New Problem... Ongoing Problem... ???? Won't rev over 4500 and backfires.
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Joined: Jul 2005
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From: Galesburg Il
New Problem... Ongoing Problem... ???? Won't rev over 4500 and backfires. My current problem is that after doing several mods (explained below) the engine won't respond w/power at any speed/rpm at anything over 50% throttle. It runs strong at low accelleration but accelleration over about 45% throttle causes the engine to miss and fall on it's nose.
In thinking about this I"ve realized that this problem existed to some extent with the stock configuration. Bought the 02 ecsb 5.3 new in July 03. In October I added the Hypertech tune and noticed then that the truck would not rev above 5500 and figured it was a limiter still functioning. Shortly after I added the KN CAI and a Granatelli MAS.
In August 05 I installed the RADIX (I did most of the work.. I have no experience since 1962 when I built a couple 283's/301's. My help with the Radix was a guy with 50 yrs engine building experience but NO experience with computer controlled engines.) Installed the Radix tune but immediately went to a Nelson tune. The engine would not rev above about 5500 and I wondered why and went through several tunes intended to address that problem but it would never rev above about 5500. I figured it was the springs.
I then installed the 90mm tb and had problems but those problems turned out to be a defective tb (diagnosed by Speartech Fuel Injection Systems). Got a new GM tb and it ran fine but still no revs above about 5500.
A couple weeks ago I, and another novice mechanic, supervised by Zippy, installed the Comp Cam (224/230, 581-588, 114) and the Dart 225 heads (pre-asembled) and the problem is worse. The meth kit is in but not yet functioning. Zippy could not get it to run right and Nelson sent what he has described as a very rich tune but something is still wrong.
Zippy noted that he was getting a crank sensor code. I've been getting a 171 and 174 code on my Aerospace Interceptor scan guages. I just got the wb guage to work and it indicates that under any but the most minimal acceleration the engine is very lean reading 16 to 17... but... I can't be sure that the guage is functioning properly as for the first 10 days after the install it stayed on 15.5 and then started working only after a backfire jolted it into existance. It appears to now be reacting as it should to engine changes. But what do I know? I've never seen a wb guage before. I DO know that at 4000 rpm if I try to accelerate at approximately 50% throttle it backfires and noses down but feels strong at low rpm and maybe 30% throttle.
It's been suggested that I might have a fuel pressure problem or maybe the small rubber seal in the fuel regulator. My thought was the injectors are too small but it was pointed out that this would affect the engine at high rpms but probably not at low revs.
Is it possible that the original and ongoing problem of not being able to rev over 5500 is connected to the current problem?
I don't know how to check the fuel pressure or how to diagnose any other possible problem and I need suggestions that I can first try to do myself as there is no help locally. Or I could travel to get expert help.
I live about 200 miles from the expert sponsers such as FLP and Nasty, and that would be in the Chicago area. Is there anybody in maybe Springfield Il. that could do some diagnostic or fix the problem? That's only 100 miles. The Quad Cities or Peoria would be only 50 miles. Any help there?
I'm pretty lost as to what the next step is. HELP!!!
In thinking about this I"ve realized that this problem existed to some extent with the stock configuration. Bought the 02 ecsb 5.3 new in July 03. In October I added the Hypertech tune and noticed then that the truck would not rev above 5500 and figured it was a limiter still functioning. Shortly after I added the KN CAI and a Granatelli MAS.
In August 05 I installed the RADIX (I did most of the work.. I have no experience since 1962 when I built a couple 283's/301's. My help with the Radix was a guy with 50 yrs engine building experience but NO experience with computer controlled engines.) Installed the Radix tune but immediately went to a Nelson tune. The engine would not rev above about 5500 and I wondered why and went through several tunes intended to address that problem but it would never rev above about 5500. I figured it was the springs.
I then installed the 90mm tb and had problems but those problems turned out to be a defective tb (diagnosed by Speartech Fuel Injection Systems). Got a new GM tb and it ran fine but still no revs above about 5500.
A couple weeks ago I, and another novice mechanic, supervised by Zippy, installed the Comp Cam (224/230, 581-588, 114) and the Dart 225 heads (pre-asembled) and the problem is worse. The meth kit is in but not yet functioning. Zippy could not get it to run right and Nelson sent what he has described as a very rich tune but something is still wrong.
Zippy noted that he was getting a crank sensor code. I've been getting a 171 and 174 code on my Aerospace Interceptor scan guages. I just got the wb guage to work and it indicates that under any but the most minimal acceleration the engine is very lean reading 16 to 17... but... I can't be sure that the guage is functioning properly as for the first 10 days after the install it stayed on 15.5 and then started working only after a backfire jolted it into existance. It appears to now be reacting as it should to engine changes. But what do I know? I've never seen a wb guage before. I DO know that at 4000 rpm if I try to accelerate at approximately 50% throttle it backfires and noses down but feels strong at low rpm and maybe 30% throttle.
It's been suggested that I might have a fuel pressure problem or maybe the small rubber seal in the fuel regulator. My thought was the injectors are too small but it was pointed out that this would affect the engine at high rpms but probably not at low revs.
Is it possible that the original and ongoing problem of not being able to rev over 5500 is connected to the current problem?
I don't know how to check the fuel pressure or how to diagnose any other possible problem and I need suggestions that I can first try to do myself as there is no help locally. Or I could travel to get expert help.
I live about 200 miles from the expert sponsers such as FLP and Nasty, and that would be in the Chicago area. Is there anybody in maybe Springfield Il. that could do some diagnostic or fix the problem? That's only 100 miles. The Quad Cities or Peoria would be only 50 miles. Any help there?
I'm pretty lost as to what the next step is. HELP!!!
Last edited by JimS; Apr 17, 2006 at 08:51 AM.
I had a similer problem with my car one time. When I dropped the fuel tank I crimped one of the stock lines. Once the stock plastic line gets bent it's hard to straighten it. I had to cut out the kink and put in a barb connector. I'm not sure if auto zone rents a fuel pressure gauge or not but you check it at the fitting on the end of the fuel rail. That would be a good place to start and go from there.
