Cylinder 1 and 2 misfire.. got no ideas
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Cylinder 1 and 2 misfire.. got no ideas
This last Sunday, after getting 4 brand new tires put on my 03 Monte Carlo, with the 3800 series 2 V6 with 180k on it. it decided to break down. The car stalled out of nowhere and left me on the side of the road. The car would crank, start and run for a second or two, and stall. I noticed when it would start and run, it’d run fine — but stall. The next day I went to revisit the car and try to figure it out — now the car wouldn’t start. It would crank and try to start but it never successfully did it. I rolled it into a different area for me to look at further, but found nothing. The next day I went to the car with a scanner to check for codes, and I found p0300. After cranking the car I did get it to start, but only if I put my foot flat on the gas pedal. It would start, run very poorly with a flashing engine light, and then stall again but would restart if I put my foot flat on the gas pedal. The scanner showed cylinder 1 and 2 to be the misfiring cylinders. The fuel pump was replaced a month prior but I swapped it again with a known good pump — no change. I swapped the ICM with a known good one as well as with known good coils — no change. I’m stumped at this point as to what the problem can be.
Any ideas?
Any ideas?
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Yes, fuel pressure like carfixer007 said.
Also, does the tach needle indicate a couple hundred RPM while you are cranking?
How do you know the known-good fuel pump and coil are known good? I ask because it'* not often that folks have spares of these around and they are known good.
Also, does the tach needle indicate a couple hundred RPM while you are cranking?
How do you know the known-good fuel pump and coil are known good? I ask because it'* not often that folks have spares of these around and they are known good.
Last edited by CathedralCub; Feb 25, 2019 at 01:17 PM. Reason: Changed an "e" to an "a"
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If it starts and immediately stalls, could be a SECURITY problem.....
I would get a can of carb cleaner, have someone crank the vehicle, and then spray carb cleaner into the throttle body....if the car runs as long as you spray, and dies when you stop, you have a fuel delivery problem....either no pressure, or the injectors are not firing....if pressure is ok, then you probably have a security problem.....
Misfires on #1 and #2 cylinders....cylinder are on opposite sides, and use different coils........you need to check for spark at the ends of the ignition wires of coil 1/4, and coil 2/5 to see if you are getting spark....
I would get a can of carb cleaner, have someone crank the vehicle, and then spray carb cleaner into the throttle body....if the car runs as long as you spray, and dies when you stop, you have a fuel delivery problem....either no pressure, or the injectors are not firing....if pressure is ok, then you probably have a security problem.....
Misfires on #1 and #2 cylinders....cylinder are on opposite sides, and use different coils........you need to check for spark at the ends of the ignition wires of coil 1/4, and coil 2/5 to see if you are getting spark....
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Hey all, sorry for the (very) late replies and thank you all for your information.
An update on the car: Things went from bad to worse. I needed to get if off the side of the road and I don't have room at the house for a car that isn't usable at the moment, so I bit the bullet and had it towed to my mechanic. I wanted to get this thing back up and running because the spare 5.3 TrailBlazer is a gas hog. My mechanic went to take a look at it with his Snap On and the instant he went to crank the engine, it backfired through the intake and blew the entire upper intake manifold into a million pieces. So, the car is benched at the moment. I've been slowly working on getting it back together over the last few weeks but this polar vortex I'm stuck in makes it extremely hard to do just about anything outside.
CathedralCub, yes the tach does indicate a few hundred RPM when the engine was cranked and did respond to RPM when the engine ran. It was, however, very very bouncy. My guess is that this is due to the misfires. The ICM and coils came off of an Oldsmobile I used to own with the same engine. They were replaced on the Oldsmobile a year (ish) ago with a junkyard unit. The Oldsmobile has run like a top this last year with the junkyard unit but the trans finally gave out in the Oldsmobile. The engine ran amazing still so I just snatched the ICM and coils off of it before we sent it to the junkyard since I knew they were good. The fuel pump is the same story as it came out of a junkyard 03 Monte SS with the N/A 3800. The car got scrunched but still ran pretty good so I picked that out of the car before it went to the scraper as well.
Didn't get a chance to test fuel pressure before the intake exploded and now I'm stuck trying to find another fuel rail because the explosion bent the cylinder 2 side of the rail upwards and the rail is full of dents now.
Thanks again for all the replies and I'm sorry for getting back to you guys late. I'll keep everyone posted as I slowly get the car back together.
An update on the car: Things went from bad to worse. I needed to get if off the side of the road and I don't have room at the house for a car that isn't usable at the moment, so I bit the bullet and had it towed to my mechanic. I wanted to get this thing back up and running because the spare 5.3 TrailBlazer is a gas hog. My mechanic went to take a look at it with his Snap On and the instant he went to crank the engine, it backfired through the intake and blew the entire upper intake manifold into a million pieces. So, the car is benched at the moment. I've been slowly working on getting it back together over the last few weeks but this polar vortex I'm stuck in makes it extremely hard to do just about anything outside.
CathedralCub, yes the tach does indicate a few hundred RPM when the engine was cranked and did respond to RPM when the engine ran. It was, however, very very bouncy. My guess is that this is due to the misfires. The ICM and coils came off of an Oldsmobile I used to own with the same engine. They were replaced on the Oldsmobile a year (ish) ago with a junkyard unit. The Oldsmobile has run like a top this last year with the junkyard unit but the trans finally gave out in the Oldsmobile. The engine ran amazing still so I just snatched the ICM and coils off of it before we sent it to the junkyard since I knew they were good. The fuel pump is the same story as it came out of a junkyard 03 Monte SS with the N/A 3800. The car got scrunched but still ran pretty good so I picked that out of the car before it went to the scraper as well.
Didn't get a chance to test fuel pressure before the intake exploded and now I'm stuck trying to find another fuel rail because the explosion bent the cylinder 2 side of the rail upwards and the rail is full of dents now.
Thanks again for all the replies and I'm sorry for getting back to you guys late. I'll keep everyone posted as I slowly get the car back together.
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Looks like two possibilities.....
Leaking fuel pressure regulator......dumping fuel into the intake, and was ignited....
or,
Plugged cat.....when you continue to drive a 3.8 with a partially plugged cat, you create back pressure in the exhaust....this backpressure can unseat the EGR valve, causing hot exhaust gas to heat the top of the plenum above the EGR opening in the lower intake and it can blow a hole right through it....
Leaking fuel pressure regulator......dumping fuel into the intake, and was ignited....
or,
Plugged cat.....when you continue to drive a 3.8 with a partially plugged cat, you create back pressure in the exhaust....this backpressure can unseat the EGR valve, causing hot exhaust gas to heat the top of the plenum above the EGR opening in the lower intake and it can blow a hole right through it....
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Well it has been a busy couple of weeks! I've been slowly getting work done on the car and as of last Friday, it was running again. I replaced the upper intake manifold, grabbed a used fuel rail and made sure to stop and get a new fuel pressure regulator since the fuel rail had the original regular, and I'm not about to deal with an explosion again. I pulled the spark plugs out and quickly determined the causes for the misfires -- the plugs were far too fouled to fire properly. I got a set of plugs and wires and replaced those, as well as the upper intake, fuel rail and regulator, and the map sensor. I've been leaning towards the original issue of the stalling being due to the MAF sensor but had no way to test so I just put the car back together and left the MAF unplugged and behold, the car started and ran great. I plugged the MAF back in and it went back to not running. So for the meantime, I'm leaving it unplugged.
Thanks for all the great advice!
Thanks for all the great advice!
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