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Resolved Take a listen (video)... intermittent or persistent misfire?

sacrileger

Proven Member
238
18
Jun 26, 2016
Orillia, ON_Canada
methinks this engine is not running right bc it sounds as if one cylinder here and there misfires. it shakes a bit when idling but picks up when it revs higher. it lacks a bit of power when i drive it. i cleaned up and re-gapped spark plugs, same with plug wires, my injectors are working (clicking), the idle is steady but something is not right. would you listen to this and tell me if i should investigate this a bit deeper?
when i disconnected spark plug wire #4 and put a spark plug in it to see if i see a steady spark at the end of the terminals, i noticed blue sparks flying between the coil and the head.

here is the look and sound of the engine:
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and here is the sound coming from the tail pile
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perhaps this would help you tell me if my suspicion is real or if i am imaging it... thank you.
 

sacrileger

Proven Member
238
18
Jun 26, 2016
Orillia, ON_Canada
Pull the injector plugs one at a time to see which cylinder is missing, a compression check wouldnt hurt either.

I can no longer perform this test. As soon as i started the car, it ran very rough. I had to pump the gas pedal to keep it going. I could not get out of the car fast enough to get to the throttle to keep it going. Now i cannot start the engine at all and there's no indication the car wants to start. It does not even sputter or fire up one or two cylinders to give indication the car would start... I had noticed a progressive and rapid degradation in performance to the point that the engine could hardly run shortly after posting the videos

So far I have done this:
  1. put fresh gas in the tank
  2. charged up the battery
  3. made sure the fuel pump works by shorting the fuel pump switch on the firewall. I could hear the fuel reaching the fuel rail.
  4. the fuel control relay appears to function fine.. i can hear it 'click' 1-2secs after i stop cranking.
  5. the CEL comes ON and turns off after about 4s
  6. the 3 fusible links by the battery are intact
  7. checked the timing belt - it lines up perfectly at TDC on cyl#1. The belt did not jump.
  8. checked and re-gapped spark plugs
  9. using ignition spark tester, i checked the coil output. The spark jumps the 30KV distance on all leads and also two leads jump the 40KV distance... which rules out faulty coil and cables
  10. compression and leak down was done recently and it was fine.. so, since the timing belt did not jump, there would be no reason for change... especially drastic enough for the engine not even start due to low compression.
So far i have NOT done this:
  1. check ECU for error codes
  2. check fuel pump pressure regulator
  3. fuel pump pressure
  4. CAS
  5. check for proper resistance reading on fuel injectors (they all would not fail at the same time anyways)
What am i missing? Is there anything else i should check?
 
Last edited:

sacrileger

Proven Member
238
18
Jun 26, 2016
Orillia, ON_Canada
New coolant temp sensor unless you can verify that the old one is good, unplug the mass air sensor and try to start it.
  1. i unplugged the MAF and the engine did not start
  2. checked the coolant temp. sensor: the resistance b/w the two sensor terminals should be between 2,200-2,700 ohms... i got infinity
  3. with the ignition key ON, i unplugged the connector to the CTS and checked for signal voltage going to the CTS. It should be 4.5-4.9V... i got nothing, no voltage.
  4. checked fuses and did not see any blown... which makes me wonder why i get no voltage to the CTS.
  5. i checked ECU for diagnostic codes. I expected code 21 which is the CTS. Instead, i got 13 and 25. Code 13 is likely the disconnected MAF (intake air temp sensor). Code 25 refers to "barometric pressure sensor"...
  6. I cleared the ECU diagnostic codes, reconnected the MAF, cranked the engine, .. no error/ diagnostic codes appeared after that...
  7. with the ignition ON, I unplugged the connector to the MAF and checked for signal voltage going to the MAF sensor. It should be 4.8-5.2V... i got 4.5V
  8. with ignition ON, continuity of the ground circuit for the barometric pressure sensor from terminal #4 (non-turbo) checked out
  9. the resistance readings b/w terminal #4 and #6 (n/a) of the airflow meter sensor side show about 2.5Kohm at 19Celsius (sorta Ok)
Needless to say, that was some spot on lead you gave me regarding the CTS in your previous reply. thanks.

Any ideas how to track this thing down?

Edit 1: here Troubleshooting methodology query: On codes from ECU 4G37 i read that "The MAF contains the Air Intake Temperature Sensor, and the Barometric Pressure sensor, along with the Mass air flow sensor.

Edit 2: as i recall, there was no problem showing temp on the instrument panel... it would increase gradually and stop mid-range (operating temp) where one would expect the needle end up, in the middle, when engine op. temp reached.

Edit 3: predictably, the CTS wires snake up around the intake manifold along with the rest of wires connected to injectors, CAS, TPS, etc. and into the firewall and likely into the ECU. I have no idea where the CTS picks up power.

Edit 4: here's similar info re MAF, no power to CTS, etc. however, it's not clear how the OP got the engine run as it should:
Help with my 1g. Not starting, running hot..
 
Last edited:

motomattx

Proven Member
3,687
1,430
Dec 9, 2010
wampum, Pennsylvania
Remember that the coolant sensor that displays on the dash is not the same sensor that the ecu uses for its input, one can read fine and the other can go bad or have no voltage going to it etc, there are two of them.
 

sacrileger

Proven Member
238
18
Jun 26, 2016
Orillia, ON_Canada
Remember that the coolant sensor that displays on the dash is not the same sensor that the ecu uses for its input, one can read fine and the other can go bad or have no voltage going to it etc, there are two of them.
i was not sure which one was which and did the reading for dash. the suspect CTS is likely read by the ECU. i have not been able to determine where the source of power is. Is it the ECU that send the signal voltage? If yes, which pin? The ECU is mint and i am ruling out any problems with the ECU. Is there a relay or some type of voltage regulator between the ECU and the CTS i need to check?
 

motomattx

Proven Member
3,687
1,430
Dec 9, 2010
wampum, Pennsylvania
The 5v supply voltage comes from the ecu, there is nothing in between the ecu and the provided 5v impinged voltage on the sensors, if you in fact are missing that voltage to the sensor then you have a wiring problem likely.
 

sacrileger

Proven Member
238
18
Jun 26, 2016
Orillia, ON_Canada
The 5v supply voltage comes from the ecu, there is nothing in between the ecu and the provided 5v impinged voltage on the sensors, if you in fact are missing that voltage to the sensor then you have a wiring problem likely.

well, this should be fun... if i am reading el. diagrams correctly, the EGR temp sensor is somehow involved in the scheme of things too... i just put in a refurbished ECU which came from US... anyways...

this 1G ECU pinout tells me that pin #20 supplies the 5V
http://www.vfaq.com/mods/ecu-harness-1G.html

furthermore, the 1G circuit diagram at this link
https://tinyurl.com/y2al2fbs

leads me to believe i may have some conflict with the EGR sensor

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anyway, .. any ideas would be appreciated

Edit 1: whether the ignition key is in ON or OFF position, there's no continuity on wires going to the CTS.
Edit 2: checked ECU pin #20 (yellow w/ green stripe wire): with the ignition key in OFF... i get resistance but not continuity, with the ignition key in ON position, the pin #20 gives me 2V... instead of the 5V i should get.
Edit 3: the ECU pin #20 wire is yellow w/ green stripe, ... the wire which connects with and carries power to the CTS is green with yellow stripe; thus, there has to be a junction or another connector in between where the wire changes from yellow w/ green stripe to green w/ yellow stripe)
 
Last edited:

sacrileger

Proven Member
238
18
Jun 26, 2016
Orillia, ON_Canada
Make sure your checking voltages with the sensor unplugged.
the wire from ECU pin #20 does not appear to be directly connected to the CTS. The wire going out of pin #20 is yellow w/ green stripe, ... the wire directly at the CTS is green with yellow stripe; thus, there has to be a junction or another connector in between where the wire changes from yellow w/ green stripe to green w/ yellow stripe.. do you know where this switch might be happening?
 

sacrileger

Proven Member
238
18
Jun 26, 2016
Orillia, ON_Canada
Heck it could be anywhere, my point is to find out if you have +5v at that pin on the ecu first.

The voltage reading directly on the ECU pin #20 with the CTS unplugged is 2V. I checked by jamming a probe into the connector at the ECU to get direct reading of the output voltage as it comes out on pin #20. It appears that the voltage is regulated by some other component based on some feedback loop and depending on the resistance of the component the output voltage (on pin #20) is, in my particular case, 2V. So something else is feeding information into the ECU which then drops the voltage... but in my case the 2V do not show on wires at the coolant temp sensor... and i am having difficult time finding information where the yellow w/ green stripe wire goes and changes to green w/ yellow stripe.
 

motomattx

Proven Member
3,687
1,430
Dec 9, 2010
wampum, Pennsylvania
That voltage should always be +5v with the sensors unplugged, that is a ecu constant supply voltage, it has a pull up resistor on it in the ecu is all, are you sure that your meter is a good one and that you have a good ground? are you sure that your battery is fully charged and showing 12v at the ecu? test the voltage supplied to your other sensors also, your tps when unplugged should also have +5v on one side and a ground on one terminal.
 

sacrileger

Proven Member
238
18
Jun 26, 2016
Orillia, ON_Canada
That voltage should always be +5v with the sensors unplugged, that is a ecu constant supply voltage, it has a pull up resistor on it in the ecu is all, are you sure that your meter is a good one and that you have a good ground? are you sure that your battery is fully charged and showing 12v at the ecu? test the voltage supplied to your other sensors also, your tps when unplugged should also have +5v on one side and a ground on one terminal.

I replaced the coolant temp sensor and followed the wires from the CTS to the ECU to see where the green w/ yellow stripe wire changes to yellow w/ green stripe wire which exits ECU pin #20 and discovered that the wires were severed/replaced and later re-attached with regular twist-on electrical connectors and tucked back into the insulation with the rest of the ignition wires for whatever reason by the previous owner of this engine. One of the connectors must've come undone. I trimmed the wires, rechecked, reconnected and the engine started without hesitation and any signs of misfire. Needless to say, i get solid 4V at the CTS instead of the desired 5V; however, since the engine runs just fine, I will leave it as it is for now.
Regardless, the suggestion to check CTS in answer #4 above was brilliant as that where the problem was.
 
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