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iTrader: (20)

Ok, well I have been having bad luck with my LT8 ever since I installed it, and it seems to be getting worse. Once I had it installed, everything started up and ran fine....all be it, the idle was really high, 1300-1500rpms. But the car started, drove, and idled fine....but would not boost without feeling like it hit fuel cut. So at 0psi the car would just hit a wall for a second, and just not boost. Ok, MAP sensor line is what I thought....tried 3 different spots, same problem...but now it will boost every once in a while, but still has the same problem for the most part. But as long as I did not boost the car, it drove great....good AFR, no error codes, no problems at all.

But once it would hit that wall when I would try and boost it, for a few minutes it would behave funny....stumbling every now and then, but would eventually calm down and run good again...but still no boost.

Now it seems that the problem is getting worse.....it just started 2 weeks ago...but now just cruising down the road at any rpm with no load on the motor, or even at idle....the car will just stumble and fall on it's face....I can be going 60mph at 3000rpm and all of a sudden it will hit a wall for a second, rpm's drop down to about 2300rpm and then pick back up after about a second...then it will drive fine again. This is the same thing it used to do after I would boost it and hit that wall, but now it will do it whenever it wants to. I was sitting at a stoplight idling, 1400rpm, and then it would just drop down to like 800rpm for a second and then pick back up and be fine again.....I know that is the same problem it has when moving and when under load, I just don't feel the bucking effect since the car is stopped.

But it appears to be getting worse....used to never have any problems except when boosting, then it would do it after I would try and boost it, and now it does it whenever it wants to and it feels like it is beginning to do it more often....maybe once every 5 minutes or so. I can't think of what it could be. I am leaning towards the fuel pump, fuel pump relay, fuel pump wiring, etc....since it is more or less acting like the car is shutting off for a split second...since the rpms drop like that. The car will still start fine, no problems with compression from what I can tell...just this odd behavior. The ECU does not flash any codes when it happens, or shut off...so it is not power related...it is something shutting off mechanically since the motor dies when it does it. The TPS has been calibrated numerous times.....I am thinking I may have a bad ground, or solder joint somewhere and it is kind of on or off....but I just wanted to ask some others what they thought it may be.

I have talked with Tim at Microtech and my maps are fine...all stock base maps and settings. I have the fuel cut and boost cut shut off....and while on the dyno, the AFR would be 14.7 at idle and during acceleration it would start to richen up...13.5, 12.7, 12.1, 11.6, 11.1....and then 0psi would hit, and 17.0....like all the fuel just got turned off.

I am only running a DP/MP, stock cat back, CAI, and a BOV...and of course the LT8. The injectors were just cleaned and balanced and flow perfect, and the car never had any problems before the LT8, so I am thinking it is in the wiring of the ECU...but if you have any insights on to what it may be, please let me know.

Sorry this was so long...

Scott

10sec rx7

it sounds like you are drowning it, 11.1 before it comes onto boost is way too rich, usually i will aim for about 13.0 to 12.7 at 00hg then as it comes onto boost bring the fuel into it,

i have had times where a rich mis fire will cause the readings to go very lean, when it is just too rich,

dale

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iTrader: (20)

But at idle? at -16vacuum? why?

Poweraxel

check fuel pressure
verify base timing
verify advancement
wiring to the secondary injectors (voltage to pin)
wiring the to the CAS


good luck

HIMNI Racing

What about tunning...Have you done it?

10sec rx7

at idle i just get it where it is happy, at 16inhg usually aim for about 14.0:1

Dale

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iTrader: (20)

Can't tune it when I can't boost it.

10sec rx7

have you pulled some fuel out of it so it is not 11.0 before it comes onto boost??? that would be the first thing i would do.....

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iTrader: (20)

Well I have been trying to get my car running right ever since I installed my Microtech LT8. I have gotten alot of the bugs out of it now...but one is still getting me. The car will just hit a random wall, like fuel cut, when you are driving around. It runs fine and then the rpm drops like 800rpm for a split second, you can feel it die (fuel cut), and then it kicks right back up and runs fine again. It will do this at any random time, at any random rpm, or even at idle. Except at idle you don't feel anything since the car is not under load. You just watch the tach drop about 800 rpm and then kick right back up.

What could cause that? Where do I begin to look? I have checked the fuel pump and fuel pump relay....everything checks out fine there. And my school of thought was always that there are two things to make a car run...fuel and spark. So if the fuel is ok....then could it be spark? The only related problem I can think of about my spark/ignition situation is that when I hook a timing light up to my leading coils, I am right on the yellow 5ATDC....but if I hook it up to the trailing coils, it flashes irradically and is nowhere near the red/orange 20ATDC mark. Which makes me think that the CAS is off....but how? How could it run fine and boost perfect all the time, then I install my Microtech and now my CAS is off....it can't be, I have never removed it.

Could my rpm problem be the CAS? TPS? etc.....if you have any idea on where to look, please let me know. I have checked my plugs, leading and trailing, and both look fine....maybe a bit rich, but nothing horrible. Is there any reason that the timing light did not flash all the time on the trailing? If my CAS is mis aligned....could that cause a problem relevant to the symptoms I am having?

I also had a boost issue, where as the car would not boost....as soon as the MAP sensor read 0psi, the car would hit fuel cut more or less, even though the fuel cut option on the ECU was set to OFF. But I found out a reaon why it wouldn't boost today....my actuator rod had fallen off the wastegate flapper. I am going to get a new C-clip tomorrow for it. I am guessing that will fix the boost issue, but could that explain the sudden violent fuel cut at 0psi? or the random car surging?

Thanks,

Scott

HIMNI Racing

I couldn't boost it without tunning it. So we tuned and boost comes all day.

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iTrader: (20)

Well I think we got it figured out. I had a blown LIM gasket causing the high idle (I thought) and possibly causing the stumbling effect. So I changed it out for a new gasket and O-ring and put it all back together only to find out that I could still hear a vacuum leak....and that it still stumbled. So we looked around for more leaks....and the can of carb cleaner put up right back down around the LIM again...turns out that my new injectors from RC came back without the rubber gaskets that go around the tip in the manifold and that it was leaking out of all 4 holes. I never paid any attention to it when I installed them...because I am an idiot....but either way, we noticed it last night and sure as ****, once we put some little rubber gaskets on there, the leak went away. Problem is now that my car will not start on it's own....I have to slightly push the gas pedal in to get it to start....and I have to keep my foot on the gas to keep it running.

I had adjusted everything else before based on having that leak....I set my TPS calibration with it, set my timing with it, set my throttle cable with it, set my idle set screw based on it, etc.....so could one of those factors be causing my car to not idle or start? Also my maps are off on my LT-8 I think.

My t_rpm map is way off I feel. Could someone tell me roughly how they have theirs set? Because mine reads something like:

500 +5
1000 +10
1500 +15
2000 +25
2500 +30
3000 +30
and all the rest read +30 up to redline.

That seems way off to me. And at idle my timing is at +5 but at even the slightest bit of throttle it reads +16 on up to +20....and then at 2500 or more, it is constantly reading +35 which is what my T_max is set at. If someone could help me get some halway decent maps on my car it would be greatly appreciated.....you can PM me your number and a time to call and I can call you and talk with you, or you could just post what yours are set at, etc....my car is more or less stock.

DP/MP
BOV
Intake
LT8
TB Mod
etc....nothing big.