89BlueTA

Hey guys,

I finally got the time and weather to g-tech my car after my unplanned winter mods. It ran decent with a lot more power down low than I thought it would have. But at the top of second it has a very pronounced stutter, before it shifts. It misses on all cylinders, goes another 100-200 rpm then shifts. On my last run it also stuttered at the top of first gear. The FP was steady at @47-48 psi. All ignition components have maybe 8000 miles and a 1 1/2 yrs old. With new plugs, and an old pick-up coil. She runs really well besides the stutter. If anyone has any ideas please let me know! 13deg. timing, knock sensor hooked to resistor, 93 octane, no cats, no muffler. Full tank of gas.

g-tech runs(I have never g-teched car before)
#1 15.10@104 Full throttle start lots of tire smoke
#2 14.22@104.5 Eased out of the hole, still no traction
#3 14.23@105.1 Eased out again, no hook, stutter top of 1st and 2nd

thanks guys

nblanchard

you by-passed your knock sensor? why?

89BlueTA

I bypassed the knock sensor, when I was having trouble with a plugged cat., I thought maybe that was the problem at the time. And the wire going to it and the sensor were already beat to hell.

nick

nblanchard

I woul dhave to say that could very well be your problem.

89BlueTA

I have run it for over a year like that, without any problems, I always run premium gas. I think if I was getting spark knock bad enough to cause a hesitation that I would hear it, though the car is very loud. I will get the tech1 on it this week and see what kind of data I can get.

Thank you for the reply

nblanchard

I was told the knock sensor allows the computer to sense knock , then it backs the timing off a tad, so you get maximum timing out of your engine. Thats the only thing I can think of. Keep us posted

89BlueTA

You are right about the knock sensor, I am just telling the computer that there is no knock. So that it will not take any timing out. There is a gas station down the road that sells torco race fuels. I will get some 100 or 104 unleaded later this week to verify that there is no knock. Maybe it will help.

nick

nblanchard

I am not saying there is knock, what I am suggesting is, that the ECM can't adjust the timing, because it always sees the same value of "knock" Maybe I am talking out of my A$$.

89BlueTA

I do not think it is a timing issue, it misses on all eight cylinders, completly shuts down, then goes, then shifts.

89BlueTA

Well I just got the tech1 on her and I seem to have some sort of electrical demon, first of all I am getting a code 42 for EST bypass fail, also when you start the car, the alternator is not charging and the tach is bouncing all over the place. Then for no reason, the tach will steady and the ALT will start charging, then it will switch off just like someone flipped a switch. It just cycles back and forth. I assume something is grounding out, all the wires I can see seem to be fine, so I am thinking that it might be the pickup coil or ignition module.

Let me know what you guys think
thanks
nick

Thanks nblanchard you seem to be getting me down the right path.

nblanchard

no problem dood.... electrical problems take a lot of patience, I wish you luck. One piece of advice is maybe to get a new engine harness I have seen some on e-bay at times... give them a shot. Wish I could scoot over and help ya, but I think you're a little far

Greg90iroc

Maybee it is supposed to have that problem. I drove a 01 Z-06 that had the same problem. no traction in 1st 2nd or 3rd. The traction control was disabled and the problem was still there i was hitting the rev limmiter. Oh if the knock sensor is disabled don't have it hooked to a resistor. just disable it.

89BlueTA

Well the stutter seems to have been fixed with a new ignition module. I made three passes with the tech1 hooked up instead of the g-tech and they were all smooth. Though opn the way to my 1/4 mile spot it did stutter once at part throttle.

My O2 readings in first are 950, in 2nd 900, in third 800,
with injector pulse widths starting in the 10.8ms then leveling off in the 10-10.5ms range, that seems like a lot of pulse width. I am not sure what the maximum duty cycle for the injectors is. But with that long of pulse width, mine must need at least 14 ms to complete a cycle.

Let me know what you guys think.

nick