lazy o2 sensors
Thread Starter
Teching In
Joined: Jun 2013
Posts: 9
Likes: 0
From: Michigan
lazy o2 sensors Hey y'all. I have a 98 trans am. About a year ago I was hit by a drunk driver and I had the car in storage for tenish months. I started the car up and let it run for a while at least every 2 or 3 weeks. I never went more than a month without running it. I took it to the body shop about six weeks ago. It was running well when I drove it there. I picked the car up a few days ago. It was in the body shop for 5-6 weeks. I don't know if they ever started it up while it was there. I picked it up last Friday. The car was showing an SES light and bogging down pretty hard around 2.5-3k rpm. I took it to a mechanic and he told me it was throwing low voltage codes for all four o2 sensors. He said he had a hard time believing that all four sensors went at once and told me the fuel has probably gone bad. I had put a couple gallons in it beforehand, but he recommended that I fill it up and put some fuel treatment/injector cleaner in it. I've also changed the oil, flushed the coolant system, replaced the water pump, and replaced my spark plugs. It was running like a charm for the first mile or so with no SES, but as soon as I got on to main roads it started bogging down again. The SES light came back on and when I had it checked it was still throwing codes for all four sensors. Any suggestions on what may be wrong? Is it possible that all four sensors would take a crap at once like that? Could a dirty MAF cause the car to run to lean or rich and cause the o2 sensors to freak out? Clogged cats? Any suggestions would be greatly appreciated.
Thread Starter
Teching In
Joined: Jun 2013
Posts: 9
Likes: 0
From: Michigan
update on the problem. I've run a full tank of gas through the car with some Lucas. car runs well as long as i baby it. it has the pull it should through 2k rpms but still bogs down pretty hard at 2.5k. i can sometimes get it through but it bogs down again around 3.2k rpm. if it bogs down too hard it'll start running rough even at 1.5k. i can pull into a parking lot and shut it off and give it a few minuets to sit and it'll run fine until i hit it too hard again. it seems that the only time it's running rough even low in the power band is when i hit half throttle or more. if i stay at a third of full throttle it'll run well. and ideas?
It sounds dumb but to go from running fine to running like crap just get under the hood and check for something that was left unplugged or a ground connection the body shop painted over causing a bad connection. You may have to start by monitoring short term fuel trim to see if its running rich or lean and go from there. Pull a plug or two and see if they are fouled, check to make sure the maf sensor is clean (and plugged in). What codes is it throwing exactly because upstream and downstream O2 sensors have two different jobs?
Thread Starter
Teching In
Joined: Jun 2013
Posts: 9
Likes: 0
From: Michigan
quick update. grabbed a fuel pressure gauge and checked my pressure. running at 40 psi. fuel pump and filter have less than 1k miles on them. could be clogged fuel lines? will bad gas kill a pump or clog the filter?
I'll check the fuse tonight when i get home.
I'll check the fuse tonight when i get home.
Thread Starter
Teching In
Joined: Jun 2013
Posts: 9
Likes: 0
From: Michigan
checked the fuse. it looks intact, but I'll replace it to see if it just looks that way.
does anyone know how to check fuel pressure before the filter without dropping the tank? is there a special attachment that will clip into the plastic piece that the filter normally clips to? I'm trying to rule the filter and lines between it and the engine out.
i too was thinking it might be something left unplugged when the body work was done, but to replace the water pump and flush the block we unplugged pretty much everything that would have been unplugged or moved during the body work anyway. I'll check the grounds, but the only thing that was painted on the frame was the radiator support. the hood and bumper were painted off the car. fenders were blended but idk if they stayed on the car or not.
does anyone know how to check fuel pressure before the filter without dropping the tank? is there a special attachment that will clip into the plastic piece that the filter normally clips to? I'm trying to rule the filter and lines between it and the engine out.
i too was thinking it might be something left unplugged when the body work was done, but to replace the water pump and flush the block we unplugged pretty much everything that would have been unplugged or moved during the body work anyway. I'll check the grounds, but the only thing that was painted on the frame was the radiator support. the hood and bumper were painted off the car. fenders were blended but idk if they stayed on the car or not.
Last edited by shambooki; Jun 5, 2013 at 10:43 PM.
Trending Topics
Thread Starter
Teching In
Joined: Jun 2013
Posts: 9
Likes: 0
From: Michigan
update for anyone that has this problem in the future. i noticed that after i would prime the pump it would get to 40psi and almost instantly lose pressure when it stopped priming. i figured this meant there was a leak somewhere in the system. i wasn't hemorrhaging fuel at an unreasonable rate so i suspected the fuel pressure regulator. took it to the shop because i don't want to drop the tank myself and my mechanic got under and blocked the return line from the fpr and instantly had adequate fuel pressure. should have the car back in a day or two. I'll clean her up and post pics in the new members section. thanks for your responses!
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Thread Starter
Teching In
Joined: Jun 2013
Posts: 9
Likes: 0
From: Michigan
my mistake. saw gen III and didnt read the rest of the forum title so I missed the whole 'internal' part. i'll read the forum title better next time :p. could a mod move this to a more appropriate section for future reference?
