LS1 in my 55
Thread Starter
Teching In
Joined: Sep 2007
Posts: 34
Likes: 2
LS1 in my 55 Hello,
I'm hoping someone can either help me or direct me to the proper thread to help with my issue.
I've built my 55 with a 98 LS1/T56. I sent off my ECM to madz28 and he programmed it with new cam specs, tire size, gear ratio, removed VATS,etc. My son had it running pretty smooth and I was one my way to having it tuned in Las Vegas. I'm sorry to say we lost our son last March. I have pretty much let the car sit in my shop until recently. I drove the car a fewe weeks ago and it ran just fine.
I wanted to hard wire my battery tender to the battery and in doing so I unhooked the battery. Since then it dosen't run well at all. Starts fine but idles at about 2300 RMP most of the time. When I come to a stop it the idel will drop to 1100 or so but then it stumbles and dosen't want to take the throttle smoothly, It stumbles. Other huge issue is if I want to get after it and mash the pedal it just falls flat on it's face, I have to get out the throttle and let the ECM catch up. I mean it just dies.
I have tried to relearn teh ECM by letting it idle for 15~20 minutes. I took it out for a drive and it was running much better but the drive today was really acting up. It's not sending any codes my light. I have the scanner my son used but I have no expirence other than seeing him use it.
Any help or suggestion would be greatlt appreciated.
Here's what it looks like
I'm hoping someone can either help me or direct me to the proper thread to help with my issue.
I've built my 55 with a 98 LS1/T56. I sent off my ECM to madz28 and he programmed it with new cam specs, tire size, gear ratio, removed VATS,etc. My son had it running pretty smooth and I was one my way to having it tuned in Las Vegas. I'm sorry to say we lost our son last March. I have pretty much let the car sit in my shop until recently. I drove the car a fewe weeks ago and it ran just fine.
I wanted to hard wire my battery tender to the battery and in doing so I unhooked the battery. Since then it dosen't run well at all. Starts fine but idles at about 2300 RMP most of the time. When I come to a stop it the idel will drop to 1100 or so but then it stumbles and dosen't want to take the throttle smoothly, It stumbles. Other huge issue is if I want to get after it and mash the pedal it just falls flat on it's face, I have to get out the throttle and let the ECM catch up. I mean it just dies.
I have tried to relearn teh ECM by letting it idle for 15~20 minutes. I took it out for a drive and it was running much better but the drive today was really acting up. It's not sending any codes my light. I have the scanner my son used but I have no expirence other than seeing him use it.
Any help or suggestion would be greatlt appreciated.
Here's what it looks like
Beautiful car. Sorry about your son. You have come to the right place, I'm sure someone on here can help. 
When I have problems like that I usually missed plugging in something all the way - which typically sets a code. Most code scanners are far simpler to use than they appear, the problem in your case would be finding where the OBDII plug is on your car since the ECM is in the trunk. Have you tried to find a manual for your scanner? The store bought ones are typically powered by the car with the key on and have a "go" button that starts the scan process. They typically say all clear or give a code after a few moments communication with the vehicle. For basic functions there isn't too much more interaction unless there are multiple codes.
When I have problems like that I usually missed plugging in something all the way - which typically sets a code. Most code scanners are far simpler to use than they appear, the problem in your case would be finding where the OBDII plug is on your car since the ECM is in the trunk. Have you tried to find a manual for your scanner? The store bought ones are typically powered by the car with the key on and have a "go" button that starts the scan process. They typically say all clear or give a code after a few moments communication with the vehicle. For basic functions there isn't too much more interaction unless there are multiple codes.
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Teching In
Joined: Sep 2007
Posts: 34
Likes: 2
It's not throwing any codes and yes the MAF is built into the Air cleaner a S&P set up. I took the car out last night and it fell right on it's face 1/4 mile from my house, had to tow it back into my shop, It started right up this morning 
I'm still perplexed by the high idle. You mentioned in your original post that the car idles at 2300 RPM, then 1100 in gear.
This is just a guess but... Is there a possibility you don't have the Throttle Position Sensor plugged in or the sensor itself is bad. This SHOULD throw a code but I unplugged mine to work on some stuff and forgot to plug it back in then mistakenly started the car without it. I didn't make it out of the driveway before the car started acting really strange (actually before I put it in gear). Mine wasn't off long enough to set a code but I was thinking the results may be the same. If memory serves me correctly I had a high erratic idle and poor throttle response. If you have a scan tool that shows live data it can read the % of throttle while the engine is off or running. Most less expensive scan tools don't have this function, but if you do it should be smooth and proportionate to your position on the throttle.
Hope this helps.
I'm still rattling other ideas around my head on this...
Thread Starter
Teching In
Joined: Sep 2007
Posts: 34
Likes: 2
Fell on it's face like died or wouldn't run well enough to get home? Have you checked the fuel pressure at the rail? If the fuel pressure isn't 58 PSI you aren't going to run well or possibly at all.
I'm still perplexed by the high idle. You mentioned in your original post that the car idles at 2300 RPM, then 1100 in gear.
This is just a guess but... Is there a possibility you don't have the Throttle Position Sensor plugged in or the sensor itself is bad. This SHOULD throw a code but I unplugged mine to work on some stuff and forgot to plug it back in then mistakenly started the car without it. I didn't make it out of the driveway before the car started acting really strange (actually before I put it in gear). Mine wasn't off long enough to set a code but I was thinking the results may be the same. If memory serves me correctly I had a high erratic idle and poor throttle response. If you have a scan tool that shows live data it can read the % of throttle while the engine is off or running. Most less expensive scan tools don't have this function, but if you do it should be smooth and proportionate to your position on the throttle.
Hope this helps.
I'm still rattling other ideas around my head on this...
I'm still perplexed by the high idle. You mentioned in your original post that the car idles at 2300 RPM, then 1100 in gear.
This is just a guess but... Is there a possibility you don't have the Throttle Position Sensor plugged in or the sensor itself is bad. This SHOULD throw a code but I unplugged mine to work on some stuff and forgot to plug it back in then mistakenly started the car without it. I didn't make it out of the driveway before the car started acting really strange (actually before I put it in gear). Mine wasn't off long enough to set a code but I was thinking the results may be the same. If memory serves me correctly I had a high erratic idle and poor throttle response. If you have a scan tool that shows live data it can read the % of throttle while the engine is off or running. Most less expensive scan tools don't have this function, but if you do it should be smooth and proportionate to your position on the throttle.
Hope this helps.
I'm still rattling other ideas around my head on this...
I was dealing with low fuel pressure with the last pump I now have an inline Walbro with more than 60psi at the rail.
Last night it was idling right around 1000
When I say it fell on it's face it just stops like the key was turned off. Most of the time if I get off the throtle it will catch and take off like it never happened. Last night I wasn't going fast enough and would not restart. It acted like it wanted to start once but I had to tow it back to my shop. I went out there this morning and it fired right up. Is it possible it's flooding? O2 bad and not giving propper readings? I have electric cut outs but the opening to the O2 sensor is about 18''
Thread Starter
Teching In
Joined: Sep 2007
Posts: 34
Likes: 2
I had my sons scan tool hooked up but not know what paramiter to set it to didn't help but it didn't read any codes
it might not have codes but may have a high long term addaptive driving your fuel system out of wack. Or one o2 may be just sluggish.. I'd swap em out then if still acting up check into the MAF
Thread Starter
Teching In
Joined: Sep 2007
Posts: 34
Likes: 2
I have the car up in the air on stands so now would be a good time to swap them out. What would new O2's cost?
50-100 usually depending on brand and supplier... Do not use Bosch! I always buy factory O2's
http://www.newgmparts.com/partlocato...layCatalogid=0
http://www.newgmparts.com/partlocato...layCatalogid=0
Thread Starter
Teching In
Joined: Sep 2007
Posts: 34
Likes: 2
I'll swap the O2's with some others and see what happens. We have the stainless all sheared and bent for the tank so I should have it back in this weekend. I hope the O2's do it.
Thanks for the GM link
Thanks for the GM link