LT1 Power Drop
Thread Starter
Staging Lane
Joined: May 2007
Posts: 57
Likes: 0
From: Chico, Ca
LT1 Power Drop I did some searching around, and couldn't really find anything that really pin-pointed this problem.
This started two days ago...
The car's always started up just fine, hot or cold.
Now, in the morning it's fine, but if it's heat soaked, I can turn the key, hear everything turning/firing like normal, but it takes like 10 seconds before it actually kicks in and gets running. The gauges read 100-200 rpm during that long turning phase. Afterwards no idle problems at all, 900-1000 rpm very little flux.
Now, usually within 5 mins of starting the car up (open loop?) if I drive down the road it feels like the car loses power at random moments for a half a second, just enough to send you forward a little in the seat. It feels like you were to tap your brake suddenly during acceleration. It's actually pretty scary when in happens, it even does it on the freeway although it's much less noticable. But after the car's been running for a little bit, it's fine. Also, at higher RPM's (4000-5000) it feels weaker than usual.
I had a bad O2 last year, and I know what that feels like. It's not a power loss then power surge, it's more of a power drop.
The car just turned over 92,000 miles. Never missed an oil change since i've had it. No cooling problems, just put new rotors and pads on, no major engine modifications, just a K&N hi flow filter. Havn't done anything with the ignition side since i've had it (opti, sparks, wires). We have been having a heat wave, it's 111 today.
What could be causing this? My only guess would be ignition or fuel related? Any suggestions would be much appreciated, thanks guys.
This started two days ago...
The car's always started up just fine, hot or cold.
Now, in the morning it's fine, but if it's heat soaked, I can turn the key, hear everything turning/firing like normal, but it takes like 10 seconds before it actually kicks in and gets running. The gauges read 100-200 rpm during that long turning phase. Afterwards no idle problems at all, 900-1000 rpm very little flux.
Now, usually within 5 mins of starting the car up (open loop?) if I drive down the road it feels like the car loses power at random moments for a half a second, just enough to send you forward a little in the seat. It feels like you were to tap your brake suddenly during acceleration. It's actually pretty scary when in happens, it even does it on the freeway although it's much less noticable. But after the car's been running for a little bit, it's fine. Also, at higher RPM's (4000-5000) it feels weaker than usual.
I had a bad O2 last year, and I know what that feels like. It's not a power loss then power surge, it's more of a power drop.
The car just turned over 92,000 miles. Never missed an oil change since i've had it. No cooling problems, just put new rotors and pads on, no major engine modifications, just a K&N hi flow filter. Havn't done anything with the ignition side since i've had it (opti, sparks, wires). We have been having a heat wave, it's 111 today.
What could be causing this? My only guess would be ignition or fuel related? Any suggestions would be much appreciated, thanks guys.
OPTI going out 
sorry couldn't resist, when I had the near identical situation happen on mine years ago when I had PEPE it turned out to be a burn plug wire from the headers, replaced the OPTI but wasn't the problem, so years later when I put in the stroker the old opti was crap and a new one took care of the intermittent miss.
You need to scan it though, could be a bazillion things and you'll get a bazillion opinions on here as to what it could be...like my smartass OPTI comment
...but it was at least ignition related. You said when your 02 sensor when it out it was a power-loss, that's a first because for me it was an absolutel miss, change them both out and cleared it up.
sorry couldn't resist, when I had the near identical situation happen on mine years ago when I had PEPE it turned out to be a burn plug wire from the headers, replaced the OPTI but wasn't the problem, so years later when I put in the stroker the old opti was crap and a new one took care of the intermittent miss.
You need to scan it though, could be a bazillion things and you'll get a bazillion opinions on here as to what it could be...like my smartass OPTI comment
...but it was at least ignition related. You said when your 02 sensor when it out it was a power-loss, that's a first because for me it was an absolutel miss, change them both out and cleared it up. ehh not really, sure someone will pipe-in if otherwise but they typically run as-programmed with no ill effects because they are static (non-moving) pieces of hardware/software. Moreso the real hardware, engine, ignition, fuel, blah blah blah would be the culprit.
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Well at my age for all the missfires I've ever experienced it's a knee-jerk feel going down the road and a miss, depending on if you're accelerating or decelerating would warrant different effects. Accelerating would feel like you described originally where you feel that slight forward motion and it re-gains. Decel would be different based on the principles involved (might be more audible, etc) but if the clutch was in (manual) then you wouldn't no more than just hear it, otherwise it would be feel like a jerk on decel and if you run rich at all would pop a little if it were an ignition miss.
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Verdad Gallardo Thread Starter
Staging Lane
Joined: May 2007
Posts: 57
Likes: 0
From: Chico, Ca
Ok, I'll check the plug wires first. I had been meaning to replace them and the sparks soon anyway. I've had the car for 20,000+ now and don't know if/when the previous owner worked on them. If not, i'll get the PCM scanned. Thank guys.
