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It’s very possible it’s bad. It could have been sitting out in the elements for some time before you got it. I’d go back to the other one of the van was running better with that one.
It’s very possible it’s bad. It could have been sitting out in the elements for some time before you got it. I’d go back to the other one of the van was running better with that one.
Yeah, without a scope I couldn’t see anything other than the bad fuel trim numbers and poor performance that would indicated it being bad….and I found an OTC scope on craigslist for $400…darn if I don’t have the extra cash to snag that up! I’d SOOO love to have an automotive scope to play with…so much to learn, so much to do! ( scanner danner got me hooked on scoping MAF’s, etc )
Anyway, I’d like to say that I had some progress, but lo and behold, I got into an accident with the van last thursday ( nobody hurt, just a fender bender ) and I literally just got the van back from the body shop. PRETTY!
So, I got this nice silicon union to prevent leaks between the MAF and the air inlet and if I don’t get any improvement with it, I’m going to see what I can do about completely making sure the gm inlet is completely sealed as well, just to prevent any sources of air entering past the MAF throwing it off.
Oh, and I returned that old MAF to the JY and got another in exchange as well as cross referenced part numbers to make sure there weren’t any goofy single year issues with the MAF. Didn’t expect to find anything being that it’s GM and I didn’t. So, the replacement MAF with screen is sitting in the basement ready to be put in and tested on Sunday. I will report back once I’ve had a chance to run the van and get some numbers.
Yeah, without a scope I couldn’t see anything other than the bad fuel trim numbers and poor performance that would indicated it being bad….and I found an OTC scope on craigslist for $400…darn if I don’t have the extra cash to snag that up! I’d SOOO love to have an automotive scope to play with…so much to learn, so much to do! ( scanner danner got me hooked on scoping MAF’s, etc )
Anyway, I’d like to say that I had some progress, but lo and behold, I got into an accident with the van last thursday ( nobody hurt, just a fender bender ) and I literally just got the van back from the body shop. PRETTY!
So, I got this nice silicon union to prevent leaks between the MAF and the air inlet and if I don’t get any improvement with it, I’m going to see what I can do about completely making sure the gm inlet is completely sealed as well, just to prevent any sources of air entering past the MAF throwing it off.
Oh, and I returned that old MAF to the JY and got another in exchange as well as cross referenced part numbers to make sure there weren’t any goofy single year issues with the MAF. Didn’t expect to find anything being that it’s GM and I didn’t. So, the replacement MAF with screen is sitting in the basement ready to be put in and tested on Sunday. I will report back once I’ve had a chance to run the van and get some numbers.
Okay, got a good MAF with a screen going in the van. At idle under load, I was pulling 13 LTFT and STFT hovering around 0. Under load at 2500rpm , LTFT goes to 25 and STFT hits 15. I didn’t think to test the numbers in Park at home at idle, 1500rpm and 2500rpm, but I think the variance would be similar.
Seems to me that I have a fuel problem. My fuel pressure was in the right range, but it certainly wasn’t as high as it could be with a new pump.
Something that caught my attention though was when I first took off from the body shop today, she stumbled under hard acceleration ( cold, probably in open loop ) and the van had been parked nose up at the body shop. Not a steep incline by any stretch, but enough for gravity to have an effect. At my home though, I usually park nose down as I back my van in most days, though I park nose up when the wife is with me ( lets her get out on the good part of our driveway ). In both situations I’ve never had an issue with sputtering.
This was just over the course of the day today, it was parked indoors last night and then only started up to pull it around front until I got it. Not sure if it’s got much to do with anything, but I wouldn’t think I should be experiencing a stumble. Might be the new MAF. I think I’m going to use the shops scanner and put the van into relearn again…reset the fuel tables and see what happens.
Okay, got a good MAF with a screen going in the van. At idle under load, I was pulling 13 LTFT and STFT hovering around 0. Under load at 2500rpm , LTFT goes to 25 and STFT hits 15. I didn’t think to test the numbers in Park at home at idle, 1500rpm and 2500rpm, but I think the variance would be similar.
Seems to me that I have a fuel problem. My fuel pressure was in the right range, but it certainly wasn’t as high as it could be with a new pump.
Something that caught my attention though was when I first took off from the body shop today, she stumbled under hard acceleration ( cold, probably in open loop ) and the van had been parked nose up at the body shop. Not a steep incline by any stretch, but enough for gravity to have an effect. At my home though, I usually park nose down as I back my van in most days, though I park nose up when the wife is with me ( lets her get out on the good part of our driveway ). In both situations I’ve never had an issue with sputtering.
This was just over the course of the day today, it was parked indoors last night and then only started up to pull it around front until I got it. Not sure if it’s got much to do with anything, but I wouldn’t think I should be experiencing a stumble. Might be the new MAF. I think I’m going to use the shops scanner and put the van into relearn again…reset the fuel tables and see what happens.
So, with the “new” MAF, I’ve been running around and randomly checking fuel trim numbers and such.
The new MAF doesn’t seem to like a load off closed throttle sometimes, though it runs fine through the rest of the power band. I don’t really get it. I’m thinking of disassembling the 2nd MAF and using the honeycomb body with the old MAF circuitry that gave me no running issues.
HOWEVER, something that I’d like to try but don’t know how/where to get it done is inspired by one of Eric’s videos from a while back.
Remember the truck he had to get into the old shop with a bad fuel pump and he used the air tank and the doo-hickey that held fuel and powered the vehicle through this tiny microcosm of a fuel delivery system? I haven’t got the faintest idea where to get one, how to ask a mechanic if they have one or what the specific process is called, but it dawned on me that if the vehicle was getting starved for fuel volume/pressure, it would be a simple way to determine if at least the motor side was good and there was a fuel pump issue before the motor ( deteriorated fuel line, filter, pump, pump screen, fuel tank…. )
I’d like to hook that device up, run the fuel pressure to 65psi and see if the fuel trim numbers improve. It would probably be the easiest way to eliminate a fuel delivery issue regarding that expensive GM vortec fuel pump ( 3-400 bucks! )
Right now, running in closed loop after driving the van for 25 miles, my STFT fuel numbers are around zero at idle and LTFT are around 10. @ 1500RPM my LTFT hits 25 and STFT is in the high single, low double digits with some wavering. 2500 rpm is pretty much the same as 1500.
Under load at highway speeds though, I’m showing STFT and LTFT numbers that add up to over 40-50!
This could be partially due to the 2nd MAF, so I need to double check my numbers with the old MAF, but regardless, it sure seems like I’m not pushing enough fuel to the injectors.
It would be nice to have a scanner that could tell me the injector pulse width.
The van runs and starts just fine though, seems to have good power. It makes me wonder though, if I put in a new fuel pump and get the strong delivery I suspect that I don’t have and a more precise injector PWM that I won’t have an immediate increase in the old Butt Dyno.
So, with the “new” MAF, I’ve been running around and randomly checking fuel trim numbers and such.
The new MAF doesn’t seem to like a load off closed throttle sometimes, though it runs fine through the rest of the power band. I don’t really get it. I’m thinking of disassembling the 2nd MAF and using the honeycomb body with the old MAF circuitry that gave me no running issues.
HOWEVER, something that I’d like to try but don’t know how/where to get it done is inspired by one of Eric’s videos from a while back.
Remember the truck he had to get into the old shop with a bad fuel pump and he used the air tank and the doo-hickey that held fuel and powered the vehicle through this tiny microcosm of a fuel delivery system? I haven’t got the faintest idea where to get one, how to ask a mechanic if they have one or what the specific process is called, but it dawned on me that if the vehicle was getting starved for fuel volume/pressure, it would be a simple way to determine if at least the motor side was good and there was a fuel pump issue before the motor ( deteriorated fuel line, filter, pump, pump screen, fuel tank…. )
I’d like to hook that device up, run the fuel pressure to 65psi and see if the fuel trim numbers improve. It would probably be the easiest way to eliminate a fuel delivery issue regarding that expensive GM vortec fuel pump ( 3-400 bucks! )
Right now, running in closed loop after driving the van for 25 miles, my STFT fuel numbers are around zero at idle and LTFT are around 10. @ 1500RPM my LTFT hits 25 and STFT is in the high single, low double digits with some wavering. 2500 rpm is pretty much the same as 1500.
Under load at highway speeds though, I’m showing STFT and LTFT numbers that add up to over 40-50!
This could be partially due to the 2nd MAF, so I need to double check my numbers with the old MAF, but regardless, it sure seems like I’m not pushing enough fuel to the injectors.
It would be nice to have a scanner that could tell me the injector pulse width.
The van runs and starts just fine though, seems to have good power. It makes me wonder though, if I put in a new fuel pump and get the strong delivery I suspect that I don’t have and a more precise injector PWM that I won’t have an immediate increase in the old Butt Dyno.
I think you’re getting into deep water now. As for the tool it’s available from OTC. It’s actually a fuel injection cleaning kit. It will set you back quite a bit to test a ‘theory’ however. You might be better off finding someone that has one that you could use. There is actually a way to check fuel pump operation from the fuel pump fuse but you need a lab scope. Honestly, it sounds like you’re hitting a wall with your tools. At this point you could either take it somewhere or start throwing parts at it. I can’t stress enough how any air leaks or vacuum leaks after the MAF sensor can effect the fuel delivery. In situations like this the simple solutions are often the ones that prove out. Keep us posted.
I think you’re getting into deep water now. As for the tool it’s available from OTC. It’s actually a fuel injection cleaning kit. It will set you back quite a bit to test a ‘theory’ however. You might be better off finding someone that has one that you could use. There is actually a way to check fuel pump operation from the fuel pump fuse but you need a lab scope. Honestly, it sounds like you’re hitting a wall with your tools. At this point you could either take it somewhere or start throwing parts at it. I can’t stress enough how any air leaks or vacuum leaks after the MAF sensor can effect the fuel delivery. In situations like this the simple solutions are often the ones that prove out. Keep us posted.
Ah, well thanks for the clarification on the tool..I have a few “friends” that may have one, so I will have to check around.
I dunno. The codes come on, then they go away. They go away when it’s “misty” outside and then come back, but then they go away for no real reason, and then come back. I’ve got to be hovering on the edge of whatever parameter sets the codes off, but I just can’t see what exactly it is that sets the code. I know that it has to be in a state for a certain amount of time before the code actually sets.
My neighbor just had the same codes pop up on his expedition, but his was the suspect PCV elbow and easily diagnosed ( fuel trims went closer to zero with more throttle, and you could hear it sucking air, especially when you shut the motor off and the last few gasps of air were drawn through it ).
I’d like to think it’s something simple, but I haven’t been able to find it. I sprayed the entire upper half of the motor with a spray bottle and had no change in rpm, smoothness or sensor readings. The fact that my fuel trim readings went to almost 60% combined under medium throttle with the screened MAF and not that high with the non screened MAF have me baffled.
As it sits, the van at 19 LTFT and hovers above and below 0 for my STFT.
The lack of rear O2 sensors ( which have been disabled in the computer…they read .445-.450v on my scan tool )is what the local mechanic blamed on my codes, but to the best of my reading about O2 sensors, the rear O2 sensors main job is to monitor the efficiency of the catalytic converters. Am I wrong in this assessment?
Ah, well thanks for the clarification on the tool..I have a few “friends” that may have one, so I will have to check around.
I dunno. The codes come on, then they go away. They go away when it’s “misty” outside and then come back, but then they go away for no real reason, and then come back. I’ve got to be hovering on the edge of whatever parameter sets the codes off, but I just can’t see what exactly it is that sets the code. I know that it has to be in a state for a certain amount of time before the code actually sets.
My neighbor just had the same codes pop up on his expedition, but his was the suspect PCV elbow and easily diagnosed ( fuel trims went closer to zero with more throttle, and you could hear it sucking air, especially when you shut the motor off and the last few gasps of air were drawn through it ).
I’d like to think it’s something simple, but I haven’t been able to find it. I sprayed the entire upper half of the motor with a spray bottle and had no change in rpm, smoothness or sensor readings. The fact that my fuel trim readings went to almost 60% combined under medium throttle with the screened MAF and not that high with the non screened MAF have me baffled.
As it sits, the van at 19 LTFT and hovers above and below 0 for my STFT.
The lack of rear O2 sensors ( which have been disabled in the computer…they read .445-.450v on my scan tool )is what the local mechanic blamed on my codes, but to the best of my reading about O2 sensors, the rear O2 sensors main job is to monitor the efficiency of the catalytic converters. Am I wrong in this assessment?
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