Odd surging on low RPM acceleration?
03-25-2009, 07:51 PM
#1
Odd surging on low RPM acceleration? Did a search in the general area for the LS1 related tech forums and came up with nothing other than it could be a MAF, but don't want to blow the money on one right now if that isn't the problem so thought I would ask and get opinions first. 
Today driving home I was cruising with the car in 5th @ about 1200 RPM and gave it a bit of gas to accelerate and the shifter started shaking violently and the car surged. I went down to 4th at a slower speed (about 1800 RPM) and would get a little bit of pulsing than at around 2000 RPM it would stop and go like normal. The further up in RPM it gets the better it gets. It seems at about 2200 RPM it just totally stops. If I stay on the throttle and go WOT I will get a little bit of knock and some back firing.
I went and did a scan and the timing dips into the single digits the second it starts to happen and bounces a bit. The Injector pulses look like they surge a bit also. I was wondering if it was a fueling issue but doing a short WOT run through 1st and 2nd it didn't have issues off the line or anywhere else through the RPM range.
No codes or anything have been tripped and the MAF seems to be reading fine on HPT scanner. Nothing has been changed on the car in the last two years, Just have LT headers, Lid and mild timing tweaking done on the mid - high rpm range with no KR at all.
Am wondering if maybe I just got a bad batch of gas? I was planning to fill it up tomorrow and give it the seafoam treatment and change the filter after a day of driving it around. The Fuel filter is two years old.
Just posting in the off chance that maybe someone has dealt with this before and knows exactly what the problem is. If not will work with through form the fuel system, to spark than to sensors.
Car is a 01 TA M6 with LT headers, Lid and Mild timing tweaking.
Today driving home I was cruising with the car in 5th @ about 1200 RPM and gave it a bit of gas to accelerate and the shifter started shaking violently and the car surged. I went down to 4th at a slower speed (about 1800 RPM) and would get a little bit of pulsing than at around 2000 RPM it would stop and go like normal. The further up in RPM it gets the better it gets. It seems at about 2200 RPM it just totally stops. If I stay on the throttle and go WOT I will get a little bit of knock and some back firing.
I went and did a scan and the timing dips into the single digits the second it starts to happen and bounces a bit. The Injector pulses look like they surge a bit also. I was wondering if it was a fueling issue but doing a short WOT run through 1st and 2nd it didn't have issues off the line or anywhere else through the RPM range.
No codes or anything have been tripped and the MAF seems to be reading fine on HPT scanner. Nothing has been changed on the car in the last two years, Just have LT headers, Lid and mild timing tweaking done on the mid - high rpm range with no KR at all.
Am wondering if maybe I just got a bad batch of gas? I was planning to fill it up tomorrow and give it the seafoam treatment and change the filter after a day of driving it around. The Fuel filter is two years old.
Just posting in the off chance that maybe someone has dealt with this before and knows exactly what the problem is. If not will work with through form the fuel system, to spark than to sensors.
Car is a 01 TA M6 with LT headers, Lid and Mild timing tweaking.
03-26-2009, 08:04 AM
#4
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Way too many possibilities.....could be bad gas, could be your MAF resistors are coated (clean them CAREFULLY with a Q-tip & alcohol), could be the fuel filter, could be the pump going away, could be the O2s are dying. It definietly sounds like it's going lean for some reason. 
03-26-2009, 11:47 AM
#5
Way too many possibilities.....could be bad gas, could be your MAF resistors are coated (clean them CAREFULLY with a Q-tip & alcohol), could be the fuel filter, could be the pump going away, could be the O2s are dying. It definietly sounds like it's going lean for some reason.
Hopefully I can narrow it down today.
03-26-2009, 01:25 PM
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That's similar to what I experienced in my LS1 before we found a worn ring land on the piston in cylinder 5... What's your oil consumption like? I drove it around over a year before it got bad..
Of course not trying to scare you, hopefully it's something simple like a dirty MAF (electric contact cleaner works great for me -- just don't spray it up into the engine ) But it seems there's a bit of local history with 2001s and oil consumption leading up to a bit of required internal work...
Does the check engine light start flashing at all when you're lugging it? (Misfire indication). Anyway to tell if you're getting misfires on any particular cylinder over the others? HP-tuners cylinder balance test might show one cylinder not pulling its weight at lower RPM (tho I never noticed much issue at high RPM myself), or even a compression test (easy to DIY) could at least give you some peace of mind.
Of course not trying to scare you, hopefully it's something simple like a dirty MAF (electric contact cleaner works great for me -- just don't spray it up into the engine
) But it seems there's a bit of local history with 2001s and oil consumption leading up to a bit of required internal work...Does the check engine light start flashing at all when you're lugging it? (Misfire indication). Anyway to tell if you're getting misfires on any particular cylinder over the others? HP-tuners cylinder balance test might show one cylinder not pulling its weight at lower RPM (tho I never noticed much issue at high RPM myself), or even a compression test (easy to DIY) could at least give you some peace of mind.
03-26-2009, 03:05 PM
#7
That's similar to what I experienced in my LS1 before we found a worn ring land on the piston in cylinder 5... What's your oil consumption like? I drove it around over a year before it got bad..
Of course not trying to scare you, hopefully it's something simple like a dirty MAF (electric contact cleaner works great for me -- just don't spray it up into the engine ) But it seems there's a bit of local history with 2001s and oil consumption leading up to a bit of required internal work...
Does the check engine light start flashing at all when you're lugging it? (Misfire indication). Anyway to tell if you're getting misfires on any particular cylinder over the others? HP-tuners cylinder balance test might show one cylinder not pulling its weight at lower RPM (tho I never noticed much issue at high RPM myself), or even a compression test (easy to DIY) could at least give you some peace of mind.
Of course not trying to scare you, hopefully it's something simple like a dirty MAF (electric contact cleaner works great for me -- just don't spray it up into the engine
) But it seems there's a bit of local history with 2001s and oil consumption leading up to a bit of required internal work...Does the check engine light start flashing at all when you're lugging it? (Misfire indication). Anyway to tell if you're getting misfires on any particular cylinder over the others? HP-tuners cylinder balance test might show one cylinder not pulling its weight at lower RPM (tho I never noticed much issue at high RPM myself), or even a compression test (easy to DIY) could at least give you some peace of mind.
Oil consumption doesn't seem like a big issue on it. I have about 1000 miles on this oil change and the dip stick is still showing that it is full and no metal shavings.
If I park the car on a steep hill and put it in first it very slowly will creep. Could that be a possible compression leak and leading to the rings being worn? The car has about 91k miles on it. It has the factory wire's on it, when I did the headers Napa didn't have any wires for it so we just did plugs. I had a similar problem with my GTP that when the wires were getting worn/hot it would have this same type of hesitation like it was misfiring but nothing ever showed up, no ses light flashing or anything just like right now. Changed the wires and all was dandy.
Will have to find the parts for doing the compression test, think they might be out at my grandfather's and see what happens. Will see if I can find the load thing on HPT, not sure if I have ever seen it but doesn't mean it isn't there.
The car only does it under load, I could hold the revs at 1500 all day and not have an issue, just when I am in a higher gear than usual and I might give it a little more throttle than usual. Maybe it could have always been there but I just never noticed?
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03-26-2009, 03:17 PM
#8
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Bad gas and a clogged fuel filter? PLug wires? Check their resistance values. Could also the throttle positions sensor. Check the wires and plug. Then check the sensor. Or just replace it. They are cheap online. Just some more ideas.
03-26-2009, 03:50 PM
#9
Going to change the plugs and wires next I guess. Suggestions on plugs and wires to get? Working on a college budget so wherever I can get the best the cheapest is the best for me.
03-27-2009, 09:04 PM
#10
Found the issue, and feel kind of dumb. The #8 spark plug backed out from not beign tightened when we did the headers a year and half ago. I got wires today and was putting them on and when I crawled under to put the 8th wire on I noticed it seemed to just slide off. So I figured it just wasn't on all the way, than when I went to put on the wire I felt the spark plug move and got a good 8 turns by hand before I had to tighten it down.
Best I can figure is when we did the headers I couldn't twist my fat hand just right so my father-in-law got it started and must have waited for me to tighten it, and I never did. So it has been running on only 7 cylinders for the most part possibly and maybe I have even more power now!
Best I can figure is when we did the headers I couldn't twist my fat hand just right so my father-in-law got it started and must have waited for me to tighten it, and I never did. So it has been running on only 7 cylinders for the most part possibly and maybe I have even more power now!
03-28-2009, 12:32 PM
#12
