Car stutters when going WOT!....Stock ECU/SD on 93 Oct
Apr 2, 2013, 07:55 AM
#1
Car stutters when going WOT!....Stock ECU/SD on 93 Oct
Mod list: 950cc, 255 wally, HTA86, 3.5'' ic, and 3'' exhaust. 93octane @ 28psi on stock ECU/SD
I recently switched from MAF to SD using rom ID#94172715, and been working on tunning it......fast forward....I finished the VE map, and everything seemed to be working fine. Then I started increasing the boost slightly and moved on to the fuel and ignition maps, and still everything seemed to be in working order till one night I started experiencing this behavior where if I try to do a 3rd or 4th gear pulls or even while cruising in 5th gear then downshift and going WOT (basically higher loads) ...the car would stutter...no cel's, but it does feel like misfiring. It sometimes does it in the lower gears in 1st and 2nd gears as well…rarely but occasionally it happens. It sometimes does sound like a Subaru at idle as well.
What I have done so far is boost leak test, swapped coil packs with the stock coils (I had a non cdi cop b4), and swapped the plugs to NGK iridium BR8eix (I think the code)....gapped them first at .024 then re-gapped them again to .018-.019 to see if that would fix the issue and still no good.
Now I am leaning more toward the fueling.... I am currently running FIC 950cc and a single walboro. The injectors did sit on the shelf for almost a year but in a clean bag so not sure if that had anything to do with it. Any other ideas or things I should check for are welcomed as well.
Attached is a screen shot of one of my runs.
Thanks in advance!
I recently switched from MAF to SD using rom ID#94172715, and been working on tunning it......fast forward....I finished the VE map, and everything seemed to be working fine. Then I started increasing the boost slightly and moved on to the fuel and ignition maps, and still everything seemed to be in working order till one night I started experiencing this behavior where if I try to do a 3rd or 4th gear pulls or even while cruising in 5th gear then downshift and going WOT (basically higher loads) ...the car would stutter...no cel's, but it does feel like misfiring. It sometimes does it in the lower gears in 1st and 2nd gears as well…rarely but occasionally it happens. It sometimes does sound like a Subaru at idle as well.
What I have done so far is boost leak test, swapped coil packs with the stock coils (I had a non cdi cop b4), and swapped the plugs to NGK iridium BR8eix (I think the code)....gapped them first at .024 then re-gapped them again to .018-.019 to see if that would fix the issue and still no good.
Now I am leaning more toward the fueling.... I am currently running FIC 950cc and a single walboro. The injectors did sit on the shelf for almost a year but in a clean bag so not sure if that had anything to do with it. Any other ideas or things I should check for are welcomed as well.
Attached is a screen shot of one of my runs.
Thanks in advance!
Apr 2, 2013, 02:34 PM
#4
Evolved Member
Mod list: 950cc, 255 wally, HTA86, 3.5'' ic, and 3'' exhaust. 93octane @ 28psi on stock ECU/SD
I recently switched from MAF to SD using rom ID#94172715, and been working on tunning it......fast forward....I finished the VE map, and everything seemed to be working fine. Then I started increasing the boost slightly and moved on to the fuel and ignition maps, and still everything seemed to be in working order till one night I started experiencing this behavior where if I try to do a 3rd or 4th gear pulls or even while cruising in 5th gear then downshift and going WOT (basically higher loads) ...the car would stutter...no cel's, but it does feel like misfiring. It sometimes does it in the lower gears in 1st and 2nd gears as well…rarely but occasionally it happens. It sometimes does sound like a Subaru at idle as well.
What I have done so far is boost leak test, swapped coil packs with the stock coils (I had a non cdi cop b4), and swapped the plugs to NGK iridium BR8eix (I think the code)....gapped them first at .024 then re-gapped them again to .018-.019 to see if that would fix the issue and still no good.
Now I am leaning more toward the fueling.... I am currently running FIC 950cc and a single walboro. The injectors did sit on the shelf for almost a year but in a clean bag so not sure if that had anything to do with it. Any other ideas or things I should check for are welcomed as well.
Attached is a screen shot of one of my runs.
Thanks in advance!
Attachment 204284
I recently switched from MAF to SD using rom ID#94172715, and been working on tunning it......fast forward....I finished the VE map, and everything seemed to be working fine. Then I started increasing the boost slightly and moved on to the fuel and ignition maps, and still everything seemed to be in working order till one night I started experiencing this behavior where if I try to do a 3rd or 4th gear pulls or even while cruising in 5th gear then downshift and going WOT (basically higher loads) ...the car would stutter...no cel's, but it does feel like misfiring. It sometimes does it in the lower gears in 1st and 2nd gears as well…rarely but occasionally it happens. It sometimes does sound like a Subaru at idle as well.
What I have done so far is boost leak test, swapped coil packs with the stock coils (I had a non cdi cop b4), and swapped the plugs to NGK iridium BR8eix (I think the code)....gapped them first at .024 then re-gapped them again to .018-.019 to see if that would fix the issue and still no good.
Now I am leaning more toward the fueling.... I am currently running FIC 950cc and a single walboro. The injectors did sit on the shelf for almost a year but in a clean bag so not sure if that had anything to do with it. Any other ideas or things I should check for are welcomed as well.
Attached is a screen shot of one of my runs.
Thanks in advance!
Attachment 204284
I take it the plugs look ok? none of them looking too dark around the ceramic?
I'd take the valve cover off and visually inspect the springs and rockers to make sure a spring isn't starting to give up
Apr 2, 2013, 08:09 PM
#5
Ya sometimes at idle the car sounds like a Subaru, before it didn’t constantly do it, but now days (3 past start-ups) it seemed to be consistent.
Other things worth mentioning is I did a compression test on the motor (50k miles),
moderately warm, and the results came out as the following:
Cylinder #1, 2, & 3 = 135psi
Cylinder #4 (closest to tb) = 90psi
So I added maybe a table spoon worth of oil into cylinder #4 and redid the compression test on it, and it came out around 155psi. Is this expected? Keep in mind the car doesn’t smoke at all….
Also, while doing the boost leak test, the valve cover breather (that’s facing the battery) leaks quite a bit, could this be a result of a bent valve? I had to cap it to keep the system pressurized.
Thanks for the help!
Other things worth mentioning is I did a compression test on the motor (50k miles),
moderately warm, and the results came out as the following:
Cylinder #1, 2, & 3 = 135psi
Cylinder #4 (closest to tb) = 90psi
So I added maybe a table spoon worth of oil into cylinder #4 and redid the compression test on it, and it came out around 155psi. Is this expected? Keep in mind the car doesn’t smoke at all….
Also, while doing the boost leak test, the valve cover breather (that’s facing the battery) leaks quite a bit, could this be a result of a bent valve? I had to cap it to keep the system pressurized.
Thanks for the help!
Apr 4, 2013, 09:16 AM
#6
Update: I replaced my injectors with another set of PTE 1000's, and the car idled better...more on the leaner side and closer to stoich. However, the problem of stuttering at partial and WOT still exists......I didnt spend much time tunning the new injectors so it could afterall be my injectors that are causing the issue. I did send my FIC injectors to FIC for a cleaning session, so will see what they say.
In the meantime, any comments on my experience above with the compression test on Cylinder#4?
Thanks
In the meantime, any comments on my experience above with the compression test on Cylinder#4?
Thanks
Apr 5, 2013, 04:38 AM
#7
Evolved Member
my experience is this:
air coming out of breather during boost leak test: mine and a few others always do this.
sounding like subaru at idle: for me one of my valve springs had snapped it was hard to see at first, but with the cover off I counted the visible "turns" on each spring and found one didn't match. Another car I heard that on, had something stuck in the valve (I know, crazy!) keeping it from shutting..
since you mentioned a cylinder with lower compression than the rest, might be worth a closer look
air coming out of breather during boost leak test: mine and a few others always do this.
sounding like subaru at idle: for me one of my valve springs had snapped it was hard to see at first, but with the cover off I counted the visible "turns" on each spring and found one didn't match. Another car I heard that on, had something stuck in the valve (I know, crazy!) keeping it from shutting..
since you mentioned a cylinder with lower compression than the rest, might be worth a closer look
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Apr 5, 2013, 05:47 PM
#9
Liqquid....you were right on
I think I found my issue, the valve spring off cylinder #4 is broken. In the process of swapping it temporarily to a stock spring to get the car running again.
I think I found my issue, the valve spring off cylinder #4 is broken. In the process of swapping it temporarily to a stock spring to get the car running again.
Last edited by detroit pistins; Apr 5, 2013 at 05:56 PM.
Apr 6, 2013, 02:51 PM
#12
Glad you found your problem. I thought I'd put in my two cents about the valve cover breather leaking during a boost leak test because I read quite a few posts about this.
Although it could be due to air leaking past the valve stem seals in the head, more than likely it's simply air leaking past the pcv valve because the stock pcv valve is pretty weak. When you pressurize the intake system, air will leak past the pcv valve, get into the valve cover, and come out the breather. I replaced the stock pcv valve with a in-line check valve capable of holding 40+ psi, and I don't get air coming out of the valve cover breather anymore while conducting boost leak tests.
Although it could be due to air leaking past the valve stem seals in the head, more than likely it's simply air leaking past the pcv valve because the stock pcv valve is pretty weak. When you pressurize the intake system, air will leak past the pcv valve, get into the valve cover, and come out the breather. I replaced the stock pcv valve with a in-line check valve capable of holding 40+ psi, and I don't get air coming out of the valve cover breather anymore while conducting boost leak tests.
Apr 6, 2013, 07:28 PM
#14
Glad you found your problem. I thought I'd put in my two cents about the valve cover breather leaking during a boost leak test because I read quite a few posts about this.
Although it could be due to air leaking past the valve stem seals in the head, more than likely it's simply air leaking past the pcv valve because the stock pcv valve is pretty weak. When you pressurize the intake system, air will leak past the pcv valve, get into the valve cover, and come out the breather. I replaced the stock pcv valve with a in-line check valve capable of holding 40+ psi, and I don't get air coming out of the valve cover breather anymore while conducting boost leak tests.
Although it could be due to air leaking past the valve stem seals in the head, more than likely it's simply air leaking past the pcv valve because the stock pcv valve is pretty weak. When you pressurize the intake system, air will leak past the pcv valve, get into the valve cover, and come out the breather. I replaced the stock pcv valve with a in-line check valve capable of holding 40+ psi, and I don't get air coming out of the valve cover breather anymore while conducting boost leak tests.
I think my failure was due to the cheap springs that were used on the head. On my previous evo I had supertech duals, and reved high for almost 30k miles, and never had an issue. So a combo of good parts and proper installation should do the job.
