That top left number is 150, not 100. As a master craftsman of sloppy handwriting, I can see it clearly.
Rough idle, P0300, Help!
- Thread starter wiscomick
- Start date
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My 97 4.3 had the dreaded P0300, rought idle, a few months back, running great one day, next not so much.
Had just put in new O2's (4) a week or so back.
Did same as you, cap, rotor, leads and plugs, no dif.
Put the old stuff back, including 02's, checked dist for play etc, looked good.
Did the compression test, mine were even 200-210psi.
Next, check fuel pressure, good, check how lokng it held pressure, good.
Used a timing light to check for spark, all good.
Getting pissed now ... only have a scan tool.
Go old school, put the new plugs back in, run for a bit, check plugs.
#1 absolutely clean, rest aren't.....
Still old school, pull leads one at time while running, see what happens.
#1 makes no difference, all the other do.
Pull lead #1 put in new plug to see if I can see it spark, yep.
replace spider, back in action.
From the good info here, going to get a laptop and that obd1/obd2 cable (http://aldlcable.com/products/aldlobd1u.asp) so it shouldn't take so long to sort out the codes.
post up if you get it sorted.
Had just put in new O2's (4) a week or so back.
Did same as you, cap, rotor, leads and plugs, no dif.
Put the old stuff back, including 02's, checked dist for play etc, looked good.
Did the compression test, mine were even 200-210psi.
Next, check fuel pressure, good, check how lokng it held pressure, good.
Used a timing light to check for spark, all good.
Getting pissed now ... only have a scan tool.
Go old school, put the new plugs back in, run for a bit, check plugs.
#1 absolutely clean, rest aren't.....
Still old school, pull leads one at time while running, see what happens.
#1 makes no difference, all the other do.
Pull lead #1 put in new plug to see if I can see it spark, yep.
replace spider, back in action.
From the good info here, going to get a laptop and that obd1/obd2 cable (http://aldlcable.com/products/aldlobd1u.asp) so it shouldn't take so long to sort out the codes.
post up if you get it sorted.
Dirty Bird
Newbie
Had an Astro van with similar problem. Turned out to be a bad distributor. It was made of ABS plastic and wobbled around a lot after a hundred K or so miles. Also needed intake manifold gaskets because I used regular antifreeze instead of Dex Cool. Regular antifreeze ate through Factory intake manifold gaskets causing O2 sensors to constantly foul out. anti freeze was getting sucked into engine so I never saw the leak.
My apologies for the crappy handwriting. As Erik said, it's a 150.
I replaced the intake manifold gaskets about 2 months ago, and didn't replace the clearly OEM spider at that point. I'm heavily leaning towards it being the issue at this point due to the input received here and knowing that it's the original one. At this point, it needs to be replaced regardless of whether it's the actual issue, but with all the new parts I've put into this thing in the last few months I have my doubts about it being much else. I replaced anything I could get my hands on when I did the gaskets.
A crack in the injector tube leaking excess fuel anywhere near the 3/5 close-together intake ports would likely come up as a misfire, would it not?
The distributor did have a noticeably worn gear when it was pulled to do the lower intake gaskets, but wouldn't the symptoms of a worn gear be misfires on all 8 cylinders?
Another thing to note is that as I limped it home, it was pretty smooth at speed, but idle and from-stop acceleration was screwy. Another indicator to me that the spider is pissing fuel where it shouldn't be going.
I replaced the intake manifold gaskets about 2 months ago, and didn't replace the clearly OEM spider at that point. I'm heavily leaning towards it being the issue at this point due to the input received here and knowing that it's the original one. At this point, it needs to be replaced regardless of whether it's the actual issue, but with all the new parts I've put into this thing in the last few months I have my doubts about it being much else. I replaced anything I could get my hands on when I did the gaskets.
A crack in the injector tube leaking excess fuel anywhere near the 3/5 close-together intake ports would likely come up as a misfire, would it not?
The distributor did have a noticeably worn gear when it was pulled to do the lower intake gaskets, but wouldn't the symptoms of a worn gear be misfires on all 8 cylinders?
Another thing to note is that as I limped it home, it was pretty smooth at speed, but idle and from-stop acceleration was screwy. Another indicator to me that the spider is pissing fuel where it shouldn't be going.
RawbDidIt
I'm Awesome
Yeah, the weird thing is a few of your spark plugs look like they're indicating rich conditions to me, but only cylinders 3 and 5 are misfiring. It's possible the o2 sensors are throwing information at the ECM to lean out on bank 2 and compensate enough to prevent a misfire, but without the fuel trim numbers, it's just conjecture.
Sent from my SM-N976V using Tapatalk
You'll like the MPFI conversion. I sold my Suburban this weekend, and it has the MPFI conversion. In addition, when I rebuilt the motor I balanced the rod and piston assemblies. The brother-in-law of the guy buying it was impressed with how smooth it ran. Too bad the block was cracked...
I think at this point the MPFI is something that needs to be done either way, so as much as it's kinda a 'throw parts at it' situation, it's probably smart to put it in anyway. Last thing I want is a leak that dumps a **** ton of fuel into the crankcase and washes out the rod/main bearings. Already had that happen years ago on a Blazer.
Only other thing I could possibly replace at this point is the distributor, but I don't think that's the cause of this particular issue seeing as how I'm seeing 0 misfires on any other cylinders other than 3/5.
Only other thing I could possibly replace at this point is the distributor, but I don't think that's the cause of this particular issue seeing as how I'm seeing 0 misfires on any other cylinders other than 3/5.
OutlawDrifter
Long Roof K2500 Driver
Sorry, I did not read through every reply.
I once chased this code on a LS swap, ended up being a ground wire at one of the injector clips...took a noid test light to find it. Definitely could be a wiring/ground issue in your injection setup.
+1 for the upgrade to the newer spider injection
I once chased this code on a LS swap, ended up being a ground wire at one of the injector clips...took a noid test light to find it. Definitely could be a wiring/ground issue in your injection setup.
+1 for the upgrade to the newer spider injection
Scott Martin
Newbie
I get these problems a couple of times a year and it's usually resolved with plugs and wires and a new cap and rotor, for some reason every time it rains or if it's humid out my Yukon runs like total **** but if it's dry then it runs great.
First two things I'd look at:
1. PCV operating properly? Not restricted, pulling reasonable air through the engine? Crankcase vent attached to air ducting as intended, so it can't pull "wet" air from road splash? If the PCV doesn't pull enough fresh, clean air through the crankcase, "wet" air/blowby can pass through the distributor bushings so that the inside of the cap gets wet and becomes conductive. This is especially a problem when the distributor bushing get worn; and that in itself is a common problem on Vortec distributors.
2. Missing rubber seal/weatherstrip where the rear of the hood would seal to the cowl? Allows rainwater to drip onto the distributor area.
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