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Discussion Starter · #1 ·
ok, i had the car in the shoppe for some work this past week trying to get
rid of a couple problems. one is still outstanding/existing. at low to no
throttle, going down the highway, the car stumbbles every now and then.
kinda feels as if there were air getting in the fuel line. it only lasts
for a second each time the car does it. i figured this was being caused by
a clogged fuel filter, which i replaced. but the problem is still there.
could 160 thermo without reprogramming cause such a thing. when it stumbles
the "check engine" light appears for a brief minute. i have not run the
codes yet, and am hoping that one of you might have a good solve for this.
please dont tell me to drop the tank and check the fuel pump & wiring.

Sam Benischek
[email protected] http://www.geocities.com/bgdstmpassta/index.html
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Vinni
95 ImpaSSta
Rollin' Solo
"Anything less, Is everything else"

http://www.geocities.com/bgdstmpassta/index.html

HTTP://WWW.STREETSCENEMAG.COM/VIEWOWNERPROFILE.ASP?PROFILEID=398

Airbags, Rancho Air adj. shocks, 17" "wannabe" mercury 5's by Eagle Alloys, Custom paint by Maxed Out Paint Wurx, eclectic compilation of stereo equip, Pepboys Sewerpipe intake, relocated MAF, Flo-master catback exhuast, "Krome Klamps" radator hose covers and chrome sleeves, two tone grey tweed interior
 
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Discussion Starter · #2 ·
This might not help but here's my story.

My car started to stumble and hesitate from standing start and low RPM highway. First I replaced the check valves. Both were shot. First run out I hear a bang. Driveability was worst. I purchased the AIR pump mod, still no improvement. I got the F-body EGR and I'm back! When I removed the OEM EGR it sounded like a baby rattle.
 
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Discussion Starter · #3 ·
with out the stumble, the car drives fine. no problems out of the hole. i already had the problem from the EGR and replaced it a year ago.
 
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Discussion Starter · #4 ·
Reading the listservers and forum my other thought would be Otispark or fuel pump. It seems that cars that are frequently driven with low fuel tanks have their fuel pumps go out more often than otherwise.

Maybe Dr Karl and Master Ed will help soon.
 
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Discussion Starter · #5 ·
Have you checked the fuel pressure? This sounds like the first symptoms I had when my fuel pump started going out.

Fletch
 
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Discussion Starter · #6 ·
Describe the Check Engine Light for us. When this happens does it blink or come on for a few seconds and does it ever go off completely?

When I was having O2 problems my Check Engine light would actually blink during the stumble. It felt exactly like what your describing. (Lack of Fuel).. In my case it was TOO much fuel and was causing a misfire.

For what it's worth have you checked your O2's.. and if you have 4 o2's don't get the O2 Harness mixed up like I did. My problem turned out to be the front right O2 harness was reading the rear left O2.

-Brian.


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1996 Impala SS BBB, Limo Tint, Red bowtie, Crossed Flag Emblems, Impala SS Airdam Impala Script, Dynomax Ultra flow Mufflers, Export Pipes, Meziere H20 Pump, Transgo Shiftkit, S10 Vortec Stall, K&N Cold air intake, MSD ignition, Bypassed TB Coolant, Ported MAF, Relocated IAT, Home plate & First base delete, Hypertech 160 Tstat, Walker Stealth Brake bolt,NGK TR6 plugs, SST 2" Lowering Springs, CompuCar N20 Wet Kit jetted @ 100shot.
 
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Discussion Starter · #7 ·
when the light comes on after the stuble it stays on for a couple days. usually it will stay illuminated for 3 or 4 days from startup. i hardly ever let the tank get below a quarter of a tank. sometimes i fill up at half. i know that the fuel actually acts as the coolant for the pump. how do you check the o2's? i am guessing that i will have to run the codes on a computer. that is why i think the 160 thermo is part of my problem. the car thinks it is too cold and i'm running rich all the time. this is what the car does to get itself up the running temp. however my 160 thermo does not allow this to ever happen. i hate these smart cars.
 
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Discussion Starter · #8 ·
Ive been running a 160 stat all winter without programming and my mechanical fan is allways running. its been damn cold!
I recommend everyone get a scan tool.
id check the O2 sensors!with a scan tool look at the readings and compair the left to right banks readings. the numbers go up and down and are random. when mine was bad it gave the exact same number a few times in a row while the oposite side was allways different.
good luck
 
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Discussion Starter · #9 ·
When I replaced my fuel pump I noticed how a cracked fuel line INSIDE the fuel tank could cause fuel starvation. A rubber line connects the pump to a metal line that exits the tank. When the fuel level falls below the level of the crack, the pump will suck air.



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'96 SS- SStored for winter, BBB, Tint, HPP+, Pep Boys Intake with K&N, Walbro Pump,March Pulleys, 160 'Stat. Coated SLP's going on soon.
'93 Caprice Classic Wagon- DCM, No Woodgrain, Lowered, Tint, AR 15" Rims, Just turned 180K Miles.
'86 Firebird- Black, No Winters, 305 Auto with Corvette Servo, Derale Oil Cooler, Exhaust Upgrades, 3.73's w/Zexel-Torsen Posi, Peeling Clearcoat. Wife thinks it's HER car. He He.
[email protected]
 
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Discussion Starter · #10 ·
Yeah, Unfortunately you don't have a Scan Tool and the Answer to all your problems lie right there waiting to be scanned. Don't pull your hair out or waste any effort trying to guess what this might be. You'd be surprised how WAY off you could be. I really doubt the 160 Tstat is causing the problem. Lots of people run those.

Concentrate your efforts instead on getting ahold of a Scan Tool. Even if you have to buy one of those Achtron's from Autozone. When your done just take it back for a refund.. hahah.. Once you know the codes you'll be home free on fixing the problem.

-Brian.
 
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Discussion Starter · #12 ·
ok, i put on a new belt today and when i started the car to see if my squeeking noise was gone, i noticed that from a cold start, both fans were running. could this throw a check engine light from startup?
 
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Discussion Starter · #13 ·
Yep.. The achtron runs $150 @ Autozone. Usually when the coolant fans are on it signifies an Emissions fault. Definitely O2's fall into this category..

-Brian.
 
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Discussion Starter · #15 ·
Would the O2's cause the stumble?? ABSOLUTELY! Data from your O2's are one of the biggest things your ECM uses to determine how much fuel to add or subtract from each side.. In my case my Right Bank was reading the O2 in the Rear and of course being so far back it was lean. SO the ECM dumped in a ton of fuel which is what caused my misfire.

Keep in mind that WOT the O2 Data is bypassed and the ECM runs off the Long Term Fuel Tables.

-Brian.
 
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Discussion Starter · #16 ·
i was told by another source the only the 96 (OBDII) threw codes from the O2s. this is because of the O2s before and after the cats. that was why i asked---
 
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Discussion Starter · #17 ·
ok, rick came over to the house last night and we hooked up his scanner to my car. o2s read fine along with everything else. but the MAF was reading the default or something in the 300+ range. i played with the extension wire harness for the MAF a few times anf restarted the car till the light went out, then the MAF readings were good. i think i have a bad wiring harness.
 
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Discussion Starter · #18 ·
SSweet! There isn't nothing quite like knowing exactly what's going on is there.. Gotta love those Scanners.

Good deal.. Keep us posted!

-brian.
 
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Discussion Starter · #19 ·
I just went through the same stumble, stalling stuff at around 2000 to 2200 RPM range. Got it fixed now. Hard to believe what the problem was! I have the old SSRI plexiglass air intake setup and the edge of the plexiglass had rubbed all the rubber coating off of all THREE wires going into the MAF! Apparently around the two thousand RPM range the plexiglass vibrates and was shorting out the MAF signal. So if you are running the SSRI, check your corner where the wires hook up and make sure the edge of the air box is not rubbing on the harness. A Dremel and slight remod of that left edge fixed my problem. (This after Stabil in the tank, a new fuel filter and a new Throttle Position sensor!! Found the problem once we hooked a scanner up to the car!!
Jay
 
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Discussion Starter · #20 ·
Righto, Jay. Coincidently, I just now finished cleaning the MAF sensors (quite dirty). While the SSRI was apart, I did check around for chafes at sharp edges. BTW, Larry Cigar mentioned replacing the vacuum grommets and hoses and such, and sure enough I found a dry-rotted elbow hiding underneath the PCV tubing at the intake. The PCV grommet is lose and baked hard too.

fx_ImpaSSta,
With identical symptoms as yours, I did the AIR Delete and F-Body EGR and solenoid (fuel pump already replaced 2 years ago). I got rid of my stumble with new plugs (without ever having replaced them for 130k miles
). I just need a good recommendation on wires now.

Other intermittent stumble culprits seem to be:
-Rain on bad wires
-Rain in the Opti
-Clogged/disconnected Opti suction tube (on those years that got one).
 
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