odd idling oscillations

Tankcruiser

Original poster
Member
Oct 29, 2018
108
Toledo
Hello the idling no matter rain sun hot cold snow is slight up and down idling at 600 rpm to 650 ish rpm.
Any ideas?
i have ac delco 41 103 plugs in few yrs ago first thing i did when i gotten this truck
Also power seems to be down..... accel not as it used to be..... 3.42 gearing
Thank you folks
 

Ilikemy3s

Member
Dec 3, 2011
367
What year, engine and mileage do you have? Have you cleaned the throttle body? Replaced coil packs or are they original? Knowing some history would help as some issues could have various causes.
 

Ilikemy3s

Member
Dec 3, 2011
367
I also have a 2005 with a about 225k I would change the coil packs, clean the throttle body and make sure the air filter is not too dirty. To start at least.
 

gmcman

Member
Dec 12, 2011
4,656
How old are the O2 sensors, mainly the upstream?

Some had issues with a clogged reresonator, would have hair-like fibers protruding from the tailpipe.

Does it have a "Service Engine Light" on?

Another area to check would be an exhaust backpressure test, taken from the port where the upstream O2 sensor is.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
When you clean the throttle body, don't forget to either disconnect the battery or pull fuses #10 and 28 for at least 30 minutes.
 

Tankcruiser

Original poster
Member
Oct 29, 2018
108
Toledo
yes mine doing it badly almost like misfiring on all cyls....
wonder if coils all going too orginal... cel very slooowwww to light up..... i know some aint right.... still adding new parts like raybestos brakes fronts being shipped
still to do list.....
front bushings and lower ball joints
water pump..... gmb brand
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Did you clean the throttle body yet? This is the most common cause of idle issues.

How are the spark plugs? This engine only likes ACDelco 41-103 Iridium and be aware there are counterfeits of these on Amazon and eBay.
 
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Mektek

Member
May 2, 2017
656
FL
The cheap counterfeit spark plugs are all of inferior quality to the ACDELCO/NGK - a good reason to be cautious of what you're buying.
 
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Reactions: Redbeard

Tankcruiser

Original poster
Member
Oct 29, 2018
108
Toledo
ive gotten sparkplugs from napa in person when i got the truck 4 yrs ago....
been doing fuel pump assembly now need new filler neck..... rusty crusty barnacles..... researching it...
 

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