Chasing a lean spike

Mike T

Well-Known Member
#1
Have a couple of logs of this lean spike. It does break up a little and I can't determine if it boost or rpm related. Car pulls really hard to about 15 pounds and when the problem does show up it's over 15 psi and 5300 rpm.

WB doesn't really agree with o2 during the spike. Replaced o2 but it still there.

Thanks for looking
Mike
 

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Mike T

Well-Known Member
#2
Maft Pro speed density, logging FP (rising 1-1), over half tank of fuel (pump shouldn't be uncovered), new nkg plugs gapped .028 (trying to rule out misfire) , no ecm codes.

Would turn 6200 easily before this.
 

Mike T

Well-Known Member
#4
Mike I did replace the coil pack and module with a used one that has ran well in the past, maybe it's going bad too?

Car runs good otherwise, I took a couple of easy passed at the track (12 psi and kept rpm under 5300).
It picked up 24 mph from the I/8 @ 109 out the back.

At those levels it barley started to stumble. Will a bad coil pack behave this way?
 
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Mike T

Well-Known Member
#6
Plugs are new set at .028.
Actual voltage the pack is getting has been difficult to determine.
PL usually shows 12.8 to 13.2 but testing at the alternator 14.3, fuse block around 14.0, at the pump 13.7
 

Mike T

Well-Known Member
#9
Turbo nasty I'll most likely be calling you on the cam sensor kit. Car does have a lot of oil pressure and I'm starting to question if the cam sensor is feeling the strain.
 

mikestertwo

Well-Known Member
#10
Mike I did replace the coil pack and module with a used one that has ran well in the past, maybe it's going bad too?

Car runs good otherwise, I took a couple of easy passed at the track (12 psi and kept rpm under 5300).
It picked up 24 mph from the I/8 @ 109 out the back.

At those levels it barley started to stumble. Will a bad coil pack behave this way?
Measure the resistance between the coil towers. It should be in the 11-12K range. It's a place to start. Check your crank sensor to make sure it isn't loose or hitting the reluctor wheel on the damper.
 

Mike T

Well-Known Member
#12
Thank you fellas, Hopefully I'll get a chance today to check out your suggestions. Been running around in too many directions on other stuff.
Need to get this figured out because I have 15 gallons of 110 to dump in the tank...….at 10 dollars a gallon I don't want to waste a drop;)
 

Mike T

Well-Known Member
#13
Unplugged cam sensor and did a few pulls. On the final pull the car quit after the 1-2 shift making me think it dropped the crank signal. Sound logical? File attached.
I think the boost and fuel pressure is all over the place due to the way the WG is set up at the moment.
 

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Mike T

Well-Known Member
#14
Crank end play is good. Sensor was not centered and almost touching but readjustment didn't solve the issue. Had a new crank sensor on hand and that didn't do it either.

Guess I need to revisit the coil and module like Mike said.
 

Mike T

Well-Known Member
#15
The exhaust even has a slight lean or raspy sound as it approaches 15psi but the wideband isn't backing this up. Almost tempted to put some mainscale fuel in just to see.
 
#16
If you can hear it's rich or lean, that's typically way off the mark. When fueling is close the sound should be virtually the same. Try reading the plugs yet? Old school is a good way to reset your compass every now and then.
 

Mike T

Well-Known Member
#18
Yes and no on the plug reading. Never been able to read a plug right after a hard run. The darker of these two plugs is a set that has been in a few motors and I ran them for about 1000miles in this motor. The brighter new plug only has about 100 miles on it in this motor
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.
 

Mike T

Well-Known Member
#19
This plug has about 3000 hard miles on it. Had dyno time on it too. Took them out because some dislike iridium plugs in our motors. Motor has been upgraded since but close to the same tune.
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