Hard starting

Tiny
CHIEFMITCH2003
  • MEMBER
  • 1996 CHEVROLET CAPRICE
  • 180,000 MILES
This is for a 1996 Chevy Caprice (cop) LT1. I replaced opti for MSD distributor, cap, and coil along with ICM, wires and plugs, fuel pump, MAF, Fuel filter. Car now runs like a dream. But, since I made those changes, my car is hard starting after sitting for like 30 minutes. And that was never an issue before.

I have to sit there and just keep the key turned for about 10-12 seconds before it will fire up. While im cranking, it is not even trying to fire. There is no spark from the Coil. Then it will just fire up and run great. If I drive a few minutes and then shut it off and try to start again, it fires right up within a sec or two.

Things I have already replaced to fix thix this issue:
ICM, MAP, CPS, TPS, ECT, IAT, checked fuel pressure and fuel pressure regulator. New vacuum lines, no vacuum leaks

What am I missing? The only thing showing up on scan is an o2 sensor.
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Thursday, August 18th, 2011 AT 1:02 AM

19 Replies

Tiny
RASMATAZ
  • MEMBER
Check and test the ignition switch could be coming from there.
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Thursday, August 18th, 2011 AT 3:48 AM
Tiny
CHIEFMITCH2003
  • MEMBER
I have done all that and replaced all the components. Fuel pressure is right where it should be and is working as soon key is turned.

No blown fuses, no vacuum leaks. The only time it does this is when its cold or has been sitting for about 30 minutes after driving. It will start right back up after it has been driven for a few minutes. The car runs excellent once its started. There are no codes showing up, battery is not the issue, fuel is not the issue. About the only thing I have not replaced is the ECM.

I have replaced the crankshaft position sensor to.

When it hard starts, there is no spark. Since I have already replaced ALL the sensors involved with this, how do I figure out which new part it is?

As far as we can tell, everything is working as is supposed to. Its like it has a cold start feature that is not functioning. And I think that has to do with the Engine Coolant Temperature sensor for the PCM. I have replaced that as well.

What sensor or "thing" would tell the coil "not to spark" when it cold or cooled off?

I have spent over $1200 over the last month on this issue with 2 mechanics and they cant find the problem.
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Thursday, August 18th, 2011 AT 11:31 AM
Tiny
RASMATAZ
  • MEMBER
The crankshaft position sensor tells the computer when to fire a specific coil-Could be the computer itself-Might want to have the ICM tested
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-1
Thursday, August 18th, 2011 AT 11:41 AM
Tiny
CHIEFMITCH2003
  • MEMBER
I have replaced the crankshaft position sensor. I did put a new MSD coil in it to. Does the computer need to be reset somehow to accept the MSD coil? The new ICM (Ignition Control Module) was installed yesterday.

Will disconecting the battery reset the computer?
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Thursday, August 18th, 2011 AT 11:47 AM
Tiny
RASMATAZ
  • MEMBER
You can give it a try but bear in mind might make things worst that the computer has to go thru relearning itself again or be reflashed
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Thursday, August 18th, 2011 AT 11:53 AM
Tiny
CHIEFMITCH2003
  • MEMBER
Since it appears to me to be a "Temperature" issue, like when the engine has cooled off, does that most likely indicate the Engine Coolant Temperature sensor for the ECM to you?
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Thursday, August 18th, 2011 AT 11:58 AM
Tiny
RASMATAZ
  • MEMBER
Test the CTS resistances-Hot and Cold if its within specs
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Thursday, August 18th, 2011 AT 12:04 PM
Tiny
JBUCO315
  • MEMBER
Hello, did you ever figure out what was causing your issue? ECT, ignition, third optispark? Thanks.
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Thursday, September 17th, 2015 AT 9:31 AM
Tiny
KEN
  • ADMIN
Hi Jbuco315,

We never got to the bottom of this problem, but it sounds like it would be the distributor to me, because the computer must see correlation between the cms and the cks are it creates hard starting like in this case, the cam sensor is internal distributor style.

Let me know if you find anything

Best, Ken
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Thursday, September 17th, 2015 AT 4:33 PM
Tiny
JBUCO315
  • MEMBER
Thanks for advice; I have now discovered that if I give it a single full pump of the gas pedal just before starting (on a cold start), it starts just fine. About a 1-2 sec turn of the key. Hummmm

New parts installed; Air filter, fuel filter, fuel pressure regulator, temp sensor, checked/gapped/cleaned plugs, tested continuity or wires, sprayed MAF with maf cleaner, and checked/rechecked all vacuum hoses and connections (i assume). FYI mine is a '95 Roadmaster with 52K on it.
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Saturday, October 3rd, 2015 AT 2:07 AM
Tiny
KEN
  • ADMIN
Hi Jbuco315,

I am wondering if there are any codes, even though the check engine light is off, this can happens sometimes with a soft code, can you read the pcm to check please?

Also, without pumping the gas, just crank it with the throttle open slightly to see if it starts? I want to see if the IAC is operating when the key is turned on.

Best, Ken
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Saturday, October 3rd, 2015 AT 9:50 AM
Tiny
JBUCO315
  • MEMBER
Hello again, sorry its been so long. In my haste, I went out and got a code reader, once home I discovered that although its a '95, it was made in 'Oct '94 and is OBD 1. I do not have and adapter yet, still looking. Not sure if the codes would still be present, I disconnected the battery and then jumped the two leads together (to completely drain/reset the computer), thinking maybe it needed to go through the "learning process" again and might fix itself. But, yes, as you mentioned, there is No light, however it does work/light up at ignition on, like the rest of the lights.
Yes, holding the throttle open a little bit does help and it does still start right up and revs slightly before I can get off the gas.
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Sunday, October 11th, 2015 AT 6:38 PM
Tiny
KEN
  • ADMIN
Hey Jbuco315,

It sounds like the IAC is weak and slow, which would not set a code, this was a big problem back in 96, can you try replacing it?

Best, Ken
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Monday, October 12th, 2015 AT 6:55 AM
Tiny
JBUCO315
  • MEMBER
Great, I appreciate the help. Will start on this soon and let you know, Thanks, John
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Friday, October 16th, 2015 AT 11:08 AM
Tiny
JBUCO315
  • MEMBER
And VOIL√. I pulled out the IAC valve and it was caked with black soot. I cleaned out its reservoir and the rest of the throttle body with spray carb cleaner until it ran/dripped clean. Also replaced the IAC with a new one, and wow, so far that seems to be it! This morning was approximately 50 degrees and with all the cleaner still floating around in the throttle body, it fired up within the first second and runs like a champ. I have shut it off and restarted it a couple more times after a short drive and all seems to be good. If things change, I will let you know. For now, thanks a million! This was driving me nuts. I guess after 20 years a little sediment should be expected.
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Tuesday, October 20th, 2015 AT 7:58 AM
Tiny
KEN
  • ADMIN
Hey Jbuco315,

Nice work! Glad to hear we got to the bottom of it and you are motoring once again! Please visit us anytime we are happy to help. Thanks for using 2CarPros. Com

Best, Ken
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Tuesday, October 20th, 2015 AT 2:24 PM
Tiny
JBUCO315
  • MEMBER
UPDATE;
Ken, had to let you know this. I hate to sound like a teenager but, OMG! Throttle response is unbelievable! I have a 2000 Grand Prix GTP with the 3.8 Supercharged motor, well, this old LT1 has that beat hands down now! I have found I barely need to touch the gas anymore, but when I do, it responds. I would swear it is even shifting better through the gears as well as the/it's kick down. If I am under 35 and stomp on it, it will shift down, break loose a little AND THEN catch a chirp hitting second! And this is with very good tires on it. Now for the most amazing thing, I checked this twice, my mileage in now 18.1 and 17.7! That's with I assume 85% in town driving (300 +/- miles each time). My longest hwy trip is only about 9 miles. Before, I was lucky to see 15. For as big as this car is, Dang, it's doing really good now!
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Friday, October 30th, 2015 AT 7:41 PM
Tiny
KEN
  • ADMIN
Hey Jbuco315,

O wow! That is such good news, I like things that turn out better than expected, you must be living right! Enjoy the car@!

Please use 2Carpros. Com anytime, tell a friend!

Talk to you soon, Best, Ken
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Saturday, October 31st, 2015 AT 7:57 AM
Tiny
BEEGEEY00
  • MEMBER
Wow I had the exact same problem! I replaced just about everything you had replaced and was dealing with two mechanics that couldn't find the issue and this car cost me money but never found the issue! This was so helpful so now I know to try to IAC! Thanks for the info
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Sunday, January 29th, 2017 AT 4:40 AM

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