Basic questions '94 GT

GTamas

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I have a couple of basic questions, due to the lack of my experience and other cars to compare to. Would appreciate your help. :)

1. Engine shake during idle. It can be felt in the seat when standing still, it is not very strong or annoying, but clearly felt. Engine seems to idle nicely based on RPM and sound. Engine mounts were replaced 5 years 2.000 miles ago to Summit Racing black PU mounts. Balancer also replaced same time to OEM replacment PowerBond Premium balancer. Is it normal, or shall I investigate?

2. Vibrating clutch when slowly taking off and releasing clutch pedal slowly. Like in stop/go traffic. Clutch was replaced same time as the above mentioned parts with a Perfection MU Series Clutch MU48-1M. I don't know if it was same behaviour right after replacing because at that time it was not my car. Is this normal behaviour, or something is not well set up maybe? I plan to replace my clutch quadrant and cable to adjustable Steeda kit because the pedal feels very heavy, but I guess this does not have to do much with the vibration.

3. Triax short throw shifter (Summit version). I think I have it correctly installed and the stop screws correctly set. Shifting feels vely precise, but some force has to be applied especially when shifting to 2nd gear. Is it normal?

I know, it might be difficult for you to judge because I can't objectively tell how much vibration and force is normal and how much is too much with these stuff...
 

shovel

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If you can record a video of the idle that could be helpful. Check that base idle timing is correct (with the spout connector removed) and also check that timing does not wander while slowly revving and returning to idle. The point here is to check not only that timing is correct but also that your timing chain assembly is not worn. The distributor is turned from the camshaft, which is turned by the crankshaft through the timing chain assembly so a sloppy chain will first show up as ignition timing that changes as engine speed increases and decreases.

clutch chatter can come from a lot of causes, some more simple than others but most of them require disassembly to fix even if you diagnose them externally. Even applying too much grease to the pilot can grease contaminate the clutch and make it chatter. Sometimes that will go away over time, sometimes it won't.

I looked up the clutch model you have and they advertise it as a street/daily friendly clutch so it should not have excessive pedal effort, of course any cable clutch will have slightly more effort than hydraulic. If you plan to replace your cable and quadrant anyway I would suggest just doing that and then see where you stand. It would not be a waste even if some other diagnosis needs to be done later.
 
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GTamas

GTamas

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Thank you guys.
#2 sounds like flywheel is warped
Any way to diagnose this without disassembly?

If you can record a video
I will do that at the end of the week. Will have a look at the timing, too.

should not have excessive pedal effort
The clutch with this car has a long history. My mother always had problems with it. All this might be related to the heavy pedal feel and/or possible flywheel problem somehow:
My mother bought the car new in 95. She is relatively short and pushing full out the clutch pedal was sort of difficult for her, so I imagine she used it often not fully disengaging the clutch when shifting. Over time the clutch developed a chirping sound when the clutch was engaged (pedal not pushed). Mechanics said it was the throwout bearing, so we replaced that. The sound disappeared, but with time it came back. So the clutch and another TOB was replaced. Then 5 years ago another clutch. Now is the 3rd clutch and the car only has 56k miles. I have a spare TOB on the shelf. :)
The pedal feel was always kinda heavy, but I think it was a bit lighter in the past. Anyways I have the new quadrant, FW-adjuster and cable already, just waiting that I have time to install them.

Could this be that such use over the years wore down the flywheel after just 57k miles?
 

shovel

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Now is the 3rd clutch and the car only has 56k miles.

There is something going on there, I would freak out if I had a clutch last less than 100k miles.

Ultimately I think it will be necessary to have it apart. If the flywheel surface is scored or damaged from wearing down to the rivets for example, there is nothing to do except resurface or replace the flywheel.
 

dalpoas83

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Looks like that would work. Maybe someone else will confirm also or you could probably even call summit. You may want to wait and take it apart first just in case that isn’t the problem. I’ve seen it a few times.
 
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GTamas

GTamas

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If you can record a video of the idle that could be helpful. Check that base idle timing is correct (with the spout connector removed) and also check that timing does not wander while slowly revving and returning to idle. The point here is to check not only that timing is correct but also that your timing chain assembly is not worn. The distributor is turned from the camshaft, which is turned by the crankshaft through the timing chain assembly so a sloppy chain will first show up as ignition timing that changes as engine speed increases and decreases.
I checked the timing today, it is at 10°. When slowling increasing rpm, there isn't any movement of the timing. When giving it a push to rev quickly from idle to app. 2000, the timing moves a very little (hard to say but I think lass than a degree), but catches back to 10° quickly. Is that okay?
I will upload some video of the engine idle later today.
 

shovel

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If the change is very little (and if you did have the SPOUT disconnected) 1713629475257.png then that sounds OK. A worn out timing assembly will move all over several degrees when raising and lowering RPM.
 
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GTamas

GTamas

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If the change is very little (and if you did have the SPOUT disconnected) then that sounds OK. A worn out timing assembly will move all over several degrees when raising and lowering RPM.
Yes, spout was disconnected and movement was very little. Thanks for your feedback!
 
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GTamas

GTamas

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Here is a video, engine was still cold, spout connected. The idle sounds stable to my ears and I can't see the engine shaking with my bare eyes, but the chassis is shaking irregularly, like if the engine would be running unevenly... But I think it runs well. This shaking is unfortunately not really visible on the video, maybe a little on the hood prop and the mirrors.
 

Michael Plummer

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Engine mounts: While polyurethane engine mounts can provide performance benefits for certain applications, they may not be suitable for every vehicle or driver preference due to the potential downsides outlined above. Considering these factors and weighing them against the desired benefits before deciding to upgrade to polyurethane engine mounts is important.
Polyurethane engine mounts have advantages, such as improved durability, reduced engine movement, and potentially better performance than stock rubber mounts. However, there are also some downsides to using polyurethane engine mounts:

1. Increased vibration and noise: Polyurethane is a stiffer material than rubber, which can transmit more engine vibrations and noise into the vehicle's cabin. This can lead to a harsher and louder driving experience, which may not be desirable for some drivers.

2. Harder ride quality: The increased stiffness of polyurethane mounts can also result in a firmer ride quality. This can make the vehicle feel more rigid and less comfortable over rough roads or bumps, potentially compromising overall ride comfort.

3. Potential for increased wear on other components: The stiffer nature of polyurethane mounts can transfer more vibration and impact forces to other vehicle components, such as the exhaust system or drivetrain. This increased stress may lead to premature wear and potential failures in these components over time.

4. Installation challenges: Installing polyurethane engine mounts can sometimes be more difficult than installing stock rubber mounts due to their increased stiffness. Proper alignment and torque specifications must be followed to ensure the mounts are installed correctly and function as intended.

5. Cost: Polyurethane engine mounts are typically more expensive than stock rubber mounts, which can deter some vehicle owners, especially if they do not prioritize the performance benefits.

IMHO, on your setup, a stock OEM rubber engine mount would be best.

I hope that helps
Michael Plummer
 

Michael Plummer

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Clutch chatter Is a term used to describe a specific type of vibration or shuddering that occurs when engaging the clutch in a manual transmission vehicle. It typically occurs when the clutch disc makes partial contact with the flywheel and pressure plate, causing it to grab and release rapidly and unevenly.

Clutch chatter can manifest as a jerking or juddering sensation felt through the vehicle when starting from a stop, shifting gears, or engaging the clutch pedal. It often feels like a series of rapid vibrations or shakes that can be both felt and heard by the driver.

Several factors can contribute to clutch chatter:

1. Worn or contaminated clutch components: If the clutch disc, pressure plate, or flywheel is worn, damaged, or contaminated with oil or debris, it can cause uneven engagement and lead to clutch chatter.

2. Improper clutch adjustment: Incorrect clutch pedal free play or improper clutch linkage adjustment can result in incomplete clutch disengagement, causing chatter during engagement.

3. Misaligned or damaged transmission components: Issues such as a misaligned transmission, damaged input shaft, or worn pilot bearing can also contribute to clutch chatter by causing uneven contact between the components.

4. Driving habits: Aggressive driving, such as riding the clutch or slipping it excessively, can generate excessive heat and wear on the clutch components, leading to chatter over time.

5. Poor quality or mismatched clutch components: Using low-quality or mismatched clutch components not designed to work together can result in uneven engagement and contribute to clutch chatter.

To address clutch chatter, it is essential to diagnose and address the underlying cause. This may involve inspecting and replacing worn or damaged clutch components, adjusting the clutch properly, ensuring proper alignment of transmission components, and adopting smooth driving habits to minimize stress on the clutch. Professional assistance may sometimes be required to diagnose and resolve clutch chatter issues properly.

I hope this helps
Michael Plummer
 

shovel

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From the video my first thought is have you confirmed 100% that there is nowhere the exhaust system is contacting the chassis? My v6 is an inherently shaky engine but the mounts mask that fairly well - when I was installing the aftermarket exhaust there is only a very narrow area it can fit and before I got that just right it would contact the chassis in the rear and the whole car sounded grumbly and vibrated. The sound in your video had a little bit of that character.
 
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GTamas

GTamas

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From the video my first thought is have you confirmed 100% that there is nowhere the exhaust system is contacting the chassis? My v6 is an inherently shaky engine but the mounts mask that fairly well - when I was installing the aftermarket exhaust there is only a very narrow area it can fit and before I got that just right it would contact the chassis in the rear and the whole car sounded grumbly and vibrated. The sound in your video had a little bit of that character.
I will have a look at it. It's fully stock exhaust. Only the replaced engine mounts could have changed the exhaust clearance to some extent.
 
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GTamas

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I will try to find out which hardness engine mounts were installed.
It's Summit Polyurethane Motor Mounts SUM-7741124. It says street & track. One of the reviewers also mentioned more vibration on the chassis, so I guess this could be the reason.
20240420_204626.jpg20240420_204638.jpg20240420_205154.jpg
 

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