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Every once and a while when I accelerate from a stop at WOT the car doesnt shift into second and bounces off the rev limiter for a second or 2 and then shifts. Does anyone have any idea what could be wrong?
 

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Pardon me for a bit of plagerism, but this info is posted on the Technical Discussions page. Hope it helps.

Occasional Full-Throttle Acceleration Is Good For Your Engine (check this discussion for references): (back to the top)

There are many advantages to occasional full throttle accelerations with a Northstar and any engine.

It keeps the carbon cleaned out of the combustion chamber. This is maybe a little more important with the Northstar than some other engines due to the tight squish volumes between the piston and the cylinder head. It's designed this way to promote good in-cylinder mixture motion (good combustion) but it has the down side of providing a ready place for carbon build-up to touch the piston - causing noise. Ever heard of the Northstar "cold carbon rap" problem?? Simply put you'll hear a rythmic, piston slap-like noise when the engine is cold. Very prominent and very annoying. Cause: excessive carbon build up causing the the piston to contact the carbon on the head - causing it to rock in the bore and "slap" Much more evident when the engine is cold and the pistons haven't expanded to full diameter yet. Simplest and easiest "fix" for this: A few good WOT (wide open throttle) accelerations to clear the carbon out. That is all it takes to eliminate the problem and prevent it from re-occurring.

Occasional WOT accelerations also help seat the rings to the ring lands and exercise the rings and keep them mobile and from becoming stuck in carbon in the ring lands. At high RPM and WOT the rings move around on the piston - they actually rotate on the piston and will polish away any carbon and seat themselves to the sides of the ring grooves. This is especially important on the 2000 and later Northstars which had hard anodized top ring lands on the pistons. Very hard and wear resistant - also harder to break-in and seat the rings to the sides of the ring-lands to promote the best possible seal. Many oil consumption complaints on the 2000 and later engines are related, to some extent, with the rings never seating to the sides of the ring-grooves due to lack of load as the engine was babied around forever. Even engines with rings stuck in the ring-grooves due to carbon build up can eventually be freed up with enough high RPM operation.

WOTs warm up the engine thoroughly and clean out the exhaust due to temperature in the exhaust and high flow rates blasting particles, rust and such out of the system.

Frequent WOT operation will not hurt the engine or the transmission. They're designed for that. The healthiest engines that I have seen at high miles are always the ones that are run the hardest. Rings are free on the pistons and sealing; no carbon buildup.

The exercise that I think works best for many things is to select manual 2nd gear on an isolated stretch of expressway. This takes the transmission shifting out of the question if you are worried about hurting it. Start at 55 MPH or so and go to WOT in 2nd gear and hold it until the RPM reaches near the normal shift point - i.e. 6500 for an L37 and 6000 for an LD8. Hold the throttle wide open until the engine reaches, say, 6200 for an STS and then just let completely off the throttle. Leave the transmission in 2nd so that the engine brakes the car and creates some pretty heavy over-run conditions at high vacuum levels. Let it slow until it is about 55 or so and then go to WOT again and repeat. This exercise really loads the rings, allows variable RPM operation at WOT for several seconds continuously, creates heavy over-run which tends to unload the rings and make them move and thus exercise them in the ring grooves and it will blow-out carbon and the exhaust - all without creating a spectical of yourself and attracting the attention of cops. You can do it on most any freeway and stay within the 70-75 MPH range allowable. Once a week like this will keep the engine cleaned out and healthy and is DEFINITELY recommended for the Northstar in particular.

The Northstar engine was designed/developed/validated to be run hard. It was expected that people would use the performance of the engine - which few people seem to do. The biggest single problem that many issues stem from is lack of use at full throttle by the owners. It just doesn't like to be babied around. The rings are low-tension by design for good high RPM operating characteristics and low friction/good power. They work best if "used" and kept free.

In every conversation with owners I have had, once the owner started doing the WOTs and using the power of the engine they report no more carbon rap, better oil economy, no "smoke" when they do light it up (keep the exhaust cleaned out. If you notice a "cloud" at WOT then you are not doing enough WOTs...) etc... A bit of judicious use of the other end of the throttle travel is a GOOD thing...
 

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Yeah, that didn't really have much to do woth what he asked did it..hehe. If the car is not shifting at redline liek it should be, and bounces off the rev limiter before shifter, I would look into a new 1-2 shift solenoid. It sounds liek it's not producing a shift when it should, and is lagging behind a little. How often does it happen? I know my car slipped out of second into first the other day and let out a screach as the clutches slipped when it happened. My solenoids are on their way otu though, as they click loudly everytime the car shifts. If you can find a concrete median along a road that you can pull along side and stop at, try accelerating from a stop at maybe half throttle with your window open, and listen for any unusual noises. With my window open, I can her the click of the 1-2 and 2-3 shift solenoids bouncing back at me, before wind noise get's to great. Also, check for any codes that might have been thrown, as an intermittent problem might not set a light, or display a message.
 

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I never heard any clicking noises but I will try and listen for something like that. It doesn't happen that often and I checked the codes and got 1 code, I don't remember exactly which one but I'm pretty sure it was loss of communication with PCM that wasnt currently present. I'm not sure if that has anything to do with that. I still have a warranty on the car that expires October 28th. If I tell them about this problem will they try accusing me of beating on the car and not cover it. I don't beat on my car at all. I baby it and every once and a while I like to see what the car can do.
 

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If the code was something like U1064 or whatever, don't worry about it. Sometimes, the PCM send data to slow, or in the wrong direction..ect, and it throws that code. It's just saying that the PCM made a mistake while sending or recieving some info over the network. I have heard a few people say that occasionally, their car's would go above 6300RPM or so, before the car would shift. Sometimes (and I don't think this is your issue though) the Tachometer will register a little higher RPM, than where the car is actually shifting, because of the lag from electrical signal, to mechanical action. In other words, the needle will keep rising a little further, even though the car has already shifted. Basically the same as whne you pull up to a light and even thoguh you've already come to a stop, the Speedometer is still indicating about 5 or so MPH before it drops all the way back down to zero. Normal RPM for shifting at WOT is about 62-6300RPM If this is where the car is shifting, than there's nothing to be concerned about. If it is going past 6300RPM up to around 7000, and then dropping back down to 6300RPM or so before shifting, than I would say there some lag in the shifting, or possibly an electrical fault causing the PCM to react late. I supposed a faulty input shaft speed sensor could cause this, but not likely as it would probably throw a code, or just stop working all together. If you don't here anything when you listen with the window open, I woudl take it to the dealer and see what they have to say. The occasional rare shift over redline will not really hurt the engine, since they were testing at WOT for extended periods of time. If it starts happening all the time though, I would be concerned about damaged not so much to the engine, but the rest of the drivetrain (i.e. tranny, CVD, wheel bearings,..ect) do to the increase shock of shifting at such high RPM's. If you can't find anything wrong yourself, take it to the dealer. Better safe than sorry...Good Luck.
 

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A WOT from a dead stop with the gear selector in any forward gear will initiate an extreme load on the transaxle, especially on a five year old car with questionable maintenance. Questionable only means that I don't know the maintenance history.

Up shift should be pronounced and exact, no slipping excessive rev limits, nothing other than boiling tires.

danbuc is correct. The computer or solenoids are not responding to the up shift correctly. The rev limiter is working correctly, than God.
 
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