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Pass side miss,huff,chug
- Thread author wcamaddox
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wcamaddox
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OK sorry reread my post and I wasn't clear( I was confused and I wrote it) the probes or leads from the oscilloscope are actual test leads with alligator clips. I used an old set of EV1 wiring pigtails with bare spots in the middle and and solder-less connectors on the ends between the factory harness and the injectors so the car could run while the scope was hooked up to it and I didn't have to mess up my harness. So the injector operates as it should and I can hook up my scope.
Yes with it hooked up all 8 of the signals duplicate each other from cold to warm up and when applying throttle just seem to speed up is all. Which is part of the reason it took me a while to test all of them in this manner and post again...
Checked the resistance of the injectors themselves and according to the guy that emailed me from fuelinjectorconnection they pass muster.....
I will definitely try the contact cleaner(when I find the can here in a bit) and inspect them closely and re-seat the connectors. I have contacted a local guy. He and his brother are really sharp when it comes to the LT and LS engines (his brother has an Impala that he sprays with nitrous)I am just waiting to hear back, nice thing is he does own a TECH 2 tool and we've done some swapping so I think he will be more reasonable than the dealer.....
Yes with it hooked up all 8 of the signals duplicate each other from cold to warm up and when applying throttle just seem to speed up is all. Which is part of the reason it took me a while to test all of them in this manner and post again...
Checked the resistance of the injectors themselves and according to the guy that emailed me from fuelinjectorconnection they pass muster.....
I will definitely try the contact cleaner(when I find the can here in a bit) and inspect them closely and re-seat the connectors. I have contacted a local guy. He and his brother are really sharp when it comes to the LT and LS engines (his brother has an Impala that he sprays with nitrous)I am just waiting to hear back, nice thing is he does own a TECH 2 tool and we've done some swapping so I think he will be more reasonable than the dealer.....
buickwagon
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Ok, let's review for a moment.
You are getting a P0304 (Cylinder #4 misfire) code. #4 spark plug is a dry, sooty black, suggesting it is running rich or not getting a consistent spark. Once the engine goes into closed loop, the right bank short term fuel trim goes down to -50%, and the right bank long term ft drops to -15%. The Bank 2 O2 sensor voltage stays high at all times, around .75 volts. All the above suggests at least one cylinder in the right bank is running rich and the PCM is attempting to compensate by leaning out the right bank. A scope verifies that the PCM is properly modulating the injector pulse width compared to an adjacent cylinder.
The problem was not noticed until after you changed the ignition wires, plugs, and intake gaskets. There is a possibility that the #4 wire was damaged when pinched by the AC compressor, but you replaced both the #4 wire and the sooty plug again with no improvement.
Other things you have tried replacing include the TPS (had some rough spots) and injectors (some leaked), Opti (rotor was crumbling) and the O2 sensor (just in case). You also checked the compression and fixed various vacuum hose leaks.
I really don't think there is a problem with the PCM. Everything points to the PCM working properly -- it is reading a rich mixture (as confirmed by the sooty plug and reaction to a vacuum leak), it is apparently outputting the correct signal to the injectors.
I wonder if the vacuum leaks you fixed were (in some freak way) actually compensating for whatever is causing the current rich condition.
Disconnecting the hose from the PCV valve (again, an introduced vacuum leak) smooths out the idle , makes the miss disappear, but I don't believe you have posted any O2 or fuel trim statistics when running with the PCV disconnected. And I don't see that you replaced the PCV valve with a new one for the RMW -- you mention that you had accidentally installed one for a different car (Regal?) and swapped in the original RMW valve again.
I think I'd look very closely at the PCV system. The PCV valve has to regulate the amount of flow depending on vacuum and if it's excessive, it acts like a vacuum leak. Presumably the opposite is true too -- if it's clogged it might cause a richer than normal condition? So I'd try replacing the valve and carefully check both the hose from the PCV valve to the manifold and also the air supply hose -- from the intake to the engine. The PCV valve can't flow any air unless there's a supply of fresh air going into the engine.
The only problem with this theory is it does not explain why only #4 would be affected.
You are getting a P0304 (Cylinder #4 misfire) code. #4 spark plug is a dry, sooty black, suggesting it is running rich or not getting a consistent spark. Once the engine goes into closed loop, the right bank short term fuel trim goes down to -50%, and the right bank long term ft drops to -15%. The Bank 2 O2 sensor voltage stays high at all times, around .75 volts. All the above suggests at least one cylinder in the right bank is running rich and the PCM is attempting to compensate by leaning out the right bank. A scope verifies that the PCM is properly modulating the injector pulse width compared to an adjacent cylinder.
The problem was not noticed until after you changed the ignition wires, plugs, and intake gaskets. There is a possibility that the #4 wire was damaged when pinched by the AC compressor, but you replaced both the #4 wire and the sooty plug again with no improvement.
Other things you have tried replacing include the TPS (had some rough spots) and injectors (some leaked), Opti (rotor was crumbling) and the O2 sensor (just in case). You also checked the compression and fixed various vacuum hose leaks.
I really don't think there is a problem with the PCM. Everything points to the PCM working properly -- it is reading a rich mixture (as confirmed by the sooty plug and reaction to a vacuum leak), it is apparently outputting the correct signal to the injectors.
I wonder if the vacuum leaks you fixed were (in some freak way) actually compensating for whatever is causing the current rich condition.
Disconnecting the hose from the PCV valve (again, an introduced vacuum leak) smooths out the idle , makes the miss disappear, but I don't believe you have posted any O2 or fuel trim statistics when running with the PCV disconnected. And I don't see that you replaced the PCV valve with a new one for the RMW -- you mention that you had accidentally installed one for a different car (Regal?) and swapped in the original RMW valve again.
I think I'd look very closely at the PCV system. The PCV valve has to regulate the amount of flow depending on vacuum and if it's excessive, it acts like a vacuum leak. Presumably the opposite is true too -- if it's clogged it might cause a richer than normal condition? So I'd try replacing the valve and carefully check both the hose from the PCV valve to the manifold and also the air supply hose -- from the intake to the engine. The PCV valve can't flow any air unless there's a supply of fresh air going into the engine.
The only problem with this theory is it does not explain why only #4 would be affected.
wcamaddox
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Thats it in a nutshell, which is why I feel like I am chasing my tail..... And I have four of my mechanic friends shaking there heads and asking WTF right along with me......
I replaced the hose from the manifold port to the metal tube for the PCV, the 90 rubber hose bend at the valve, and the valve its self.....
"I wonder if the vacuum leaks you fixed were (in some freak way) actually compensating for whatever is causing the current rich condition."
Those are my EXACT thoughts on this issue. Before I pulled the engine/tranny it ran fine. Fixed the vacuum leaks while I was installing it. Replaced some leaking gaskets and oil level sensor and BAM misfire...... Unless I got a faulty PCV valve from the mfgr.....
Short term fuel trim with the hose off is 0% on both banks with the hose off. Long term is still -15% on bank 2 but it hasn't ran long enough like that to change that number. O2 readings fluctuate from lean to rich on both sides like I would assume they should under normal operational circumstances.....
Yep still doesn't explain why it is ONLY P0304.... Weird. Could the car have ran for soooo long with the vacuum leak that it thinks too much air is its normal? Kind of out there but seen weirder stuff....
I replaced the hose from the manifold port to the metal tube for the PCV, the 90 rubber hose bend at the valve, and the valve its self.....
"I wonder if the vacuum leaks you fixed were (in some freak way) actually compensating for whatever is causing the current rich condition."
Those are my EXACT thoughts on this issue. Before I pulled the engine/tranny it ran fine. Fixed the vacuum leaks while I was installing it. Replaced some leaking gaskets and oil level sensor and BAM misfire...... Unless I got a faulty PCV valve from the mfgr.....
Short term fuel trim with the hose off is 0% on both banks with the hose off. Long term is still -15% on bank 2 but it hasn't ran long enough like that to change that number. O2 readings fluctuate from lean to rich on both sides like I would assume they should under normal operational circumstances.....
Yep still doesn't explain why it is ONLY P0304.... Weird. Could the car have ran for soooo long with the vacuum leak that it thinks too much air is its normal? Kind of out there but seen weirder stuff....
buickwagon
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Short term fuel trim with the hose off is 0% on both banks with the hose off. Long term is still -15% on bank 2 but it hasn't ran long enough like that to change that number. O2 readings fluctuate from lean to rich on both sides like I would assume they should under normal operational circumstances....
If the STFT is @ 0% then the LTFT won't move. STFT would have to go positive to move the LTFT towards 0. If the O2 is oscillating above/below .47, then the STFT is happy where it is. But it's still richer, overall, than the theoretical neutral. Are the left bank fuel trims similar?
Maybe we're looking at this the wrong direction. Maybe instead of #4 running rich, the real problem is #2, #6 and #8 are running lean, biasing the compensation for the entire bank. I know you replaced the intake gaskets. Any chance something is warped?
paart
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I a little tired tonight, and may not looking at this correctly but---
If #4 isn't firing, won't that "dump" unburned O2 into the manifold, causing the sensor to detect a "full lean" mixture, signaling the ECM to richen the mixture on the entire bank?
Have you determined that #4 fires normally when cold, but starts to misfire exactly when the engine switches to open loop?
This is a little far fetched but a possibility (which I have seen); any chance that when you reassembled the rockers etc. that you may have tightened #4, particularly the exhaust, a little tight? As the engine heats clearances are reduced, and a valve that's not fully seated will leak and cause a misfire. It doesn't take much. Hydraulic lifters have fairly short limits of compensation.
If #4 isn't firing, won't that "dump" unburned O2 into the manifold, causing the sensor to detect a "full lean" mixture, signaling the ECM to richen the mixture on the entire bank?
Have you determined that #4 fires normally when cold, but starts to misfire exactly when the engine switches to open loop?
This is a little far fetched but a possibility (which I have seen); any chance that when you reassembled the rockers etc. that you may have tightened #4, particularly the exhaust, a little tight? As the engine heats clearances are reduced, and a valve that's not fully seated will leak and cause a misfire. It doesn't take much. Hydraulic lifters have fairly short limits of compensation.
wcamaddox
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OK so I wanted to post how and what was going on. and how I resolved it. Went to my buddies garage who has the Tech2. Hooked it up and we saw how bank2 was dumping fuel into the engine and the other side was running like it should. All of my sensors were reading as functioning. I explained to him start to finish what I had done. So at this point we were kinda stumped and he wanted to make sure the wiring going to the O2 sensors wasnt damaged when i pulled/installed the engine. He showed me a trick using a piece of MIG wire to ground the O2 sensor wire it would make it show lean. While we were doing this we noticed that the sensor we grounded wasnt showing as the correct one on the scanner. I had somehow gotten the rear O2 sensor on bank1 wiring ran to the front O2 sensor on bank2. So it was reading way to lean and pouring fuel to bank2. fouling out my plug in cylinder #4 and causing the miss. lesson learned when you have four O2 sensors that have identical wiring, mark which is which. LMAO
Thanks everyone for their thoughts and input and riding along with me as we figured out I am sometimes an idiot..... lol
Regards
Bill
Thanks everyone for their thoughts and input and riding along with me as we figured out I am sometimes an idiot..... lol
Regards
Bill
paart
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Glad you finally have it "fixed"!
Any thoughts on why only #4 was misfiring? I'd think that under those conditions that all the cylinders on the bank would misfire, at least intermittently.
I believe there is an ECM mod that will cause it to ignore the second (rear) O2 sensor. If I had a '96, that would be one of the first things I'd do, and it's one of the reasons that when I bought my RM, I "side-stepped" a couple "96s and purchased a '95.
Any thoughts on why only #4 was misfiring? I'd think that under those conditions that all the cylinders on the bank would misfire, at least intermittently.
I believe there is an ECM mod that will cause it to ignore the second (rear) O2 sensor. If I had a '96, that would be one of the first things I'd do, and it's one of the reasons that when I bought my RM, I "side-stepped" a couple "96s and purchased a '95.
buickwagon
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Any thoughts on why only #4 was misfiring? I'd think that under those conditions that all the cylinders on the bank would misfire, at least intermittently.
That has always been the confusing part, hasn't it? All 4 should be roughly the same.
Perhaps it's simply a tolerance thing, and something about #4 was just on the wrong side of a fine line somewhere in the chain. I'm glad to hear you finally got it sorted and I'll definitely file that one away for future reference! And while it may seem like this cost you some unanticipated coin at the moment, I think most of the things you changed were changed for good reason, preventing more problems from arising in the near future.
wcamaddox
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I like my 96, plus the price was right..... my mom and step-dad bought a couple Porsches and they knew I was gaga over the car so they gifted it to me. I said "Sure I will come get it, hate to have that Buick slumming up the place with your fancy European stuff now" lol
My buddy and I think it could be one of a few things. That #4 is the weakest cyl in terms of compression or leakdown. Or that particular injector flows more than the others on that side thus it fouled first. Or that that runner doesn't flow as much air as the other three. I am sooo not complaining about replacing the opti. I knew it was marginal when I put it in and I honestly believe with a new cap/rotor and the new bearing i put in it will be viable if/when i need one later down the road. Also the injectors I knew two were bad so no biggie and those Boschs are way better than the rochester ones are.... all in all a good learning experience.... Now on to the next things I wanna do.... just need to locate the mounting hardware for the 9C1 sway bars I found at the local pull-a-part...... lol
My buddy and I think it could be one of a few things. That #4 is the weakest cyl in terms of compression or leakdown. Or that particular injector flows more than the others on that side thus it fouled first. Or that that runner doesn't flow as much air as the other three. I am sooo not complaining about replacing the opti. I knew it was marginal when I put it in and I honestly believe with a new cap/rotor and the new bearing i put in it will be viable if/when i need one later down the road. Also the injectors I knew two were bad so no biggie and those Boschs are way better than the rochester ones are.... all in all a good learning experience.... Now on to the next things I wanna do.... just need to locate the mounting hardware for the 9C1 sway bars I found at the local pull-a-part...... lol
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