Running Rough at Idle
12-14-2018, 04:12 PM
#42
Le Mans Master
Thread Starter
Finally back. Got the newly cleaned and flowed injectors back. Installed them today. The car runs much better. So this really needed to be done.
The idle is considerably better. I still have a very slight miss that I can hear at the tailpipes.
Plans are to check for a light show under the hood tonight. Check the conditions of all spark plugs. To see if one is cracked or fouled.
I must have a bad ignition wire or spark plug. Those parts are new.
Suggestions....
The idle is considerably better. I still have a very slight miss that I can hear at the tailpipes.
Plans are to check for a light show under the hood tonight. Check the conditions of all spark plugs. To see if one is cracked or fouled.
I must have a bad ignition wire or spark plug. Those parts are new.
Suggestions....
12-14-2018, 04:33 PM
#43
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Finally back. Got the newly cleaned and flowed injectors back. Installed them today. The car runs much better. So this really needed to be done.
The idle is considerably better. I still have a very slight miss that I can hear at the tailpipes.
Plans are to check for a light show under the hood tonight. Check the conditions of all spark plugs. To see if one is cracked or fouled.
I must have a bad ignition wire or spark plug. Those parts are new.
Suggestions....
The idle is considerably better. I still have a very slight miss that I can hear at the tailpipes.
Plans are to check for a light show under the hood tonight. Check the conditions of all spark plugs. To see if one is cracked or fouled.
I must have a bad ignition wire or spark plug. Those parts are new.
Suggestions....
Last edited by C5 Diag; 12-14-2018 at 05:17 PM.
12-17-2018, 01:09 PM
#45
Le Mans Master
Thread Starter
Took her out this morning on the tollway to see if any other codes would set. I ended up with...
Po171
Po 171
Po174
These indicate a lean fuel system.
My fuel trims are crazy
Lows are about 3%
Highs are above 20%
There are several things that the scan tool shows as possible problems.
The shop manual is directing me to check HO2S parameters next.
What say you guys?
Po171
Po 171
Po174
These indicate a lean fuel system.
My fuel trims are crazy
Lows are about 3%
Highs are above 20%
There are several things that the scan tool shows as possible problems.
The shop manual is directing me to check HO2S parameters next.
What say you guys?
12-17-2018, 01:39 PM
#46
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Both banks are running in the 20’s ??...what are they at idle ??... run the engine at 3,000-4,000 RPM...if short term fuel trims decrease and long term fuel trims start to ratchet down slowly you have a “classic” vacuum leak...check that first and then we can proceed...if they don’t decrease you’d be looking at a fuel delivery or a MAF sensor problem...as far as fuel delivery issues with fuel trims in the 20’s I’d say it’s fuel and not ignition related !!
12-17-2018, 01:52 PM
#47
Le Mans Master
Thread Starter
Originally Posted by rwobs777
Both banks are running in the 20’s ??...what are they at idle ??... run the engine at 3,000-4,000 RPM...if short term fuel trims decrease and long term fuel trims start to ratchet down slowly you have a “classic” vacuum leak...check that first and then we can proceed...if they don’t decrease you’d be looking at a fuel delivery or a MAF sensor problem...as far as fuel delivery issues with fuel trims in the 20’s I’d say it’s fuel and not ignition related !!
12-17-2018, 02:30 PM
#48
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Super !!...let’s check those fuel trims at higher RPM’s and see what happens...yes, it can be a faulty O2 sensor “reporting” a lean condition but both faulty...doubtful !!
12-17-2018, 02:51 PM
#50
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Does your scan tool show “freeze frame” data ??...that will show us what kind of RPM, engine load etc... what caused the DTC to set ??...helps in diagnosis !!...also does your scan tool show MAF airflow ??...grams/second or lbs/second !!..,do you own a fuel pressure gauge ??
Last edited by C5 Diag; 12-17-2018 at 03:26 PM.
12-17-2018, 02:53 PM
#51
Safety Car
More than likely vacuum leak.
If it were me, I would get a can of starting fluid and while the engine is running, sparingly spray the fluid on vacuum hose connections, where the intake meets the heads while monitoring the fuel trims. If you see a wild swing in the trims when you spray an area, you have found a leak.
The main thing is to be careful and not spray so much that you ignite the fluid. It may be a little scary but it does work.
If it were me, I would get a can of starting fluid and while the engine is running, sparingly spray the fluid on vacuum hose connections, where the intake meets the heads while monitoring the fuel trims. If you see a wild swing in the trims when you spray an area, you have found a leak.
The main thing is to be careful and not spray so much that you ignite the fluid. It may be a little scary but it does work.
12-17-2018, 03:04 PM
#52
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More than likely vacuum leak.
If it were me, I would get a can of starting fluid and while the engine is running, sparingly spray the fluid on vacuum hose connections, where the intake meets the heads while monitoring the fuel trims. If you see a wild swing in the trims when you spray an area, you have found a leak.
The main thing is to be careful and not spray so much that you ignite the fluid. It may be a little scary but it does work.
If it were me, I would get a can of starting fluid and while the engine is running, sparingly spray the fluid on vacuum hose connections, where the intake meets the heads while monitoring the fuel trims. If you see a wild swing in the trims when you spray an area, you have found a leak.
The main thing is to be careful and not spray so much that you ignite the fluid. It may be a little scary but it does work.
12-17-2018, 03:57 PM
#53
Le Mans Master
Thread Starter
Originally Posted by rwobs777
Does your scan tool show “freeze frame” data ??...that will show us what kind of RPM, engine load etc... what caused the DTC to set ??...helps in diagnosis !!...also does your scan tool show MAF airflow ??...grams/second or lbs/second !!..,do you own a fuel pressure gauge ??
I don't own a fp gauge but my neighbor might.
He's coming over to help later today.
12-17-2018, 04:18 PM
#54
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If your freeze frames for either the 171 or 174 showed a high load or RPM when the DTC set it might be a fuel pressure problem... if fuel pressure drops when you snap the throttle the fuel pressure can’t keep up with that higher engine load hence the lean code...actually the VOLUME is what’s more important...clogged fuel filter etc...looking at the pump amperage wouldn’t hurt either...you can remove your fuel pump fuse and check AMPS...your DVOM if you have one should have a 10 AMP limit...your pump should be less than that...somewhere around 5-6 AMPS !!
Last edited by C5 Diag; 12-17-2018 at 04:25 PM.
12-17-2018, 06:43 PM
#55
Le Mans Master
Thread Starter
Whoa
Let's go back to the original problem.
I just discovered that the injectors given to me are for an LS2. They flow less than the LS3 injectors. Hence the lean codes!
So I'm back to sending my factory '08 LS3 injectors in for flow and repairs.
Let's go back to the original problem.
I just discovered that the injectors given to me are for an LS2. They flow less than the LS3 injectors. Hence the lean codes!
So I'm back to sending my factory '08 LS3 injectors in for flow and repairs.
Last edited by Street Rat; 12-18-2018 at 06:44 AM.
12-17-2018, 07:12 PM
#56
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WHOA is right !!...you solved your own problem !!..,keep us advised what everything is back together and running.
12-25-2018, 07:03 PM
#57
Le Mans Master
Thread Starter
Well I'm back. Didn't want to keep everybody hanging during the holidays. Here's my current status. I just received the original set of injectors back from the shop yesterday. I purchased some intake gaskets as well. Don't know if I'm going to change them or not.
So with any luck I'll be back under the hood tomorrow getting this C6 repaired.
Hope everyone had a great Christmas.
So with any luck I'll be back under the hood tomorrow getting this C6 repaired.
Hope everyone had a great Christmas.
12-27-2018, 05:08 PM
#58
Le Mans Master
Thread Starter
Finally had a chance to put the correct injectors on today.
I cleared the previous lean codes from the computer before start up.
Started and ran.
Still has a little blip in it. So I took it out to the tollway to see if it would trigger any codes.
No codes triggered.
Car is more responsive after cleaning the injectors.
ALTHOUGH the car runs somewhat smoother at idle my original problem persists.
The car has a definite misfire that is detectable by the rear exhaust as well as sitting in it.
Tonight we are under the hood looking for a light show.
I cleared the previous lean codes from the computer before start up.
Started and ran.
Still has a little blip in it. So I took it out to the tollway to see if it would trigger any codes.
No codes triggered.
Car is more responsive after cleaning the injectors.
ALTHOUGH the car runs somewhat smoother at idle my original problem persists.
The car has a definite misfire that is detectable by the rear exhaust as well as sitting in it.
Tonight we are under the hood looking for a light show.
12-27-2018, 05:30 PM
#59
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Glad it's running better....any misfires DTC's while running ??...if not you might have a sticky valve and sometimes they don't throw a misfire DTC...Seafoam or GM Top End Cleaner might help...watch this video...paper or a dollar bill works !!
12-28-2018, 02:32 PM
#60
Le Mans Master
Thread Starter
Darn it. I fell asleep before the light show!
Got some new misfire information. Here is what is stored on the scan tool...
Cylinder EWMA Other
1 0 0
2 1 0
3 2 0
4 1 0
5 4 1
6 3 1
7 2 0
8 3 0
I don't know what EWMA means. That seems to be where a problem lies
Hell who am I fooling? This is really burning me out. It's frustrating as hell.
Got some new misfire information. Here is what is stored on the scan tool...
Cylinder EWMA Other
1 0 0
2 1 0
3 2 0
4 1 0
5 4 1
6 3 1
7 2 0
8 3 0
I don't know what EWMA means. That seems to be where a problem lies
Hell who am I fooling? This is really burning me out. It's frustrating as hell.