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03 Chevy Short Bed W/5.7l Ls1


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I'm new to the forum and need a bit of help figuring something out. We (my dad) picked up a 2003 Chevy Standard Cab Short bed at an auction. It's been lowered, has stock 20" SS wheels, and it has a completely custom LS1 in it from what appears to be a corvette. It also has a TCI Turbo 400 transmission with a 3600 stall converter. Anyway the engine has a cam in it, doesn't idle below 1100 rpm and shakes the hole truck. The computer has been tuned by the last owner because when I connect a scan tool to it and check the Emission monitors it says the rear oxygen sensors have been deleted it also says there are no codes. The problem I'm having with it is that it seems to be running fine and you will be coming to a stop or slowing down a bit off the throttle and the engine will just start to die out! :( On the message center it says "reduced engine power" then the truck just turns off and won't restart no matter how much gas you give it. :confused: When it does this it has about 55-60 psi + fuel pressure according to the gauge on the pressure regulator mounted to the firewall. Anyway any help would be greatly appreciated.

Thanks in advance!

 

Engine's covered in bondo dust because I've been pulling dents, also replaced both bedsides, and going to replace front clip with new sheet metal.

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Edited by Matt*
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You just got a hell of a deal on that truck! that was my truck! it was stolen back in september before i got to finish everything. here are the details of the engine its an ls1 out of a camaro but im unsure of the year. it has forged wisco-2cc pistons for some where around 11.5 compression, scat forged i beam rods, factory crank. the engine was built for spray. it will handle an easy 300 shot. it has prc 2.5 heads, a small tsp cam 224/581 on a 112 lsa, yella terra ultra light roller rockers, caddy race lifters. it has a complete front assembly from an 02 camaro, an ls2 intake with tb, pacesetter headers with off road y and a flowmaster 80 series muffler with a dmh cut out. it has a yank pro ss 3600 converter, a tci th 400 built to handle around 800hp, a 241 t-case, new driveshafts. it has magaughy's shackle and hanger kit in the back with their torsion keys up front. i never intended it to be a ss clone i just got a good deal on the wheels. the truck was far from being done! it still needed alot of stuff. actually i had a lot of it in my garage after it was stolen but ended up selling all of it. im sure there is a lot more that im forgetting about that thing. but it definatly needs a tune BAD! we where working on it, but we kept getting set back because of bad sensors and a severe lack of time. is you have any more questions just ask or send me a pm!

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You just got a hell of a deal on that truck! that was my truck! it was stolen back in september before i got to finish everything. here are the details of the engine its an ls1 out of a camaro but im unsure of the year. it has forged wisco-2cc pistons for some where around 11.5 compression, scat forged i beam rods, factory crank. the engine was built for spray. it will handle an easy 300 shot. it has prc 2.5 heads, a small tsp cam 224/581 on a 112 lsa, yella terra ultra light roller rockers, caddy race lifters. it has a complete front assembly from an 02 camaro, an ls2 intake with tb, pacesetter headers with off road y and a flowmaster 80 series muffler with a dmh cut out. it has a yank pro ss 3600 converter, a tci th 400 built to handle around 800hp, a 241 t-case, new driveshafts. it has magaughy's shackle and hanger kit in the back with their torsion keys up front. i never intended it to be a ss clone i just got a good deal on the wheels. the truck was far from being done! it still needed alot of stuff. actually i had a lot of it in my garage after it was stolen but ended up selling all of it. im sure there is a lot more that im forgetting about that thing. but it definatly needs a tune BAD! we where working on it, but we kept getting set back because of bad sensors and a severe lack of time. is you have any more questions just ask or send me a pm!

 

Funny that you replied to this forum, just a bit ago I found your username on LS1tech (XLR8N) and found your posts about the truck! We've been doing a lot of work to the truck mostly bodywork, but we finished the exhaust out the back and fixed all the exaust leaks. We also installed all new glass, got new tires, and fixed all the interior stuff that got broken. Your definetly right about it needing a tune, how should I go about getting the software to tune it? Is HPTuners what you used? Its difenetly got a problem because when your driving it just randomly stalls when slowing down and says "reduced engine power"! Then to top things off it won't restart for a couple minutes...while driving in it wendsday it crapped out 4 times in the middle of traffic so I've got to figure out how to tune, or have someone do it?? It's great to find out what exactly is in it because it was a sort of a mystery...Thanks!

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You just got a hell of a deal on that truck! that was my truck! it was stolen back in september before i got to finish everything. here are the details of the engine its an ls1 out of a camaro but im unsure of the year. it has forged wisco-2cc pistons for some where around 11.5 compression, scat forged i beam rods, factory crank. the engine was built for spray. it will handle an easy 300 shot. it has prc 2.5 heads, a small tsp cam 224/581 on a 112 lsa, yella terra ultra light roller rockers, caddy race lifters. it has a complete front assembly from an 02 camaro, an ls2 intake with tb, pacesetter headers with off road y and a flowmaster 80 series muffler with a dmh cut out. it has a yank pro ss 3600 converter, a tci th 400 built to handle around 800hp, a 241 t-case, new driveshafts. it has magaughy's shackle and hanger kit in the back with their torsion keys up front. i never intended it to be a ss clone i just got a good deal on the wheels. the truck was far from being done! it still needed alot of stuff. actually i had a lot of it in my garage after it was stolen but ended up selling all of it. im sure there is a lot more that im forgetting about that thing. but it definatly needs a tune BAD! we where working on it, but we kept getting set back because of bad sensors and a severe lack of time. is you have any more questions just ask or send me a pm!

 

Wow! That sucks. Also I wouldnt go near a 300 on stock casting heads..... the deck of a factory cast head is thin and can lead to lifting problems.

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  • 3 months later...

Bump! Anyone got any ideas on this problem :confused: . The trucks been parked since I posted this basically. It seems to go into reduced engine power mode randomly. It has an LS2 throttle body and intake manifold along with a spear tech box to control the throttle body I believe. Also when the headlight relay is installed the fuel pump doesn't turn on so the truck won't start unless you take out the relay or have the headlights off weird.... :uhoh: I took apart the fuse box expecting to find a short of some kind causing this but all the wires looked perfect.

Let me know what you guys think...

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Just get someone to tune your truck... live if possible. It just sounds like it needs a lot of tunning

 

 

:withstupid: check the jets and see what they are and how much the spray is shooting and then start with like a 150 and go from there.

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Just get someone to tune your truck... live if possible. It just sounds like it needs a lot of tunning

 

I don't believe there is anyone in the state of Alaska that can tune really, there are some shops but I don't think there capable of doing it. I think my only option would be mail order, but my question is how dialed in can they get the tune from just a mail order? I was also thinking of getting HP tuners and seeing whats going on with it, since the last owner had started tuning it with that.

I guess I just thought the only reason it would go the reduced engine power would be something related to the electric throttle body, not the tune?

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REP is always caused by the tune being off. Even if there is a failure in the throttle-by-wire, the PCM will see that there is more/less airmass than 'reasonably expected' and will assume throttle failure. On FI motors it is common that we tune this diagnostic table to maximum values, essentially disabling the feature in the PCM because when you've got a blower you can get a ton of airmass at half-throttle and the PCM decided there must be a malfunction and goes into REP. My point is, the ETC system never 'talks' to the PCM, the PCM has no idea the ETC exists, all it knows is that there is a lot more/less airmass than it was expecting so it pops the REP mode on you. Ultimately, it's a tuning issue.

 

The malbehaved idle, is all PCM tuning - nobody put in the time or effort to dial-in the idle, and you really can't do that until you dial-in the AFR first so you have an 'unknown quantity' when it comes to your PCM tune.

 

AFA mail order tunes, things have gotten a lot better in the last couple years. Firstly, most reputable tuners have now amassed huge libraries of customer tunes and it is likely they have already tuned a LS1 with your cam & induction, so they can offer you a very close (if not exact) base tune. Also now there are 'black boxes' that log information from the PCM, you can buy or rent them from your tuner; basically he will instruct you how to drive the truck to log specific data from specific driving situations and then have you upload that data from the black box over the internet, he can then examine the log and email you a tune for a reflash.

 

Of course you could buy HPT or EFILive and log the data yourself, and hire a tuner to help you read & decide what changes to make in your tune.

 

Mr. P. :)

Edited by Mr. P.
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REP is always caused by the tune being off. Even if there is a failure in the throttle-by-wire, the PCM will see that there is more/less airmass than 'reasonably expected' and will assume throttle failure. On FI motors it is common that we tune this diagnostic table to maximum values, essentially disabling the feature in the PCM because when you've got a blower you can get a ton of airmass at half-throttle and the PCM decided there must be a malfunction and goes into REP. My point is, the ETC system never 'talks' to the PCM, the PCM has no idea the ETC exists, all it knows is that there is a lot more/less airmass than it was expecting so it pops the REP mode on you. Ultimately, it's a tuning issue.

 

The malbehaved idle, is all PCM tuning - nobody put in the time or effort to dial-in the idle, and you really can't do that until you dial-in the AFR first so you have an 'unknown quantity' when it comes to your PCM tune.

 

AFA mail order tunes, things have gotten a lot better in the last couple years. Firstly, most reputable tuners have now amassed huge libraries of customer tunes and it is likely they have already tuned a LS1 with your cam & induction, so they can offer you a very close (if not exact) base tune. Also now there are 'black boxes' that log information from the PCM, you can buy or rent them from your tuner; basically he will instruct you how to drive the truck to log specific data from specific driving situations and then have you upload that data from the black box over the internet, he can then examine the log and email you a tune for a reflash.

 

Of course you could buy HPT or EFILive and log the data yourself, and hire a tuner to help you read & decide what changes to make in your tune.

 

Mr. P. :)

 

Thanks Mr. P! Great info, I'm glad its just as simple as a tuning issue, so I'll check into getting a mail order or just buy HPT or EFILive and do it myself, but that might be a learning curve.... :chevy:

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Thanks Mr. P! Great info, I'm glad its just as simple as a tuning issue, so I'll check into getting a mail order or just buy HPT or EFILive and do it myself, but that might be a learning curve.... :chevy:

 

 

u can always get on the site of the software u buy and start asking questions and looking for help.

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Does it have the tac module or the Dr. X harness to controll the 90MM tb, the original owner did't say which one it had

 

I think its got a Speartech module to control the 90mm tb.

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I think its got a Speartech module to control the 90mm tb.

 

 

yes its def a tuning issue . . . it has a TAC modual from speartech, and i have a feeling that it make be part of the problem, also like i said in the pm's the map sensor was acting up and will need a new one. my roomate and i tune and will be back stateside in feb/mar time frame, which should be good cause the roads might start clearing up by then. we had the tune pretty close and was running 12.60's in it n/a. then about a week later it started doing the rep mode thing. i had a few issues come up and had to leave it sit for a few weeks, thats when it was stolen.

 

If you could like i asked 3 times, i would appriciate it if you could help me out with how you bought it from the insurace company and how much you paid for it. they told me that they couldnt sell it for two years, then all of a sudden you have it 6 months later . . . .

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