Gremlin still kicking my a$$

[Amelio]

I have been fighting this freaking thing for a while and it seems a lot of other guys are having very similar problems but I have yet to see some good answers to the issue. I have not been able to throw parts at it cause money is real tight plus I don't like buying a part unless I know that is the fix.

I am having the notorious bucking and car nosing over problem that so many others are experiencing. Basically the car is falling on its face and and will not recover unless I lift. It is also 100% boost related because it will only do this at 15 psi and I assume higher obviously cause it wont go past 15psi. This is not an rpm issue because it runs great at any throttle position at any rpm up to 14 psi. So this tells me that the increased pressure in the cylinders is a problem but what is causing it is got me.

Just before this issure arouse I installed a TT chip went to the track made 3 really good passes, came home parked the car and it sat for 2 weeks> when I went to go drive it after sitting I bucked and popped real loud at 10spi and ruptured the fuel return line> I replaced the fuel lines with steel braided lines and an inline filter it has now been doing the below described issue ever since.

Also while very light throttle just cruising I can faintly hear it dropping cylinders every so often which leads me to believe it"s an ignition issue.

I have a Type II coil/module I put new Ac R42 gaped at .030- No fix

I swapped out with a Stock coil and module that I had- same condition.

I swapped out plug wires (not new just spares)- same condition

I removed my crank sensor to inspect, it looks like it has just barely rubbed in the slightest way but I dismissed this as a cause due to the car running great all the way through the rpm band with lower boost.

I have verified my fuel is rising correctly with increased boost, plus when the issue occurs I am getting 780mv to 805mv which tells me it is not lean. I am also showing zero Kr except one time it showed .5

My charging system is working good at 14.5volts at idle and I have a voltage booster and hot wire kit.

I have checked TPS all grounds, cam sensor all wiring and have not found an issue. I unplugged the cam sensor one time and same issue occurs. I unplugged the maf which is an LS1 wit translator to try and drive it and the car shuts off as soon as I unplug it.

The only thing I have not done is buy a new module, coil pack or wires, and I doubt that is the problem because I swapped them with others and the problem did not change the least bit. I don't have a spare ecm so that is a possibility and I don't have a data logger which I am sure would help determine the cause.

If you see anything I have over looked please chime in, this is extremely frustrating and I am just about out of ideas and places to look.

Thank you!

 

[Nasty]

What valve springs are you using?

 

[garyk1970]

three guesses ....

1)bad o2....too rich (my car does this when too rich)
2)does maf go to 255 at wot?
3)fuel lines are crossed.....fuel supply from pump goes to pass side of fuel rail.....HTH....sorry just some internet guesses....hard to diganose when the car cant be seen in person...

 

[86GN-862+2]

Does going back to your other chip get rid of the problem?

 

[TurboDave]

Certainly sounds like it might be ignition module/coil pack related. Are confident of the grounding of your ignition module/coil assembly? This is a critical item that often gets overlooked.

 

[Chuck Leeper]

Just diagnosed a similar problem w/ an LS engine. Up on boost backfires, lays down.
Sounded to me perhaps the crank was moving around, and the crank sensor was loosing signal. Checked the thrust =.142"
The owner pulled the engine, the crank was toast, and was even cracked at the thrust face.
Your crank "staying put"????

 

[Amelio]

What valve springs are you using?

I do not have the part numbers but they are the comp bee hive springs that came in the cam kit from Full throttle. The car prior to this was running great as mentioned before went to the track 2 weeks prior no problems.

 

[Amelio]

three guesses ....

1)bad o2....too rich (my car does this when too rich)
2)does maf go to 255 at wot?
3)fuel lines are crossed.....fuel supply from pump goes to pass side of fuel rail.....HTH....sorry just some internet guesses....hard to diganose when the car cant be seen in person...

The o2 is a brand new delco purple wire, I am getting anywhere from 750mv to 805mv in condition so I do not think it is too rich.

yes maf goes to 255

hmmmm i dont think the car would even run if they were backwards????

Thanks for the suggestions!

 

[Amelio]

Does going back to your other chip get rid of the problem?

I have not tried that because the TT chip the car was having some kr issues< i put the TT chip in and a few weeks later went to the track car went an 11.54 on 19-20psi

I can try but I dont think it will fix the issue.

 

[Amelio]

Certainly sounds like it might be ignition module/coil pack related. Are confident of the grounding of your ignition module/coil assembly? This is a critical item that often gets overlooked.

yeah I am with you I definitely think it is ignition..... no I am not certain of the coilpack/module ground....... unless it is one of the grounds on the back side of the passenger head. All those grounds are good, I actually found a broken ground thinking that was it....I fixed it but it did not change a thing.

Where else should I be looking for proper ground?

 

[Amelio]

Just diagnosed a similar problem w/ an LS engine. Up on boost backfires, lays down.
Sounded to me perhaps the crank was moving around, and the crank sensor was loosing signal. Checked the thrust =.142"
The owner pulled the engine, the crank was toast, and was even cracked at the thrust face.
Your crank "staying put"????

chuck that is a great point, I did remove my crank sensor to look it over and it looked as if it had barely rubbed....very slightly I had to almost get out my magnifying glass to see any marks. To answer that question I suppose i would have to pull the pan and check the thrust....I have never done this in the car with an engine that has a girdle....is it possible?

Also chuck I have spoke to you a few times years back when the Buick crew here in Gwinnett used to meet at the Hooters on Jimmy carter......we spoke about checking injectors I was thinking if this could possibly be an injector falling off?

I have been monitoring my mv's to make sure the car is not leaning out.....I just got back from putting around town....for the hell of it I bumped up the fuel in all gears almost 12% and it did not change a thing in my mv's. I dont know what to make of that.

 

[TurboDave]

yeah I am with you I definitely think it is ignition..... no I am not certain of the coilpack/module ground....... unless it is one of the grounds on the back side of the passenger head. All those grounds are good, I actually found a broken ground thinking that was it....I fixed it but it did not change a thing.

Where else should I be looking for proper ground?

You could try a temporary ground. Run it from one of the module mounting bolts (the ones that mount the module to the plate) to a good spot near by on the firewall. There's a ground screw pretty close.

 

[Chuck Leeper]

Yep..

You could try a temporary ground. Run it from one of the module mounting bolts (the ones that mount the module to the plate) to a good spot near by on the firewall. There's a ground screw pretty close.

I put a permanent ground strap to the intake stud, from the module mount bolt. Has the mount plate been powdercoated? All the nuts/bolts in and tite?

Checking the thrust is easy. You can pry the crank forward and back at the flexplate. If it's shot, you'll know it!
As for the injs, we can check/clean them in a day. Or, U can drive down and we'll pull them, and do the clean here. [I'm in Bostwick. South of Monroe on 83.]
How old are the injs??

Give me a call. Maybe we can put your head and my 1/2 head together,[CRS has set in!], and figure out what's going on! 706-342-3152 h/s, or 770-265-5144 c. I'm here most all the time.

[I have a coilpak/module tester. So, if you come down, bring any extra paks, and we'll test them, too.]

 

[87NAT]

Did you maybe loosen up or blow off a hoseclamp on any of the intercooler or up-pipe connections? I have had that experience after some hard track passes.

 

[Amelio]

Thanks Chuck and Dave that is a good idea I will put a ground strap on it to see if that fixes the issue. Yes the intake and plenum both have been powder coated but the engine has been together for a little while and was at the track running good. I will still run a additional strap to see if it helps.

The injectors are pretty old if I had to guess they are about 9-10 years old

Chuck i will give you a call I live in Loganville about 6miles from Maxi Price Chevrolet we are pretty close.

 

[Amelio]

Did you maybe loosen up or blow off a hoseclamp on any of the intercooler or up-pipe connections? I have had that experience after some hard track passes.

yeah I have checked all of that, I have also experienced that before and that is pretty much how the car acts when doing it....loud popping or backfiring....I think it is blowing out the spark.....but yes all the clamps are good and tight.

 

[TurboBuRick]

I don't see it in your sig. Are you running alky?

 

[LOT]

Cable

Could your + battery cable be touching header when enough torque is applied (15 psi) ?

 

[Amelio]

I don't see it in your sig. Are you running alky?

I do have a setup but I am not running it right now, before this issue I was able to run 19-20 psi on 93oct. I was going to start running the alky to go 22-24psi on the street. At the track the car made 19psi all the way down and just bumped 20psi around 1000 foot mark.

 

[Amelio]

Could your + battery cable be touching header when enough torque is applied (15 psi) ?

Yeah I looked it over good I have had that problem before a long time ago, I actually did see my negative bat cable was burned pretty bad from the DP and heavily corroded. I thought that was the issue....I replaced but still no fix.