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Jerry
Jerry, Master Mechanic
Category: Pontiac
Satisfied Customers: 17218
Experience:  ASE Master tech. 30+ years mechanic, shop forman, service manager
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LT1 no start condition

Customer Question

LT1 no start condition
Submitted: 1 year ago.
Category: Pontiac
Expert:  Jerry replied 1 year ago.

Hello and welcome. My name is ***** ***** you for visiting the site, I will be happy to assist you today.

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Do you hear the fuel pump come on for 2 seconds when the key is first turned on?

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Does the engine turn over?

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Do you know what the fuel pressure is?

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Have you checked for spark at the plugs?

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Does the engine have good compression?

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Customer: replied 1 year ago.
1997 Pontiac Firebird LT1
over the past few months the MIL would come and go then finally set p0400.
during this time i noticed at steady speeds on freeway the car would straight die for a split second and keep on going like it was fine. it became more frequent to stalling and hard starts 50% of the time with WOT it would fire, stumble at half throttle and the smooth out so i could let off the pedal and idle smoothly.
installed new EGR, erased codes, ran a drive cycle p0400 came back, stalling and hard starts the same becoming even more frequent to the point that when it started i could put it in gear and idle around the block but if i touch the gas pedal it dies.
so i have installed new
ACCEL opti spark, MSD wire set, AC Delco plugs, timing cover seals, water pump, ECT, IAC, TP, PCV, took apart TB cleaned, new gaskets, topped off coolant and bleed, re connected battery.
car starts idles high for 2 seconds drops way low motor shakes trying to idle so i shut down.
try to start again nothing. pump pedal WOT it starts barely running at WOT going "puh puh pupuh puh" out the tail pipes. now no start and throws a p0122 TP code. put old TP back on cleared code still no start same code p0122.
fuel pressure 40psi, pulled #2 plug wire and have spark to that plug. sprayed starting fluid into TB still no start not even a pop.
Expert:  Jerry replied 1 year ago.

I see, thanks. Does the engine have good compression? Also a good flow out the exhaust? Can you see what it does with the MAF sensor unplugged? (just as a test)

Customer: replied 1 year ago.
compression ranges from 142-150psi. exhaust flow is good. when the was running i unplugged MAF it would stumble then smooth out. same when i plug it back in. when the problem was intermittent i drove around for a week with MAF unplugged and still had same issues as plugged in. 1 in 20 were hard start, 19 were nornal. on a 50 mile trip the car would cut out at steady speed (as if the key was turned off and back on) maybe twice but ran great otherwise.
Customer: replied 1 year ago.
i have been trying to start it with MAF unplugged and no luck.
Expert:  Jerry replied 1 year ago.

I see, thanks, ***** ***** explaining it. It seems to sound like it could be in the ECM but I hate to say to try a new one, (like the tests will sometimes do). One of the actual tests that come to mind on them was to tap on the ECM with a rubber hammer, when the problem is present to see if it helps it to run better. I sometimes would tap on them when it is running normally to see if starts to skip and stumble.

Expert:  Jerry replied 1 year ago.

Please don’t forget to rate the answer in a positive way, . EVEN IF YOU HAVE A SUBSCRIPTION ****THAT IS THE ONLY WAY I GET PAID ****