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2000 S10 4.3 Runs rough when engine is cold

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Old 06-20-2012, 09:53 AM   #1
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2000 S10 4.3 Runs rough when engine is cold

I have a 2000 Chevy S10 4x4 4.3. The problem I am having is after the truck has been put away for the night around 5pm and sits all night in the garage and then when I go to drive it again the next day around 7:30am the engine is chugging when giving it gas. Once I arrive at work the truck sits again until about 1pm and you get in a it runs great. The truck comes back to work at around 2pm and sits again until 5pm and then I drive it home and it runs great. This tells me it has something to do with the truck warming up.
I have done the following
Replaced MAF Sensor
Replaced EGR Valve
Replaced Plugs, wires, Cap and rotor
MAP Sensor
Replaced TPS Sensor
Replaced Air Intake Sensor
Replaced PCV Valve
Replaced Fuel filter
Replaced Fuel Pump
Replaced 3 O2 Sensors
Cleaned entire Throttle body and checked IAC valve

The weirdest thing is sometimes the truck will run great for 4 or 5 days and then it will start acting up again.
This is driving me nuts.
I have tried checking for vacuum leaks around the intake, PCV valve, and plenum and there does not appear to be any leaks there.
It has been checked for fuel pressure.

I hope someone has some suggestions for me. The truck on has 47,500 on it and is in great shape but I need tit to run right.
Old 06-20-2012, 11:56 AM   #2
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Re: 2000 S10 4.3 Runs rough when engine is cold

Have you checked the (ECT)Engine Coolant temp sensor?

http://troubleshootmyvehicle.com/gm_...sor_code_1.php
Old 06-20-2012, 12:07 PM   #3
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Re: 2000 S10 4.3 Runs rough when engine is cold

Quote: Originally Posted by burned
Have you checked the (ECT)Engine Coolant temp sensor?

http://troubleshootmyvehicle.com/gm_...sor_code_1.php

Truck is not over heating and does not start hard nor is it throwing those codes for this. Thanks for the advice.
Old 06-20-2012, 01:40 PM   #4
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Re: 2000 S10 4.3 Runs rough when engine is cold

What codes do you get?
Old 06-20-2012, 01:42 PM   #5
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Re: 2000 S10 4.3 Runs rough when engine is cold

Quote: Originally Posted by KSZR2
What codes do you get?
Currently the SES light is out but last time it was throwing codes it was 0174 and 0175.
Old 06-20-2012, 02:16 PM   #6
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Re: 2000 S10 4.3 Runs rough when engine is cold

Quote: Originally Posted by GregG1968
Currently the SES light is out but last time it was throwing codes it was 0174 and 0175.
So on the passengers side you had both a rich and lean condition? Did these codes come up at the same time?
Old 06-20-2012, 02:59 PM   #7
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Re: 2000 S10 4.3 Runs rough when engine is cold

Quote: Originally Posted by KSZR2
So on the passengers side you had both a rich and lean condition? Did these codes come up at the same time?
Yes they did. But are not there now and interestingly enough it was stumbling and chugging some at lunch.

I also forgot to mention that when in park if you give it gas it backfires out the exhaust.
Old 06-20-2012, 03:19 PM   #8
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Re: 2000 S10 4.3 Runs rough when engine is cold

Quote: Originally Posted by GregG1968
Yes they did. But are not there now and interestingly enough it was stumbling and chugging some at lunch.

I also forgot to mention that when in park if you give it gas it backfires out the exhaust.
Definitely sounds rich. I bet you have an issue with the poppet injectors. So heres a theory... poppet went bad and created a lack of fuel which threw the lean code. Then the computer compensated by dumping in fuel to the entire bank which creates a rich condition and throws the rich code. So the reason you felt the hesitation in the morning could be from a cold poppet not supplying enough fuel. Once it warms up, that poppet may work a little better so you don't experience the hesitation quite as often. This is just a theory but pulling off the upper intake to check isn't THAT difficult of a job. And you can easily convert to fuel injection which would be more reliable anyway.
Old 06-20-2012, 03:39 PM   #9
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Re: 2000 S10 4.3 Runs rough when engine is cold

Link below is what I am referring to. The less expensive spider injector kits you might find are the older poppet style which is currently on your truck unless upgraded already. I believe GM switched over to the upgraded fuel injectors sometime in 2002-2003. That fuel injection kit is a bolt in application so no modification is required.

http://www.ebay.com/itm/CHEVY-S10-4-3-SPIDER-FUEL-INJECTOR-96-97-98-99-00-01-02-/120536022988?pt=Motors_Car_Truck_Parts_Accessories &hash=item1c1081bfcc&vxp=mtr
Old 06-20-2012, 06:38 PM   #10
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Re: 2000 S10 4.3 Runs rough when engine is cold

Quote: Originally Posted by KSZR2
Definitely sounds rich. I bet you have an issue with the poppet injectors. So heres a theory... poppet went bad and created a lack of fuel which threw the lean code. Then the computer compensated by dumping in fuel to the entire bank which creates a rich condition and throws the rich code. So the reason you felt the hesitation in the morning could be from a cold poppet not supplying enough fuel. Once it warms up, that poppet may work a little better so you don't experience the hesitation quite as often. This is just a theory but pulling off the upper intake to check isn't THAT difficult of a job. And you can easily convert to fuel injection which would be more reliable anyway.
So how do I check if it is a poppet that is having the issue or are you just saying this is how to check if I have the poppet? I have dumped in pretty much every kind of injector cleaner people have recommended.
Old 06-21-2012, 09:37 AM   #11
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Re: 2000 S10 4.3 Runs rough when engine is cold

Quote: Originally Posted by GregG1968
So how do I check if it is a poppet that is having the issue or are you just saying this is how to check if I have the poppet? I have dumped in pretty much every kind of injector cleaner people have recommended.
I know its pretty easy to check if a poppet is leaking but determining if one is plugged would be more challenging. To find out if its leaking, simply pull off the upper intake and pull each each injector out of the bung... then pressurize the system and check for leaks. Hate to say just throw money at it but upgrading to spider EFI over the spider poppet injection is going to help prevent issues in the future anyway and there is a good chance, based on what is happening, that it could fix your current problem. Maybe others can chime in on this. My 2003 came with the EFI from the factory so I have never experienced these problems.
Old 06-21-2012, 12:30 PM   #12
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Re: 2000 S10 4.3 Runs rough when engine is cold

It could have a leaky fuel pressure regulator. You want to check fuel pressure and that it holds. 60-66psi and it drops no lower than 55psi after 5 minutes. If it does drop fast then its a leaky FPR.

A replacement injection spider:
Amazon.com: Delphi FJ10565 Fuel Injector: Automotive Amazon.com: Delphi FJ10565 Fuel Injector: Automotive

Poor mans rebuild:
http://www.instructables.com/id/Poor...Vortec-Fuel-I/
Old 06-21-2012, 01:46 PM   #13
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Re: 2000 S10 4.3 Runs rough when engine is cold

Quote: Originally Posted by burned
It could have a leaky fuel pressure regulator. You want to check fuel pressure and that it holds. 60-66psi and it drops no lower than 55psi after 5 minutes. If it does drop fast then its a leaky FPR.

A replacement injection spider:
Amazon.com: Delphi FJ10565 Fuel Injector: Automotive

Poor mans rebuild:
http://www.instructables.com/id/Poor...Vortec-Fuel-I/

Fuel pressure was checked awhile back and it was good. Thanks for the advice
Old 07-01-2012, 07:54 PM   #14
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Re: 2000 S10 4.3 Runs rough when engine is cold

Quote: Originally Posted by GregG1968
Fuel pressure was checked awhile back and it was good. Thanks for the advice
So I put the new injector assembly in and I still have the same issue.

Does anyone have any other advice?

Getting to be that I am just throwing money at it and nothing is fixing the problem.
Old 07-09-2012, 03:19 PM   #15
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Re: 2000 S10 4.3 Runs rough when engine is cold

Quote: Originally Posted by GregG1968
So I put the new injector assembly in and I still have the same issue.

Does anyone have any other advice?

Getting to be that I am just throwing money at it and nothing is fixing the problem.
I also just replaced the Engine coolant temp. sensor

Still having this issue only after truck sits for extended period of time like overnight but not after 4 hrs etc.
Old 07-23-2012, 02:20 PM   #16
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Re: 2000 S10 4.3 Runs rough when engine is cold

Did you ever find the problem. I have a 96 that just started the same thing a week ago. I drove it one Saturday morning then let it sit over the weekend. Started up Monday morning and drove like crap. Left work that evening and drove fine. Does this everyday now.

Did some of the checks you have done as well as replaced the injectors to new set two years ago.
Old 08-07-2012, 02:58 PM   #17
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Re: 2000 S10 4.3 Runs rough when engine is cold

Quote: Originally Posted by yjjeep43
Did you ever find the problem. I have a 96 that just started the same thing a week ago. I drove it one Saturday morning then let it sit over the weekend. Started up Monday morning and drove like crap. Left work that evening and drove fine. Does this everyday now.

Did some of the checks you have done as well as replaced the injectors to new set two years ago.
I did find the issue. Have you replaced plugs and or cap and rotor recently? My problem was I did not use OEM plugs or cap and rotor.
Took into a repair shop and they put 6 AC delco plugs and OEM cap and rotor and now it runs like new.
Old 03-20-2013, 05:21 PM   #18
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Re: 2000 S10 4.3 Runs rough when engine is cold

Just bought my 2000 S10 a few days ago. It has the exact symptoms you had. In the morning runs real bad choppy acceleration until it gets up to temp. By the time I am at work it is running ok still a bit on the rough side. After work still seems to be ok. I have a P0300 random misfire code, and I am hoping it is not a mechanical compression related issue. I will slap some new AC Delco Plugs in when I do my compression test. Hopefully your fix will work for me as well.
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