Missing/popping @ 14lbs boost

Scarab

Member
Joined
Nov 8, 2007
Ok here is what I have done so far

Replaced coils with new MSD...still pops
Replace module with Factory new GM---still pops
Checked wires (msd 8.5) all check good with meter still pops
Replaced plugs---still pops
Regapped plugs to .28 still pops
Run new grounds to fender/and firewall as well as motor...still pops
blocked off egr still pops


motor is a 231 v6 109 block, gn1 heads, comp 218/218 cam, front mount precision and te 60 turbo with Alky injection. Motor has 900 miles on it with type 2 ignition. Also TT 5.7 alky chip

Will run great with no problems until you floor it and it comes up on boost and misses like it is loosing fire. That is the reason I replaced all the ignition.

Don't know fuel pressure but no knock and running 10.2 on wide band under boost. 1st gear it will pin you and smoke the tires but once it gets to 14lbs boost it noses over and seems like it is dropping cylinders. if you ease into it, it will not pop and run up to 14lbs smooth but you have to ease into it slowly. It is not lean so I think it is either ignition or something like a cam sensor? But I don't know what the cam sensor would have to do with it after it starts? How can it make it pop? Also new alternator and battery. I am tired of throwing money and parts at it. Has to be something simple. Any ideas
 
Exactly what kind of plugs do you have in there as above poster stated? I gapped mine to .25 at one time to stop the popping.
Do you have a scan master?
yup Fuel psi would be very helpful. Not very expensive gauge with a hose from parts store. ( What type of fuel pump you have how old is it? Gauge would take the guessing out of that. Remember Fuel/Air/Spark too much or not enough of either will cause problems you're experiencing. & checking in that order is probably most reasonable.
 
Never ceases to amaze me. Guys want answers, and have no data to help w/ the solution.
A new engine, trying to boost it to, who knows what level, and when it doesn't work, call for help.
A suggestion, from someone that's done this same thing.
Don't worry w/ the 14# limit. Quit throwing parts at it. Get a Powerlogger, and some sensors, and provide some good data.
May sound a bit nasty...Nasty is driving over the crank. AKA joining the DOTCC.
 
I have a scanmaster and a powerlogger, Just need to get some files saved with out getting a ticket. ]
I only have a fuel pressure guage on the motor, but with a wideband at 10.2 I would not think it is leaning out, no knock just feels like it is dropping cylinders.

Autolite 104's gapped at .28
flat tappet cam, thought it may have a wiped lobe but the car did this before then cleared up and ran right. Now it is back to the same thing so I don't think it has a wiped #3 lobe.

Alky has been tested between 4 and all the way to 8 still same.
ran a few test hits the other day and the power logger failed to save file. I will have t o play with that to and try to find out why. Said recording but did not save for some reason.

And don't worry I don't take comments the wrong way. Hell I know I should have more info, but trying to work 13 hour days and find time to test is hard. Was hoping someone would have that one magic bullet that they found that would be the same fix I need.

Maybe the alky is making the wideband read rich? I may invest in a hood mounted fuel gauge just to rule that out.

It was so much easier back in 1988 when my gn was stock and was easy to just get a red Armstrong chip, volt booster and te 60 turbo and run 11:70's. Now not so easy. I miss the old days. :0
 
I have a scanmaster and a powerlogger, Just need to get some files saved with out getting a ticket. ]
I only have a fuel pressure guage on the motor, but with a wideband at 10.2 I would not think it is leaning out, no knock just feels like it is dropping cylinders.

Autolite 104's gapped at .28
flat tappet cam, thought it may have a wiped lobe but the car did this before then cleared up and ran right. Now it is back to the same thing so I don't think it has a wiped #3 lobe.

Alky has been tested between 4 and all the way to 8 still same.
ran a few test hits the other day and the power logger failed to save file. I will have t o play with that to and try to find out why. Said recording but did not save for some reason.

And don't worry I don't take comments the wrong way. Hell I know I should have more info, but trying to work 13 hour days and find time to test is hard. Was hoping someone would have that one magic bullet that they found that would be the same fix I need.

Maybe the alky is making the wideband read rich? I may invest in a hood mounted fuel gauge just to rule that out.

It was so much easier back in 1988 when my gn was stock and was easy to just get a red Armstrong chip, volt booster and te 60 turbo and run 11:70's. Now not so easy. I miss the old days. :0
If the engine missfires the unburned air in the charge should be read as a lean condition on the wideband. Since yours is holding at 10.2 afr something else seems to be going on.
 
10.2 is extremely rich . Have you tried leaning it out ? I target 10.9-11.0 WOT
 
Did you try unplugging the cam sensor and going for a ride?

Also what cam? Roller or flat tappet?
 
Did you try unplugging the cam sensor and going for a ride?

Also what cam? Roller or flat tappet?
I have not tried unplugging the cam sensor because I thought it doesn't effect anything once the engines starts? so can it effect the running of it after it starts? also I have a comp cam 218/218 flat tappet. I ruled out a wiped lobe because it did run right for a few days and then back to this. If the lobe was wiped it should do the same all the time correct?
 
Do you have a factory (not type 2) ignition you could try? Preferably ac Delco?
 
Do you have a factory (not type 2) ignition you could try? Preferably ac Delco?
no I don't, it had this on it when I bought it. Started the popping so I upgraded to the brand new MSD coils. Then a brand new ACDELCO module. still doing the same thing. really just feels like it is dropping cylinders under boost. I will data log it as soon as I get some time off.
 
I have not tried unplugging the cam sensor because I thought it doesn't effect anything once the engines starts? so can it effect the running of it after it starts? also I have a comp cam 218/218 flat tappet. I ruled out a wiped lobe because it did run right for a few days and then back to this. If the lobe was wiped it should do the same all the time correct?
A wiped lobe can occur shortly after firing a new engine if the lifters don't begin to spin slightly. The spinning action keeps them healthy.
 
The cam sensor does still play a role when the engine is running. When you unplug it, the injectors will batchfire.
Try that first. If it still has the miss, pull the valve covers and check the lift on all the rockers. That’s the only real way to verify the cam is good. Start on the driver side. #3 exhaust is notorious for wearing out the cam lobe. That lobe is not positioned right and the cams are not hardened good enough. Plus today’s oil does not support it. It all adds up to failure.

Good luck. Keep us posted.
 
Well what you can do since you have a gauge on the engine right now is check the pump & injectors. Turn Ignition on,,, or crank the car.. pop the hood see if stays & holds at 42 ish with the vacuum line still attached. Switch off the car to see how long it holds the psi from when you switched off...… if it bleeds down reeeaallll slow say like 10-15 min or so you may be fine; quicker than that.. look for a bad injector I would say...…… you can also do the same to the fuel pump.. Take the smaller vise grips put a fuel hose or electrical tape around the jaws & pinch the return line to see if psi goes up to 80-100psi. If so pretty good if not hmmmmm.
 
You could also crank the car with insulated gloves or insulated plug pullers while the car is running pull one plug at a time to see if the engine idle or sound changes if you suspect a dead cylinder.. (I think you have to disconnect the IAC to do this though). dunno about the injector maybe a volt meter to make sure all are firing. Just to rule the simple stuff out before spending anymore on things.... just a suggestion....after you try the cam sensor thing Rick suggestion in an earlier post.
 
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