Car still sputters under load.
Thread Starter
Drifting
Joined: Sep 2002
Posts: 1,614
Likes: 7
From: South Florida
Car still sputters under load.
The car sputters under load at WOT or near WOT. The car backfires occassionally while sputtering.
I have run three tanks of gas through. Drained a quart of oil (down to appropriate mark on dipstick) I have run gas dry, injector cleaner, and octain boost, in that order with each tank of gas. I replaced the fuel filter.
Reccomendations that I am going to try.
Air intake blockage
Vaccumn leak
Catalytic Converter Clog
Bad O2 sensor
Fouled plugs
I don't think it's an 02sensor, because I'm not throwing codes and my HPTuner shows both working.
In fact I've thrown no codes and I don't think my scanner is showing problems (granted I still don't know how to use this thing.)
Any thoughts
I have run three tanks of gas through. Drained a quart of oil (down to appropriate mark on dipstick) I have run gas dry, injector cleaner, and octain boost, in that order with each tank of gas. I replaced the fuel filter.
Reccomendations that I am going to try.
Air intake blockage
Vaccumn leak
Catalytic Converter Clog
Bad O2 sensor
Fouled plugs
I don't think it's an 02sensor, because I'm not throwing codes and my HPTuner shows both working.
In fact I've thrown no codes and I don't think my scanner is showing problems (granted I still don't know how to use this thing.)
Any thoughts
Thread Starter
Drifting
Joined: Sep 2002
Posts: 1,614
Likes: 7
From: South Florida
update
okay pulled the number three plug...it looks fine, some oil on the threads.
Also pulled the air filters, maf, and air bridge off. No blockage and all was connected properly.
There was some oil on the forward, bottom edge of the TB blade, but putting my finger inside produced no oil.
Where should I look for a vaccumn leak and how?
Also pulled the air filters, maf, and air bridge off. No blockage and all was connected properly.
There was some oil on the forward, bottom edge of the TB blade, but putting my finger inside produced no oil.
Where should I look for a vaccumn leak and how?
Thread Starter
Drifting
Joined: Sep 2002
Posts: 1,614
Likes: 7
From: South Florida
How do I test spark plug wires?
Good idea on the maf, I'll swap the stock one back in. There is no visual prob with the maf.
I'll check the valve springs as soon as I do a cylinder balance test.
I'm also wondering about my plug wires. I have aftermarket and the number 4 plug wire's base (right above the heat shield, but not on the wire) has melted a slight bit because of the headers. I might hook up one of the stock plug wires to see if there is a prob.
How do I test spark plug wires?
I'll check the valve springs as soon as I do a cylinder balance test.
I'm also wondering about my plug wires. I have aftermarket and the number 4 plug wire's base (right above the heat shield, but not on the wire) has melted a slight bit because of the headers. I might hook up one of the stock plug wires to see if there is a prob.
How do I test spark plug wires?
Safety Car
Joined: Aug 2000
Posts: 4,537
Likes: 84
From: St. Joseph MO
Cruise-In III Veteran
Cruise-In IV Veteran
Originally Posted by Smokin Joe
How do I test spark plug wires?
Pro
Joined: Mar 2004
Posts: 512
Likes: 0
If you haven't already, I would definitely change the spark plugs. While I'm not all that familiar with the LS1s, DFI and all this computer stuff yet, the symptoms you discribe sound exactly like what an old hot rod would do when it's time to change the spark plugs.
The plugs don't always look all that bad, but can still cause a misfire. Put some new ones in there and see if it helps. That's the first thing I'd do before going any further.
Checking the plug wires as you mentioned above is also a good idea.
The plugs don't always look all that bad, but can still cause a misfire. Put some new ones in there and see if it helps. That's the first thing I'd do before going any further.
Checking the plug wires as you mentioned above is also a good idea.
Last edited by Donovan 572; Dec 26, 2004 at 05:38 PM.
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Race Director
Joined: Aug 2000
Posts: 10,649
Likes: 31
From: Central Florida
Originally Posted by Smokin Joe
The car sputters under load at WOT or near WOT. The car backfires occassionally while sputtering....
So, if you haven't done so already, check the seating of each connection from the air filter to the intake manifold. Tighten the clamps. Even a small air leak can cause those exact symptoms.
FWIW, I've had a dead plug (loose plug wire), the symptom was a miss, rather than a sputtering under load.
Let us know what it turns out to be.
Ranger
Thread Starter
Drifting
Joined: Sep 2002
Posts: 1,614
Likes: 7
From: South Florida
Got it, man I'll be busy...I replaced the plugs with NGKs less than 10k ago...how do I check them when I pull them?
The air fittings all looked right, but I took them all off, and will clean the filters before I replace them, then retighten everything...we'll see if that works.
I have to get my old MAF out of storage.
What about my cats, I've been running Long tubes since Feb and haven't had it tuned...I'm working on a tune with HPTuner right now, but it's slow going. Could my cats be clogging? They are the metal matrix ones. I'll post some results of the fixes as I execute them.
The air fittings all looked right, but I took them all off, and will clean the filters before I replace them, then retighten everything...we'll see if that works.
I have to get my old MAF out of storage.
What about my cats, I've been running Long tubes since Feb and haven't had it tuned...I'm working on a tune with HPTuner right now, but it's slow going. Could my cats be clogging? They are the metal matrix ones. I'll post some results of the fixes as I execute them.
Le Mans Master
Joined: Nov 2002
Posts: 7,179
Likes: 2
From: Charlotte, NC
I've had a similar symptom with my 95' I had put new Delco Platinum plugs and about 3K miles later I had a missfire underload. and had found that that #2 cyclender the plug was open internaly. I saw this on the ignition scope. I pulled the plug it still looked like new. No visual signs of a problem but replacing the plug solved the problem. I was also able to prove this with the ignition scope. So I had a base line to work with seeing the before and after patterns.
I guess I am just trying to say, don't rule something out until you gather enough facts to rule it out. I hope this helps.
-=Rick
I guess I am just trying to say, don't rule something out until you gather enough facts to rule it out. I hope this helps.
-=Rick
Instructor
Joined: Jul 2003
Posts: 126
Likes: 0
From: Baton Rouge LA
Had a simular problem recently. Thought is was bad gas. Ran about $20 worht of fuel cleaner thru the system but still had the problem.
Took it to my mechanic. He checked the fuel pressure, etc ...
all OK. next he hooked up the engine analyzer and plug 5 indicated
a constant miss. He opened the hood and started to pull the plug and found the plug wire for #5 had melted to the header thus shorting
the spark to ground. Wish I had found this sooner instead of worrying
about the situation for 2 weeks thinking it was bad gas
Took it to my mechanic. He checked the fuel pressure, etc ...
all OK. next he hooked up the engine analyzer and plug 5 indicated
a constant miss. He opened the hood and started to pull the plug and found the plug wire for #5 had melted to the header thus shorting
the spark to ground. Wish I had found this sooner instead of worrying
about the situation for 2 weeks thinking it was bad gas
