Miss at idle and transmission shudder

[68c10owner]

picked up my 97 gmc recently and it runs pretty good, has about 50k on a crate engine. Guy told me he just replaced the plugs and wires, ect. I noticed that its got a "miss" at idle. Its not consistant. Just seems to shudder every once and a while. It feels similar to the transmission issue Im having. When in high gear at slower speeds, the transmission will shudder on acceleration unless I tap the brake to unlock the converter. Transmission has about 50k miles on a GM reman but unfortunately its well out of warranty. I talked to a friend of mine who is a transmission guy and he said it sounds like the converter lock up clutch and said something about replacing the valve body but cant remember not what he said. He is 2 hours away otherwise Id just take it to him to fix it. I really dont want to start throwing money at it without having some direction. Any suggestions?

[68c10owner]

Anyone?

[bighaas79]

The miss you are having in the engine could be your transmission shudder. When the t.c. is in lockup, engine drivability issues are more pronounced. I would get the engine running properly first, before worrying about the trans. Make sure he put the plugs on correctly, check cap and rotor, and have an injector test done to make sure all your injectors are working properly. Fuel pressure tests would be a good idea as well.

[68c10owner]

Originally Posted by bighaas79

The miss you are having in the engine could be your transmission shudder. When the t.c. is in lockup, engine drivability issues are more pronounced. I would get the engine running properly first, before worrying about the trans. Make sure he put the plugs on correctly, check cap and rotor, and have an injector test done to make sure all your injectors are working properly. Fuel pressure tests would be a good idea as well.

I think my "miss" is transmission related. Engine runs fine, very smooth. Just has the shudder at idle once and a while. I also noticed when it does shudder at idle, I can hear like a electrical arcing sound like maybe a exposed wire in the trans harness or something. Havent had time to get under it and take a look. I think Im going to have to take it in cuz I dont have the room to work on it, only have a car port.
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[bighaas79]

That arcing sound would most likely be a bad plug wire.

[68c10owner]

Originally Posted by bighaas79

That arcing sound would most likely be a bad plug wire.

I have had that happen but the strange thing is I didnt hear it under the hood, I heard it coming from under the truck and it does do it when it shudders at idle. Im not saying its not a bad wire cuz I honestly havent looked yet. Been busy working on my other car but Im just about finished with that one and then its time to get the truck fixed up.

[1tonblaze]

I had this same problem with my burb . found the plugs where wrong type and only finger tight in the block and my wires where toast . seemed to make the problem go away when we did the major tune up . last guy who worked on it before i got it didnt know the purpose of tight since the intake manifold bolts where loose also a few weeks ago when i fixed that .

[OrangeAnimal]

I agree with others. You have an engine issue not a trans issue. If you just replaced anything on there then I would go back and check it out again.

It may and can run fine at idle in neutral with little or no load, then once you start putting load on it the truck will miss and or hesitate. If you can get someone to help you try this. Block the front wheels put it in drive and start applying throttle do it just to the point before it breaks the tire (or tires) loose. You will be able to visually see anything going on. If you can do it once it's dark out in little to no ambient light watch around the Distributor cap the coil and wires look for arcing. It can be hard to see around the coil but I'd be willing to bet the coil or the cap and rotor are very likely to be your issue.
.

[68c10owner]

Originally Posted by OrangeAnimal

I agree with others. You have an engine issue not a trans issue. If you just replaced anything on there then I would go back and check it out again.

It may and can run fine at idle in neutral with little or no load, then once you start putting load on it the truck will miss and or hesitate. If you can get someone to help you try this. Block the front wheels put it in drive and start applying throttle do it just to the point before it breaks the tire (or tires) loose. You will be able to visually see anything going on. If you can do it once it's dark out in little to no ambient light watch around the Distributor cap the coil and wires look for arcing. It can be hard to see around the coil but I'd be willing to bet the coil or the cap and rotor are very likely to be your issue.
.

I can see the miss at idle being ignition but my trans issue is for sure a trans issue. It only shutters when in OD and 45-60mph. If I tap the brake to unlock the converter it goes away. I know a ignition miss and its not that. I feel it in my seat and the whole truck shakes. My friend has been a GM trans specialist for over 30 yrs and we diagnosed it over the phone and he thinks its either the converter lock up clutch or the solinoid but without it in front of him thats the best he could do. He's 2hrs away otherwise Id just have him fix it.

The guy I bought the truck has a mobil auto repair and he told me he replaced all the ignition parts recently but Im not so sure he's been 100% honest about things. He had to know about the trans but claims he didnt but it did it the first time I hit the freeway. If I drive around town in 3rd gear I have no issues untill I put it in OD.
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[OrangeAnimal]

You won't feel it in the other gears cause there is not two things present enough load and a low enough engine speed. When it goes into lockup at it's lowest speed I would be willing to bet that's when it is the absolute worst. Lockup is usually around 50 mph your rpm assuming stock gearing is probably 1200rpm.

If it's the trans and it's shuddering as it goes into lock up the clutches or the convertor are to blame. The solenoid doesn't normally bounce in and out most of the time they just get stuck. How's the fluid in the trans? Is it brownish and smell burnt? Any metal particles in it? Those would all be signs that something is wrong with the trans. If it shudders a lot then the fluid would be getting burnt.

Generally the trans won't cause the whole truck to shake like that. If it is you can bet it won't do it for much longer till it won't move the truck. If the fluid looks perfect and clean then you need to look elsewhere.

I hope I am not coming off poorly on this I just hate to see people waste time and money.

My bet is still on the ignition stuff. I am a ASE L1 Cert tech with 20 years experience.

Also is the check engine light on?

[OrangeAnimal]

Just thought of one more thing you should check if it's the extended cab in the pic I bet it has a two piece driveshaft. If so check your carrier bearing. That will make the truck shake like crazy and act as you have described. The rubber isolator falls apart on those and I have replaced a ton of them and every person complained the truck shook like the crazy.

[68c10owner]

Originally Posted by OrangeAnimal

You won't feel it in the other gears cause there is not two things present enough load and a low enough engine speed. When it goes into lockup at it's lowest speed I would be willing to bet that's when it is the absolute worst. Lockup is usually around 50 mph your rpm assuming stock gearing is probably 1200rpm.

If it's the trans and it's shuddering as it goes into lock up the clutches or the convertor are to blame. The solenoid doesn't normally bounce in and out most of the time they just get stuck. How's the fluid in the trans? Is it brownish and smell burnt? Any metal particles in it? Those would all be signs that something is wrong with the trans. If it shudders a lot then the fluid would be getting burnt.

Generally the trans won't cause the whole truck to shake like that. If it is you can bet it won't do it for much longer till it won't move the truck. If the fluid looks perfect and clean then you need to look elsewhere.

I hope I am not coming off poorly on this I just hate to see people waste time and money.

My bet is still on the ignition stuff. I am a ASE L1 Cert tech with 20 years experience.

Also is the check engine light on?

I havent checked the fluid. I honestly havent had time to do anything with the truck. My mom passed a couple months ago and Ive been busy cleaning out her house so we can put it on the market. And Ive got 2 young kids that keep m plenty busy.

Your not coming off poorly but I dont think you guys are hearing what Im saying. Im not ASE certified but I was a Harley Davidson mechanic for 7yrs before becoming a truck driver and Ive been working on cars for 25 yrs so I do know the difference between a ignition miss and a transmission shutter. Im not a transmission guy so I called my friend who has been at the same Chevrolet dealership since 94 or 95 and has been building trannys for over 30 yrs and he is ASE certified. He said its either the converter lock up clutch or a bad solinoid. but he couldnt verify it 100% without the truck in front of him.

My wifes 2010 Impala just had a trans shutter just like this and it turned out to be the converter. Without getting into the trans this is all just conversation.

I can see my miss at idle being ignition but it acts like a slight shutter, not a ignition miss. Its cheap enough to throw a tune up kit on it and see what happens.

I do have a CE light on but its not for a trans, its for the O2 sensors.

[68c10owner]

Originally Posted by OrangeAnimal

Just thought of one more thing you should check if it's the extended cab in the pic I bet it has a two piece driveshaft. If so check your carrier bearing. That will make the truck shake like crazy and act as you have described. The rubber isolator falls apart on those and I have replaced a ton of them and every person complained the truck shook like the crazy.

That is a very good idea. Didnt think about that at all. BTW, trans is a GM reman with a bout 52k on it but unfortunately it was installed in 2007 so its not under warranty anymore.

[OrangeAnimal]

I hate to say it but do you have proof of mileage and the origin of the parts? In my own experience the GM replacement engines and transmissions are top notch. With only 52K on it that seems odd that you would have issues with it even though it's several years old. We have installed several and they all perform flawlessly right from the start.

It's rare that the 4l60e or the 4l80e trans shudders like that with that low mileage. How many miles have you put on it with this going on?

Check it out when you get some time let us know what you find.

[68c10owner]

Originally Posted by OrangeAnimal

I hate to say it but do you have proof of mileage and the origin of the parts? In my own experience the GM replacement engines and transmissions are top notch. With only 52K on it that seems odd that you would have issues with it even though it's several years old. We have installed several and they all perform flawlessly right from the start.

It's rare that the 4l60e or the 4l80e trans shudders like that with that low mileage. How many miles have you put on it with this going on?

Check it out when you get some time let us know what you find.

I have the receipt frpm the shop that installed it and the date and mileage is listed. I also have the GM reman paperwork that states 3 yr or 100k miles. This truck sat for a little while but not sure for how long. As you know, anything mechanical can fail. My wife`s Impala only had about 80k on it when her trans acted up.

Ive put several thousand miles on the truck since I bought it, its my only vehicle. I have been able to find ways to stop the shutter from happening so it rarely happens but cant stop it 100% untill I get into the trans and figure out what the problem is.

[OrangeAnimal]

You should try some lubegard stuff. We always used it in our rebuilds.

Here is a link. I believe they still carry these products at Oreilly Auto and possibly Napa. You may have to go to the counter and ask them for it.

http://www.lubegard.com/~/C-230/Dr.+...t+Shudder+Fixx

[68c10owner]

Originally Posted by OrangeAnimal

You should try some lubegard stuff. We always used it in our rebuilds.

Here is a link. I believe they still carry these products at Oreilly Auto and possibly Napa. You may have to go to the counter and ask them for it.

http://www.lubegard.com/~/C-230/Dr.+...t+Shudder+Fixx

Thanks. Its worth a try.
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[OrangeAnimal]

A lot of people have reported that it actually works and stopped the shudder and it never started doing it again.

[68c10owner]

Just real quick, Ive had the check engine light on for a while, had code po430. Didnt want to delete it till I found out what it was. turned out to be a code for the o2 sensor. so today i decided to delete it. Hooked up my pocket scanner and found a new code, PO300. Did some reading and it could be anything from ignition to power train. Got some time this week, going to replace the plugs and wires and see what happens and go from there. Still going to get some of that shudder fix stuff.

[OrangeAnimal]

P0300 is random misfire. It is probably related to several things. Worn plugs wires cap etc.

Your P0430 is not for the O2 sensor but the Cat efficiency is low. If you don't have a cat on there you will get this code. If your cat is worn out you will have it too as well if it starts to clog up.

The best way to verify this is with a scan tool that shows the data for the system. You warm up the engine and then watch the voltage switching on the upstream o2 sensors you should see them switch quickly if you hold the engine rpm's to about 1200-1500. Then you look at the downstream o2 which is what you have the code for (its the one just past the cat) it should be a steady or pretty close to steady voltage if it is switching around back and forth like the upstream ones then your cat is more than likely not on there or work out. If the voltage is real low it could be the sensor but it's not likely as the heater element in them usually fails first and you would get a code indicating that.

Hope this helps you. I think at this point fixing the misfire should be the first thing you do.

[68c10owner]

Originally Posted by OrangeAnimal

P0300 is random misfire. It is probably related to several things. Worn plugs wires cap etc.

Your P0430 is not for the O2 sensor but the Cat efficiency is low. If you don't have a cat on there you will get this code. If your cat is worn out you will have it too as well if it starts to clog up.

The best way to verify this is with a scan tool that shows the data for the system. You warm up the engine and then watch the voltage switching on the upstream o2 sensors you should see them switch quickly if you hold the engine rpm's to about 1200-1500. Then you look at the downstream o2 which is what you have the code for (its the one just past the cat) it should be a steady or pretty close to steady voltage if it is switching around back and forth like the upstream ones then your cat is more than likely not on there or work out. If the voltage is real low it could be the sensor but it's not likely as the heater element in them usually fails first and you would get a code indicating that.

Hope this helps you. I think at this point fixing the misfire should be the first thing you do.

your right, I was just calling it the o2 issue but my gm tech friend told me before its usually when the front and rear 02 sensors dont match up. It passed smog with flying colors. I just have a cheap $50 scanner that doesnt allow much. A clogged cat would make since though because this thing feels very low on power compared to my old truck with the vortec 5.0. And the fuel mileage is terrible, 13-15mpg.

Will be replacing the ignition parts this week and see how it goes. The guy I bought it from said he just replaced everything but that doesnt mean any thing.

[OrangeAnimal]

Yeah, I am kinda going thru the same thing with mine. I bought it drive it less than 5 miles since I got it two weeks ago. Have now spent about 1000 bux on it. If I hadn't gotten a good deal on it I would have been PO'd.

There was a lot of new parts on it but I have had to even replace some of the new parts they installed incorrectly also found some hidden issues. All said and done though I will know everything there is to know about the this truck and will ultimately feel more confident about it's ability to get me there.

The cat on these trucks is know for coming apart due to vibration and age. It would not surprise me at all if you took it off and were able to pour pieces of it out. If you just get under there and hit it with the heal of your hand a couple times I bet it will rattle around.

If it did come apart don't forget to check the muffler cause all the pieces make their way back there and slow down the flow thru it as well.

Don't forget to replace the fuel filter. So many people over look it.

[68c10owner]

I thought I would give a long over due update. Finally got around to changing the plugs and wires. Cant believe how long it took me to do it but this thing fought me every step of the way. Found #2 plug was cross threaded and only in about 1/2-1 turn. will have to fix the threads later as I was able to get the new plug in straight and further in than the old one. #4 plug didnt look so good and threads were slightly buggered but got it in ok. The miss is now gone completely. It did seem to have a slightly rough idle at first but after a test drive it idled smooth at 750rpms. I do feel a slight vibration at my feet while driving so looks like I got something else to check out. Just replaced the tires and it drives alot smoother than before so maybe I need to address that carrier bearing and engine/trans mounts. Thanks Orange Animal for the help, you were 100% correct that it was a ignition miss and not a transmission shutter.