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Sudden Engine Knock When Engaging And Disengaging Ac While Driving In Slow Speeds (10-30Kmh)


PerfMad

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Three things,

1. Spark plug wires - Not "seems good" they should be confirmed good and I do not see a reason not to do so. It is just a resistance measurement and a visual check for cracks in insulation.

2. Fuel pressure - 60psi is too high provided the gauge used is accurate. Did they check the pressure both with engine on (at idle) and off? There should be a noticeable difference even if the gauge is inaccurate. It could be the pressure regulator on the way out.

3. If they replaced crank oil seal then they must have removed the timing belt. It is quite possible that they did a mistake and slipped off the timing mark by one or two ribs.  Remove T-belt cover and get the belt setting confirmed. 

Edited by Rumesh88
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On 11/24/2016 at 7:40 AM, Rumesh88 said:
6 minutes ago, Rumesh88 said:

Three things,

1. Spark plug wires - Not "seems good" they should be confirmed good and I do not see a reason not to do so. It is just a resistance measurement and a visual check for cracks in insulation.

2. Fuel pressure - 60psi is too high provided the gauge used is accurate. Did they check the pressure both with engine on (at idle) and off? There should be a noticeable difference even if the gauge is inaccurate. It could be the pressure regulator on the way out.

3. If they replaced crank oil seal then they must have removed the timing belt. It is quite possible that they did a mistake and slipped off the timing mark by one or two ribs.  Remove T-belt cover and get the belt setting confirmed. 

 

Hi @Rumesh88 - They checked for any cracks in insulation, and couldn't find any.. didnt check for resistance though..( they told its highly unlikely to be the plug wires, since car doesn't have any misses, and runs smoothly and idles smoothly)

Even he told fuel pressure is too high, ideally it should be around 50.. didnt start the car but asked me to turn on the ignition to check the fuel pressure... Then only i asked him to check the filter as well, since i didnt find any history saying this was changed, and he confirmed this is the original one which came with the car..

They said they can also check with some other plug wire set, but unfortunately they couldn't find any at that moment just to check.. also he mentioned this could be due to bad coil in distributor, since he mentioned it, i checked my car history and found out that ignition coil has been replaced in 2012 from TECK motors..So i assume its highly unlikely to be that.. so i left it there to check the timing adjustment.. hopefully that will resolve my issue..hmmm

but now i feel the car is more powerful than before...

Yes they did replace the crank oil seal as well.. that is the only possible way that even they could think of.. however i kept the car to check on that as well.. hope that will resolve the problem..

Im just curious, will it do any harm to my car if i ignore this issue and keep using it daily (only if they couldn't resolve the issue) ??

 

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When you can measure and confirm you need not assume things. As for the pressure he may have used a direct connection to the fuel line not a T-joint. In that case it is not possible to start the engine. It is quite possible that you get a reading of 60psi in this case and there is nothing wrong with the reading (I visualized the use of a T-joint when commenting above). However, had he used a T-joint he could have checked the regulator function as well.

It is not good to use it as it is in the long run because the knock may put the engine mounts and engine parts like piston bearings on undue stress. But it all depends on how severe the knock is.

 

 

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1 hour ago, Rumesh88 said:

When you can measure and confirm you need not assume things. As for the pressure he may have used a direct connection to the fuel line not a T-joint. In that case it is not possible to start the engine. It is quite possible that you get a reading of 60psi in this case and there is nothing wrong with the reading (I visualized the use of a T-joint when commenting above). However, had he used a T-joint he could have checked the regulator function as well.

It is not good to use it as it is in the long run because the knock may put the engine mounts and engine parts like piston bearings on undue stress. But it all depends on how severe the knock is.

 

 

yes, u are correct, he did direct plug in.. not with a T joint..

Well, since i know the knock i was releasing the paddle bit slowly so it won't knock, unless i have to quicky stop the car due to bumper to bumper traffic.. will see his findings, and i will update u on that.. meantime if you come across any other possible fault, pls keep me posted so that i can get that checked as well..

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Could be a symptom of weak ignition but before that just get them to disconnect the IACV connector while engine is fully warmed up and running at idle with AC off. This is easily said than done cos the connector is at an awkward place and care should be taken not to damage wires/connector. Ignore the CEL indication. Once you disconnect it still engine should continue to run. If it stalls your idle adjustment should be re-done.

Edited by Rumesh88
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8 minutes ago, Rumesh88 said:

Could be a symptom of weak ignition but before that just get them to disconnect the IACV connector while engine is fully warmed up and running at idle with AC off. This is easily said than done cos the connector is at an awkward place and care should be taken not to damage wires/connector. Ignore the CEL indication. Once you disconnect it still engine should continue to run. If it stalls your idle adjustment should be re-done.

Could it be DELCO by any chance ?? 

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9 minutes ago, PerfMad said:

Could it be DELCO by any chance ?? 

Can be but less chances. There is no way to check it other than replacing. That's a chance you would have to take but only if all other things fail to resole the issue.

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2 minutes ago, Rumesh88 said:

Can be but less chances. There is no way to check it other than replacing. That's a chance you would have to take but only if all other things fail to resole the issue.

hmmmm... looks like um gonna end up in a real mess :(

 

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Hi @Rumesh88 I took the car yesterday, and they said they were able to overcome the issue by advancing the distributor with removing the cap and t=fixing it with 1 bolt or something (which cannot be done by normal fix), however they said this cannot be done as a permanent fix. They say its due to bad distributor..

And replacing the distributor for a recon one will cost about 20k and will be bit difficult to find a VTEC one for my car as well..

His suggestion was to use the car like i did, untill i get an engine miss and its time to replace the distributor ..

He also mentioned that this knock will not harm my vehicle as well ( fingers-crossed)

 

@pasindups - thanks for the headsup machan... um gonna run this for sometime and iif this get worst of if i feel any difference then i will get what you mentioned checked as well.. Im tired of spending money and time at garage and finding out nothing at the end.. hmmmm

 

Thanks everyone (specially @Rumesh88 & the rest) for the support given, and will keep you all posted if i come across any solution.

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  • 1 year later...

Hey Folks,

Its been awhile and im still having the issue as it is. Today I went to another mechanic, he did an engine tuneup and did a test drive, and issue remains same. He's suspecting its the KNOCK sensor and told me there is, no other way to check it whether its faulty or not, other than replacing..

Also he wanted to check prior by connecting it to the obd port but unfortunately mine has a port like the attached, and his connector wasn't supporting mine.

What are the possible areas that i could check for? and is there anyway to diagnose the KNOCK sensor prior to replacing?

FSX9QXVF6S8S0A5.LARGE.jpg

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18 minutes ago, MAS said:

DId you clean the MAF sensor ?   I had a low RPM engine knock and it went away after the sensor was cleaned.  Try the cheap fixes first.

@MAS Yes, the thing is car idles without any hesitation.. Only problem is when i release the gas paddle in between 1000-2000 this knock comes and settles down again around 1100-1200 rpm range..

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21 minutes ago, PerfMad said:

@MAS Yes, the thing is car idles without any hesitation.. Only problem is when i release the gas paddle in between 1000-2000 this knock comes and settles down again around 1100-1200 rpm range..

I don't think  this is a knock, what you experienced is a "jerk" when you release the gas pedal.anyway there is around 1 second time delay in between the "jerk" and your action. if this is the case, do a additional test. try to recreate the problem, but this time press the clutch completely and release the gas pedal and observe the RPM (it is obvious that you will not be able to feel the jerk because clutch pedal has been fully pressed, but observe the RPM ) . if there is no RPM fluctuation (it should start to decrease and settle) then the problem might be a mechanical issue (or there might not be a problem at all).

one possibility is excessive load (ex: AC fully with a broken bearing, brake binding) , the other possibility is  "wrong gear" which is normal and not a problem.there is a thin chance that problem is in the gearbox.

 

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On 11/29/2016 at 3:48 PM, PerfMad said:

Hi @Rumesh88

Today i checked below areas:

- Spark plugs (in good condition- including the gap) [Checked with some used iridium plugs as well]

- Spark wires (seems good as well)

- Cleaned distributor cap and contacts

- Cleaned throttle body and checked the adjustment

- Cleaned IACV

- Checked fuel pressure and it was having 60PSI

- Checked and replaced fuel filter as it was bit clogged

- Finally did timing adjustment again and revert it to original state as well

But still the knock is there... Mechanic told, that he needs to take the cover off and check the timing (i'm not quite sure whether they removed the timing belt during my oil seals replacement which was done 5months ago[i had lot of oil leaks therefore i asked them to replace all oil seals in engine bay]), but i cant remember whether i had this knock before :(

I'm clueless, can you please shed some light ? I would highly appreciate ur inputs on this..

Hi machan

Looks like i need to rename the titile of the thread..the issue has nothing to do with the ac ..i get the knock even when the ac is on.

This issue can be recreated anytime hence its comin always..only thing is if i keep the fas paddle bit steady n release it then rpm comes down slowly as expected..this happenes only if i release it suddenly..

However i will check this clutch thing u suggested n chek the rpm meter readings..

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1 hour ago, PerfMad said:

Hi machan

Looks like i need to rename the titile of the thread..the issue has nothing to do with the ac ..i get the knock even when the ac is on.

This issue can be recreated anytime hence its comin always..only thing is if i keep the fas paddle bit steady n release it then rpm comes down slowly as expected..this happenes only if i release it suddenly..

However i will check this clutch thing u suggested n chek the rpm meter readings..

In that case you need to get  your IACV checked for its full range of movement. As you accelerate IACV adjusts itself by opening up the idle air path so that if the throttle is suddenly closed (I mean mechanically) the engine wouldn't stall. The IACV then slowly closes and home-in at the idle position under electronic control. If the IACV has a mechanical restriction in its upper movement range then you may get a sudden jerk as you release the throttle suddenly from a high RPM because engine doesn't get the required amount of air. 

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On 12/12/2017 at 12:27 PM, Rumesh88 said:

In that case you need to get  your IACV checked for its full range of movement. As you accelerate IACV adjusts itself by opening up the idle air path so that if the throttle is suddenly closed (I mean mechanically) the engine wouldn't stall. The IACV then slowly closes and home-in at the idle position under electronic control. If the IACV has a mechanical restriction in its upper movement range then you may get a sudden jerk as you release the throttle suddenly from a high RPM because engine doesn't get the required amount of air. 

@Rumesh88 How to diagnose whether IACV is faulty or not? in neutral if u accelerate upto 5000-6000 and release still it will slow down as normal without any hesitation.
Last year when i did the engine tuneup i asked to clean the IACV value twice and second time i was there when it was performed and it was cleaner and i saw it was moving freely (when it was disassembled for cleaning)..
This issue occurs only when moving.. 

Add to that after cleaning the injectors and its filters, car is more smoother again and powerful too..

Just curious could this be due to someother reason, my front shocks are also now in bad shape and i hear daga daga noise as well.. but i believe this has no relation.

Edited by PerfMad
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Hey folks, i just recorded the behavior of the RPM meter for your reference.

Please note that the sudden loss of RPM shown in the video is only when i press the clutch paddle on the move.. and at other time even with the knock rpm will reduce smoothly.

**note: really sorry about the noise, i forgot to mute the radio prior.


Please use below link to view the video, if there are any issues with the video viewing please do let me know.

http://www.mediafire.com/file/h74dev1ur4hfih6/20171212_193332.mp4

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