'94 hard start when ambient temperature rises significantly
Thread Starter
Instructor
Joined: Mar 2002
Posts: 105
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From: Leesburg VA
'94 hard start when ambient temperature rises significantly
Maybe someone can explain this one.
My '94 is more difficult to start after work after the temperature has risen 20 to 30+ degrees. The starter just spins the engine over but it just doesn't seem to fire. Usually, like every morning, I barely have to hold the key over at all, and it jumps to life. But on those infrequent afternoons, I hold the key for a couple seconds and nothing. A couple more seconds and then it fires up. Everything seems to run great once it is running. No misfires, no service engine light. 15.7 mpg on my 6mi commute (usually with the pedal to the floor, rowing through the gears). Once I cycled the ignition a few times prior to starting (to make sure I had fuel pressure), it took time to start that time too. 100K miles, original opti, new water pump, no leaks, original wires, 40K on platinum plugs. Northern Virginia weather.
Are we thinking fuel pressure?
leaking injector(s)?
O2 sensor?
Opti?
None of the above?
Thanks,
Ken
My '94 is more difficult to start after work after the temperature has risen 20 to 30+ degrees. The starter just spins the engine over but it just doesn't seem to fire. Usually, like every morning, I barely have to hold the key over at all, and it jumps to life. But on those infrequent afternoons, I hold the key for a couple seconds and nothing. A couple more seconds and then it fires up. Everything seems to run great once it is running. No misfires, no service engine light. 15.7 mpg on my 6mi commute (usually with the pedal to the floor, rowing through the gears). Once I cycled the ignition a few times prior to starting (to make sure I had fuel pressure), it took time to start that time too. 100K miles, original opti, new water pump, no leaks, original wires, 40K on platinum plugs. Northern Virginia weather.
Are we thinking fuel pressure?
leaking injector(s)?
O2 sensor?
Opti?
None of the above?
Thanks,
Ken
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Re: '94 hard start when ambient temperature rises significantly (rockken_vette)
How hot are the car's cooling temps when this is going on. Mine does a similar thing, not related to ambient temperature so much as coolant temperature.
Read this and see if it looks at all familiar http://forums.corvetteforum.com/zerothread?id=806904
Read this and see if it looks at all familiar http://forums.corvetteforum.com/zerothread?id=806904
Thread Starter
Instructor
Joined: Mar 2002
Posts: 105
Likes: 1
From: Leesburg VA
Re: '94 hard start when ambient temperature rises significantly (Nathan Plemons)
Nathan,
I seem to have a different problem,
because I never have the problem if the
car has just been run, no matter what
coolant temperature. I only see the
problem in the late afternoon getting
ready to go home, after the car has been
sitting for several hours, and only if it has
gotten significantly warmer outside since
I drove it last. I replaced the fuel filter
about 2000 miles ago, when I replaced my
clutch. I have not performed any vehicle
checks yet, because it happens really
infrequently. Perhaps 5-10 times over the last
6 months, for a car driven 8-10 times a week.
Ken
I seem to have a different problem,
because I never have the problem if the
car has just been run, no matter what
coolant temperature. I only see the
problem in the late afternoon getting
ready to go home, after the car has been
sitting for several hours, and only if it has
gotten significantly warmer outside since
I drove it last. I replaced the fuel filter
about 2000 miles ago, when I replaced my
clutch. I have not performed any vehicle
checks yet, because it happens really
infrequently. Perhaps 5-10 times over the last
6 months, for a car driven 8-10 times a week.
Ken
Thread Starter
Instructor
Joined: Mar 2002
Posts: 105
Likes: 1
From: Leesburg VA
Re: '94 hard start when ambient temperature rises significantly (rockken_vette)
Happened again today. 55 deg this morning, 79 going home.
Delta T = 24 degrees. ????
Tried starting for 2-3 seconds, engine spinning, no firing.
Tried again, and after 2-3 seconds fired right up.
turned it off. Tried again. Started immediately.
???
Ken
[Modified by rockken_vette, 8:59 AM 4/30/2004]
Delta T = 24 degrees. ????
Tried starting for 2-3 seconds, engine spinning, no firing.
Tried again, and after 2-3 seconds fired right up.
turned it off. Tried again. Started immediately.
???
Ken
[Modified by rockken_vette, 8:59 AM 4/30/2004]
Thread Starter
Instructor
Joined: Mar 2002
Posts: 105
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From: Leesburg VA
Re: '94 hard start when ambient temperature rises significantly (c5homer)
Yes, starter works great.
Spins motor very well.
acts as if there was zero
fuel or flooded, not even
a hint that it wanted to fire.
Ken
Spins motor very well.
acts as if there was zero
fuel or flooded, not even
a hint that it wanted to fire.
Ken
Race Director
Joined: Feb 2003
Posts: 11,672
Likes: 20
From: Lake Wylie SC
Re: '94 hard start when ambient temperature rises significantly (rockken_vette)
Just curious, you say you have platinum plugs. Are they AC Delco Pro Platinums? If so, take a few out and check the gap. Some guys have lost the platinum pucks and had a huge gap.
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
Re: '94 hard start when ambient temperature rises significantly (rockken_vette)
I know you said you checked the FP but just as a test the next time the temp is correct just turn the key to the on position to let the FP run but not to start and let the FP go through the compleate cycle then turn the key to the off position then try cranking and see what happens. The only thing I can think of is somthing is expanding due to the temp change and causing your fuel presure to drop or your ECM is not ajusting to the ambiant temp correctly for a cold start condition.
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Thread Starter
Instructor
Joined: Mar 2002
Posts: 105
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From: Leesburg VA
Re: '94 hard start when ambient temperature rises significantly (84LT1)
84LT1:
Actually, I thought that was a good test, and I did that yesterday,
before trying to start it. I cycled the key twice and allowed the
fuel pump to run and pressurize the system. Then I tried starting it.
Clearly some kind of setting is not right for cold coolant starts in warm ambient conditions, when it was last running and warmed up for cold
ambient conditions. Do I have a temperature sensor problem?
I don't have a code reader, and I am not getting a service engine soon
light (the bulb is good).
Are there codes I could read through the onboard diags?
I do have a GM manual that I can reference any procedures.
What should I try when I start it this afternoon? Should I blip the gas or anything like that? Hold down the throttle as if it were flooded?
Thanks,
Ken
Actually, I thought that was a good test, and I did that yesterday,
before trying to start it. I cycled the key twice and allowed the
fuel pump to run and pressurize the system. Then I tried starting it.
Clearly some kind of setting is not right for cold coolant starts in warm ambient conditions, when it was last running and warmed up for cold
ambient conditions. Do I have a temperature sensor problem?
I don't have a code reader, and I am not getting a service engine soon
light (the bulb is good).
Are there codes I could read through the onboard diags?
I do have a GM manual that I can reference any procedures.
What should I try when I start it this afternoon? Should I blip the gas or anything like that? Hold down the throttle as if it were flooded?
Thanks,
Ken
Thread Starter
Instructor
Joined: Mar 2002
Posts: 105
Likes: 1
From: Leesburg VA
Re: '94 hard start when ambient temperature rises significantly (Strick)
Strick:
I need to look at the plugs. I never had them out in the 40K I owned the car, but they were supposed to be new when I bought it. I'll take a look this weekend.
Ken
I need to look at the plugs. I never had them out in the 40K I owned the car, but they were supposed to be new when I bought it. I'll take a look this weekend.
Ken
Safety Car
Joined: Jun 1999
Posts: 3,641
Likes: 2
From: Southern California
Re: '94 hard start when ambient temperature rises significantly (rockken_vette)
Start with the little things. Check your coolant temperature sensor to see if it's reading correctly as well as your MAT sensor that is in your air intake bellow. I have the same problem but I haven't found the time to check these. These two sensors play a big role in the start up of the car. They decide how rich or lean the intial mixture will be.
