Rockers In!! Valvefloat? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 03-05-2006, 12:06 AM   #1
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Default Rockers In!! Valvefloat?

First of all thanks to Seth and Travel for installing them. The light came back on again and I see what the TPS sensor does now.

I might have valve float. Not sure though. Its not like a rev limiter that dbtk said valve float feels like. Its more like a minor misfire. I am hoping thats what it is, a misfire or related to that vacume hose being cut. Its a minor lurking feeling as the revs increace under WOT.
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Old 03-05-2006, 12:09 AM   #2
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What are your fuel trims and WOT O2'*? When I was running lean it felt like I had valve float when all I really needed to do was add some more fuel.
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Old 03-05-2006, 12:23 AM   #3
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We didn't have a chance to test anything really. I wish I knew that. We just checked the TPS code, cleared it and that was it for the time being. I didn't even notice anything untill the drive home from the meet.
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Old 03-05-2006, 01:25 AM   #4
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When did this misfire type thing occur? At all RPM'*, low rpms, mid-rpms, or high rpms? At WOT or part throttle?

Valve float will only occur at high rpms (like 5500+) unless your springs are REALLY bad. And the engine will not want to rev anymore after it occurs. I should've video taped my trans am before I replaced the valve springs. Depending on what it felt like that day, it would valve float between 4400 & 4800 rpms. Once it hit those RPM'* it would just die. It was like a rev limiter that the engine was bouncing off a lot quicker than it would a rev limiter. Put new springs in it and it revs to 6000 with no complaints (besides the redling being 5k rpms and the engine making NO power that high).

Shawn
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Old 03-05-2006, 02:08 AM   #5
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It can't be valve float then cause it will rev right up to the shift point. It just intermittently surges a little on the way up. The vaccum line might be messed up cause it snapped and I found a replacement line that was too long so we had to cut up closer to the boost control silinoid. This is a metal line up there so when we got through it, it was closed shut. We opened it up the best we could but it may be restricted. Could vaccum line problems cause surging? And what could have messed up the thrttle position sensor?
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Old 03-05-2006, 02:15 AM   #6
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travel=travis

prescott,

what metal piece are you talking about? the hose that i stole from gordy to put on there is just as good as the one that was there before.. and when i heard the car idling, there was no surging.. but yes, vacuum leaks usually show rough idles...

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Old 03-05-2006, 02:29 AM   #7
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Yup, thats the metal piece. If that only affects idle then that ain't it. I think the car may just need to learn this as it is a whole different ballpark for the PCM. I dropped the pedal on the highway and whoa 70-90 is a flash. I think the car may just nned to adapt to the new found power.

The TPS is still a mistery. It acted up on the way back. I had to fully let off the gas in order for the trans to shif out of first. 1/4 throttle= WOT for the trans shift scedule. I think that is what the TPS does is determine where the trans shifts? Anyways, I pulled off the road unpuged it and pluged it back in and the syptoms were gone yet the SES remains.
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Old 03-05-2006, 11:00 AM   #8
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Good to see you love your rocker, i want some

For your strange tranny shift:
When you installed the rockers, you probably unplugged the battery, when the PCM is reseted, it take some time for the PCM to adjust time shift and even more because you have more power now, thats what happen to each time i reseted, the shift are long and very smooth.

BUT doesnt mean it cant be something else.

We are waiting for a vid of the new LSS
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Old 03-05-2006, 12:04 PM   #9
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It was throwing two codes: TPS Pedal Position Sensor CKT(something else, dont remember) and TPS Pedal Position Sensor Circuit low input. No idea what these mean.
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Old 03-05-2006, 12:23 PM   #10
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That sounds like the 5V from the PCM isn't getting to the TPS, or it'* lower than the 5V it should be. Check your TPS for 5V on the input line and inspect the wires for damage and the connector for corrosion/proper contact.

Other than that, the TPS itself may be bad.

I too had what I thought was valve float at one time on the 93. It was running lean at the top. That doesn't mean you have either problem, though. Just backing Mike up on that suggestion of something to look at.

You are going to have to give the PCM a little time to relearn the fuel curves. Not sure how long the OBD2 PCM'* take to learn.
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