188K miles on them.

I do not think it is a injector issue, but have 2 other sets of injectors can clean and test then install them.

 

Currently just frustrated with it and need to step away from it before I blow it up  

 

 

 

 

 

 

 

 

[Sniper]

On 12/16/2024 at 9:47 PM, JBNeal said:

This may or may not help:

 

When I fiddled with PCM mapping back in the day, the problem here sounds like the PCM is trying to switch to closed loop mode but the injectors are stuck in open loop mode, hence the rich fuel code, almost like a relay is sticking somewhere.  I'm not familiar with the Chrysler specific fuel delivery circuitry, so I'm not sure if this relay is modular or soldered to the PCM.

 

The only relay in the mopar injector circuit is the one that feeds 12v to all the injectors.  The computer uses injector drivers (solid state device, not a relay) to trigger the injectors on/off via the ground.  Those usually either work, or do not work, very rarely are they intermittent. 

 

Either the coolant temp sensor, the one for the computer not the dash gauge, is flaky, you have a leaky injector or the PCM is wonky.  If you have the ability to measure the fuel pressure at the injector rails you can see how fast that pressure bleeds down, if it's quick you have a leaky injector(s).

 

Have you run the codes?

Edited yesterday at 03:47 AM by Sniper

[Los_Control]

5 minutes ago, Sniper said:

Either the coolant temp sensor, the one for the computer not the dash gauge, is flaky, you have a leaky injector or the PCM is wonky.  If you have the ability to measure the fuel pressure at the injector rails you can see how fast that pressure bleeds down, if it's quick you have a leaky injector(s).

 

Have you run the codes?

Only code right now is (52) rich fuel mixture.

I have replaced the fuel pump, fuel filter, fuel pressure regulator.

I have checked the fuel pressure at the rail and is exactly what it should be .... pressure takes several minute to bleed down when shut off.

 

I did swap the original pcm with a used pcm, and made zero difference .... pcm is good or both bad in the exact same way.

 

Not sure what you mean by coolant sensor .... have done nothing with it .... dash gauge seems to be accurate.

[Sniper]

8 hours ago, Los_Control said:

Not sure what you mean by coolant sensor .... have done nothing with it .... dash gauge seems to be accurate.

 

Back then there were two coolant temps sensors, one for the gauge and one for the computer.  If the one for the computer is sending bad data to the PCM then it may be the reason it's running rich.  Essentially, it's telling the computer I am not warmed up so the computer stays in open loop and it runs rich once the engine is actually up to temperature.

 

Gauge sender

 

 

PCM sender

 

 

OBD1 isn't sophisticated enough for you to actually look at the data and see if this is the case, unfortunately.  OBDII is smart enough to let you do that, which cuts down on the issue of shotgunning parts, but at the expense of a costly scanner. 

Edited yesterday at 12:51 PM by Sniper

[Los_Control]

Thank's @Sniper, I was not aware there are 2 coolant sensors.

OTOH, I have lots of spare parts with 2 junk engines. 🙄 .... Sure I have another one around to test with.

 

Certainly is plausible ... never happens til after you run it a ways on the highway and always after the same period of time on the same stretch of road ..... shortly after the engine is good and warmed up.

And it started after installing this engine, could have been DOA.

 

Kinda puzzled now, it has been a few months since I installed engine .... really can not remember that sensor .... wondering if I even plugged it in? 🤔 ... sure I did but am curious. I have since changed every sensor on the engine and just cant place that one.

I will have to take a look today and see if I can change it.

 

[JBNeal]

17 hours ago, Sniper said:

...

Either the coolant temp sensor, the one for the computer not the dash gauge, is flaky, you have a leaky injector or the PCM is wonky.  If you have the ability to measure the fuel pressure at the injector rails you can see how fast that pressure bleeds down, if it's quick you have a leaky injector(s)...

You're absolutely correct, if that PCM temp sensor is sending faulty information, then the PCM gets "confused" and spits out codes...I learned a long time ago that oxygen sensors are prone to getting "lazy" as they age since the sensor materials are in a harsh environment.  I had a friend with a 2004 Matrix that she bought new, and in 2021 I told her it did not sound right, asked her when she last changed the O2 sensors, she just looked at me funny and changed the subject...6 months later in February, the CEL illuminated, my scanner kicked out O2 sensor codes, swapped those 2 rusty cusses out, and that thing ran smooth and quiet and was FAST, she said it had not run that good in years and accused me of being some kind of witch...a few weeks later, she got her first speeding ticket in a school zone, and she blamed my witchcraft skillz and not her lead foot 😁

[Los_Control]

I tried changing the sensor and made no difference .... It started acting up as normal about 20 miles outside of town as it always does. .... took the back way home at 50mph and ran fine.

 

Not sure how to test the wiring there ... turned the key on and with a 12V test light got no power to the sensor.

It could be less then 12V or may need car running to actually get a signal .... have to remove the coil to get to it  so no starting the car.

 

I honestly believe now I have changed every sensor that connects to the pcm .... back to removing the plenum and go over all the electrical and vacuum  

[Sniper]

The PCM sensor uses 5v from the PCM, it sends a voltage back to the PCM that varies depending on it's temperature and the PCM interprets that returned voltage as a temperature reading.

 

OBD1 is not nearly as sophisticated as OBD2.  Example:

Coolant temp reads 50F, ambient reads 70F, intake air temp reads 125F.  All are "valid" temperatures as far as the range of over all expectations go.  After 5 minutes of running the coolant temp doesn't change.  OBD1 thinks "it's in a valid range",  OBD2 says "wait a minute",  OBD2 knows that value should have gone up and based on load, run time, ambient temps and intake air temps has a pretty good estimation of where it should be and if it's not there will throw a code.  OBD1 will not as it doesn't do that type of calculations.

 

Now if the coolant temp sensor returns an invalid signal, such as not having 5v going to the sensor, OBD2 will throw a code.  OBD1 might.  This is really where being able to view the live data from that sensor comes in handy,

 

One thing I found when putting together the parts for my EFI swap was a source that listed the data and values from the various sensors I am using.  Microsquirt (my PCM) will let me look at that data live so I can see a flaky sensor that returns an "in range" value that is not correct.  Such as telling me my coolant temperature is 50F, which is "in range" for that sensor, when it's actually past the thermostat opening temperature.

 

Don't forget a grounded signal line from the sensor to the PCM will also confuse it.  Unfortunately, I only have GM sensor data, but if we knew what the data was for your sensors we could back probe the voltage to the PCM and see if what's going there is rational or not.

 

 

 

[Los_Control]

45 minutes ago, Sniper said:

OBD1 is not nearly as sophisticated as OBD2.

Thats why it is suppose to be easier to work on older OBD1 cars  🤣

 

I have been thinking about one of the MT2500 scanners, several on Ebay for about $300 .... they have some cheaper .... think it is important to get all the literature and extra connections that come with them .... A complete set.

This one seems to be all there and $300 .... will not give the same info as a OBD2 scanner but will be better then what I have now.

 

To be honest, I'm not sold on the idea this scanner would really help me much in my current situation .... it might give me a better clue though.

[Sniper]

I don't know enough to know if it reads lie data or not.  The factory too is called DRB scan tool. In Ebay it's in excess of $2k.  I did find the user manual online though, It doesn't specifically mention it can read OBD1 sensors