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Engine runs rough and dies when cold

Tiny
RAILROADERTWO
  • MEMBER
  • 1996 CHEVROLET CORSICA
  • 3.1L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 150,000 MILES
1996 Chevy Corsica 3.1L 150,000 Miles
The Engine runs rough and dies after idling for approximately 2 or three minutes. It only does this when first started when cold, after it warms up no problems.
There are no service engine soon lights
Replaced the lower and upper intake manifold gaskets
Replaced both oxygen sensors
Just Replaced the Coolant temperature sensor
Replaced spark plug wire and plugs
I feel like it's a sensor problem, but don't have a clue which one it might be, I thought it might be the EGR Valve, but I don't know what the symptoms are with those.
This engine runs Great after I restart it and let it warm up a little, , which led me to believe it was the Coolant temp sensor, appears this was not the case. Thank You
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Friday, May 15th, 2015 AT 5:20 PM

20 Replies

Tiny
HMAC300
  • MECHANIC
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Check fuel pressure with a gauge auto parts rent it. Clean throttle plate on both sides and iac hole with choke cleaner.
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Saturday, May 16th, 2015 AT 5:57 AM
Tiny
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Thanks, I have my own fuel pressure tester, and I will check the Throttle plate and IAC hole. I have also put on a new fuel pressure regulator, I also did a vacuum check just for grins, was 38 and steady.
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Saturday, May 16th, 2015 AT 8:32 AM
Tiny
HMAC300
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You need a new vacuum gauge as it should be no higher than 21 at idle or anytime if you mean fuel pressure that may be your problem fuel pressure should be 41-47 psi no lower key on engine off.
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Saturday, May 16th, 2015 AT 8:52 AM
Tiny
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Well, Grin, I could have read it wrong. I will look at it closer next time. Thanks
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Saturday, May 16th, 2015 AT 9:42 AM
Tiny
HMAC300
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  • 48,601 POSTS
Rethinking this it may be the fuel pressure you read and not vacuum which would be to low to run or start the engine.
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Saturday, May 16th, 2015 AT 11:43 AM
Tiny
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I put on a new IAC Valve, did not help, but I have not yet checked the fuel pressure, I did when I was having previous problems that eventually turned out to be a leaking lower manifold gasket, at that time the Fuel Pump Pressure was 38 to 40lbs
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Sunday, May 24th, 2015 AT 1:01 PM
Tiny
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Addition: Two of three Coils have been replaced, swapped the third one with another one, same symptoms.
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Sunday, May 24th, 2015 AT 1:07 PM
Tiny
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Recap: Here is what I have done so far.
Replaced Plug Wires
Replaced Plugs
Replaced Fuel Filter
Replaced Fuel Pressure Regulator 1 yr ago
Checked Fuel Pump Pressure 38 to 40lbs
Replaced Both Oxygen Sensors
Replaced Upper and Lower Intake gaskets
Replaced injector Filters and O-Rings
Replaced Coolant Temp Sensor 3 wks ago
2 Out of 3 Coils Replaced (did swap coils around, no change)
Replaced IAC Sensor
Cleaned the Mass Air Flow Sensor with Sensor Cleaner.
Failing Camshaft Sensor?
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Sunday, May 24th, 2015 AT 1:27 PM
Tiny
HMAC300
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Fuel pressure has to be 41-47 minimum you said it was 39-40 - not enough that is why it's running rough if at all
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Sunday, May 24th, 2015 AT 1:57 PM
Tiny
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I will re-check later, in any case I have ordered a replacement fuel pump.
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Sunday, May 24th, 2015 AT 3:15 PM
Tiny
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Re-tested Fuel pressure at the fuel rail connector, when switch first turned on, 39 lbs, quickly leaks down to 30 or less, is this normal? Maintains 38 lbs when idling. Thanks
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Tuesday, May 26th, 2015 AT 6:45 PM
Tiny
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Is the leak down normal, not the pressure, according to service manual, it is too low.
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Tuesday, May 26th, 2015 AT 6:47 PM
Tiny
HMAC300
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You need another pump and filter, it should be 41-47 psi key on only and not drop more than 5 psi in 5-10 minutes
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Wednesday, May 27th, 2015 AT 6:51 AM
Tiny
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Put a on a new fuel pump with new pump seal, and 2 new filters, I now have 47 lbs pressure when the ignition switch is turned on, but leaks down to about 38 lbs as before, also only maintains approx 38 lbs when idling, and the rough idle is still there only when cold, for a few couple minutes. I am at a loss for a cause. It acts like a bad coolant temp sensor, but I just replaced that a month ago. What does the fuel pressure regulator do? Thanks
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Wednesday, June 3rd, 2015 AT 1:32 PM
Tiny
HMAC300
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It should only leak down about 2-10 psi also check for a vacuum leak. It may be a vacuum leak like a hose off becaue the computer picks I tup as lean and richens the mixture to stop running rough so check for that and then do check in pic except for pump
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Wednesday, June 3rd, 2015 AT 1:45 PM
Tiny
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Here is an updated symptom description:
When car is first started, it will idle just fine for about 5 minutes, at which time it starts to run very rough, for about a minute or two, I'm guessing, did not time it. Then the engine will rev up above normal idle and then return to normal idle. I have not yet got around to run another vacuum test, will do that in a day or so. This is my son's old piece of junk, He (we) can't afford to buy him another car, so will just have to keep at it till I find out what is wrong with it. It runs great except for that little short spell it has every day.
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Sunday, June 7th, 2015 AT 7:51 PM
Tiny
HMAC300
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These were known for inlet port gasket problems but leaked anti freeze, check at front an drear of manifold if you see antifreeze at corners then it probably needs them. Without actually seeing this and testing I can give no other suggestions. If fuel is ok and pressure doesn't drop like I stated which if it does it may be a vacuum hose leading to regulator or bad regulator.
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Monday, June 8th, 2015 AT 6:54 AM
Tiny
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Well I replaced both manifold gaskets, and there appears to be no visible signs of any antifreeze leaking outside or inside the engine now, it was leaking on the outside before. I checked the vacuum again and it is steady at 15hg when engine first started at normal idle, however after a few minutes the engine starts running very rough, and sometimes it dies, and the vacuum drops to near 0, for a minute or so, when restarted at idle, then it recovers to 15hg again. So during this time of rough idle, I assume something is causing a vacuum leak.
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Tuesday, June 9th, 2015 AT 4:02 PM
Tiny
HMAC300
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Check for a clogged converter if at 15" that si a sure sign of it. Are you sure you don't have a 420 or 430 code?
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Wednesday, June 10th, 2015 AT 7:18 AM
Tiny
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For the what it's worth department, it was the upstream oxygen sensor I had replaced less than a year ago.
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Friday, July 17th, 2015 AT 6:23 PM

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