Rock crawler 5.3L spits and splutters HELP
11-09-2013, 07:17 PM
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Rock crawler 5.3L spits and splutters HELP Before I burn my vehicle to the ground and pull my hair out… I signed up for this site to post what my problems are. I hope someone is smart enough to help me because I have no idea what else I can do.
I have a dedicated Rockcrawler which I use for rock crawling competitions. You can see pictures in my profile. It has a 5.3 engine in it. The transmission is a 700r4. The engine is a 5.3 out of a 2003 suburban. Stock computer. In has no cats on only the two front O2 sensors.
When I got the vehicle it would idle okay and start quickly but anytime you would give it wide-open throttle It seemed to lack power and would spit and splutter. The best way to describe it is as though it was running on six or seven cylinders.
I took it to a custom tuning shop. He checked the engine out and the computer would not work right or let him access it correctly. So I replaced the computer and had him attempt to tune it. He still could not get the engine to respond properly
So rather than take the engine out, open it up and diagnose it further I opted simply to replace the engine. You can get a used 5.3 for 600 bucks. So I had it replaced and took it back to the tuner. He put in a custom tune and the engine ran great. According to the tuner the air fuel mixture was perfect and it ran that way. I was the happiest guy in the world
I took it out to the Desert opened it up and it ran like a dream. However after about five or 10 minutes it reacted almost like a fuse blowing. I know it wasn't a fuse but It was as if the engine instantly went back to his old ways. It ran like crap would spit and splutter even at one quarter to half throttle.
Where it seems to have problems is when you put it under load. If you're going up even a small hill and step on the gas it's like it's flooding. Absolutely no power even in low range four-wheel-drive. It sounds almost like it's running out of fuel or has too much. The power is almost nonexistent. Running at low speeds without wide-open throttle it still runs poorly but will at least operate at some fundamental level.
The only components left on the vehicle from when I purchased it are the wiring harness and the fuel lines coming from the fuel tank and the intake manifold. It also has the old fuel rail and injectors. The injectors appear to be working as I put a stethoscope to each one and I can hear it clicking. Fuel filters are clear. Coils have all been swapped out. Plugs and wires are new and did not change behavior. It does not appear to have any vacuum leaks and fuel pressure is perfect. I get no codes from the engine to indicate what the problem is except p0140 and p0160 and p0650. Sometimes it is worse than others. It also is hard to start and it takes a few attempts to get it started. Once it starts it takes 5 seconds to smooth out.
Because I have nothing else I can change in the vehicle, I am tempted to replace the wiring harness under the assumption that somewhere in the wiring is a bad connection or frayed wire that I cannot see. I only say that because it's one of the last things left on the vehicle. But I would think it would throw a code. Which it is not.
Does anyone have experience with a bad wiring harness causing problems similar to what I'm having but not throwing the code? I don't know what to make of the fact that the tune that was placed and it seemed to work great for very short period of time then instantly in the blink of an eye it went back to his old ways. HELP
I am in Camarillo California.
I have a dedicated Rockcrawler which I use for rock crawling competitions. You can see pictures in my profile. It has a 5.3 engine in it. The transmission is a 700r4. The engine is a 5.3 out of a 2003 suburban. Stock computer. In has no cats on only the two front O2 sensors.
When I got the vehicle it would idle okay and start quickly but anytime you would give it wide-open throttle It seemed to lack power and would spit and splutter. The best way to describe it is as though it was running on six or seven cylinders.
I took it to a custom tuning shop. He checked the engine out and the computer would not work right or let him access it correctly. So I replaced the computer and had him attempt to tune it. He still could not get the engine to respond properly
So rather than take the engine out, open it up and diagnose it further I opted simply to replace the engine. You can get a used 5.3 for 600 bucks. So I had it replaced and took it back to the tuner. He put in a custom tune and the engine ran great. According to the tuner the air fuel mixture was perfect and it ran that way. I was the happiest guy in the world
I took it out to the Desert opened it up and it ran like a dream. However after about five or 10 minutes it reacted almost like a fuse blowing. I know it wasn't a fuse but It was as if the engine instantly went back to his old ways. It ran like crap would spit and splutter even at one quarter to half throttle.
Where it seems to have problems is when you put it under load. If you're going up even a small hill and step on the gas it's like it's flooding. Absolutely no power even in low range four-wheel-drive. It sounds almost like it's running out of fuel or has too much. The power is almost nonexistent. Running at low speeds without wide-open throttle it still runs poorly but will at least operate at some fundamental level.
The only components left on the vehicle from when I purchased it are the wiring harness and the fuel lines coming from the fuel tank and the intake manifold. It also has the old fuel rail and injectors. The injectors appear to be working as I put a stethoscope to each one and I can hear it clicking. Fuel filters are clear. Coils have all been swapped out. Plugs and wires are new and did not change behavior. It does not appear to have any vacuum leaks and fuel pressure is perfect. I get no codes from the engine to indicate what the problem is except p0140 and p0160 and p0650. Sometimes it is worse than others. It also is hard to start and it takes a few attempts to get it started. Once it starts it takes 5 seconds to smooth out.
Because I have nothing else I can change in the vehicle, I am tempted to replace the wiring harness under the assumption that somewhere in the wiring is a bad connection or frayed wire that I cannot see. I only say that because it's one of the last things left on the vehicle. But I would think it would throw a code. Which it is not.
Does anyone have experience with a bad wiring harness causing problems similar to what I'm having but not throwing the code? I don't know what to make of the fact that the tune that was placed and it seemed to work great for very short period of time then instantly in the blink of an eye it went back to his old ways. HELP
I am in Camarillo California.
Last edited by Paultyler; 11-09-2013 at 07:50 PM.
11-09-2013, 07:43 PM
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Fuel pressure was tested at the fuel rail. Shows 55 from the moment the pump primes. It will advance to 60 as you open the throttle
11-09-2013, 09:05 PM
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Have you had a second opinion on the tune to rule out its not a tuning issue? Email me the tune if you have a way to or mail me the PCM and pay for return shipping and I will look at it for free. We tune ls swaps every week in old cars, rock crawlers, race cars, you name it for many different shops. I bet 90% of the ones that were tuned before were not set up correctly for standalone use.
11-09-2013, 09:36 PM
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Have you had a second opinion on the tune to rule out its not a tuning issue? Email me the tune if you have a way to or mail me the PCM and pay for return shipping and I will look at it for free. We tune ls swaps every week in old cars, rock crawlers, race cars, you name it for many different shops. I bet 90% of the ones that were tuned before were not set up correctly for standalone use.
