Revving too high before it will shift...

[9CZ71Denali]

Hello all,

I have an '03 Z that has been well maintained. Recently the engine is revving higher than normal before it shifts, sometimes I have to let off the pedal to get it to shift. Is the tranny going bad or maybe an engine problem? Also quite a bit of pinging and knocking lately. No CE codes when I scanned it. Ran seafoam through it and cleaned the TB about a month ago.

Recently switched wheels from 18"s to 16"s, I havent re-programed the bcm, so my speedo is off too. Could this issue be with the TCU?

Thanks :confused:

[DarkTahoe00]

I'd lean more towards the tranny.but I've heard some people been able to put the vette servo in and it help to stop it. With the seafoam it may have loosen some of the stuff up and that might be why your getting the pinging/knock. I'm sure some of the other guys will chime in and correct me if I'm wrong or with some other insight!

[Justin]

Have you adjusted your intake tube or modified your MAF in any way? Unmetered air would be my first thought with respect to an abruptly new pinging problem.

When the transmission does get around to shifting, how is the shift quality? Does it feel like it's sliding out of gear and then snaps into the next gear or is the shift quality pretty decent?

[Grebbler]

Are you running with the TOW button on? :D

[Rollin Thunder]

Are you running with the TOW button on? :D

Its sounds like it, But the tow button must be hit every time you start the vehicle.

[9CZ71Denali]

The truck has 81K miles on it, trans fluid/filter changed over the winter. Maybe that is what is killing (killed) it?
When it does finally shift, it is smooth.

I am having a multitude of other issues all of a sudden...

When I accelerate hard (in 4th or 5th), it revs high but doesn't accelerate (as if I were in neutral). When it does respond, there is a rattle from the drivers side or center of the engine compartment.

The engine is louder than normal when accelerating.

Idling rough, the whole vehicle vibrates and shakes.

Tow mode is off, but it drives as if it were on.

My baby is dying! Help!

Thanks in advance... :emotions122:

[shsportsfan12]

start building a new motor/tranny

[munks06denali]

check tranny fluid level, quality of fluid(brown/smells burnt) As far as rough idle , check your fuel pressure regulator. If I remember correctly its on the drivers side valve cover sticking out of the fuel rail with a little vacuum line running to it. Pull that line off and start the truck, if there is fuel present the nthe bellows in the regulator are bad. I have seen this a few times i friends trucks as well as my old 2K Z71. Hope this helps.

[nc6600]

The truck has 81K miles on it, trans fluid/filter changed over the winter. Maybe that is what is killing (killed) it?
When it does finally shift, it is smooth.

I am having a multitude of other issues all of a sudden...

When I accelerate hard (in 4th or 5th), it revs high but doesn't accelerate (as if I were in neutral). When it does respond, there is a rattle from the drivers side or center of the engine compartment.

The engine is louder than normal when accelerating.

Idling rough, the whole vehicle vibrates and shakes.

Tow mode is off, but it drives as if it were on.

My baby is dying! Help!

Thanks in advance... :emotions122:My old Tahoe did that turned out to be Intake gaskets, as for the rest i really dont know sounds like your transmission is taking a :poop:

[9CZ71Denali]

check tranny fluid level, quality of fluid(brown/smells burnt)

Clean/smells fine...

The thing that is getting me the most is when I accelerate, I don't go anywhere...

[Rollin Thunder]

my tranny did that on the silverado. Replaced it, better but not 100% the first to second shift was crap. Rest were great. Got a BB tune, now its like butter at low speeds, and firm shifts at heavy throttle. Best investment ever for my silverado, and thats on a 4l80e, I would love to see what It could do to a 4l60e Like you guys have.

[Grebbler]

With all these thing happening at once I wonder if the PCM went south.

Wasn't there a condition where a bad/dirty MAP or MAF sensor would cause most of these conditions?

[HitandRunDriver]

Havent heard of that...but honestly try the vette servo, one of the best investments i've had on the truck so far

[9CZ71Denali]

Where is the MAP and how do I clean/replace it? Sorry for the newb question. Thanks for the help guys!

[tybardy]

well, would you say ALL these problems started at the same time or at least within a few weeks of one another... if it was a progresion of problems, do you know which one happened FIRST?

[9CZ71Denali]

The high revving before it shifts was the first problem. Thats been going on for awhile, but it is smooth, so I didn't worry about it. Yesterday, on my way to work, the other symptoms appeared. On my way home I got a P0301 code - Cyl 1 Misfire - after hitting a bump around 70mph. Took it easy on the way home. Today (Monday), I tried romping on it a bit to see if there was an issue, and things just got worse. The rough acceleration, rattling and the rough idling.

I will clean the MAF and my CAI (dirty) tomorrow. I will try the MAP too if someone could give me some guidance. I will look at the service manual in the morning.

Thanks!

[tybardy]

The high revving before it shifts was the first problem. Thats been going on for awhile, but it is smooth, so I didn't worry about it. Yesterday, on my way to work, the other symptoms appeared. On my way home I got a P0301 code - Cyl 1 Misfire - after hitting a bump around 70mph. Took it easy on the way home. Today (Monday), I tried romping on it a bit to see if there was an issue, and things just got worse. The rough acceleration, rattling and the rough idling.

I will clean the MAF and my CAI (dirty) tomorrow. I will try the MAP too if someone could give me some guidance. I will look at the service manual in the morning.

Thanks!


Well in cases where your problems seem to be snowballing, you can useually track your problem back to the first one, and if your lucky, fixing the first will then fix the rest. But for argument sake, lets say the high reving isnt the culprit, what was the second symtom? was it the P0301 code or did something happen before that?

my next suggestion, IMO, would be to stop driving it if you can because it does sound like you might be working on some real problems

[9CZ71Denali]

It was accelerating rough before the code, and when you'd accelerate, you wouldn't move anywhere, it would just rev up like you were on the gas in neutral.

[tybardy]

all of that sounds like tranny problems.... From what i can tell, and this is all just my assesment based on prior experince, it sounds like your tranny is almost gone. not sure why that would throw the misfire code, someone else may help with that... but my guess is you need a new tranny fast, it seems like it would explain like 90% of the symptoms...

[9CZ71Denali]

I will take it to a mechanic in the morning. Thanks for the help.

[tybardy]

I will take it to a mechanic in the morning. Thanks for the help.

keep us all posted man, i am interested to see what develops

[Rollin Thunder]

keep us all posted man, i am interested to see what develops

I think somthing is wrong with his truck. IDK I could be wrong. lol.

[tybardy]

yes but seemingly large problems can develope from very small and easy fixes, like sensors or computer work

[9CZ71Denali]

Mechanic is on vacation until tomorrow, but he will look at it bright and early.

Today, on my way down there I the CEL came back on and gave me 2 P0420 codes and later on while accelerating, I lost all power and the CEL flashed with P0300. I am starting to think it's a bad cat or O2 sensor...

[tybardy]

it sounds very likely that you are looking at something like a sensor or even a control module issue... for your sake, i hope so! just be easy on her because driving with a sensor gone bad can cause your motor to try and "fix" itself, which will in turn end up doing a lot of damage

[9CZ71Denali]

O2 sensors, knock sensors, intake manifold gasket all good. New MAF & fuel filter, throttle body cleaning and seafoam fix nothing... Looks to be the cat, will have them done friday.

How bad would it be to just hammer them out?

[tybardy]

Who said it was the cats? as far knocking them out, i havent done that since i had my 82 GMC and that was easy as pie, pull it off and smash the shit out of the interior media with a flat head till its empty.

i dont understand why the cat would be causing all those problems...

[Yukonxl]

Mine just started with high rev from 2-3 gear, but it was after I had my trans oil flushed and changed. The mechanic thinks it is a vacuum thing and that the oil change loosened up something. I am taking it in next week, I guess we will see.

[9CZ71Denali]

Had both cats and banks replaced, runs like new now!

Thanks again for the help.

[tybardy]

good to hear... do you really have a Z71 Denali? i was unaware they made such a thing? you got pics?

[bigpapapete]

my tranny did the same thing for a while ,I couldn't figure out the problem until I lost second gear then fourth, sorry hope you have better luck than I did