by "Wrong Wheel Drive (41%)" (rduncan5678)
Published 10/12/2017 at 09:00
by "Wrong Wheel Drive (41%)" (rduncan5678)
Published 10/12/2017 at 09:00
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STARS: 0
So my 1998 Dodge Neon is still throwing a check engine light for a random misfire (P0300). And I have done many things to attempt to fix this. But alas, after all of my work the code has come back to haunt me again! Here is a list of everything I have done:
Changed spark plugs and wires (properly gapped too)
Changed the coil
Changed the Crank position sensor
Changed the rear O2 sensor (got a separate code, now gone)
Had a shop replace my fuel pump (car wouldnt run, they told me my intake gasket had a leak which was causing my P0300 and P0301 codes)
Changed the intake gaskets (both the upper and lower gaskets) and also cleaned out the intake while I had it off to clean the passageways. Those old gaskets were REALLY bad. P0301 has gone away and has not come back.
Turned the car on and it ran like shit, like a huge vacuum leak. Sprayed brake clean around the intake and injectors. Found that Cyl 1 injector was leaking. After pushing it in a bit more, spraying more brake clean and running it, this problem went away. Then idles smoother and quieter than ever before!
So then I drove home from the hobby shop I do my car work at and it just ran beautifully. Before it ran like dogshit when revving it out and now it happily went out to 6k and actually felt kinda quick! First time I got to enjoyable drive the car and really beat on it a bit. Made it about 25 minutes into my 30 minute drive home and then the dame flashing light came back on for P0300. No noticeable change in performance, just that damn light. Had it blink at me again the next day on the way to work, around the same amount of time into the drive. Now I am stuck scratching my head trying to figure this shit out.
Maybe the problem is when it heats up enough, a small vacuum leak occurs somewhere, causing a random misfire?
Maybe that injector that gave me trouble needs to be replaced? Bad o ring or just faulty in general? Not sure if I need/should do all four then.
Maybe something entirely different is at play here? Messed up exhaust valve springs? Some other crazy problem? A wiring fault? A different sensor?
At this point it runs pretty good so I am at a loss as to why it would be throwing the code. Im gonna try playing with brake clean some more and unplugging cylinders while running to see if any particular one affects the idle. It will require some much finer troubleshooting to figure this crap out. And really the only reason to fix this is for resale value.
"nerd_racing" (nerd189)
10/12/2017 at 09:08, STARS: 0
Just out of curiosity, what would you be asking for it? I’ve always had a soft spot for the RT Neon Coupes. I’d also check the crank position sensor again for crud or possibly re-gap it. The thickness of a business card is usually the right gap.
"Rustholes-Are-Weight-Reduction" (rustholes-are-weight-reduction)
10/12/2017 at 09:11, STARS: 0
MAP sensor and wiring? I had all kinds of issues on a car once because the wiring for the MAP sensor had an issue. Car was probably overcompensating for the faulty signal
"pip bip - choose Corrour" (hhgttg69)
10/12/2017 at 09:15, STARS: 0
pull the injectors and get them cleaned properly put new seals on them and see how it goes
"Wrong Wheel Drive (41%)" (rduncan5678)
10/12/2017 at 09:20, STARS: 0
Well I paid $1000 for it so I’d like to get at least that amount for it lol. But I think I should be able to get more if I get everything running right and provide the receipts and stuff for all the crap I’ve replaced. Hoping for like $1200-$1300 if I get everything done. But I will list it for like $1800 and REALLY hope someone wants to pay like $1500. That is pie in the sky money though and I really gotta get it perfect lol.
The crank position sensor just bolted down, I didnt think there was a way to set a gap on it? It mounts flush with the rear of the block. There is quite a bit of oil on and around it, could be something to try cleaning. I know on my Miata I had to gap the crank sensor correctly, but it didnt mount flush inside a hole like this does.
"Wrong Wheel Drive (41%)" (rduncan5678)
10/12/2017 at 09:21, STARS: 0
Is it worth cleaning injectors instead of just replacing them? Unless I can easily clean them at home. New ones run about $40 each though so I didnt want to replace all of them really. I saw rebuilt ones for about $30.
"Wrong Wheel Drive (41%)" (rduncan5678)
10/12/2017 at 09:23, STARS: 0
I would think the car would run like shit because of it. And isnt there another code for the MAP sensor? Im only getting the P0300. And it must be actually misfiring since it does blink on occasion. I’ve also read that the accessory belts could cause the code somehow. I am entirely missing my power steering/AC belt since neither system is running and I took it off. I guess I could fix that.
"pip bip - choose Corrour" (hhgttg69)
10/12/2017 at 09:25, STARS: 0
might get away with cleaning them.
try new seals first.
"Powershiftmedia-ResidentDSMGuru" (matt-powershiftmedia)
10/12/2017 at 09:26, STARS: 0
Gonna solve your problem for you, it’s the ECU. Trust me, there’s companies on eBay that rebuild them. We went through this not long about. Pay the 150-250 and thank me later, I promise you I’m right on this.
"Wrong Wheel Drive (41%)" (rduncan5678)
10/12/2017 at 09:34, STARS: 0
But thats the only code it would throw if the ECU was shit? And nothing else would go wrong?? That seems like quite a hefty expense to end up with.
Its showing a pending 301, 302, 303, 304. And the logged 300. Im thinking it should be something actually wrong, either vacuum related or electrical connection. Cant notice a misfire but I think there might be a barely perceptible one, I just have to listen closer.
"Wrong Wheel Drive (41%)" (rduncan5678)
10/12/2017 at 09:35, STARS: 0
Seals as in the orings?
"Powershiftmedia-ResidentDSMGuru" (matt-powershiftmedia)
10/12/2017 at 09:46, STARS: 0
Yep it’s always the misfire code. Every single time.
"Rustholes-Are-Weight-Reduction" (rustholes-are-weight-reduction)
10/12/2017 at 09:58, STARS: 1
P0107 I think. I’m not sure if it could cause misfires though. I mostly had a rough idle, bad throttle response, and terrible fuel economy
"Wrong Wheel Drive (41%)" (rduncan5678)
10/12/2017 at 10:03, STARS: 0
Thats wild lol. And if I never changed it? Would something get worse. Im having trouble finding this anywhere else on the neons.org forum or elsewhere. Im assuming you are speaking from first hand experience though?
Im more curious if there is a way to definitively prove it.
"Wrong Wheel Drive (41%)" (rduncan5678)
10/12/2017 at 10:19, STARS: 0
Well yeah thats what I was thinking would be the case. Id have those obvious problems. It idles smooth as butter now after the intake gasket.
"Powershiftmedia-ResidentDSMGuru" (matt-powershiftmedia)
10/12/2017 at 10:25, STARS: 1
I’ve seen it on four different neons. In all four cases, a rebuilt ECU remedied the entire issue.
"Urambo Tauro" (urambotauro)
10/12/2017 at 10:28, STARS: 0
Any chance that it’s just a solder joint or two that one could easily remedy after opening the ECU?
"Dash-doorhandle-6 cyl none the richer" (dash-doorhandle-and-bondo)
10/12/2017 at 10:30, STARS: 1
been through this, changed all the sensors etc, after 6 or 700 dollars it was the ground strap from the head to the rad support. it loooked fine but the corrosion took effect between 2500 and 3500 rpm and gave the random multiple misfire code. wasn’t a neon but the same vintage getting old.
"Wrong Wheel Drive (41%)" (rduncan5678)
10/12/2017 at 10:42, STARS: 0
Hmm, I think thats the ground strap immediately visible at the front of the car. That would be an easy fix to try!
"Wrong Wheel Drive (41%)" (rduncan5678)
10/12/2017 at 10:43, STARS: 0
Isnt that in effect, rebuilding the ECU?
"Wrong Wheel Drive (41%)" (rduncan5678)
10/12/2017 at 10:44, STARS: 0
Hmm, I wonder if I can get one cheap. That seems like an easy change since its right there in the engine bay. Does it just plug and bolt right in? Doesnt something need to be flashed and such?
Found a ridiculously cheap one used on ebay. I wonder if that route is unsafe to try and go. I feel like it could end up being a crap part if these commonly fail.
"Dash-doorhandle-6 cyl none the richer" (dash-doorhandle-and-bondo)
10/12/2017 at 10:45, STARS: 0
cheapest and most effective part of my 700 dolla fix regimen
"Urambo Tauro" (urambotauro)
10/12/2017 at 10:49, STARS: 0
Yeah, but some modules are known to have simple solder joint issues. Others require de-soldering components to install new ones. I tried to rebuild my CCRM earlier this year, but I couldn’t even look up the right parts to fix it. Newer modules are more difficult to work on, and need the touch of an experienced hand.
"nerd_racing" (nerd189)
10/12/2017 at 11:02, STARS: 0
That’s perfectly reasonable for that car. I don’t think you will have a problem selling it at that price.
That’s interesting. I would make sure it is really really clean, does it read off of the ring gear on the flywheel then?
"Powershiftmedia-ResidentDSMGuru" (matt-powershiftmedia)
10/12/2017 at 11:05, STARS: 0
I think it’s the newer ones that need flashed. When we did it on a newer one we literally sent the vin number and the ECU in. Done. :)
"Wrong Wheel Drive (41%)" (rduncan5678)
10/12/2017 at 12:13, STARS: 0
Im not sure exactly how it works, id have to look into that. Its kind of hard to actually see what its doing since you have to just reach up above the oil filter blindly to get to it. I know on my Miata the car doesnt start if you do not gap it correctly though, so it seems odd that would be my problem here without obvious symptoms.
Im thinking a ground strap problem or the PCM/ECM are likely culprits. Along with maybe dirty/bad seal injector(s). Ill attack the ground strap and that funky injector first.
"pip bip - choose Corrour" (hhgttg69)
10/12/2017 at 16:38, STARS: 0
Yep