Help Little MS.

[donZ]

My 87 gn, has a Little miss or stumble, when you step on it,
any thoughts on this, i know you guys have a lot of thoughts, but be nice.
i replaced, plugs, wires, o2,fuel filter, bad vacauum hoes, cracked ds manifold,
set tps .44 and 4.64
fuel persure 40lbs
i taped on the maf, no problem. the boost goes up to 22lbs.
the car has.
42.5 injectors
307 fuel pump
hot wire kit
93 octane chip.

 

[bob86gn]

Don,

Try to set your TPS around 0.38. This helped my stumble and coupled with adjusting the cam sensor cured the problem.

Bob

 

[donZ]

with the car off it is at .44
when i start it it goes to .46

when i bring it down, the wot goes down with it. ?????????

i will give it a try,

 

[zam70]

what kind of chip...adjusting your TPS lower should have no effect...all the ECM pays attention to is UNDER .48 or over 4.42 (or what ever your chip burner has programmed for WOT) Try raising or lowering fuel pressure...you've got a tip in stumble. Usually an easy fix, you've ust got to play a little to see what the car wants.

 

[salvageV6]

IACV counts?

I'd back the idle air screw out a tad and reset everything to normal spec.s.

Start with a lower tps too.

 

[donZ]

i set the tps @ .38 car off, start the car and it goes to .40 to .42
wot is 4.40
set fuel to 42 lbs line off

i took the car for a ride still the same stumble.but pulls hard.

02's read around 825 to 835 wot
knock 10.7 to 12

at idle iac 70
bl 107

i drop the fuel down to 30 line off, i think to low
stumble just about gone, but car runs slow .

what else can i try ????????

 

[salvageV6]

Gotta get the IACV counts in spec. and then work to reset the TPS to spec.

Back the screw out and start from scratch.

Set the fuel pressure to where the chip maker recommends it.

Just my .02.

 

[zam70]

I'm with Salvage V6...your IAC #s are way to high...get them down around 20-25...lower if you dare. Sounds like your butterfly is closed down to much. This would explain why the stumble goes away when you drop the fuel pressure....I'd go through gn/ttype site and set everything accordingly. After that you can focus in on the problem.

You never did say what kind of chip. I have heard that some have problems with tip in. Keep your fuel pressure up and get more air in at idle. What is the car idling at (rpm)?

 

[donZ]

i just went and adjusted the iac, got it down to 20. reset tps
it still has a stumble.
i check it again, it is back up to 40?
the chip is a 93 octane,is what i was told not sure of the maker.

zam and salavage thanks, i am still trying..

 

[zam70]

When adjusting the iac, make a turn, let engine even out, shut off and restart. You need to get a chip you know in there....You might have old tech in there and things have come along way...

 

[donZ]

i let the run for about 5 mins at 20, turned it off restart and still at 20,
i will adjust again later.

what kind of chip do you think i should use ?

 

[zam70]

Lotsa good chips out there and everyone has their opinion.

PTE/Lubrant
Jim Testa
Red Armstrong
Thrasher

And, IMO the end all BE all, MaxEffort 16.

There are others I'm sure (sorry if I forgot anyone). Just do a search on the names above, Lots of info on the board.

 

[salvageV6]

If they are greenstripe 42lb. inj. get a 93 street chip from one of the experts.

What markings are on your current chip?

For now forget about WOT TPS we gotta get good results with the tip in problem and get some baseline values that will work.

Zam is right about the butterfly but too far open isn't good either for tip in.

Let us know about the chip first.

 

[Roger]

Check fuel pressure line off & it should be about 5-7 pounds less with line on. I had a bad regulator that wasn't lowering the pressure at idle & had a bad tip in problem. A clogged vacuum sense line to the fuel pressure regulator can also cause this problem. A clogged line can sometimes raise pressure under boost & not lower pressure at idle vacuum.

 

[Trbobuick]

have you tried tapping the maf yet?



Brian

 

[donZ]

here go's

i looked at the chip, it says on it ( street 93 42.5 20 degree)

fuel regulator is fine

taped on the maf, no problem

my iac change everytime i start the car, and go for a ride,
i set it at 20, next time it is at 40, next time it is at 30, then 20 again. it has gone as high as 50, and as low 0

ok, now i put the factory chip back in, stumble is gone.........
the car does not pull as hard, it seem's real slow..
one good thing i have very little knock now .05 to 2
i was getting between 10 and 14 before.

what do you guys think? i have a few problems?

thanks for all the input.
don

 

[zam70]

Sounds like you might have answered your own question...

Chip.

20 degrees street timing is a little high IMO. (depending on boost and fuel octane)

Your IAC should read higher in gear...the 20-25 range is at idle in park/neutral.

Since the different chip took the stumble away, I'd look at a different chip.

 

[Justaveesix]

check your coil pack while your at it, not just with a meter but with Casper's coil tester. You may have a coil starting to go bad causing stumble at idle but WOT is ok. I know I did, swapped coils and it was gone at least 95% anyways. 10-14* is way too much knock, another chip may help as said above

HTH

 

[87gnNV]

DUDE!!!!!!!! back off the boost!! If you are at 10.7-12 on knock that is WAY to much!!! If u are using 93 i would go down to about 16-17 max!!!!!! Can beleive no one cought that .

 

[zam70]

42.5s are not notorious for tip in stumble, some CHIPS for 42.5s are.

Most of the good programmers have now figured it out.


I didn't address the knock because that wasn't his concern at the moment...one problem at a time.

Knock reading is way to high. definately turn the boost down.