Cylinders 2&3 no spark (coil pack and plugs good)

[c_riggan]

I started getting a misfire and the engine felt like it was running on fewer cylinders than normal. After looking into it I have found it is not running on 2 and 3. The plugs are good, and I have replaced the coil packs. It started intermittent, but is progressively getting worse (now it rarely runs on all 4).

While it is running like this, the scan tool shows proper RPM, however, the tach is showing around 500 to 1000 less RPM, and there is absolutely no spark on 2 and 3. It's not caused by fouling plugs, gaps are correct. I have ohmed out the coil packs (good) and the plug wires (good). I am currently stumped.

I have searched the forums (maybe i skipped across the answer), but have found nothing for this problem.

Could anybody provide some insight on this problem?

Thanks for the time,

Chris


Vehicle is a 96 GST

 

[Detective Coating]

Have you checked the Power Transistor? Make sure all of your connectors are actually connecting, sometimes they need wiggled a bit.

 

[SlushBoXRacer]

+1 on the power transistor. . they get old and worn out. unplug it and check for corrosion in the connection (like a white crusty film)

 

[luv2rallye]

PT test: http://www.dsmtuners.com/forums/articles-electrical-wiring/229419-how-test-power-transistors.html

 

[XiKeiyaZI]

Just had the same issue with the PTU on my Stealth.

Exchanged for a new one and WOW.. All 6 Cylinders again! ;P

But yeah.. likely just the PTU. Thank god they're a dime-a-dozen for our cars..

 

[steele_verus]

Power transistor also powers the tach, I believe. Your tach being off is a big indicator of a bad transistor.

 

[GRAVEDIGGER]

If the power transistor doesn't fix it you may have a bad coil driver in your ecu or just a bad/loose wire. The ecu sends an on/off signal to the power transistor to make the desired coil fire. If that signal is not getting to the power transistor you will get no spark on that coil. Just something to think about if the transistor is not your problem.

 

[c_riggan]

Thanks to everybody for the replies. I have removed and tested the PTU and turns out it's bad. Ordered a new one today, should be in friday. Was getting continuity on the transistor for 2&3 and also 1&4 with NO power applied and with power applied.

 

[Chrispy0530]

I just came out of this problem as well. Instead of being the PTU, it was actually the connector that plugs into it. Stuck a small wire brush in it to clean it out a bit, and all 4 fired up again. It was like magic/music to my ears.

I'll be going around to Junk Yards looking for another connector, as the car itself while driving has a bit of the ignition break up/miss while driving for a split second. Still a huge improvement.

 

[tode5tool]

Hey, I dont meen to jack your thread. but ive got the same issue. I replaced the coil pack on the 2 and 3 cylinders not the other though, and ive replaced the PTU, and ive got a brand new 99 eproms ecu in my car and it still wont fire on all 4. the plug is kinda jacked up though. maby thats it. IDK what do you guys thingk? can a bad ground make this happen to?

 

[Grady28]

My Stealth (V6) is running on 4 cylinders right now, ive changed all coils packs even swaped the wiring harness and still coil pack 3 and 6 is not sparking, ive changed the plugs, put my ECU in my friends 3000gt and his car ran fine, I can not think of anything it could be anymore, someone please help!

 

[luv2rallye]

Ignition module? Wiring from ECU to ignition module to coil?

 

[XiKeiyaZI]

My Stealth (V6) is running on 4 cylinders right now, ive changed all coils packs even swaped the wiring harness and still coil pack 3 and 6 is not sparking, ive changed the plugs, put my ECU in my friends 3000gt and his car ran fine, I can not think of anything it could be anymore, someone please help!

Hey hey.. we have the same car.. and I had the same issue.

Below the Coil packs there is a small PTU, bolted down to the block by 2 bolts.

Take it off. I PROMISE you that you're issue. You're going to have to find another. They are VERY expensive... like $250 expensive. Your best bet is craigslist, ebay, or someone with a junked R/T.

I just changed mine and resolved the issue, but it screwed up my injectors and the car runs like complete crap now. Worst issue I've ever dealt with. I'll be burning this car soon if I don't get it fixed this weekend.

Anyway.. good luck... consider fixing and selling your Stealth ASAP.

 

[luv2rallye]

The ignition module is also known as the power transistor unit (PTU) or ignitor (just so you know what to ask for). Try swapping with another first if you can before spending all that $ and finding that's not it. However I agree it is most likely the problem.

 

[joe sobo]

last time i had a issue with no spark on 1 and 4 cyl., it turned out to be a cracked cam position sensor, from when i redid the head, and must of banged it. i did the 1g cas, and it started right up with no issues.

 

[mtchll]

similar thing happened with me and my car, ended up being the power transistor, definately check it (agreed with everyone else who mentioned it prior)

 

[smrogers5771]

Did you check the compression? or pull the plug wire off and use a plug to ground it to the car to check for spark? if no spark there then hmmm.... CAS?

 

[tweek814]

Power transistor also powers the tach, I believe. Your tach being off is a big indicator of a bad transistor.

thanks man, this post saved the day for me. i was diagnosing the same problem, my tach read 0rpm at idle. luckily i have a gsx parts car and switched out the PTU and shes back on the road.