weeding out an IMPOSSIBLE problem.
Thread Starter
TECH Apprentice
Joined: Jul 2004
Posts: 375
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From: Carolina
weeding out an IMPOSSIBLE problem. When i rev it, its breaking up down low. The car wants to cut off when I give it gas, the rpms then drop but it does idle at first.
No Codes, other then a p1810 which I think is a transmission code and it should be throwing becaus I have a th400 and a random misfire which it should be throwing becaus it has a different cam.
At first the car ran fine, then it did this sometimes, then started all the time.
No Codes, other then a p1810 which I think is a transmission code and it should be throwing becaus I have a th400 and a random misfire which it should be throwing becaus it has a different cam.
At first the car ran fine, then it did this sometimes, then started all the time.
Thread Starter
TECH Apprentice
Joined: Jul 2004
Posts: 375
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From: Carolina
Its been tuned, but it does it with the stock tune and new tune. I replaced all bad sensors, the 02s were bad and the coolant temp sensor was bad. I fixed a vacume leak from the rear of the intake and its still has the problem.
I found two intake bolts are stripped, its possible its takeing in air but dosent appear to be. Thats next on my list to tackle.
I found two intake bolts are stripped, its possible its takeing in air but dosent appear to be. Thats next on my list to tackle.
sounds like fuel issue to me......have you checked the fuel filter, fuel pressure, and cleaned the injectors?
here is WHY I think it’s the above:
if the car idles fine then its probably not a vacuum leak/issue........
since you already had it tuned and it worked fine for a while then I wouldn't think it's the tune.......
mechanical issues (other than major) wouldn't usually cause problems at low RPM (ie: valve float).......and again your idle is good so.....
it really does just sound like you are starving the engine for fuel.......
here is WHY I think it’s the above:
if the car idles fine then its probably not a vacuum leak/issue........
since you already had it tuned and it worked fine for a while then I wouldn't think it's the tune.......
mechanical issues (other than major) wouldn't usually cause problems at low RPM (ie: valve float).......and again your idle is good so.....
it really does just sound like you are starving the engine for fuel.......
Thread Starter
TECH Apprentice
Joined: Jul 2004
Posts: 375
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From: Carolina
I havent checked the fuel pressure. But it has a strong smell of gas when it is cranked and running. Its not fouling out plugs however. Do u know what the fuel pressure should be?
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Originally Posted by MakoLS1
I havent checked the fuel pressure. But it has a strong smell of gas when it is cranked and running. Its not fouling out plugs however. Do u know what the fuel pressure should be?
~58psi
if you don't have cats, it will always smell somewhat "gas like"......
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crank sensor? i've had some 02 sensors do that too but you said you already replaced them? get a scanner on theyre and let us know what your fuel trims are.also your maff sensor unplug it and see how it does.what is your map sensor reading also?
Thread Starter
TECH Apprentice
Joined: Jul 2004
Posts: 375
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From: Carolina
Originally Posted by bad0211secws6
crank sensor? i've had some 02 sensors do that too but you said you already replaced them? get a scanner on theyre and let us know what your fuel trims are.also your maff sensor unplug it and see how it does.what is your map sensor reading also?
When I first put my car together i forgot to plug the crank sensor up, and it wouldnt even fire up until i plugged it back in. I will get back to you guys about the fuel trims and map sensor. As far as I know its working.
Launching!
Joined: Jan 2004
Posts: 273
Likes: 1
From: Trois-Rivières (Québec / Canada)
Originally Posted by MakoLS1
When i rev it, its breaking up down low. The car wants to cut off when I give it gas, the rpms then drop but it does idle at first.
No Codes, other then a p1810 which I think is a transmission code and it should be throwing becaus I have a th400 and a random misfire which it should be throwing becaus it has a different cam.
At first the car ran fine, then it did this sometimes, then started all the time.
No Codes, other then a p1810 which I think is a transmission code and it should be throwing becaus I have a th400 and a random misfire which it should be throwing becaus it has a different cam.
At first the car ran fine, then it did this sometimes, then started all the time.
Thread Starter
TECH Apprentice
Joined: Jul 2004
Posts: 375
Likes: 0
From: Carolina
Originally Posted by 2001CamaroGuy
sounds like fuel issue to me......have you checked the fuel filter, fuel pressure, and cleaned the injectors?
here is WHY I think it’s the above:
if the car idles fine then its probably not a vacuum leak/issue........
since you already had it tuned and it worked fine for a while then I wouldn't think it's the tune.......
mechanical issues (other than major) wouldn't usually cause problems at low RPM (ie: valve float).......and again your idle is good so.....
it really does just sound like you are starving the engine for fuel.......
here is WHY I think it’s the above:
if the car idles fine then its probably not a vacuum leak/issue........
since you already had it tuned and it worked fine for a while then I wouldn't think it's the tune.......
mechanical issues (other than major) wouldn't usually cause problems at low RPM (ie: valve float).......and again your idle is good so.....
it really does just sound like you are starving the engine for fuel.......
i think your right, im getting 22psi at the shrader valve where it should be 60psi. I changed the filter and its not that!
Any ideas? 
Originally Posted by RGR Pete
I'm thinking fuel pump also, The old way(TPI) was to block off the return line and watch the pressure go up.
blocking off the return would only help if the pressure regulator were bad......if the pump is weak (can't pump up the pressure in the first place), it will never go higher......
I didn't think about the fuel pump (guess I was looking for the easiest/cheapest possible problems first) but if the filter is clean and you are still only getting 22 psi (WAYYYYYYYYYY LOW) at the fuel rail, then it has to either be:
the fuel pump (most likely)
the regulator (can happen)
the line is plugged (really unlikely)
plugging the return line is a good way to check if it's your fuel pump or the regulator.....get under the car, block off the return line, and see if the pressure goes high:
a) pressure goes high = regulator is bad (in the tank)
b) pressure stays about the same = pump is bad (in the tank)
either way you get to go into the tank
if you replace the pump get the whole module from gm if they sell it that way on these cars and you'll be replacing the pump and the regulator both so it wouldn't matter which of the 2 is the problem.
Originally Posted by Cody Brooks
if you replace the pump get the whole module from gm if they sell it that way on these cars and you'll be replacing the pump and the regulator both so it wouldn't matter which of the 2 is the problem.
except for the fact you have blown a bunch of money for a stock pump....
Teching In
Joined: May 2004
Posts: 33
Likes: 0
From: Indianapolis
Not to steal the glory or anything, but I'd figure I'd ask a question since I have a similar problem. Setup is a cammed LS1, Walbro 255 pump (brand new), Aeromotive regulator, Speed Inc. fuel rails. Fuel pressure is right at 20psi, even with adjusting the regulator. Not sure if air in the rails would prevent it from builing full pressure or not. Car idles, but will not rev (bogs when you give it gas). What are your thoughts if any?
my car does the same **** with the TR7IX's in.. pull out on the street take her up to about 7k rpms blow all the **** off my lugs.. problems gone.. till the next morning. 
LOL
Mike
LOL
Mike