Feels like on/off switch at WOT

T

tta1401

Member
Joined
May 13, 2002
I'm hoping the title got your attention. I've been trying to figure this out this whole summer. Been in talks with Eric Marshall and Bob Bailey and still can't figure it out. I'm going to open it up to you guys to see if I can get some more ideas and hopefully a fix action. When this first happened in May, I thought it was the plugs causing my problems (i installed alky, PLX WB and replaced 5.7 TT chip with 6.1 TT chip). Changed just about everything since then: plugs, wires, coil pack, ign module, battery cable, ecm (3 different units), new 6.1 chip, new powerlogger. Nothing helped. Checked all wiring a thousand times over. Grounds a thousand times. Below is the findings I've tested over and over the past month:
I
1- ran with PL and 6.1 TT chip and runs bad
2- ran w/o pl and with TT chip and runs great
3- ran PL and 5.7 TT chip in another car and runs great
4- ran PL and 6.1 TT chip with AFR correction turned off in chip and runs bad (my car)

All the runs above was with the same ECM.
All grounds checked out fine.
Wiggled every wire possible with no stumble.
During the times with the PL and 6.1 TT chip installed, I got a mal code 42 and 51 and then got mal code 42 and 22 after wide open blasts.
No codes with PL not installed.
I installed a new battery cable (new ECM power cable) just for kicks and no change on how bad it runs.

FYI- when I say it runs bad, it feels like an on/off switch @wot, literally. Also pops/stutters at WOT. Far also wants to slowly die at a stoplight.

Any ideas?
 
Fuel pressure rises appropriately with boost.

Yes, roller cam but I don't think it's a mechanical issue since it doesn't do it with the PL not installed.

FYI- I've been running it without the PL but with the 6.1 chip the past week, week and a half or so. Drove it this weekend like that with no problems and also took it to the track and still ran 128mph, matching last years best. I made no changes in the chip when I did that. No knock. I took it there just to prove a point to myself. It's got tons left in her but I need to find out this problem.
 
I may be overlooking something in your post but it sounds to me like the next logical move would be to try a different PL in your car? Sounds like something is shorting for sure...
 
Bob Bailey swapped his PL with mine. My old one runs fine in his car but his installed into mine runs like poo. I tried it in another car and runs fine. I'm sure it's not the PL. Eric sent me a replacement chip and that did not help. Unless I got two corrupted chips, which is highly unlikely. Weird, I know...
 
Are you sure the pl board is getting good connection to the ecm? How did you clean the coating off?
 
I've re-cleaned it several times (goo gone them alky). I've made sure it was seated correctly. My ecm and pl installed into my brothers car works perfect. I've actually had the pl since 2010.
 
I had something close to this.
PL connected the car would just shut off
Disconnected the PL white 5 pin wire and everything was fine.
Swapped out ecm and used the same PL and no problems so far.
Good luck

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AC ripple, never thought of that. What's the best way to test without having to rip the alt out and test diodes?
 
have you tried it with the alky off
how does the MAF look on logs
the alky motor tends to interfere with the maf sensor(translator) and early built alkycontrol systems had issues requiring running a separate source to the translator (hotwired through relay off the alternator), newer kits have a filter in the alky powerline to help suppress the noise

back in the day with the directscan , there were similar issues and the fix there was to shield the ribbon cable that plugged into the ecm edge connector
 
Alky off, low boost= no change
I'm having trouble with my replacement pl staying connected so I can't log at the moment.
I installed a new alky kit this past May.
 
tta1401 said:
AC ripple, never thought of that. What's the best way to test without having to rip the alt out and test diodes?
Click to expand...
Take note of your dome light at night with the car running. Does it flicker? The cause of this is a leaky capacitor. It's the black piece that isn't the diode bridge or regulator.
 
or like this :)

st_macguffins7_f.jpg
 
U check or replace crank sensor?

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