The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support Morrison Fabrications
Please Support Fuel Injector Clinic

need help soon car misfiring and stalling

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

eclipsek17

15+ Year Contributor
130
5
Aug 1, 2004
All over, Arizona
I have a 95 eclipse gst-x, with a 98 black case ecu and 98 cas. When I start the car, fires right up, it begins misfiring on all cylinders, sounds like is it constantly firing and then after about 30 seconds it stalls. My tach is also fluctuating, it will read idle speed then at times drop to 0 and stay at 0 while car still running. I thought maybe the PTU was bad so I replaced that, but still doing it. I replaced cam sensor also. I regrounded the PTU just to male sure it had good ground. I have no idea what is going on or where to start testing next. I need to figure out as soon as possible, this is my daily car. Also I have a maft installed, and my front main seal is leaking. I had thought maybe the oil on the crank sensor or maft was also causing my problem but I need to know how to test to verify my problem as well. Any help will be very appreciated.
 
Also was reading through some forums and was wondering if my wire tuck could have anything to do with it. I did a wire tuck about a year ago, after most of my wiring caught fire and i had to replace the whole harness. Since the tuck was done, i have drove the car for about 4 or 5 months with minor issues, random misfires not very often, oil leak from front main seal. The random misfires used to only being during boost though and it progressively got worse to where in 3rd, 4th, and 5th gear would start constantly firing and I would have to hold clutch when it started let it drop to idle then it would go away. I just wired in a new plug for the PTU as well, and it seemed to help for about 2 or 3 weeks, now it is worse than it has ever been.
 
Depending on how much metered air is escaping from the intake tract symptoms could range from fluctuating idle, to stalling as you described. I would start by making sure all couplers and clamps are tight and that there are no obvious vaccum leaks.
 
All intercooler piping, couplers, and vacuum look good. I was able to narrow my search down a little with an rpm drop test and realized my problem is centralized on cylinder 1 and 4. It seems like cylinder 2 and 3 are the only cylinders working at the moment. I tried swapping coil pack from the one that runs 1 and 4, with the one that runs 2 and 3, but still nothing on cylinder 1 and 4, so it is not the coil. Seems like the signal going to the coil. Also tested the crank sensor because I was wondering if the oil on it is making it short out and maybe interfering with the signal to the coils. Power and ground on crank sensor look good. I tested signal from crank to ecu and noticed it was a little off. According to Alldata the crank signal to ecu should read .4 - 4 volts during cranking and 1.5 - 2.5 volts during idle. While cranking the voltage was in range, but then during idle the voltage was fluctuating between 1.2 and 1.3 volts. Alldata said that if there was a problem with voltage while cranking then suspect problem with ecu and if it was in range with 1.5 -2.5 volts suspect problem with crank sensor wiring or crank sensor. I went and bought a new crank sensor and am going to open up timing cover now to replace it and also finally replace my front main seal while im in there, timing belt, and tensioner, just because timing belt has been soaked in oil too and I have new timing belt and tensioner already anyway.

This is where I am at with it now, any other ideas or anything else you think I should test please let me know. Also I tested the wires going from ecu to ptu and noticed a big difference between wire that runs ignition for cylinder 1 and 4, and 2 and 3. 1 and 4 was reading about 1.10 volt range and 2 and 3 was reading about .08 volt range while idling. I also dont know how accurate these readings are though because of how much the idle is fluctuating and how rough the idle is right now before it stalls out. I was also thinking that may have something to do with voltage difference, please correct me if I am wrong.
 
Going to be working on this all day and probably all night until it is figured out, so I will be checking back on here for help throughout the day every so often. I know worse case there is a chance my ecu could be messed up as well. Also noticed and was wondering when the car is put to the on position, not running, will the ptu get warm to the touch on the metal bracket? If not, would that mean it is possibly faulty or do I have a short to it somewhere?
 
Just got done changing crank sensor and fixing all my leaking seals, started the car up with no luck. It is still misfiring really bad and stalling. It is running only off 2 cylinders (cylinder 2 and 3). I can disconnect cylinder 1 and 4 and it doesnt effect anything, it acts the same with them disconnected. If either 2 or 3 is disconnected though it wont even start. I dont know what else to check. Unless the ecu or ptu is just bad, but i cant find anything on testing either one.
 

Attachments

  • dsm ignition transister.jpg
    dsm ignition transister.jpg
    23 KB · Views: 601
Last edited:
The ignition power transistor module comes to mind, maybe it's gone bad, or it has a loose connection.
how to test it [see link]
http://www.dsmtuners.com/threads/how-to-test-the-power-transistors.229419/
it looks something like this [see image below]

Had this exact problem when I put my car back together, two cylinders didnt fire. Does your tach read 1/2 what it's supposed to? If it does the transistor is bad. All 91+ transistors are the same. However, not all coil packs or coil pack brackets are the same, so keep that in mind. For instance a 1G coil and bracket from a 91 does not fit on a 1G intake with a 2G fuel rail.
 
I figured it out, my ecu was causing the problem. It looks like it was sending too much voltage to power transistor and was some how causing the 2 cylinders not to work. I was focused on the power transistor as being the problem, and did replace it but it didnt help at all for this one. Just got a different ecu put in and problem went away. At least all my sensors are new now (crank sensor, cas, tps, and ptu).
 
Yea I am really happy to finally get that oil leak taken care of, it was embarrassing. Did so much to clean up the engine bay and make it look nice, just to have the belts throw oil everywhere. I should have replaced it a long time ago, but after working on other peoples cars all day, I kinda lose motivation to work on mine at the end of the day.
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top