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| Misfire from hell http://www.club323f.com/forum/viewtopic.php?f=58&t=57921 |
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| Author: | pappy_mcfae [ Wed Jun 18, 2014 10:27 pm ] |
| Post subject: | Misfire from hell |
I'm looking for insight into my misfiring 89 323. It has progressively gotten worse over a period of about a month and a half. It is a dead miss, and it seems to roam from cylinder to cylinder. I've tuned it up, and I just got a new coil hoping the original was weak. I'm down to it either being the ECM or the distributor. Basically, it has a random misfire that causes lots of noise and lots of stumbling, and I'm sure eats a lot of gas. There are times it will clear up, and there are other times that I feel like I'm driving a Model A. I have a 'scope, and it's being shipped to me from the last place where I lived. I'm just wondering if this is an issue that others have had, and if so, what was the final resolution? What did it turn out to be in your case? Are the distributors and ECMs noted for any specific design weaknesses? For instance, the ECMs on first-gen Mitsubishi Eclipses are noted for decoupling and power supply caps leaking electrolyte, and damaging the PC board. Thanks in advance for answering. Cheers, Pappy |
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| Author: | pappy_mcfae [ Wed Jun 25, 2014 10:07 pm ] |
| Post subject: | Re: Misfire from hell |
The scope arrived, and let me know that the pulses coming from the distributor to the coil are quite regular. I am going to recheck things when it's a little cooler out this evening. I've been brushing up on reading ignition patterns, so maybe I might be able to figure out what's actually going on here. Cheers, Pappy |
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| Author: | pappy_mcfae [ Sun Jul 20, 2014 2:19 am ] |
| Post subject: | Re: Misfire from hell |
I suppose perhaps it's time to rephrase the question. Which sensor(s) (or is it the ECM), when failing, would cause backfiring during deceleration? My understanding of the system is that during deceleration, fuel injection is cut off completely. If I am getting backfiring during decel, that tells me that fuel is being injected. If that's the case, that would tell me that if I get rid of the backfire on decel, that should get rid of my issues entirely, since they appear linked. I looked at the primary ignition on my oscilloscope, and I saw nothing that would make me suspect the ignition system. After replacing everything (coil, cap, rotor, wires, plugs (and an anti-fouler)), I am left with the conclusion that it's a fuel delivery issue. The presence of a backfire at decel seems to confirm that. While the engine isn't in the best mechanical shape, I seriously doubt the present issue is mechanical in nature. So, for all the techs out there, what would cause that? What is the most likely offender? I am not made of cash, and I would really like to get it out on the road for more than when I know I'm going to be going highway speed. I'd love to get it back to how it was when I got it: smoking tires and scaring little old ladies. Thanks in advance. Cheers, Pappy |
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| Author: | jinglebells [ Mon Jul 21, 2014 10:11 pm ] |
| Post subject: | Re: Misfire from hell |
If my memory is right then an '89 BG has a carburettor, not injection. So maybe it's just the fuel solenoid? A guess, but I doubt it's an expensive part. Or it could be a vacuum leak from one of the multitude of pipes around that area... |
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| Author: | pappy_mcfae [ Tue Jul 22, 2014 6:19 am ] |
| Post subject: | Re: Misfire from hell |
It's fuel injected. Cheers, Pappy |
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| Author: | HMT [ Tue Jul 22, 2014 10:46 am ] |
| Post subject: | Re: Misfire from hell |
Did you check both water temperature sensors? If one is faulty the ECU might assume the engine is cold and flood it with fuel. Also i'd check the air flow meter. |
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| Author: | pappy_mcfae [ Thu Jul 24, 2014 7:56 am ] |
| Post subject: | Re: Misfire from hell |
So, I've had to drive the 323 the past two days, as my Saturn was having difficulties with its smog check. After looking at a few videos, I decided I'd see if giving the AFM a whack would change things. I gave it a few, but only one time did it make the engine shudder. Proof enough for me. Then came today. I had to drive a few places, and low and behold, the engine was actually running pretty good in comparison to the way it's been running. Sure, there were a few stumbles left, but for the most part, it was running really smoothly in the range where just two days ago, it was snorting and popping to beat the band. I am now inspired to open the AFM, and do a little pot wiper arm bending. While I know I'm going to have to eventually replace the AFM, after watching the videos, I smiled. In my youth, I used to rejuvenate old pots in the same way. Open it up, clean the track, and bend the wipers so they fall into unused resistor material. If I can get another few thousand miles out of it, bonus! That will allow me time to replace all the other sensors (something I planned from the get-go), which are cheaper. Eventually, I'll buy a new AFM. Until then, I'll see how much use I can get out of the undamaged tracks in this one. I am really amazed at how badly that thing can make the car run. I'm further amazed that as bad as it is, it didn't set any codes, or ever light the check engine light. Curious. Cheers, Pappy |
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