Gain extra benefits by becoming a Supporting Member Click here find out how!
Silver
Gold ***Platinum***
Jax ChevysRadar1270BelAirHT (11)1960 Apache 40vet65b (5)
cdandelivery (11)orod (5)frame304dr 57 (7)marmst64 Aldo Lorenzo
Sgt._Grumpy (11)Henrys57wagon (9)Radar12Mosa1976drshock (4)
RoadRockerSoCal52Deluxe
ForeverYoung (5)
Mike JW (3)
kerryd8 (8)
Panama Red (5)
Jerry Acheson (12)
Classic Performance Products Classic Parts
Ciadella Interiors American Auto Wire Art Morrison.com
Exile® Battery Keeper™ 6/12 volt charger w/ LED battery monitor
Low priced Genuine GM Auto PartsEcklers AutoMotive
Hellwig Products IncPerformance Rod & CustomClassic Industries
Impala Bob's Bob's Chevy Trucks Bob's Chevelle Parts Bob's Classic Chevy
 
 

Recent Hot Topics
Current Quote
"Let's ALL do what we can to TOOT THE HORN for ChevyTalk - OUR BOWTIE BROTHERHOOD IS THE BEST ON THE 'NET!!!"
~ Supporting Member
Recent Topics
LMC Truck Join the Community today Join Us Now  



 
Username Post: Help: 2002 4.3l High Idle and p0300        (Topic#255164)
jpsage 
Forum Newbie
Posts: 10

Reg: 12-06-10
01-01-11 12:49 PM - Post#2025410    

OK, I am tired of learning; it is now time for me to get this thing running well enough to get it 1250 miles home to WA.

2002 Sonoma XR2 4.3l 125K miles.

It started with a P0305 and miss so bad that you thought you were driving on over railroad tracks. I brought it back to the house and took out the plugs (worn but without symptoms), did a compression check (130-140) and decided to replace the spider in a sunny Southern CA driveway. Sure enough the old injectors were really ugly and the there were signs of the manifold leaking. Also put in new plugs, wires, rotor, cap.

I put it all back together and the idle was 1800 and it immediately threw a p0300. Worse was that the idle would continue to climb until I shut the car off. Off to Harbor Freight for a vacuum gauge that read low normal. I started reading about how to use my scangauge's Xgauge. I was able determine that the computer was commanding the IAC to 0 and telling the car to go to 600 rpm and that the system is in open loop.

I covered the idle air inlet and started the car and the idle went to approx normal. I immediately shut the car off and ran to Autozone to get a new IAC thinking that I had it solved. Well better about 1100 rpm but not right yet. I took the upper manifold off and see oil spatter around the No. 4 injector.

Oh, one more thing. I know how most of the components work but I lack information on how the whole thing works together. Like what happens when the key is turned on, on first crank, how it determines when to go into closed loop etc. I have been searching the net but haven't found anything comprehensive. Can you guyes point me to a link or recommend a book that covers that material? I want to put a LS in my 72 c20 but after this experience, I am not going there until I know more about how the whole system works.

Please don't make me take it the dealer with my tail between my legs

Sorry for the long post but thanks so much for any help,
john.


 
LMC Trucks
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3068

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-01-11 03:34 PM - Post#2025440    
    In response to jpsage

The system monitors the O2 sensor voltage as one of the main criteria to go into closed loop operation. There is other criteria, but the o2 sensor is the main criteria.

The IAC count should never reach zero. The engine has a vacuum leak. A vacuum leak will cause a high idle, and a low IAC count.

When you replace, remove and cleaned an IAC, or unplugged the IAC with the key on, the ECM may need to relearn the IAC position. This will not happen without driving the truck and meeting specific conditions or taking other steps the cause it to relearn the idle.

The EGR could be stuck open a little bit.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
jpsage 
Forum Newbie
Posts: 10

Reg: 12-06-10
01-02-11 02:35 PM - Post#2025897    
    In response to Chevytech

Well the tutorial continues

After hours of searching under the hood and on the net, "I hab no bananas" or EGR valve either I guess some the the 'W' trucks did not have an EGR just like the new V10 in my motorhome.

Seriously tho, this truck came from my daughter who was starting to have a lot of trouble with it and one of the things that she said to me just rang a bell in the back of my mind. She said that she had to replace her gas cap several times in the past year because it wouldn't hold the seal. At the time I dismissed it as being a person who knows little about cars replacing something unrelated to anything. I now think it might be the core problem.

I will now look on-line for troubleshooting techniques for the evap system. I will post what I find.

Thanks,
john.

 
gchemist 
Senior Chevytalk Moderator
Posts: 22039
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
01-02-11 06:09 PM - Post#2025997    
    In response to jpsage

Welcome to the site.
Causes: A code P0300 may mean that one or more of the following has happened:

Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer

Taken from http://www.obd-codes.com/p0300

You can find wiring diagrams and factory info at www.autozone.com. They have a good do it yourself maintenance section.
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
jpsage 
Forum Newbie
Posts: 10

Reg: 12-06-10
01-08-11 01:42 PM - Post#2028913    
    In response to gchemist

Success Some idiot--oh, that would be me--screwed up on the intake manifold installation. Re-tear down and new gasket and all seems good with the world. I will take it out on the learn cycle now and see how it runs. I will post a complete review later along with a couple of lessons learned.

Thanks guys, it is wonderful to have someone to talk to about this stuff.

john.


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3068

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-08-11 04:13 PM - Post#2028995    
    In response to jpsage

Glad to hear things worked out ok, and thanks for sharing what the problem was.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
LMC Trucks
Icon Legend Permissions Topic Options
Report Post

Quote Post

Quick Reply

Print Topic

Email Topic

4120 Views
FusionBB
FusionBB™ Version 2.1
©2003-2006 InteractivePHP, Inc.
Execution time: 0.14 seconds.   Total Queries: 15   Zlib Compression is on.
All times are (GMT -0800) Pacific. Current time is 08:06 AM
Top