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Motor idles rough and slow on hot start up

Tiny
PRECISION
  • MEMBER
  • 2003 CHEVROLET EXPRESS
  • V8
  • 2WD
  • AUTOMATIC
  • 127,000 MILES
Hi
I have a 2003 Chevy Express 3500 with 6.0 motor that has 127,000 mi.

The motor idles rough and slow on hot start up.

It also hesitates, sputters and almost stalls when you try to accelerate in this condition.

If I rev the motor it seems to clear out excess gas and run fine.

The van starts, idles and accellerates fine when engine is cold.

The van showed a blinking p0102 code a few weeks ago and I replaced the MAF Sensor with an aftermarket Cardone model.

It didn't seem to help but the code didn't come back.

Since then all 8 fuel injectors and fuel filter have been replaced (oem injectors with aftermarket filter)

Fuel pressure regulator was replaced(GP Sorenson)

Idle air control valve was replaced(Standard Brand)

I have run 2 bottles of Techron through the system.

The P0102 code came back a couple of days ago so
I swapped the new MAF sensor for a new one because it has a 1 year warranty.

The van still runs the same.

I hate throwing parts at this problem but I am at a loss to find the problem.

I am thinking maybe a problem with the MAF sensor wiring harness. The plug looks o.K. And I added some dielectric grease to it for good measure.

Could a problem with purge solenoid or evaporative emissions system cause this.

More history about the van:
*Spark plugs replaced 110,000 mi with OEM irridium tipped plugs.
*Catalytic converters 82,000 mi.
* Bank 1 Sensor 1 O2 sensor 105,000 mi
*Plug wires 65,000 mi
* Air Filter 127,000 mi
*Bank 2 Sensor 1 O2 sensor 62,000 mi.
*Gas Cap 78,000 mi.
Thanksalot
Warren
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Sunday, July 11th, 2010 AT 8:45 AM

29 Replies

Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Hi
Is this a Bi-Fuel? What is fuel pressure? Has engine compression been checked? As to the P0102 is low frequency fault will need hooked up to diagnostic scanner. If frequency is below 1200HTZ and does not increace with load and RPM then engine will have definate lack of power.
Let me know
Thanks for donate
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Tuesday, July 13th, 2010 AT 1:02 PM
Tiny
PRECISION
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Hi,
No its not a BIFUEL motor.
I don't know what the fuel pressure is running at.
I don't have a pressure tester.
Compression has not been checked.
I only have a code reader no scanner so I can't check
frequency.
If I can get my hands on a scanner would I be checking frequency of MAF sensor?
Can you tell me if the MAF sensor harness goes right to the power train control module.
I have had some mice getting into the engine compartment occasionally I don't know if they may have damaged wiring.
Thanks
Warren
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Friday, July 16th, 2010 AT 7:08 PM
Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
MAF terminal A yellow wire goes to PCM terminal 31 check continuity
MAF terminal B pink wire goes to ENG 1 fuse
Maf terminal C goes to ground
Check out and let me know
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Saturday, July 17th, 2010 AT 3:32 PM
Tiny
PRECISION
  • MEMBER
  • 7 POSTS
Hi
I got a chance to do some diagnostics today.
Yellow at MAF plug to PCM 31 = 0.5 to 0.6 ohms

Pink at MAF plug to ENG 1 Fuse = 0.6 ohms

Black and White at MAF plug to good Ground = 0.5 to 0.6 ohms

Ignition on motor not running - I get 5 VDC to Yellow signal wire and tan wire at terminal D.
0.3 VDC to Tan wire at Terminal E

I also cleaned the PCM plug with electrical cleaning solvent.

I put it back together hoping it may have been a bad connection at PCM.
But it runs the same still idling rough after hot start.
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Sunday, July 18th, 2010 AT 7:21 PM
Tiny
DOCFIXIT
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Is there 12v+ on Term B pink wire key on? Have you tried cleaning MAF
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Monday, July 19th, 2010 AT 3:02 PM
Tiny
PRECISION
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I'll have to check for 12v DC to Pink wire and get back to you.

A mechanic friend let me borrow a fuel pressure tester.

Here is the data:

* Key ignition on motor not running spikes to 65 psi then drops to 60 psi and stays steady.

*Motor running smooth 56 psi

* Running rough the needle shakes quickly back and forth 55 to 57 psi.

Thanks
Warren
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Monday, July 19th, 2010 AT 7:42 PM
Tiny
DOCFIXIT
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Check each injector resistence should be 11-14 OHMS
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Tuesday, July 20th, 2010 AT 1:52 PM
Tiny
PRECISION
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  • 7 POSTS
Hi,
I checked the pink wire at MAF sensor plug.
It held steady at 12.55 VDC

I'm kinda doubting its the injectors.

Reason being is this problem exsisted before and after replacing all 8 fuel injectors with new Delphi injectors.
The injectors have about 5,000 miles on them.

I'd like to ask you the probability of my problem being related to some parts.

1. Power Train Control Module

2. Evaporitive Emissions Purge Solenoid or anything evaporitive emmissions related.

3. EGR Valve

4. Throttle Position Sensor

5. Absolute Manifold Pressure Sensor
This seems to feed info to the MAF sensor
Two tan wires terminals D and E.

If you could rate the above listed parts from not likely, Likely, and not likely at all it would be great

Also I am going to buy a scan tool that can read real time PCM module data, O2 Sensor data.

Any things I should check when I can read PCM and O2 sensor data?

.
Thanks alot
Warren
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Tuesday, July 20th, 2010 AT 7:01 PM
Tiny
DOCFIXIT
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PCM No.1 all the rest not likely MAP semds manifold vacuum to PCM MAF sends air flow D &E are for Intake air temp. Really need diagnostic scan tool to help if you get one read missfire data also crank and cam sensor. Post results also MAF Htz
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Wednesday, July 21st, 2010 AT 2:19 PM
Tiny
PRECISION
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  • 7 POSTS
Hello again,
It looks like I am going to have to buy a scan tool.
Could I buy any scan tool that displays real time PCM and sensor data?
I am thinking about buying this one because I don't have much money.
Unless you have any suggestions.

Thanks alot
Warren
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Wednesday, July 21st, 2010 AT 5:13 PM
Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Not sure about that scanner a profesional scan tool like MODIS is @$8500.00. You may consider having a profesional run diagnostics maybe better value for your $100
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Friday, July 23rd, 2010 AT 2:44 PM
Tiny
PRECISION
  • MEMBER
  • 7 POSTS
Still can't figure out this problem.

I had it in to my mechanic because it threw a P0300

Random Multiple Misfire code on top of the other problems.

This van has had serious issues with Random Multiple Misfire codes in the past.

My mechanic suggested I change the crankshaft position sensor and bring it back in so he could do a Crankshaft Position Sensor relearning procedure.

He did the relearn procedure this morning but it didnt seem to help the hot soak rough rich idle problem.

I have a preflashed used PCM on order now and I am going to try it.

Without a hard code I think I'm chasing my tail on this.
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Saturday, September 4th, 2010 AT 3:05 PM
Tiny
RAY2012
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Did you ever figure out problem? My 2003 chevy express van doing same thing
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Thursday, April 2nd, 2015 AT 6:21 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,640 POSTS
Hey Guys,

We have seen this problem before it ended up being the spark plugs wires and the coil on the #2 cylinder.

Here is a video on how to change the wires.

https://youtu.be/h3Jmg2HRVYk

This will fix the problem.

Please let us know happens so it will help others.

Best, Ken

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Tuesday, January 10th, 2017 AT 4:50 PM
Tiny
DRELIVERYRM
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET EXPRESS
  • V8
  • 2WD
  • AUTOMATIC
  • 339,000 MILES
2004 Chevy Express V8 Two Wheel Drive Automatic 339000 miles

I have a 2004 chevy express 6.0 v-8 the van starts fine runs fine until u turn it off when you restart the van it runs bad and does not want to go seems like it want to stall out, but if I play with the gas pedal I hear a pop/tap noise and the van runs great then after a few red lights it starts to run rough again.

I also can turn the van off and restart it and it will run fine.

I have replace the cam sensor, plugs, wires, cleaned the throttle body, check for vac leaks, new alternator / battery, new throttle body gasket, checked the valve springs (none are broken).

No check engine
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Tuesday, January 10th, 2017 AT 4:57 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
A couple things. First, have you checked the EGR to make sure it isn't carboned shut? Also, the intake could be carboned inside where the EGR mounts. Check that and clean it out if it is.

Finally, with that many miles, have you checked compression?
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Tuesday, January 10th, 2017 AT 4:57 PM (Merged)
Tiny
BOMBASTIC1979
  • MEMBER
  • 2 POSTS
  • 2000 CHEVROLET EXPRESS
  • V8
  • 2WD
  • AUTOMATIC
  • 100,000 MILES
I have a 2000 chevy express 2500 w/5.7L. It runs rough. Recently had a full tune up and fuel pump test. Fuel pump is within specs but on low side. No check engine light on. Feels more like a timing/advance problem than a misfire. Any thoughts?
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Tuesday, January 10th, 2017 AT 4:57 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
https://www.2carpros.com/articles/engine-misfires-or-runs-rough

1.Defective spark plugs
2.Inadequate spark/coil,defective spark plug wire.
3.Lack of compression
4.False air leakage.
5.Faulty fuel injectors.
6.Insufficient fuel pressure.
7.Contaminated fuel.
8.EGR valve that is leaking.
9.Oxygen sensors.
10.Throttle position sensor.
11.Manifold absolute pressure sensor
12.Mass Airflow Sensor
13.Idle air control valve

Note: If it doesn't apply disregard it-
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Tuesday, January 10th, 2017 AT 4:57 PM (Merged)
Tiny
BOMBASTIC1979
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Thanx. I forgot to mention that it is an intermittent problem. Does that change your advice at all?
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Tuesday, January 10th, 2017 AT 4:57 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Yes it does, you got to catch it on the run a tough thing to do
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Tuesday, January 10th, 2017 AT 4:57 PM (Merged)

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