Rebuilt LT1 95 9c1 idle issues, dies when braking - Chevy Impala SS Forum
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post #1 of 7 (permalink) Old 07-10-2013, 08:15 PM Thread Starter
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Rebuilt LT1 95 9c1 idle issues, dies when braking

I recently am able to bring new life to my 1995 Caprice 9c1 motor was failing due to piston ring failure and I recently had the motor rebuilt with a list of other mods to the car. I love this car and it is going to be my daily driver for years to come, but I picked it up from the shop and am having issues right out the door. I would go back but the guy kept it for over a month, and during that month my car sat stagnant for over two weeks while he completed other jobs. I honestly am afraid to take it back because he might keep it and I am out of a car again which makes life difficult.
Another big reason I made this move is because I am going back to school soon and I need a reliable car, too expensive to buy a new one and I wont part with my 9C1.
As well I have been searching through these forums among others to gather the best possible information while getting advice from a good friend who is as savy on chevys, so that when I build my car no mistakes are made....guess I was wrong..

List of Mods ect.

Racetronix Fuel Pump Kit, BBK 52mm TB, Level 3 Rebuild kit w/1800 stall from PATC, Hooker headers for Impalas w/ High flow cats and Mufflers 2.25" and x pipe, K&N Intake, De-screened MAF, 3:42 Posi, Impala SS Factory Wheels 245/50 tires, 160amp alternator, new AC Delco Opti, MSD 8.5mm and Street Fire Ignition Coil, 1 Gauge battery cable kit, New HO opti cable, 180 Degree Thermostat, Full Energy suspension kit for B-bodys, Metco Upper and lower control arms (extended length), Russel Brake lines, New Master Cylinder and Brake proportion Mod, Removed the Air pump
Aluminum heads from a 95 Z28 rebuilt with Scorpion 1.6 Narrow Body Rocker Arms, Comp Cams Beehive Valve Springs, Bowl Porting Job, 3 Angle Valve Job, Comp Cams 304 Cam, Motor bored 40 over, crank ground 20/20, Balanced, and decked block, new timing chain, oil pump, and a custom tuned computer from PCMforless.

Car for one starts but isn't a very strong start, even with all the new goodies. Engine goes through a looping noise where it feels as if it is going to bog down and stall then starts to suck air in. When I drive the engine will stall most of the time when I apply the brake. And the check engine light is on.
Only discrepancy is I ordered the computer with stock compression and 355cid (bored .30 over) and at the very end I was told it was bored 40 over.

Help please, I am about to flip my lid. Comments, any other mods I can do to improve longevity. Much appreciated

Last edited by Big63; 07-11-2013 at 04:00 PM.
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post #2 of 7 (permalink) Old 07-11-2013, 02:15 PM
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Sounds to me like you have a vaccum leak. Pull the code and research it. Very possible you have a vac leak in your brake booster. I had that kill me upon brake and stop before, particularly when the car was warmed up.

95 6-speed DCM SS- "LSXT56" [email protected], 1.91 60'
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post #3 of 7 (permalink) Old 07-11-2013, 02:34 PM
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I 2nd his opinion. were the heads shaved? are they alum or steel?
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post #4 of 7 (permalink) Old 07-11-2013, 03:53 PM
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Tim is right that is the first thing to check, I would check all the connections period.

Do you still have the EGR? What brand throttle body are you running?

You are only going to get so much out of a mailorder tune to be honest and I wouldn't throw out the possibility that the VE tables are a bit askew due to the difference in the bore from what you told the tuner and what the motor actually is.

As stated,
  1. run code first and post up what it is
  2. check all connctions on the motor
  3. if EGR is still present, make sure the diaphragm isn't stuck
  4. see if tuner will change the PCM for you for a nominal fee to correct the cylinder volume

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1994 Chevy Caprice 9C1, 126,000 miles, T56, 4.10's

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post #5 of 7 (permalink) Old 07-11-2013, 04:05 PM Thread Starter
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z28 Aluminum heads shaved .005, BBK 52mm Tb, EGR is left in place, can't mess with the smog crap out here in California, and thank you for all the advice and I will get the code info asap.

Last edited by Big63; 07-11-2013 at 04:07 PM. Reason: forgot info
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post #6 of 7 (permalink) Old 07-11-2013, 07:26 PM Thread Starter
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"Update" Replaced the Throttle Position Sensor and the light went off , I will give it a drive tomorrow and hopefully that is the end of my troubles..for now.
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post #7 of 7 (permalink) Old 07-15-2013, 03:53 AM Thread Starter
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car drives great. Tps replacement solved the issue. Thanks for the advice
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