BADASS of New England
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BADASS of New England

An automobile club for the enthusiast who enjoys the last of the big GM cars. The rear wheel drive B and D bodys. Chevrolet Impala SS, Caprice, 9C1, Buick Roadmaster, Oldsmobile Custom Cruiser, Cadillac Fleetwood
 
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Most users ever online was 182 on Thu May 27, 2021 9:57 pm
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» 2021 Fourteenth Annual B & D Roundup!! Mark your calendar! Saturday October 16th
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MASShole9C1

MASShole9C1


Posts : 4294
Join date : 2009-12-16

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PostSubject: Bad stumble/misfire    Bad stumble/misfire  EmptyThu May 28, 2015 7:59 pm

(Obviously much diag is ahead, but I'm in the early stages of working this out, so here's a thread)

The roadmaster (94 LT1) has developed a strange miss/stumble. It's not consistent with weather (Wet/dry hot/cold). I've had 2 times this week where it didn't fire right away after sitting overnight. It started, but still unusual. Everyone jumps on opti being the issue, but I'm not gonna throw darts at $$$ parts. I've been reading the last 6 years about this stuff and it can be anything from the fuel pump, filter, and injectors being clogged, to fouled O2 sensors, intake leak, clogged cats, etc. I have no way to datalog and haven't checked the fuel pressure yet. I know the filter needs replacing. This happened after someone filled my gas tank with 87 from Cumberland farms. I always run shell gas. I put gumout in the tank and nothing really changed. Seems like it's getting worse. I've done no (ignition) tune up related work to this car. Thoughts before I part it out? I can't spend a ton of $ on this car to keep it going. It's not worth it. Anybody local have OBD-I data logging capabilities??

Thanks!
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sdstick

sdstick


Posts : 4292
Join date : 2009-03-20
Location : Revere, MA

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PostSubject: Re: Bad stumble/misfire    Bad stumble/misfire  EmptyFri May 29, 2015 10:33 am

You say this happened after someone put 87 octane in it
Nothing wrong with 87 but I'm assuming youre thinking water in the gas?
If so...have you burned through that tank & refilled yet?
Is the gumout youre talking about drygas?
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MASShole9C1

MASShole9C1


Posts : 4294
Join date : 2009-12-16

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PostSubject: Re: Bad stumble/misfire    Bad stumble/misfire  EmptyFri May 29, 2015 10:38 am

I didn't run the tank down, but I since put $20 worth and it's on E now. I put a bottle of system cleaner in the tank when it was 1/2 full on the gauge.

The timing is perfect with that full tank of gas and I had ZERO performance/running/driving issues prior.
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sdstick

sdstick


Posts : 4292
Join date : 2009-03-20
Location : Revere, MA

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PostSubject: Re: Bad stumble/misfire    Bad stumble/misfire  EmptyFri May 29, 2015 11:08 am

If it were me, I'd put some drygas & octane booster in there & run it through with some good gas.
Car will run better then ever (at least for that tank) & even though you pissed through $10-$15 extra it'll clean out some shyt
THEN....fuel filter for sure...just cuz youre due from the sounds of things.
If its rusted in & you cant change it, confirm pressure instead.
NEVER seen a filter cause the issue.....
Ya, I know, the friggin experts say it can happen..Rolling Eyes

Sure, you should search out other stumble issues (dirty TB, MAF)..do the free ones first
I also see you have someone gonna be looking for arcing wires...thats good.

If I were throwing darts, I'd aim at the opti & oil thru the seal only because the odds are in my favor.
You can open & clean & re-install for only the cost of front cover gasket set but its a PIA if you need the car as a daily.

Whomever borrowed your car....Do they have a big heavy right foot?.. Laughing
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1984twodoor

1984twodoor


Posts : 4068
Join date : 2010-03-30
Age : 30
Location : Wilmington/Wakefield/Andover

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PostSubject: Re: Bad stumble/misfire    Bad stumble/misfire  EmptySat May 30, 2015 6:41 pm

Start with running TECHRON through it. Nothing else compares to that stuff. I've seen a car that ran a few bottles of that then the head was pulled off (cam & lifter issue) and those valves were efin clean. You could eat off them. Use that.

Then start to look into it if it continues. The hard start after sitting overnight makes me think of a bad FP or press. regulator letting pressure bleed down. I would just hook up a gauge and check to be sure.

Steve is on the right track obviously, free stuff first clean the MAF and TB and of course try to pull an arc off a plug wire with a test light.
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MASShole9C1

MASShole9C1


Posts : 4294
Join date : 2009-12-16

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PostSubject: Re: Bad stumble/misfire    Bad stumble/misfire  EmptySun Jun 07, 2015 11:02 pm

Ran HEET and gum out through a full tank of fresh Shell gas. Was foolish and thought it had started running better.

Wrong. Finally had a night at home where I was able to check the car out. Actually brought the car to my buddy's house 4 houses down to drop off some scrap metal. It was dark out so we decided to spray some water on all the ignition components while the engine was running. Sure enough, we had a nice pre 4th of July show on our hands.

From the coil all the way to the wires we have about 1/2 a dozen or more areas arcing. Plus one of the Champion plugs was gapped at .070. Lol.

My fault since I never did plugs or anything to this car since I bought it October 2013. I'm sure after I replace the plugs, wires, and coil, I'm gonna have some other drivability issues. Seems common enough with the L99/LT1 cars.

Also found that the car overheats while idling and the fans don't turn on unless you unplug the temp sensor in the pump.

Any thoughts?
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95brmw

95brmw


Posts : 1434
Join date : 2009-11-10
Age : 39
Location : Connecticut

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PostSubject: Re: Bad stumble/misfire    Bad stumble/misfire  EmptyMon Jun 08, 2015 9:23 pm

What do you consider overheating? The LT1 fans come on at a very high temp from the factory.
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MASShole9C1

MASShole9C1


Posts : 4294
Join date : 2009-12-16

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PostSubject: Re: Bad stumble/misfire    Bad stumble/misfire  EmptyMon Jun 08, 2015 10:01 pm

Overheating as in, can smell coolant from reservoir and fans don't come on when roadmaster gauge is at 3/4 or higher.
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miniz33

miniz33


Posts : 25
Join date : 2014-03-20
Location : East Providence

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PostSubject: Re: Bad stumble/misfire    Bad stumble/misfire  EmptyTue Jun 09, 2015 10:29 pm

Double check the coolant temp sensor with an ohm-meter, any discrepancy will throw these obdI lt engines off by a landslide, including driveability and fan problems.
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MASShole9C1

MASShole9C1


Posts : 4294
Join date : 2009-12-16

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PostSubject: Re: Bad stumble/misfire    Bad stumble/misfire  EmptyTue Jun 09, 2015 11:42 pm

True. Very true. Had a bad CTS in a 95 Caprice I had a few years ago. It was waaaayyyyyy out of spec for the 75* ambient temp at the time.

Didn't even consider it for this car since I literally replaced it a year or so ago when I did the WP. I'll check it out in the day light tm. I'll report back.

Tks!
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