Re: One last shot... Breaking up!
I hate to say it and please don't think I am comming off as a di*k but I think we need to go back to some basics. (that being said, I don't like the way the dist. parts look either).
Here is where I am starting from rethinking my ideas. He has a running truck without the misfire/lean issue he has now. The engine goes south and he rebuilds it. The engine gets painted at the time of rebuild, the engine comp. gets some paint as well. The battery gets moved to the driver side. Rebuilt engine is installed and BAM, problem is there and has been there since. The engine came out a second time and that is when the vortec conversion was done (there goes my theory about a poor and irratic flowing intake - you would be suprised on what I see on the flow bench) and the problem still exists. Rules out intake gaskets leaking. Look at all the stuff that stayed the same upon the installation of the first rebuilt engine and all the stuff he has changed trying to figure this out. Some things made alot of sense and some didn't. Data master and the wide band say the same thing. Dead lean when the misfire comes on. The ecm is obviously reading correctly and working as it richens and then leans back to a proper ratio. It's these 3 damn rpm specific spots. Would a cap and rotor prob. cause a misfire problem. Absolutely, but at these 3 rpm spots, I personally don't think so (but I'm not god and never claimed to be - I try to think logically and think things thru to the end). I also think that a misfire would cause a rich condition rather than such a lean condition. Changing the injectors moved the problem up the scale 300 rpm for each problem spot so obviously the additional fuel helped but only to delay the problem by 300 rpm.
I am now thinking the problem is somewhere after the ecm as it reads from the o2 properly, reacts properly, never showed (from what I hear from those that read the files) anything that was going wrong just before the problem rpm (fuel press stayed, DC's did not drop off ect...). The grounding issue he is chasing makes me curious. 19 + bouncing around at the junction is just not right, but how is that going to effect functions to make the truck dead lean at only 3 specific rpm's. Is there an electrical interference that shuts the injector for a second at the injector. The DC readings never dropped so signals are sent and read to show things are proper but after that, something happens. I'd like to read voltage at each injector in real time throught the rpm range, have an exhaust sniffer for the rpm range as well and be able to see some other things in real time. I'd also like to get into the underhood harness and check for problems. Maybe when the battery was moved, lengthening of the harness (would assume he had to do something) caused an issue somewhere.
When he gets back from racing I am going to drive down and lend a hand. If anyone wants to fly in, I'll pick you up at the airport and we all can attack this thing.
Lastly, it seems to run fine when the engine temp is down but the problem appears when it comes up to temp and gets much worse when the temps really climb. hmmm but it does it with the o2 disconnected and at temp.
I hate to say it and please don't think I am comming off as a di*k but I think we need to go back to some basics. (that being said, I don't like the way the dist. parts look either).
Here is where I am starting from rethinking my ideas. He has a running truck without the misfire/lean issue he has now. The engine goes south and he rebuilds it. The engine gets painted at the time of rebuild, the engine comp. gets some paint as well. The battery gets moved to the driver side. Rebuilt engine is installed and BAM, problem is there and has been there since. The engine came out a second time and that is when the vortec conversion was done (there goes my theory about a poor and irratic flowing intake - you would be suprised on what I see on the flow bench) and the problem still exists. Rules out intake gaskets leaking. Look at all the stuff that stayed the same upon the installation of the first rebuilt engine and all the stuff he has changed trying to figure this out. Some things made alot of sense and some didn't. Data master and the wide band say the same thing. Dead lean when the misfire comes on. The ecm is obviously reading correctly and working as it richens and then leans back to a proper ratio. It's these 3 damn rpm specific spots. Would a cap and rotor prob. cause a misfire problem. Absolutely, but at these 3 rpm spots, I personally don't think so (but I'm not god and never claimed to be - I try to think logically and think things thru to the end). I also think that a misfire would cause a rich condition rather than such a lean condition. Changing the injectors moved the problem up the scale 300 rpm for each problem spot so obviously the additional fuel helped but only to delay the problem by 300 rpm.
I am now thinking the problem is somewhere after the ecm as it reads from the o2 properly, reacts properly, never showed (from what I hear from those that read the files) anything that was going wrong just before the problem rpm (fuel press stayed, DC's did not drop off ect...). The grounding issue he is chasing makes me curious. 19 + bouncing around at the junction is just not right, but how is that going to effect functions to make the truck dead lean at only 3 specific rpm's. Is there an electrical interference that shuts the injector for a second at the injector. The DC readings never dropped so signals are sent and read to show things are proper but after that, something happens. I'd like to read voltage at each injector in real time throught the rpm range, have an exhaust sniffer for the rpm range as well and be able to see some other things in real time. I'd also like to get into the underhood harness and check for problems. Maybe when the battery was moved, lengthening of the harness (would assume he had to do something) caused an issue somewhere.
When he gets back from racing I am going to drive down and lend a hand. If anyone wants to fly in, I'll pick you up at the airport and we all can attack this thing.
Lastly, it seems to run fine when the engine temp is down but the problem appears when it comes up to temp and gets much worse when the temps really climb. hmmm but it does it with the o2 disconnected and at temp.
Looks like its arcing inside of it and could be the miss fire issue but I dont get why it would be only at the given rpms :squint:
