tune problem? WOT power loss
Thread Starter
Staging Lane
Joined: May 2017
Posts: 52
Likes: 0
From: central ky
tune problem? WOT power loss I have a 99 trans am, just rebuilt the motor. ls1 with 243 heads, tick sns stage 2 cam, fast 90/90. running a beefed up 4l60e with edge 3800 stall. got a mail order tune and have drove it about 120 miles.
So today driving it home I pulled it down into 2nd doing a 40 roll and punched it WOT. rpms shot right up to around 5500 and just as soon as it did then the car cuts out. it took all the power away, went back down to idle and the throttle was dead when i pushed the pedal, this lasted approx 5 seconds, then power returned and it drove normal.
during those long 5 seconds the tach froze at 5500 even though rpms had instantly dropped, and multiple lights came on, I know that the ses light, the abs inop light and service vehicle light came on. I think there was more lights but I didnt catch them all before they all went off except for the service vehicle which stayed on the whole way home. but when I shut the car off and started it back up that light was gone. I connected my cheap scanner and it showed no codes.
im at a loss on what the problem is. it has cut out for a split second when I go wot a few times, but most of the time it has responded just fine.
any help or info will be appreciated
So today driving it home I pulled it down into 2nd doing a 40 roll and punched it WOT. rpms shot right up to around 5500 and just as soon as it did then the car cuts out. it took all the power away, went back down to idle and the throttle was dead when i pushed the pedal, this lasted approx 5 seconds, then power returned and it drove normal.
during those long 5 seconds the tach froze at 5500 even though rpms had instantly dropped, and multiple lights came on, I know that the ses light, the abs inop light and service vehicle light came on. I think there was more lights but I didnt catch them all before they all went off except for the service vehicle which stayed on the whole way home. but when I shut the car off and started it back up that light was gone. I connected my cheap scanner and it showed no codes.
im at a loss on what the problem is. it has cut out for a split second when I go wot a few times, but most of the time it has responded just fine.
any help or info will be appreciated
Thread Starter
Staging Lane
Joined: May 2017
Posts: 52
Likes: 0
From: central ky
tuner is shortune, a very reputable tuner with ls. I have a dyno tune scheduled with him next week to do some fine tuning that hopefully will reveal the problem and he can fix, but if someone here knew what the problem was and it wasnt in the tune id like to fix it before putting the car on the dyno.
the ecm is the one that came in my 99 transam as far as I know. I dont know a specific model number or anything, sorry.
grounds are good, and it seemed like a limiter to me. I punched the throttle wide open and when rpms shot up, it shut power down to a idle while freezing the tach at 5500 and leaving multiple lights on for a few seconds. after that it gave me full power back and ran fine.
and yes the car has pulled past 5500 before, not many times as im not pushing it too hard yet. it has done this a total of 3 times, but the other 2 times it only cut out for a split second and came back before rpms fell down hardly any at all. on those 2 occasions the ses light flashed up for the split second that it cut out, but went away instantly and never set a code that my reader detected.
the ecm is the one that came in my 99 transam as far as I know. I dont know a specific model number or anything, sorry.
grounds are good, and it seemed like a limiter to me. I punched the throttle wide open and when rpms shot up, it shut power down to a idle while freezing the tach at 5500 and leaving multiple lights on for a few seconds. after that it gave me full power back and ran fine.
and yes the car has pulled past 5500 before, not many times as im not pushing it too hard yet. it has done this a total of 3 times, but the other 2 times it only cut out for a split second and came back before rpms fell down hardly any at all. on those 2 occasions the ses light flashed up for the split second that it cut out, but went away instantly and never set a code that my reader detected.
On The Tree
Joined: Feb 2013
Posts: 183
Likes: 7
A mail order tune, if it’s the first revision or 2, is usually just meant to get you going, not WOT testing.
If you have an in person tune scheduled with him, be patient and just drive the car normally.
Keep ‘testing’ WOT and you’re going to be picking up engine pieces behind you.
If you have an in person tune scheduled with him, be patient and just drive the car normally.
Keep ‘testing’ WOT and you’re going to be picking up engine pieces behind you.
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Staging Lane
Joined: May 2017
Posts: 52
Likes: 0
From: central ky
You all are right that it was not a good idea for me to be going WOT, and I knew it but my right foot was just too itchy a few times as it took a month and a half to get a appointment for a dyno tune. But anyways I stayed out of it and had it tuned yesterday. It did repeat the sam problem multiple times on the dyno, the tuner never could get a full pull and it never set a code, but he did tell me the computer was completly losing power when it would do it. So I checked over the grounds and sure enough the ground wire that grounds the ecu to the back of the head had broke off and the end of the wire had just been sitting on the block, and so when the engine flexed it would come ungrounded. We put a new connector on and proceeded to do multiple full pulls.
So brandon6.0 you were correct about the ground, I did not check them bc I had just installed the motor 100 miles ago and I knew all the grounds were connected and clean....just didnt know the connector ring under the bolt broke off.
So brandon6.0 you were correct about the ground, I did not check them bc I had just installed the motor 100 miles ago and I knew all the grounds were connected and clean....just didnt know the connector ring under the bolt broke off.