94 lumina 3.1 stumbling in park randomly - Hot Rod Forum : Hotrodders Bulletin Board
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Old 04-02-2009, 12:49 PM
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94 lumina 3.1 stumbling in park randomly

ok working on a real nice clean 94 lumina old man owned and every once in a long while it will randomly start to stumble when sitting running in park.

new fuel pump recently, no change.

fuel pressure is very strong, lot of fuel volume at the test valve port on pressure line on top of engine at intake manifold.,

tapped on ignition coils while running, no change at all either



checked all ECM, fuel pump, and bellhousing ground wiring and plugs,

tapped on ECM while running, nothing changed while running.

cleaned IAC motor and intake hole there, no change, noticed that if i unplugged it while running nothing changed while running

tapped on digital EGR valve while running and no change.


has no mass air flow sensor.

plugs and wires new recently

cat converter is a newer aftermerket weld on replacement


banged on the fuel tank while running, with a good rubber mallet and no change either.

tapped and messed with all relays and circuit breakers in the car
car runs STRONG smooth and awesome perfect, 123k miles all original stock unmolested

CEL light never on

found only one problem at all on the entire car and that was that whoever put a new starter on the car somehow forgot to tighten up the pos cable stud nut and so the two red feed wires and cable were VERY loose and it was losing power often

so i fixed that.

this stumbling rough running in park thing has never personally happened to me, and i have driven it alot recently, it just happened to my brother a bit ago today though when he was out driving it. he was jut sitting in park minding his business talking to someone and it just started stumbling etc but didnt die on him. for me it has done nothing but run flawlessy perfect tons of power like a brand new car literally.


i dont have a scanner or fancy test equipment for electronics or ECM or BCm or PCM units etc

so dont ask me if ive checked with any such tools haha

because i dont have any and so i cant

whatever it is it is something very minor stupid and random and a PITA haha.

im thinking something bad or loose in the tank, bad pump connector terminal or hmm...


something that isnt setting off a code or the CEL light.


anyone have any ideas at all?

because i am out of them now

thanks!!!

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Last edited by fast68; 04-02-2009 at 01:05 PM.
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Old 04-02-2009, 01:27 PM
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What engine is in this car? There were a couple of different options, IIRC. 2.0 4 cyl, 3.1L T v6, and I think it may have been availiable with a 3.8 v6 as well.
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Old 04-02-2009, 01:50 PM
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Quote:
Originally Posted by sbchevfreak
What engine is in this car? There were a couple of different options, IIRC. 2.0 4 cyl, 3.1L T v6, and I think it may have been availiable with a 3.8 v6 as well.


hi i did put 3.1 in the title

thanks

Last edited by fast68; 04-03-2009 at 01:49 PM.
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Old 04-05-2009, 06:52 AM
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The first thing I would do is change the fuel filter unless you know it has been changed recently. It will always seem to be a lot of fuel at the test port on a fuel injected motor, but that port is for testing the pressure with a fuel pressure guage. Bumping the Schroeder valve just to see if you are getting pressure is very dangerous and that practice can result in very serious personal burns as well as torching your car. Once the fuel filter has been changed and you still have the problem, I would check the throttle position sensor. You need a digital volt meter to check this and you need to check the manual for the correct voltage at idle and for wide open throttle. You also watch the meter while slowly moving the throttle to the wide open position and back to idle. You are looking for a smooth decrease and increase in voltage through out the range.

Trees
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Old 04-05-2009, 01:46 PM
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hi there yes actually i did notice that the fuel filter is extremely old if not original. so yeah its probably running borderline pressure/volume

however since i tightened up the extremely loose batt cable and two hot feed wires on the cable stud on the starter solenoid its been running perfect and strong and it purrs and has so much powe it literally goes from 0-60 in like 4 seconds its crazy

hmm

but i was told that one time it did sputter and want to die in park just sitting running, although it has never done it to me. after i fixed this

gonna put new filter on it real soon.


no idea which terminals on the 3.1 TPS are the ones to use to test that

haha this thread got moved to engine tech help board, funny didnt figure it was a hotrodders type question ahah



thanks!

Last edited by fast68; 04-06-2009 at 12:21 PM.
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