2000 venture po300 code : "misfire"
March 1st, 2017, 8:53 PM
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2000 venture po300 code : "misfire"
Hello. I need help with my van. It idles rough but when you give it gas it smooths up . I've changed the fuel filter, all spark plugs and wires, cleaned the throttle, new air filter, listened to the fuel injectors (seems ok), and cleaned the idle air valve. Originally it had the code po303 ( cylinder 3 misfire) and I read somewhere to switch a coil pack and see what's happens. I did. Still idles rough but smooths out like before. HOWEVER, NOW IT READS PO300 (random misfire). I'm assuming its the coil packs and module. Before replacing them with new ones tomorrow (about $200 ouch) I'm looking for any other suggestions. Thank you.
March 3rd, 2017, 12:34 PM
#2
$200 is steep. I paid $40 for each at the parts store. If I pulled them at a junkyard I'd probably pay $20 or less for all 3.
Before you go replace all 3 coil packs, remove the one that you swapped from cylinder 3 and replace only that unit. The reason is that it has most likely caused the misfire on two cylinders it is now on.
These type of coils each fire on 2 cylinders. When the one coil misfires on a cylinder it is most likely causing a misfire on both cylinders in which it controls spark to.
Also, have you considered cleaning the mass air flow sensor? There's a specific "Mass Air Flow Cleaner" that comes in a spray can. This is a largely overlooked component that controls many important engine and even transmission functions. It has tiny resistors inside that measure incoming air flow. When debris begins to cover these resistors, the PCM detects less air flow and will respond by injecting less fuel in the engine creating a lean condition. I've had this cause a misfirr but generally a random misfire. These resistors you need to be very careful with when spraying or handling the MAF.
It is hard to determine if you have a clogged fuel injector without watching the spray pattern. I have a homemade injector machine I use to find if an injector is sticking open or has a clogged nozzle. Other than using this method, I'd never have the abiility to determine if an injector is clogged or sticking. As many times that I've used this machine, I'd have to say that it's not uncommon to find a faulty injector in an engine that is running fine. But for your issue, I'd be safe to say it is not an injector.
Before you go replace all 3 coil packs, remove the one that you swapped from cylinder 3 and replace only that unit. The reason is that it has most likely caused the misfire on two cylinders it is now on.
These type of coils each fire on 2 cylinders. When the one coil misfires on a cylinder it is most likely causing a misfire on both cylinders in which it controls spark to.
Also, have you considered cleaning the mass air flow sensor? There's a specific "Mass Air Flow Cleaner" that comes in a spray can. This is a largely overlooked component that controls many important engine and even transmission functions. It has tiny resistors inside that measure incoming air flow. When debris begins to cover these resistors, the PCM detects less air flow and will respond by injecting less fuel in the engine creating a lean condition. I've had this cause a misfirr but generally a random misfire. These resistors you need to be very careful with when spraying or handling the MAF.
It is hard to determine if you have a clogged fuel injector without watching the spray pattern. I have a homemade injector machine I use to find if an injector is sticking open or has a clogged nozzle. Other than using this method, I'd never have the abiility to determine if an injector is clogged or sticking. As many times that I've used this machine, I'd have to say that it's not uncommon to find a faulty injector in an engine that is running fine. But for your issue, I'd be safe to say it is not an injector.
Last edited by markfothebeast; March 3rd, 2017 at 12:55 PM.
March 3rd, 2017, 7:01 PM
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Thank you for all the great info!
I ended up taking the ignition module with all the coil packs to the two parts stores, where they both said the module wasn't any good. As for the coil packs, I don't have a helper to crank the engine while I test for spark (I tried checking for spark with the engine running, bad idea) so to save time and gain piece of mind, I replaced all three, plus the module. I didn't want to risk getting a bad coil from the junk yard and spending more time and money on gas for it, so I bit the bullet.....and guess what? It now runs like new! Even with 257k miles on it :-) no, that is not a typo.
I've checked the MAP in process of having to pull the engine forward a few times and it looks good. I didn't know they made a cleaner for that so now I know!
I ran sea foam through everything but I tell everyone how pleased ive always been with wal-marts $20 fuel injection cleaning service. I had a chevy s10 in the past that when it started to stutter (about once every two years), I would get it done and it would stop. I'm wondering what process you've configured of checking them? Dont you have to take the heads off for that??
I ended up taking the ignition module with all the coil packs to the two parts stores, where they both said the module wasn't any good. As for the coil packs, I don't have a helper to crank the engine while I test for spark (I tried checking for spark with the engine running, bad idea) so to save time and gain piece of mind, I replaced all three, plus the module. I didn't want to risk getting a bad coil from the junk yard and spending more time and money on gas for it, so I bit the bullet.....and guess what? It now runs like new! Even with 257k miles on it :-) no, that is not a typo.
I've checked the MAP in process of having to pull the engine forward a few times and it looks good. I didn't know they made a cleaner for that so now I know!
I ran sea foam through everything but I tell everyone how pleased ive always been with wal-marts $20 fuel injection cleaning service. I had a chevy s10 in the past that when it started to stutter (about once every two years), I would get it done and it would stop. I'm wondering what process you've configured of checking them? Dont you have to take the heads off for that??
March 3rd, 2017, 9:12 PM
#4
Fuel injector cleaning formula in my perspective is a marketing scam. If you look at the chemicals formulated in each one, these are typical chemicals you can purchase at a hardware store. I have 2 methods of cleaning injectors. I remove the tiny filter and blow them out backwards with a momentary switch and a fuel pump using either pure acetone, diesel, or kerosene while connected in a fabricated fuel rail. But I have welded together an entire setup. The 2nd method is a mix of "my" cleaning chemicals 50/50 with gasoline, disconnect the fuel pump relay, plug in to the fuel rail ON the vehicle, and force the liquid in to the rail with pneumatic pressure and start the vehicle. Only 2 methods I've found that actually fix the injector spray patterns.