stumble......

[turboculosis]

Well, my car is finally up and running w/ the new motor,but it has this annoying tip in stumble and deceleration stumble.Prior to going with a set of new 75lbs injectors and a new brutal6 chip,the car had the same problem.At the time the car had 55lbs injectors and RA's 93 chip.I figured by going with a new chip and injectors would solve the stumble problem.Here's a list of stuff we already did:
Replaced coilpack and module w/ new
Replaced cam sensor w/ new
New plugs
Check for any vaccum leaks.(guage shows no indication of a leak)
Swap LT1 MAF w/ stock one(just to verify)...no improvements
Double check I/C hoses...were tight.
.....Now,the next thing we will try to check is the ground.Other than the ground.Is there anything that we have overlooked?Oh almost forgot to mention when the stumbles occur the BLM's are @ 142-145.

 

[The Radius Kid]

What's you idle TPS setting?
I usually set mine to .42,key on/engine off.

 

[T-Type Mike]

I would check the TPS also. Its happened to me before also.
Just out of curiosity...Did you get a new chip burnt when you changed to bigger injectors?

 

[Eric Stage I]

Sometimes when I am troubleshooting tip-in stumbles, I take the fuel pressure way down, and then way up just to see if its related to fuel. If it is, then maybe an adjustment in the chip can be made. Don't adjust it a couple pounds, I'm talking an obscene amount, like down to 30psi and up to 60psi (if possible). Don't do any WOT like this, just drivability stuff.

Regards,
Eric

 

[jastrckl]

sorry everyone for his double post

 

[turboculosis]

My TPS is currently set to .42 key engine off.As far as determining if it's fuel related via chip,I haven't done that due to the car crapping out on me yesterday due to a cracked cam sensor.I was wondering if making adjustments to the translator fuel @WOT settings will have any affect on this stumble.I have it set at 6% rich.

 

[NJTurbo]

Tps looks good, are you sure this is not an engine miss, do you loose fuel pressure. What did Paul say about it

 

[turboculosis]

Originally posted by njturbo
Tps looks good, are you sure this is not an engine miss, do you loose fuel pressure. What did Paul say about it

The only time the stumble occurs is when I tap the throttle quick between idle and about 1500rpms.At this instant the fuel pressure is constant until it dies(inline pump).The other time it occurs is when cruising on 3rd(th400) and then coming to a quick stop.I've had this problem before the injector and chip change.But if I get in it slowly and let off slowly it doesn't get the stumble.As far as fuel pressure issues and misses at WOT I have none.Paul and the crew have spent alot of time and effort trying to troubleshoot the problem.Which they didn't have to do since the car already had the problem prior to me bringing the car there.They just wanted the car to run perfect before I took it home.In doing so they have concluded it to be either a chip fuel parameter or the LT1/translator setup.

 

[blackbuick87]

What are the settings on the Translator? Dip switches and MAF base & WOT

Since you have gone through all the basic stuff I would reset the cam sensor. You may need to go to an Extender chip to alter your fuel curve

 

[6=8]

Cam Sensor, eh?

After fixing the cam sensor, did the problems get worse, stay the same, or get better? Interesting, as the cam sensor signal is used for fuel timing.

Once you get the car started, unplug the sensor and drive in batch fire mode to see it that helps (That is, if your setup allows for it... mine is a stock setup.)

Ditto what blackbuick87 said. Verify the cam sensor was installed and adjusted properly!

 

[Eric Stage I]

(Sorry about that double post up there...I deleted it. Too happy with the 'back' button I guess)


How is your blm at idle? I know you mentioned some blm's in the 140's. Also, what kind of voltage are you seeing on your scantool? Are you using an ecm with the peak and hold drivers?

Eric

 

[turboculosis]

Sorry for the lateness in replies.But the car is at the shop right now.Tomorrow,as soon as I get her back and hopefully get my DS to work properly I will supply you all the info.I really appreciate all of your help.I do know that the translator MAF/WOT setting is at 6% rich(pos.#7) and after talking to Kevin @ Ramchargers,He recommends that I start off with (pos.#0).I overlooked the fact that my injectors are now bigger and chip totally different from what I had before.But I am unsure that this would even help solve the problem.As for the new cam sensor in place,I was told that the car is now running better.I will find out more tomorrow....

Thanks Again---

 

[blackbuick87]

I bet the Translator had a lot to do with it. It does funny things when you start messing with the dials and you dont have an Extender chip.

I did that with a Thrasher 100 and the car was a piece of crap. Hesitation and couldnt do a burnout to save my life

 

[turboculosis]

OK.Here's what I got so far...I checked the dipswitches and settings on the Base and WOT switches.the dipswitches were in the right positions,the Base was at Pos. #3(OK)and the WOT was at Pos. # 3(6% rich).These settings were set by the previous owner.I don't uderstand why he had the WOT knob set at #3 and not at #0 position,due to the fact it had a RA chip and not an Extender chip which would only benefit from the fuel curve settings.Another thing is that he had told me that the current MAF sensor was an LS1(3.5) when in actuality it's an LT1(3.0") which I didn't find out till after I ordered these new chips from Neal Steward.I have a feeling that this has a part if not "the" problem of this all.Could the chip parameters that are setup for the LS1 MAF cause a problem when the car has an LT1 MAF?I believe that the previous owner thought he had the LS1 MAF because when I bought the car,it had the same exact stumbles.

 

[blackbuick87]

With my Translator and a Thrasher chip, my car runs GREAT on the LS1 setting. This is despite the fact that I have and LT1 3" MAF. Others have said the same.

I put it on the 3" setting and reset the ECM, and I had Hesitation City. It was terrible. Went back to the LS1 setting. Dont know if this is typical or not but that is what my f***ed up car likes

 

[turboculosis]

Originally posted by Eric Stage I
Sometimes when I am troubleshooting tip-in stumbles, I take the fuel pressure way down, and then way up just to see if its related to fuel. If it is, then maybe an adjustment in the chip can be made. Don't adjust it a couple pounds, I'm talking an obscene amount, like down to 30psi and up to 60psi (if possible). Don't do any WOT like this, just drivability stuff.

Regards,
Eric

I tried this,and guess what....First I tried bringing up the fp @ around 60,and made it stall out.Then,I tried backing it down to 30.And stumble was gone, not even a little.I mean crisp throttle response.Looks like I have a fueling issue in the chip.And also,I changed the translator setting to th 3.5 setup and helped the idle quality and possibly the stumble problem.Thanks to all.I think I'm OK now.I hope.

 

[Eric Stage I]

I had a feeling that might help. Delphi 75's when combined with peak and holds are a "fast" injector (they open fast). This causes richness at low pulsewidths. It can be compensated for in the chip.

Yeah! You found it!

Regards,
Eric