Help with cold start!
Thread Starter
On The Tree
Joined: Aug 2005
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Help with cold start! My friend’s z28 will not idle on a cold morning (by cold I mean around 30 degrees) without him giving it throttle. If he tries to let it idle it will die. It runs fine after it warms up a little.
His car has no codes and the car is basically stock except for a lid and catback.
Any ideas?
His car has no codes and the car is basically stock except for a lid and catback.
Any ideas?
possibly crappy fuel injectors or bad spark plugs, the fuel injectors may be clogged and the cold might be making it worse have you run any fuel injector cleaner or seafoam in your gas tank??
Thread Starter
On The Tree
Joined: Aug 2005
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Originally Posted by BlaZe28
check his o2 sensors, thermostat, IAC and MAF im leaning towards one of the last two
Why would you think thermostat? do think if it were stuck open it would affect cold start?
It's a wierd problem because you would think if it was the IAC it would have a code.
I guess it could be the MAF but it would be hard to diagnose it.
Thread Starter
On The Tree
Joined: Aug 2005
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Originally Posted by Z28LS1camaroguy
possibly crappy fuel injectors or bad spark plugs, the fuel injectors may be clogged and the cold might be making it worse have you run any fuel injector cleaner or seafoam in your gas tank??
It would suck if the problems is plugs or injectors because the car is an 02 with low miles.
I'm starting to think he might of got a tank of bad gas.
On The Tree
Joined: Mar 2005
Posts: 146
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O2 sensors arent even used on cold startup. maybe water in the gas? if your temperatures (edit: ambient temperature) fell sharply and quickly that might be a problem. fill the tank up and add some seafoam or something for good measure; change the fuel filter? maybe the idle air control motor is stuck until it gets warmed up? just a few ideas... good luck
Last edited by mmmchickenboy; Nov 12, 2005 at 12:00 PM.
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Teching In
Joined: Nov 2005
Posts: 26
Likes: 0
From: In a Corn Field
Since its my car I thought I should reply.
Like ls1greyhound said the car is basically stock with a lid and catback. The car started having a rough idle a few months ago and the fuel filter was replaced 5000 miles ago. I hooked a fuel pressure gauge to it yesterday and it read approx. 58 psi during the prime cycle however it is losing pressure, ie bad injectors or pump. During idle and while snapping the throttle the pressure gauge flutters ~5 psi. So I am leaning towards bad injectors but I am not sure if I want to drop $300 on a wild guess.
A few months back I got a P300 code after visiting the drag strip so I took it to the dealer and was told that my Pass. Side Cat failed. I am not sure if this is related but I think the problems I have now might have caused my cat to fail
I checked the IAC Motor the other day while installing my new lid (Ls1greyhound I broke down and bought the slp/blackwing lid used on the firehawks) and there isnt any carbon buildup. I try to clean the throttle body regularly 10000 miles or less.
I might go ahead and replace the plugs and wires for the hell of it and see what happens but I think it is fuel related.
Has anyone removed the fuel rails from the engine with the injectors still installed to check for leaky injectors?
Thanks for the input so far and keep it coming.
Like ls1greyhound said the car is basically stock with a lid and catback. The car started having a rough idle a few months ago and the fuel filter was replaced 5000 miles ago. I hooked a fuel pressure gauge to it yesterday and it read approx. 58 psi during the prime cycle however it is losing pressure, ie bad injectors or pump. During idle and while snapping the throttle the pressure gauge flutters ~5 psi. So I am leaning towards bad injectors but I am not sure if I want to drop $300 on a wild guess.
A few months back I got a P300 code after visiting the drag strip so I took it to the dealer and was told that my Pass. Side Cat failed. I am not sure if this is related but I think the problems I have now might have caused my cat to fail
I checked the IAC Motor the other day while installing my new lid (Ls1greyhound I broke down and bought the slp/blackwing lid used on the firehawks) and there isnt any carbon buildup. I try to clean the throttle body regularly 10000 miles or less.
I might go ahead and replace the plugs and wires for the hell of it and see what happens but I think it is fuel related.
Has anyone removed the fuel rails from the engine with the injectors still installed to check for leaky injectors?
Thanks for the input so far and keep it coming.
Last edited by nbr01f; Nov 13, 2005 at 12:06 AM.
Thread Starter
On The Tree
Joined: Aug 2005
Posts: 102
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Nick,
A melted cat can cause a rough idle and performance problems. Did you replace the cat when the dealer told you it was bad?
I think a set of headers and an offroad pipe should solve all your problems.
A melted cat can cause a rough idle and performance problems. Did you replace the cat when the dealer told you it was bad?
I think a set of headers and an offroad pipe should solve all your problems.
Launching!
Joined: Jul 2005
Posts: 211
Likes: 1
From: Guatemala City.
Im looking at the IAC, IAC wires or plug, Ive seen plugs not properly connected, by "connected" I mean even if the plastic clip-assembly has snaped the metalic connectors can be "open", even in oem connectors the metallic alloy is not as "springy" (spelling) as a rough use connector, better check continuity.
even if the TB is clean in front, in the back can be a pig... REMOVE THE TB, clean all from behind, leaving the little hole in the blade free.... check the TB-to-intake gasket....
after all is done.....
bent valve?????
even if the TB is clean in front, in the back can be a pig... REMOVE THE TB, clean all from behind, leaving the little hole in the blade free.... check the TB-to-intake gasket....
after all is done.....
bent valve?????
Teching In
Joined: Nov 2005
Posts: 26
Likes: 0
From: In a Corn Field
Im looking at the IAC, IAC wires or plug, Ive seen plugs not properly connected, by "connected" I mean even if the plastic clip-assembly has snaped the metalic connectors can be "open", even in oem connectors the metallic alloy is not as "springy" (spelling) as a rough use connector, better check continuity.
even if the TB is clean in front, in the back can be a pig... REMOVE THE TB, clean all from behind, leaving the little hole in the blade free.... check the TB-to-intake gasket....
after all is done.....
bent valve?????
even if the TB is clean in front, in the back can be a pig... REMOVE THE TB, clean all from behind, leaving the little hole in the blade free.... check the TB-to-intake gasket....
after all is done.....
bent valve?????
Maybe I should add that I have had a metallic noise coming from the front of the engine that I thought was piston slap. Sounds like a bucket of marbles and seems to be getting worse. As far as I know there are no exhaust leaks and I replace the Tensioner pulley a month or so back. Maybe I should pull the valve covers... But the noise shouldnt cause the hard start condition
I appreciate the help guys!