garage_queen

iTrader: (3)

I recently converted to LTCC but this problem existed prior. The car just falls on it's face when starting to accelerate but then recovers and doesn't skip a beat...as if nothing is wrong. No matter what RPM I am cruising at, as soon as I start to accelerate it stumbles hard (not a miss, but more like shutting down) then immediately recovers and runs smooth all the way to 6500. If I stay WOT and power shift, everything is fine. If I let out, shift, and try to get back in it..it's stumbles and goes.

I'll be able to get datamaster logs on tuesday but was hoping someone has dealt with this and has an idea.

As much as I want to blame this in "tip in" being caused by the 58mm Holley TB, I don't believe it's in the tune. I have had the same tune and TB and not had the problem and nothing has changed. I put new plugs in it today and it did not make a difference. Wires all look fine, but this problem existed when I was using the opti in the stock manner with MSD wires.

I am thinking the TPS could be going bad but it's not exhibiting the normal symptom of a bad spot since it happens at any throttle position. Logs should show if there is a problem there.

Z28Camaro30Ann

iTrader: (15)

I have been having the same issue. Do you have a cam?

95z286speed

iTrader: (1)

im having the same problem..but i think i found it..arcing plug wire. i can see it at night...mine with be fine...then hesitate for a few seconds or a little longer and then be fine again..haven't been able to try full throttle though..

always faster

iTrader: (6)

If you search my user name here and also on camaroz28.com you will see that i ve chase this problem for years(mostly because lack of time)and found it.I also got an ltcc but its not the problem

My problem was a combination of a couple of things:

-Plug gap(mine was way to open because of a bad gauge)
-My first mail order tune(made by a forum member) was to rich(10:1 and lower)
-My O2 sensors was jam to .400-.500mv so the pcm didnt get the good signal and then it cause the sensors to be full of soot(no check engine)

So the car was running to rich and tended to hesitate any time you want to start or accelerate.But at wot since there is enough air the car is running perfectly to the redline.

Mine is now fixed.

~BuMps AloT~

iTrader: (5)

I had the same problem about a year ago. I ended up just replacing my o2 sensors and that was the problem. I never even had a check engine light come on.

garage_queen

iTrader: (3)

Thanks for all the replies. I know I am running rich and could easily have one or both O2 sensors failing. I do have a custom cam, below are those specs.

Duration:
Intake: 227
Exhaust: 227

Lift:
Intake: 556
Exhaust: 556

Lobe Center: 112

Centerline: 108

Z28Camaro30Ann

iTrader: (15)

I have been having a similar problem. I thought it was O2's as well so I replaced mine and it didnt help. Replaced my MAF, nothing. Checked all my plugs, wires, and changed my opti...nothing.

My tune was by madtuner, it was a mail order tune, but turned out its not my problem, it was my cam.

My cam is a TPiS ZZ409 which has:
Advertised Duration 287/287
Duration @.050 226/226
Gross Lift .520/.520
Lobe Seperation 112

Didnt jive with my setup. I am now changing everything. I am upgrading do LT1/LE2 Heads, and a custom grind cam from Comp Cams, then getting my car dyno tuned.

I'm not saying your problem is your cam though! Definately eliminate the cheaper/easier options first! If the O2's or spark plugs fix it then right on. If not have the tune checked out! If not that, might start lookig at the other things.

Green3spd

iTrader: (7)

Well, did it start after the tune or mod??
Or did the problem just arise??

Kris

Z28Camaro30Ann

iTrader: (15)

Mine started when I did the cam swap. Ran like *** after the swap before the tune, but I had sent in a PCM to Madtuner and was waiting for it. It came in the next day, I installed it and the car ran noticably better but the bog was still there.

always faster

iTrader: (6)

Before changing the O2 sensors,make a log with your datamaster.

If the O2 milivolt doesnt move quickly from .100 to .900 and stay jam at one point they need to be changed.If not look elsewhere.
Dont skip the spark plug gapping part,i thougt mine where good but my gauge was defect so i was running(badly running) with a way to much open gap.

garage_queen

iTrader: (3)

Should have logs this week. I changed the plugs last weekend. I was running NGK TR6 with a gap of .032 and have now changed to a non-projected NGK BR7EF with a gap of .025 There was no change in the issue after the plug change.

i420tom

iTrader: (11)

i have somewhat same issue and i have made several (all possible) attempts to corrrect this and what i have found that i have is a lean issue at small throttle bursts only.
full throttle is fine...
i even occasionally get the lean backfire at 10-30% thottle burst from idle or low rpm..
good luck i hope you fix it-------- subscribing......

i plan on trying to adjust the tune to give it more fuel but not sure if i should just command wot at these low rpms or what... If i figure mine out ill post here as well.

camaroz28383

iTrader: (9)

my car(bone stock) does this crap and after changing all the cheap stuff o2s, plugs, wires, coil, injectors, icm, icm relocation, my solution is build a 383 and not reuse any old componants

garage_queen

iTrader: (3)

bump for other victims of this problem. Got my cable back tonight so logs will be up tomorrow.

garage_queen

iTrader: (3)

If you can read datamaster logs, they are attached. I can also do an export to excel if anyone would like to see it that way. After reviewing the logs myself, I noticed the TPS to be acting funny. With the key on/engine off, it seems to act normally resting at .08v and 0% when closed and goes to 4.9v and 100% @ WOT. When the engine is running the voltage seems fine but the percentage value seems to stick and doesn't want to return to 0%. I had an extra (brand new) TPS so I swapped it out but it does the same thing. You may also notice the knock counter going nuts. Last time I researched that, people were telling me that it's a bug in the datamaster software but I have since logged other 93 LT1s and they do not exhibit the same behavior. It's possible that I have a knock sensor from a later year. I found out recently that the knock sensors are also specific to the 93s so I'll see about picking one up today. I don't think it's related to the stumble though. Smooth progression through the RPMs does not exhibit a stumble, only a good stab at the throttle. Seems it's just not fueling correctly for the increased airflow....like tip in. Also, the O2s seems to be acting ok. I did notice that it does not want to stay in closed loop for long. Only DTC is a TPS low but will reset the PCM since I replaced the TPS and see if that goes away. Let's see what you guys think. Any help is appreciated.


EDIT: Added export file attachment for those that can't view with Datamaster.

i420tom

iTrader: (11)

man i looked at that datmaster file and there is something seriously wrong with that file.. LOL 222 degrees of spark advance and it reads 3.9k rpms the whole time.. mine would kinda look like this when i had my laptop pluged into a powerinverter inside the car.. try running on laptop batterys only or run an extension cord.

garage_queen

iTrader: (3)

You might have to be sure that you have the datamaster setup correctly for a 93. I seem to remember having that same problem when I install datamaster originally with an OBD2 definition file or something. I could also be thinking of my CATS Tuner software.

garage_queen

iTrader: (3)

Here's a screenshot of the point right when it stumbles. Rec# 140 for those that can see everything correctly in the other files

garage_queen

iTrader: (3)

Datamaster program info...you can go to Help/About and see what you are running. If the file looks wrong, yours is likely to be different

Here's a link to the 93 version of DM. You don't need to pay for the software to be able to view datamaster files. It only limits to a certain number of allowed recordings before it expires. Even after expiration, you can still view files, just can't record them anymore.

http://www.ttspowersystems.com/softw...M-DA-setup.exe

i420tom

iTrader: (11)

LOL yeah mine is for 94-95 only...