Technical Punto hgt still shaking

[deafmazter]

Hey guys,

I'm facing the following problem. My car (punto hgt 1.8 16v 183a1000 with throttle cable, so not electronically controlled) jerks at spontaneous throttle and quick throttle release. Now I have already done the following:

1. Replaced all the bad engine mounts (2 out 3)
2. Replaced wishbones.
3 checked both the support arm and drive shafts for play. So they don't have these!
4. Filled all engine mounts with PU rubber, which unfortunately did not help. Shifting is better now because the car shakes less. But the "problem" is not solved.
5. Throttle cable adjusted and cleaned (maybe got stuck).

Other than that, I don't hear any strange noises. It is only with spontaneous throttle release and acceleration and shortly after that throttle release. Otherwise the car drives

 

[bugsymike]

When you say "jerks at spontaneous throttle and quick throttle release." I am assuming when in gear, if so is it worse in low gears as in pulling away?
A bit like a snatch in the transmission.
Does your car have a dual mass flywheel, as when badly worn they can give a similar effect?
Short of taking the gearbox off to inspect, you may get an idea if with engine off and in gear, put a socket and bar on the crank pulley if possible and see if there is a similar clonk when going back and forth on the bar. Ideally the other way to test is on a fixed garage ramp (not wheel free) have one person in car with handbrake on, engine running, repeatedly taking up drive forward and reverse, whilst some is underneath the ramp watching what is clonking around.

 

[George1982]

It sounds like a clutch issue

 

[deafmazter]

When you say "jerks at spontaneous throttle and quick throttle release." I am assuming when in gear, if so is it worse in low gears as in pulling away?
A bit like a snatch in the transmission.
Does your car have a dual mass flywheel, as when badly worn they can give a similar effect?
Short of taking the gearbox off to inspect, you may get an idea if with engine off and in gear, put a socket and bar on the crank pulley if possible and see if there is a similar clonk when going back and forth on the bar. Ideally the other way to test is on a fixed garage ramp (not wheel free) have one person in car with handbrake on, engine running, repeatedly taking up drive forward and reverse, whilst some is underneath the ramp watching what is clonking around.

Yes it is indeed in the gears, and the lower in the revs the worse. Drive away is not a problem and this problem not linked by drive away. It only shows when I’m driving at low rev. How higher the rpm is how lees the car is shaking when I left my feet from the pedal. My car does not have a dual flywheel. When my car gets inspected I'll just ask if they want to run the test you mentioned. Thanks for thinking with me.

 

[deafmazter]

It sounds like a clutch issue

Do you think replace the clutch will help ?
I do everything by myself and the clutch is on my to do list tho

 

[George1982]

If you intended to do it anyway,go ahead.My clutch begun to wear out when the bearing started making a grinding noise like a wheel bearing.After that, i noticed weird engaging pattern especially when accelerating from lower revs.I suspected motor mounts which where tired anyway,i even begun thinking about gearbox issues.It was just a clutch kit fading away.

 

[bugsymike]

If your foot is off the clutch when it happens, then unlikely to be be related.

 

[deafmazter]

If your foot is off the clutch when it happens, then unlikely to be be related.

The problem is gone when the clutch is depressed or when the car is in neutral. So the problem really occurs when the car is in gear and driving. The clutch is still good, does not slip and clutches well. I assume part of it is due to my driving style and wear and tear on various parts. After all, the car is already 21 years old.
Furthermore, it doesn't bother me that much because it rarely happens, really only when I take my foot off the gas too quickly. She is just a spicy Italian lady ghehehe

 

[Mike1alike]

The culprit could be the IACV (intake air control valve) as it is the one responsible with the engine air intake when you release the throttle. I had mine replaced, I put photo with the part no.
Also, the cat plays a role in accelerating lag, so it will help to do a cat cleaning, help the engine run smoother.

For cat cleaning you can use 1l of vinegar. And you'll need to pour it into cat, hot engine, through the pre-cat O2 sensor hole. For that, is best you prepare the action while the engine is cold, make way (take down the thermal shield) and take down the O2 pre-cat sensor. Then put it back without tightening it up too much. Start the engine and warm it up. Stop the engine, take down pre-cat O2 sensor, pour the 1l vinegar into the cat using a funnel and beeing carful not to get burned (also wash the sensor with vinegar), than put the sensor back on. Then start the engine and run it at 2500-3000 RPM for about 10 mins. Your cat will be clean after that.

Another possible reason for your problem is the spark. Consider new spark plugs and leads if needed.

 

[deafmazter]

The culprit could be the IACV (intake air control valve) as it is the one responsible with the engine air intake when you release the throttle. I had mine replaced, I put photo with the part no.
Also, the cat plays a role in accelerating lag, so it will help to do a cat cleaning, help the engine run smoother.

For cat cleaning you can use 1l of vinegar. And you'll need to pour it into cat, hot engine, through the pre-cat O2 sensor hole. For that, is best you prepare the action while the engine is cold, make way (take down the thermal shield) and take down the O2 pre-cat sensor. Then put it back without tightening it up too much. Start the engine and warm it up. Stop the engine, take down pre-cat O2 sensor, pour the 1l vinegar into the cat using a funnel and beeing carful not to get burned (also wash the sensor with vinegar), than put the sensor back on. Then start the engine and run it at 2500-3000 RPM for about 10 mins. Your cat will be clean after that.

Another possible reason for your problem is the spark. Consider new spark plugs and leads if needed.

Thanks mate, the cat is being replaced this month for a new 200 cells so I'm not going to do your "trick" hehe. But the spark and coils were replaced in 06-2022. The throttle body has already been cleaned but not the IAVC valve as you said, thanks for the tip. But a punto hgt has a very complex throttle body, many parts are integrated and not easy to remove without breaking. Also, these parts cannot be ordered separately, you would have to order a whole new throttle body. But I will is look in the workshop book where the IAVC is and see if I can clean it.