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420A Turns Over, Dies Immediately

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rawfuls

Probationary Member
22
0
Mar 29, 2019
Moreno Valley, California
1995 Eclipse, 420a NA.

Was previously riced out, threw P0122 and P0412, the P0412 has been resolved with the 6.5k resistor method.
Tore down the intake manifold, oil pan and valve cover, egr tube for new gaskets. Replaced spark plugs (factory seems to be .035, but tested at .035 and .050, both same results).

Car cranks, turns over but then immediately dies.
Fuel pressure rail is pressured, and have purged using the shrader valve.
Plugs are sparking bc it turns over.

Could a TPS or IAC be the issue here?
TPS is not the normal adjustable oval holes kind, seems to only have two holes. Is this the wrong TPS?
Seems unlikely, because the car previously ran and drove (over 30 miles into my garage), so seems like TPS/IAC would be working same as before.

Video here:
https://imgur.com/a/mWEgxnC
 
TPS is not the normal adjustable oval holes kind, seems to only have two holes. Is this the wrong TPS?
Hmm... I'm not sure what you mean by the "adjustable oval holes kind", but since there's a TPS-related code, I'd just replace the sensor to eliminate it as a possible cause of the problem.

Plugs are sparking bc it turns over.
This might just be a terminology issue, but there's no gaurantee you have spark because the engine turns over. If it turns over, you can reasonably assume the starting system and battery are okay, but not necessarily fuel, spark, or compression.
 
Hmm... I'm not sure what you mean by the "adjustable oval holes kind", but since there's a TPS-related code, I'd just replace the sensor to eliminate it as a possible cause of the problem.
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This seems to be the oval type, where you can adjust it based on the butterfly of the tb.
see: https://www.dsmtuners.com/threads/how-to-adjust-a-2g-tps.170432/

This might just be a terminology issue, but there's no gaurantee you have spark because the engine turns over. If it turns over, you can reasonably assume the starting system and battery are okay, but not necessarily fuel, spark, or compression.

Oops, you're right.
I suppose pulling the spark plugs and verifying myself is the best course of action?
 
That tps is not for the 420a motor. Ours doesn't have to be adjusted but it does need to be installed correctly. You have to the sensor needs to be spring loaded up against the throttle shaft so the throttle starts to move the sensor immediately.

The car fires up and jumps to about 2k so the plugs are firing.
 
If it where an IAC or TPS issue you would more than likely be able to keep it running by feathering the throttle. If you have a scan tool handy check what your coolant temp sensor is reading. If its bad and thinks the temp is - 60 below zero it'll dump excessive amounts of fuel. If it was just running and starts but dies it is more than likely a sensor issue.
 
The car fires up and jumps to about 2k so the plugs are firing.
Good call, I couldn't make that out in the video.

If you have a scan tool handy check what your coolant temp sensor is reading. If its bad and thinks the temp is - 60 below zero it'll dump excessive amounts of fuel. If it was just running and starts but dies it is more than likely a sensor issue.
Another good call. Listen to these guys! :D
 
Check the map sensor port for carbon build-up. Then test the map sensor itself. Freinds old 98gs would do the same thing before we rebuilt it, map sensor port was completely blocked by carbon/oil crud. Cleaned that and the maps sensor (very carefully) and fired up fine after that.

Might as well test the TPS and IAC for proper readings also.
 
That tps is not for the 420a motor. Ours doesn't have to be adjusted but it does need to be installed correctly. You have to the sensor needs to be spring loaded up against the throttle shaft so the throttle starts to move the sensor immediately.
The car fires up and jumps to about 2k so the plugs are firing.

Any other way to test to make sure the TPS is installed correctly, beyond pushing the gas pedal and making sure the throttle body opens up? How is this affected by the TPS if the throttle cable is mechanically moving the throttle body valve?

If it where an IAC or TPS issue you would more than likely be able to keep it running by feathering the throttle. If you have a scan tool handy check what your coolant temp sensor is reading. If its bad and thinks the temp is - 60 below zero it'll dump excessive amounts of fuel. If it was just running and starts but dies it is more than likely a sensor issue.

It doesn't really 'run', it starts up, revs up then dumps out.

Check the map sensor port for carbon build-up. Then test the map sensor itself. Freinds old 98gs would do the same thing before we rebuilt it, map sensor port was completely blocked by carbon/oil crud. Cleaned that and the maps sensor (very carefully) and fired up fine after that.
Might as well test the TPS and IAC for proper readings also.

This might be likely. I removed the intake manifolds and tried my best at de-gunking carbon build-up with carb cleaner and/or Zep cleaner. Any way to test the map sensor to make sure its functional?
Also, confirming MAP sensor is the vertical sensor to the left of the intake manifold cylinder? Found top left of the engine bay.

Seems like TPS/IAC are a common issue here- will the 420a run and idle with the IAC/TPS disconnected?
Any way to isolate/test these without purchasing a new sensor? RockAuto seems to have the sensors at ~$40/ea, which is a tough pill to swallow if I know if started previously.
 
Any way to test the map sensor to make sure its functional?
Check the voltage on the signal wire (yellow/black) with the engine off, but the key in the "ON" position. It should be somewhere around 4.7V. You should also have continuity between the ground wire (black/green) and chassis/battery ground. If you can put the manifold under vacuum, or even just the sensor, you can check the voltage on the signal wire to see if it's changing.

Also, confirming MAP sensor is the vertical sensor to the left of the intake manifold cylinder? Found top left of the engine bay.
Yep, that's the one.

Any way to isolate/test these without purchasing a new sensor? RockAuto seems to have the sensors at ~$40/ea, which is a tough pill to swallow if I know if started previously.
Here's how to check the TPS and IAC, but considering you have a code for the TPS, I'd say there's a good chance that's part of the problem. Do you have a junkyard nearby? The one by me sells any kind of sensor for $9.

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Disconnected the MAP sensor and she fired up with some feathering of the throttle. (Video below).
No ground/continuity between black/green and ground, but I do get +4.7v on yellow/black.

IAC/TPS was connected, received P0108 (MAP sensor?) and P0122 (TPS sensor).

Something I noticed, was with the intake off (just raw TB), it seems to want to die when pulling throttle cable.
When using the gas pedal, it doesn't behave the same way.

https://imgur.com/a/Mk4Q8gQ

I haven't checked the IAC or TPS yet.
 
Disconnected the MAP sensor and she fired up with some feathering of the throttle. (Video below).
No ground/continuity between black/green and ground, but I do get +4.7v on yellow/black.

IAC/TPS was connected, received P0108 (MAP sensor?) and P0122 (TPS sensor).

Something I noticed, was with the intake off (just raw TB), it seems to want to die when pulling throttle cable.
When using the gas pedal, it doesn't behave the same way.

https://imgur.com/a/Mk4Q8gQ

I haven't checked the IAC or TPS yet.

I can't get any audio on the vid, but to me that's a starting place. How'd the port for the map sensor look: cruddy and carboned-up or somewhat clear?

Personally I'd put a map sensor on my "to-buy" list, but finish testing the other pieces. I suspect, since you revved the car a couple times in the vid, that the tps is responding, but couldn't tell if it would idle on it's own.
 
I agree, the audio can be helpful. Upload your videos to a legit video hosting site if you can.
 
MAP port looked good, but for good measure I sprayed the hole the MAP sensor pops into, with some carb cleaner.
More than likely, that's why I got a good amount of cold liquid from the exhaust.

TPS/IAC specs, since I don't know which pin is which, measuring with the sensors in the stock locations.
Middle & Bottom Pin:
20k OHM - 5.15 ohm
0.77 - 3.92 min to max w/ valve

Top & Middle Pin:
20k OHM
1.33 - 4.47 min to max w/ valve

IAC:
Pins 1 & 4 - 50.6 ohm
Pins 2 & 3 - 49.5 ohm

I have a few LKQs nearby, worth stopping by for a TPS and MAP sensor?

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Last edited:
Thanks for reloading the vids that helped massively :thumb: Based on the first video, I'd say since it'll idle with the map unplugged, that's the first replacement part I'd get. It'll die when barely cracking the throttle cuz it can't sense the change in manifold pressure and adjust fuel finely enough, like when you work the throttle by hand. My thought is when you use the pedal, it's making large enough changes via tps to at least guess at the fuel table, but can't recover idle and dies, like shown. Without the intake tube, it will affect velocity as well.

As for the testing, I have no clue what or how you tested based on your description, but I'd wager neither are the culprit since it can idle and fluctuate throttle voltage.

My vote: put a new MAP sensor on it.
 
Idk all the vehicles, but I'm fairly positive gm sensors will NOT work without some extra effort.

Similar models should be dodge neons, Plymouth breeze, Chrysler Cirrus, and I believe you'll need them off cars with aluminum intake manifold, not the newer plastic, front intake styles.

A new one is pretty reasonable CLICK
 
TPS/IAC specs, since I don't know which pin is which, measuring with the sensors in the stock locations.
Middle & Bottom Pin:
20k OHM - 5.15 ohm
0.77 - 3.92 min to max w/ valve

Top & Middle Pin:
20k OHM
1.33 - 4.47 min to max w/ valve

You have a TPS-related code and the sensor's resistance is outside the standard range. I say replace the TPS and go from there.

EDIT: I'm having a hard time reading your test results. Could you post the numbers with units? Did you get 5.15 ohms between the middle and bottom pins, or 5.15 kohms? Is "20k OHM" a reading or your multimeter's setting?
 
You have a TPS-related code and the sensor's resistance is outside the standard range. I say replace the TPS and go from there.

EDIT: I'm having a hard time reading your test results. Could you post the numbers with units? Did you get 5.15 ohms between the middle and bottom pins, or 5.15 kohms? Is "20k OHM" a reading or your multimeter's setting?

Doesn't seem to be out of spec to me.
20k is the setting of the multimeter, so I believe it's within spec.
 
Okay, I see. For future reference, this is how you should write those values:
Middle & Bottom Pin:
5.150 KΩ
0.77 - 3.92 KΩ min to max

Top & Middle Pin:
1.33 - 4.47 KΩ min to max

Did you measure the resistance between the two outer pins (pins 1 and 3)?
 
My fault, structured it wrong.

Top & Bottom Pin (Pin 1 & 3):
5.150 KΩ

Middle & Bottom Pin:
0.77 - 3.92 KΩ min to max

Top & Middle Pin:
1.33 - 4.47 KΩ min to max
 
Did the resistance change smoothly when you rotated the sensor? The ECU's throwing an error, so there's something about this sensor it doesn't like.
 
Did the resistance change smoothly when you rotated the sensor? The ECU's throwing an error, so there's something about this sensor it doesn't like.

Sure did.
Seemed to behave correctly AFAIK.
 
Went to local LKQ, picked up a TPS and MAP sensor.
TPS turned out to be incorrect (even though the Chrysler Cirrus seems to use the same model.
-When inserting the original TPS, I drop it in smoothly, and rotate just a few degrees counter-clockwise (looking down at the TPS, screws vertical) in order for the holes to line up. It seemed like dropping it in the other end of the spectrum would not allow it to line up with the screw holes appropriately.
-Is this the correct method of installing?

MAP is the exact same part, but behaves the same.
-When inserted in the intake manifold and connected to the harness, car dies almost instantly.
-When MAP sensor is disconnected, car runs the same as the video, can stay alive for a few mins, can rev and accelerate, throttle is responsive
-When MAP is connected but removed out of the intake manifold, the car starts and instantaneously revs to above 4,500 rpm.

Intake Manifold Vacuum Line Tee
In the attached photo, there's a three tee vacuum going from left to right:
Left: attached to fuel rail (fuel injector pressure regulator?)
Middle: capped off (thinking this was capped off when the pulsed secondary air injection system was removed)
Right: EGR valve
 

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