1G Intermittent sputtering, loss of power and shaking

[sacrileger]

After about a 30 min very smooth evening drive, my 1990 Plymouth Laser n/a suddenly turned on CEL, lost power and started sputtering. i was reasonably certain the timing belt jumped a tooth or two because I have already experienced this scenario and the engine behaviour was the same so I had the car towed.

The tow truck rolled the car into my garage and I put on the battery charger overnight to make sure my battery is full when I start working on the car the next day. The next afternoon I checked the timing marks and they were perfect so I proceeded to start the car and it ran like new. I was relieved but also surprised.

I concluded that the battery was too weak the prior day and my charging up the battery "fixed" the problem temporarily which means I still have a problem in the charging system. I checked the alt/wp belt and it was worn out and split along one of the grooves. Well that had to be it, right?

So I replaced the belt, started the car, went around block with it and it ran perfectly. At this point there was no reason for me to think the car was not fixed so I took it to town which is about 15 min drive down the highway from my home. I get to town, park the car for about 30 min and when I came back and started the car the CEL went on immediately and the engine was sputtering, shaking and lost a lot of power again. Since i knew it was not the belt this time, I decided to drive the car home in limp mode. Somehow I got the car home, parked it in the garage but this time I did not hook up the charger to the battery and went about my business.

The next day I checked the timing marks again; they were perfect so I proceeded to start the car and .... it ran flawlessly; to my surprise. I figured the problem exhibits itself after roughly 15 min drive so I let the car idle for the next half hour. The idle was also flawless and steady at 750 rpm for the entire 30 min.

I checked the CEL codes and I read 25, 43, 12, 13 in that sequence. I cleaned the MAF and it made no difference.

As you may appreciate this type of problem is the worst of all problems, if the car was straight up broken, I would be fixing it but in a situation like this I do not know what to fix, it all looks fine.

What would you recommend I do next?
Thank you in advance for your suggestions.

 

[Dericsh]

Try unplugging the MAF while it’s messing up and see what happens? Wouldn’t hurt to pull the ecu out and check for cap leakage, if that’s never been inspected before?

 

[sacrileger]

Try unplugging the MAF while it’s messing up and see what happens? Wouldn’t hurt to pull the ecu out and check for cap leakage, if that’s never been inspected before?

Thank you for the suggestions, unfortunately I have stopped driving the car as I have now zero confidence the car wont let me stranded so I wont be able to unplug the MAF while the car is acting up. I wish I would know how to get the car act up while it's sitting in the garage. Now I am kicking myself for not diagnosing the car as soon as I got home with it and could hardly get it up the driveway. It was that bad; hardly any power.

I just checked my private messages and the ECU was replaced in the month of July, 2019. The refurbished ECU came from @steve (dsm wiseman) so I trust the caps would still be fine. Ihe caps wouldn't deteriorate that quickly, would they?

What do you think I should try next? I am ruling out the alternator since I put in a new one about 2-3 years ago. I am totally at a loss.

 

[steve]

I checked the CEL codes and I read 25, 43, 12, 13 in that sequence. I cleaned the MAF and it made no difference.

After spending too much time trying to find the documents on the ECU to figure out why you might see a 43 Fault (EGR) that is California ECU specific. The MD166255 I sold you shouldn't throw that. I've not seen the capacitors I used fail in 5 years, it's been almost 14 years since I last offered ECU repairs and I haven't heard of any that I've repaired having cap related issues, so the odds are low.

I suggest monitoring your voltage and make sure it stays close to 13-14 volts all the time the car is running. Also there is nothing to clean inside the Mitsubishi MAF and doing do can damage it. It's not like a hot wire sensor that can get crudded up and throw off the output.

Are you still getting the faults?

 

[sacrileger]

After spending too much time trying to find the documents on the ECU to figure out why you might see a 43 Fault (EGR) that is California ECU specific. The MD166255 I sold you shouldn't throw that. ....

Are you still getting the faults?

thank you for bringing the fault code 43 to my attention... i am using an analog voltmeter to read the codes and i might have made a mistake and misread the code.... i will recheck the codes again this evening when i get home from work and report back...

i unplugged the maf and sprayed only the connectors and surfaces with an electrical circuitry cleaner to remove surface dirt and oil contaminants from connectors... i had the car 'oil sprayed' for winter and some oil always gets everywhere depending on the shop and operator that does it... but i will definitely rescan the codes...

 

[sacrileger]

Are you still getting the faults?

initially 'yes' but since you said only california gets code 43 i went back to the manual to make sure i counted the needle sweeps correctly.. and it turns out i was not... (thank you steve for directing me to go back and re-check!)

it's been so long since i scanned for codes that i forgot how to do it because every repair in the last many years was easily identifiable and no codes had to be read... i did not realize that the first code checks the ecu and then it reads the codes over and over again without any pause between the last and first code.

in any case, the new codes that i pulled out of the ecu are: 11 and 41

a/ code 11 suggests it might be oxygen sensor as well as fuel pressure and defective injectors
b/ code 41 suggests it might be injector coil resistance

in all the decades i have been around these cars, i haven't dealt with 'injector coil resistance' yet... in fact, i did not even know 'injector coil' is in the car let alone know where it is located.

i searched it up on this forum and the 'injector coil' appears to come under various names, such as 'injector resistor pack' in this thread:

https://www.dsmtuners.com/threads/car-still-won%E2%80%99t-start.540943/post-153867524

whereabouts in the car is the injector resistor pack located? do i just follow the leads from the injector and see where they merge?

it appears that the procedure to test the resistance will be somewhere on this forum

 

[steve]

NT cars don't have an injector resistor. They have high impedance injectors that don't require one.

The tests the 1G ECU performs to identify a fault are usually pretty simple, is the thing connected, is it providing a signal, is that signal in normal range, does it do so at the right time, etc.

I haven't looked at the code for those faults in a long time so I can't say exactly what the tripping conditions are. So I'm guessing that your O2 sensor has failed and that one or more injector has a coil that goes open under heat and load.

It could be wiring or the ECU but when I had a 41 it was the injector that was bad. It went open when it got hot.

I suspect that if you reset the ECU by removing power the faults will go away, the car will run nicely until it gets hot and then it will fail again. At that point you need to figure out which cylinder is having the problem and then you could swap injectors to make sure it's the injector. (does the problem follow the injector or stay on the same cylinder). A 1G datalogger would help as this point because it would allow you to turn off a cylinder to see if the engine runs the same or worse. Without one, you can pull spark plugs one at a time to look for the one that doesn't make the engine run worse or die.

You can also try wiggling the wires going into the ECU to make sure it's not a connection/connector issue.

I never threw an O2 sensor fault but I have had to replace the sensor twice on my 91. Each time it was because I failed emissions testing and the sensor had become lazy. So I'm assuming the conditions for getting the 11 fault have to be pretty much it's dead or disconnected.

 

[sacrileger]

thank you steve for the wealth of information

NT cars don't have an injector resistor. They have high impedance injectors that don't require one.

good to know... the manual led me to believe i had one as the fault codes listed in the manual are divided into codes for "1.8L engine" and codes for "2.0L engine" which means the "2.0L engine" section would also include the turbo version as well.

The tests the 1G ECU performs to identify a fault are usually pretty simple, is the thing connected, is it providing a signal, is that signal in normal range, does it do so at the right time, etc.

it's been so long since i pulled codes out of an ecu using a voltmeter that i forgot that the first needle sweep and pause is to show the ecu is in good working order and on top of it all the first code was 11 which blended in nicely with the initialization code and then the code 11 which came after hence the wrong codes i listed in the starter post.

So I'm guessing that your O2 sensor has failed and that one or more injector has a coil that goes open under heat and load.

It could be wiring or the ECU but when I had a 41 it was the injector that was bad. It went open when it got hot.

i would not be surprised at all if the o2 is no longer viable... i have no idea how old the o2 sensor is... i replaced the original 4g37 that came with this body with a 1992 4g63 in 2018 and i am still using the original o2 that came with the 1992 engine.

I suspect that if you reset the ECU by removing power the faults will go away, the car will run nicely until it gets hot and then it will fail again. At that point you need to figure out which cylinder is having the problem and then you could swap injectors to make sure it's the injector. (does the problem follow the injector or stay on the same cylinder).

the difficult part in this scenario is to get the car malfunction and act up again... i have been trying to idle the car in the garage to the point when the radiator fan comes on and the car just keeps running steadily... i am thinking that i could erase the codes, replace the o2 since it's likely old, drive it to places not too far from home and wait for the engine to act up again and then check the codes one more time

You can also try wiggling the wires going into the ECU to make sure it's not a connection/connector issue.

this definitely is a possibility because the engine swap i did in 2018 required that i also transfer the 1992 electrical harness with the engine but i had to rewire the connectors because the 1990 4g37 harness was not compatible with the 1992 4g63 harness:

Resolved - swap 4G37 for 4G63 n/t - wiring/harness

I am taking my 4g37 engine from a 1990 Laser and replacing it with a 4g63 n/t 6-bolt motor from a 1992 Talon. The '90 Laser has no A/C, cruise, etc. The Talon does. I already took both engines out and noticed that some of the connectors dont match up, i.e. the O2 sensor. I figured I might as...

www.dsmtuners.com

I never threw an O2 sensor fault but I have had to replace the sensor twice on my 91. Each time it was because I failed emissions testing and the sensor had become lazy. So I'm assuming the conditions for getting the 11 fault have to be pretty much it's dead or disconnected.

we dont do emissions testing where i live so this o2 is likely dead and since the first code i pulled was "fault 11", i think it is pretty safe to replace the o2 just to rule out one variable and take it from there...
thanks for the great help!

 

[sacrileger]

I haven't looked at the code for those faults in a long time so I can't say exactly what the tripping conditions are. So I'm guessing that your O2 sensor has failed and that one or more injector has a coil that goes open under heat and load.

It could be wiring or the ECU but when I had a 41 it was the injector that was bad. It went open when it got hot.

I suspect that if you reset the ECU by removing power the faults will go away, the car will run nicely until it gets hot and then it will fail again. At that point you need to figure out which cylinder is having the problem and then you could swap injectors to make sure it's the injector. (does the problem follow the injector or stay on the same cylinder). A 1G datalogger would help as this point because it would allow you to turn off a cylinder to see if the engine runs the same or worse. Without one, you can pull spark plugs one at a time to look for the one that doesn't make the engine run worse or die.
I never threw an O2 sensor fault but I have had to replace the sensor twice on my 91. Each time it was because I failed emissions testing and the sensor had become lazy. So I'm assuming the conditions for getting the 11 fault have to be pretty much it's dead or disconnected.

steve, thank you for the suggestions^...

As I wrote in my posts above, I pulled two fault codes out of my ECU: 11 and 41.

I went for the low hanging fruit and replaced the O2 sensor. I was quite reasonably certain that would fix the problem as I figured the O2 sensor has never been replaced so that had to be the issue and as far as the fault code 41, I figured it was a fluke and somehow connected to the dead O2. So with tons of confidence I went for a drive and guess what, exactly the same thing happened exactly at the same place from which i towed the car home the last time - the car suddenly flicked the CEL on, lost power and started sputtering. I made it back home, checked codes and what I got was fault 41, no more code 11 (oxygen sensor).

I started the car in my driveway and it sounded like it was running on 3 cylinders. I borrowed my wife's stethoscope and went to listen to each injector for 'clicks'. I could hear distinct clicks generated by three injectors but one injector, cylinder 2, was generating no 'clicks' so i disconnected the injector from the source of power, started the car again and there was no diff in the way the engine ran.

While the engine was still hot and the injector disconnected from the electrical circuit, i checked for resistance with a digital multimeter and read some nonsensical value of 35 Mega Ohms. I checked the other injectors and I got 19 ohms on the rest of them.

By the time I took the fuel rail out, the injectors were back to ambient temperature and I re-checked the resistance on all 4 injectors and this is what i got: 14.7 ohms, 14.7 ohms, 14.7 ohms, 14.7 ohms exactly!!

Since this is a N/T engine, I expected the resistance to be between 2-3 ohms and not 14.7 ohms as if it was a turbo engine which requires injectors with a resistance between 13-16 ohms.
I looked for some product codes which would tell me what type of injectors I have in the engine and all I found was this code: N240H.

After a quick search, I determined that these are Mitsubishi injectors which are color coded and have unique casting numbers. Nippon Denso (ND) was so kind to stamp identification numbers on both sides of the plastic body which helped me find this info:

Pink connector = 240cc – DSM 4G63 1g 2.0L NA – Stamped N240H, casting # INP-059 – high Impedance

My questions:
1/ what would make all injectors, including the faulty injector which gives no 'clicks', generate the exact same resistance of 14.7 ohms?

2/ What is the impact on the way the engine runs if the injectors are out of spec, i.e. 13.7 ohms instead of 2-3 ohms?

Thank you.

 

[steve]

Since this is a N/T engine, I expected the resistance to be between 2-3 ohms and not 14.7 ohms as if it was a turbo engine which requires injectors with a resistance between 13-16 ohms.

I looked for some product codes which would tell me what type of injectors I have in the engine and all I found was this code: N240H. After a quick search, I determined that these are Mitsubishi injectors which are color coded and have unique casting numbers. Nippon Denso (ND) was so kind to stamp identification numbers on both sides of the plastic body which helped me find this info:

Pink connector = 240cc - Stamped N240H, casting # INP-059 - high Impedance - 1G DSM 4G63 2.0L NA

My questions:
1/ what would make all injectors, including the faulty injector which gives no 'clicks', generate the exact same resistance of 14.7 ohms?
2/ What is the impact on the way the engine runs if the injectors are out of spec, i.e. 13.7 ohms instead of 2-3 ohms?Thank you.

Somewhere along the line you got mixed up. As noted N/T Injectors are the high impedance ones (high AC resistance) and the Turbo Injectors are the low impedance (low AC resistance) ones used with an injector resistor.

The N/T N240H injectors spec is 13-16 ohms @ 20*C. Yours would seem to be in specification when cold but when hot that one goes open (35 Megaohms) and the others rise to 19 ohms which is fine. Sound like your seeing the same problem I mentioned. You need a new injector.

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[sacrileger]

Somewhere along the line you got mixed up. As noted N/T Injectors are the high impedance ones (high AC resistance) and the Turbo Injectors are the low impedance (low AC resistance) ones used with an injector resistor.

The N/T N240H injectors spec is 13-16 ohms @ 20*C. Yours would seem to be in specification when cold but when hot that one goes open (35 Megaohms) and the others rise to 19 ohms which is fine. Sound like your seeing the same problem I mentioned. You need a new injector.

ahhh... that's so embarrassing... i should have made the connection b/w impedance and resistance and realize my data was wrong.
thank you for shining light on this subject...