Missing lt1 power help

[RichardP]

Still no go on finding the missing 70 hp on Dan's Camaro and I could use some suggestions...

Background: Orange CMC 2 4th gen with a ’93 speed density lt1. Car runs and sounds fine with a smooth idle. It doesn't overheat on track. It seemed like the car started to lose power progressively, maybe at Hallett, more noticeable at a DE in Houston, definitely at a DE in Cresson. Found an exhaust leak including lose/missing header bolts. Replaced the header gasket and tightened everything up. Sent it to the dyno to confirm. It blew a disappointing 194 hp in the same configuration that showed over 260 earlier this year.

Did a compression check with all cylinders at about 180 psi. Replaced the knock sensor. Connector seems fine. There are no relevant codes. Fuel pressure is fine with the vacuum line off and reacts as expected with it hooked up. Replaced the optispark, cap, rotor, and plug wires. Found missing motor mount bolts right next to knock sensor. Replaced those…

Back on the dyno, no change in hp. A wideband shows A/F at 14:1 straight across the board. Given the fuel pressure and consistent ratio, it seems like the computer is commanding a lack of fuel rather than there not being enough fuel?

Probably unrelated but I’ll throw it out there anyway: Car seems to want to kill the battery enough to keep the starter from turning over after only about a week. New battery before Hallett. Everything seems fine once you get the starter to turn over a bit…

Any suggestions on what to do next are appreciated. Dan is willing to arbitrarily throw money at low probability replacement parts to try and fix this. He doesn’t have much time to work on this and time is short before nationals. He really wants to go…


Richard P.

[Alien]

Is the dyno graph smooth?

I'm still trying to figure out these LT1 things myself. Could it be a lack of a good spark? How about getting the ignition control module tested? Coil? Alternator?

I had a 1500 V6 truck that died/wouldn't start. Had spark from the coil, but it was a weak yellow spark. I didn't think that it would make much of a difference. Spark is spark, should ignite the mixture, right. Well, I was wrong. Replaced the coil, ran just fine.

[Alien]

*edit* Now that I think about it, check the simply things. I dyno'd at 273 (unrestricted) at the beginning of the year. At TWS, I dyno'd at 202. Later discovered a plug wire had fallen off. One cyl, ~70hp difference like you're experiencing.

[Fbody383]

Replaced the optispark, cap, rotor, and plug wires.

checked all the plugs themselves? One bad plug would screw you.

Car seems to want to kill the battery enough to keep the starter from turning over after only about a week. New battery before Hallett. Everything seems fine once you get the starter to turn over a bit…

Some kind of ground leakage? bad coil? If fuel is good is there good +12V at the coil when it's running? Is there good voltage at the PCM when it's running?

try pulling a plug wire at a time to see if it makes a difference? pull an injector plug one at a time?

I sure hope you guys make it.

[Crumpacker]

It seemed like the car started to lose power progressively, maybe at Hallett, more noticeable at a DE in Houston, definitely at a DE in Cresson.

Not sure if an updated timeline will help much, but he had plenty of power through R4 at Hallett.

[GlennCMC70]

New O2's?
Check to make sure each injector is working?

[AllZWay]

Since it wasn't the knock sensor, I would also lean toward maybe o2's, but I wouldn't think it would be a 70hp loss.

[Casey_SS]

New O2's?
Check to make sure each injector is working?

I'll also throw O2's out as a possible culprit. It's a common misunderstanding that the computer doesn't use O2's at WOT. While that's correct, they ARE used to select the starting fuel map and timing mode prior to WOT which throws everything off. If the computer thinks the O2's are bad it will never put you in the right maps for max power. O2s can "fail" in a number of ways - only a couple of which have corresponding SES codes.

If you have access to a digital pyrometer, try to get header temps for each cylinder. If one is noticeably out of range of the others, that'll help guide you to an injector or spark problem.

[AllZWay]

R4 at Hallett.

Dude...that video makes me nervice to watch. Great racing Sam.

R1... great battle with Jeremy. I thought you were going to move him a couple of times coming out of bus stop.
R2... WOW...great run.. TWICE. This race especially made me nervous watching.
R3...What was that racing in the grass? Looking for a short cut.
R4... Too bad about the tranny, but still some good close racing.

[AllZWay]

sorry for the spelling.. couldn't edit it.