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stumbling above 4K rpm

manikbastrd

Well-known member
Joined
Nov 19, 2009
Messages
660
So, I swapped a rebuilt throttle body into my galant, then found that the FIAV must have been bad on it, because I had idle surge. Changed back to the old one and now she Idles fine, however I now have what feels like spark blowout or fuel cut or something around 4500 RPM when WOT. No problems when not on it hard, and when I log it, link has no data for any knock, and I have checked and re checked for boost leaks, can't hold over 10lbs but I think that is because of the compressor I am using. I haven't changed anything besides the throttle bodies, and yet have this issue. I tried putting in some fresh BPR7ES plugs gapped around .025 and that did not help.

I didn't have any issue like this before so this is something new. I tested my coil pack and harness and they are both fine. Compression is 152-157 for all four cylinders, and I am definitely not running lean...maybe a little rich if anything. The only other thing I can think of that this could be is that I jumped a tooth in my timing somehow...but I feel like I would have other issues going on as well. If that is the case, would this explain why my boost doesn't hold very well and I get weird knock when trying to tune her?

I am really at a loss here. I am going to check my timing marks on the cams in a few minutes, but figured I would post up here and ask for help for other possibilities. Mod list is up to date.

Thanks in advance to anyone who has some advice.
 

prove_it

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Joined
Jul 3, 2008
Messages
4,201
Location
Sioux Falls, SD
Are you sure your not leaking air from around the throttle body? I would check that out. Also check your TPS signal.
 

manikbastrd

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Joined
Nov 19, 2009
Messages
660
I have tried a couple of methods to see if I am leaking air from there. I have used starter fluid, boost leak test with soapy water. The gaskets are new as well. I can't find any leaks. As for the TPS, on Link V3, the voltage reads properly, and the sensor tests correctly. The only thing that is questionable is the harness. When I tested voltage it was fine, but the resistance from pin 1 to pin 4 was not what I expected. Does anyone know the expected values for the TPS harness? I will look it up in my FSM when I get home and retest it.
 

prove_it

Well-known member
Joined
Jul 3, 2008
Messages
4,201
Location
Sioux Falls, SD
You have link, so pull up the datalog and run the gas pedal smoothly while charting just that. Make sure the line increases smoothly and doesn't dip out. Before you tear anything apart, go make a pull in 2nd from 2k. Datalog everything you can, post me a link and I can go through and see if anything stands out.

If your timing was off, your idle would be effected too, not just above 4k.

Do you have a cyclone manifold by the way?
 

manikbastrd

Well-known member
Joined
Nov 19, 2009
Messages
660
I am on a stop USDM manifold. I have an FP exhaust manifold, E316g, and 3' mandrel bent TBE w/o cat. I think I was running super rich because I leaned it out a bit and it doesn't have the same issue /ubbthreads/images/graemlins/banghead.gif. Nub mistake I know...However I am still having knock in first but none in second or third. I just played with timing a bit to eliminate the small amounts of knock I did have in third. I don't know how to post a log to this forum unfortunately, so if you can advise me I will do so asap. I am thinking it may just be heat soak in first gear though. I am going to try and make some kind of custom air box to help get cooler air through the intake in first gear.
 

Tommyd

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Joined
Jan 18, 2013
Messages
106
Location
Fishkill, NY
Go to your max timing map and click track datalog, you can also detach it and scroll across your log as your do your first gear pull. Find the individual cells at which its knocking in first, lower those and the few surrounding ones.
 

Tommyd

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Joined
Jan 18, 2013
Messages
106
Location
Fishkill, NY
You're very welcome. Its easier than you think to build a timing table rather than using sliders and much more effective.
 

manikbastrd

Well-known member
Joined
Nov 19, 2009
Messages
660
Yeah it actually was pretty straight forward...I am sure there are some hotkeys of shortcuts that would make it easier, but I just went through my log where I had knock and lowered the associated timing values. I don't know if that is the right way to do it, but it definitely settled out the knock.
 
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