SES Light on.. Codes.. 171, 174, 0300 Plz help..
Thread Starter
Staging Lane
Joined: Aug 2006
Posts: 53
Likes: 0
SES Light on.. Codes.. 171, 174, 0300 Plz help.. Just got the car 02 Z28 6 speed with only 54k miles. Car has shorty eldlebrock headers, stock Y pipe, corsa catback, and that is it.. Also an SLP MAF (why the SLP MAF?? I dont know..). Anyways, I checked the codes after the light came on once. It threw just the code 171 (fuel trim bank one condition). So I said ok, maybe the O2 sensor is bad on the driver's side. The guy put a brand new O2 sensor in the trunk.. ?? SO ok maybe that's the problem?? ANyways, I can't get to the sensor to replace it with a stock jack.. (lol) So i've been waiting to take it to a shop and get them to replace it. But then the next day, the car started missfiring when giving it about 1/8 of throttle. It would stop when I gave the car 1/2 throttle or more. Car drops to 400-500 rpms when driving then coming to a stop. It runs greatttt when I put the pedal to the metal... I take it back to auto zone to have the codes checked.... and now it's throwing codes 0171(fuel trim bank one cond.), 0174(fuel trim bank 2 cond.), and 0300(multiple random cylinder missfire).. Now.. the car also has an exhaust leak.. a very bad one at that.. It is after the first O2 sensor on the driver's side, right at the collector where it bolts up to the cat (I'm pretty sure). It may leaking at the Cat, but I can not tell for sure..... what should be my first approach to fixing this?? Get a stock MAF(heard SLP's can mess up the LS1s sometimes)? I got a new fuel filter I'm about to put on... put fuel injector cleaner in too.. I'm also going to seafoam the car tonight.. Plz help and thank you so much for whoever reads all this!! lol. I appreciate any help guys... Thank you
Jeremy
Jeremy
Joined: Aug 2007
Posts: 24,241
Likes: 89
From: Turnin' Wrenches Infractions: 005
Honestly, I wouldnt seafoam the car just yet. I have had trouble with seafoam fouling plugs and causing misfires and irratic idles. One problem at a time. Obviously there is something going on with part throttle fueling. This is controlled by the front O2s. I would start by replacing those. They can go afoul by getting exposed to too much moisture from rain and/or puddles and also age. The fuel filter and plugs I would do for good measure as they are cheap and easy enough to replace. If that doesn't work I would try swapping in a stock MAF. It also would hurt to look at the SLP MAF carefully to make sure the thin wires inside of it are intact and it doesn't have any debris inside of it possibly altering the reading.
Thread Starter
Staging Lane
Joined: Aug 2006
Posts: 53
Likes: 0
I checked the SLP MAF and the fillaments are intact and not burnt and don't show any defects. I just seafoamed the car and it is actually running a little smoother now. Probably shouldn't have but I did! I'm thinking maybe fuel might actually BE a problem after the experience with the seafoam (added it to the gas too). And also I noticed some black powdery stuff coming from the exhaust tips on my driveway after revving it a few times.. I smelled it and it didn't smell like gas or oil, but more like just dirt (Carbon??)... That's another reason I did the seafoam.. Thought there was alot of gunk in the motor.. Anways What do you think about the exhaust leak??? Like I said it's after the first O2 sensor.. Could that cause any issue relating to my problem at all??? Thnx for all the input I appreciate it alot man.
Jeremy
Jeremy
I don't think Seafoam is to blame for fouling plugs. Its 100% petroleum. Yes, it may help down the line, but get all the codes cleared up then go for a good cleaning with it.
Joined: Aug 2007
Posts: 24,241
Likes: 89
From: Turnin' Wrenches Infractions: 005
It has caused fouled plugs (so bad after a month or two that the car had terrible misfires) and erratic idles in several of my vehicles. I wont use it again.
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Staging Lane
Joined: Aug 2006
Posts: 53
Likes: 0
Sorry i've been without internet for a while... Heres an pdate that might help ya'll help me: The tuner I have said the fuel trim on bank one and two have a lean condition. And the multiple random cylinder, missfire of course. I pulled a few plugs and they looked good but I found out that that they are BOSCH PLATINUM spark plugs. Aren't those bad for LS1's? I thought I had heard that once, but wasn't sure.. Could those plugs be bad for the motor and be causing the multiple random cylinder missfire?? Any input is appreciated. Thanks ,
Jeremy
Jeremy
TECH Enthusiast
Joined: May 2004
Posts: 735
Likes: 1
From: St. Louis, MO
Did you fix it? sounds like a vacuum leak. If it's setting both banks lean, then I'd check the pcv hose or the intake gaskets. Spray around with brake cleaner, see if you can get it to idle up. If it's running that bad there probably is a large leak. Or fuel pressure is really low.
P0171 and 174 are bank 1 and 2 system lean. A lean condition will cause misfire at idle, but go away as the throttle opens further. Before replacing anything, diagnose the problem. If you are not capable or don't have the tools or equiptment to do so, pay someone else to. You will be better off paying someone to diagnose it than guessing yourself. Personally, I wouldn't just go and replace the O2 sensors. You should check for a vacuum leak. System lean= too much air, or not enough fuel. Check fuel pressure AND fuel volume. Try swapping the MAF with a known good part. If you have access to a scan tool, montior fuel trim. System lean will set if the fuel trim is greater than somewhere around +15 I think, not sure the exact spec but at least +12. Normal is around zero. Unplug the MAF with it running. If the MAF reading is skewed and causing the issue= bad MAF, the fuel trim will drop to normal.
Thread Starter
Staging Lane
Joined: Aug 2006
Posts: 53
Likes: 0
Cool I appreciate the input. I'll try putting my dad's stock MAF on my car tomorrow. See if that fixes it. Sounds like the SLP is messing it up to me. I checked for vacuum leaks and couldn't find any (doesn't mean there aren't any).. I'll get a fuel pressure gauge and check it asap also if the stock maf doesn't do anything.. A leak around the intake manifold is possible though, as the car was sitting for a while and the gasket coulda dried out. Thanks again for the input and i'll keep ya'll updated also so someone else can benefit from this too.
Jeremy
Jeremy
Thread Starter
Staging Lane
Joined: Aug 2006
Posts: 53
Likes: 0
I put my dad's stock MAF on the car and drove it for about 10 minutes.. Did seem to run a little better, but still had the missfire. Changed the fuel filter and oil after the seafoam as well.... And I got the exhaust leak fixed, it was the driver's side header collector gasket. Also put a new O2 sensor on the driver's side (before the cat). I put the SLP MAF back on, and now it is running even worse! ???? I floor it and The low end and mid range power is great, but when the RPM's get up to about 4500, it just feels like the power is at a loss and flattens out until 6k. I've tried running it without the MAF connected and it runs the exact same.. So does that rule out the MAF? I hooked my predator scanner up to it and its saying the fuel trim on bank 1 and 2 are at a LEAN condition (this is after I changed the 02 sensor as well).. Also, the SES light will turn off randomly and stay off for a day, but still run badly. One more thing- I got the driver's side collector gasket replaced, and the very same day, the passenger header collector gasket blew out and is still out, so now i have another exhaust leak.. WTF ?
Jeremy
Jeremy
The gen III and IV engines frequently leak at the intake gaskets, specifically cylinders 7 and 8, and will cause the two lean codes and misfires. GM came out with a re-designed intake gasket set to fix this. The gaskets should have green sealing surfaces if they're the re-designed ones. The old ones were orange.
I'd bet money that it's the intake gaskets. Spray some carb clean around where the intake mates to the heads with the engine running and listen for an RPM change for a second or two. That'll pinpoint a vacuum leak.
I'd bet money that it's the intake gaskets. Spray some carb clean around where the intake mates to the heads with the engine running and listen for an RPM change for a second or two. That'll pinpoint a vacuum leak.
Launching!
Joined: Sep 2008
Posts: 234
Likes: 0
From: Ashland,VA
Check the pcv hose where it connects to the intake. There is a rubber elbow just before it connects to the intake manifold that always cracks where you can't see it. I personally have never seen a ls1 with a 171,174,and 300 code that was intake gaskets just the truck engines as they have a diff style intake gasket. I would lean more toward a fuel issue or that hose. All of the ones I have experienced at the shop was the pcv hose cracked.
