Jetta2 IDLING ISSUES

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jetta786
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Jetta2 IDLING ISSUES

Post by jetta786 » Tue Jun 05, 2018 8:49 am

Good Day Folks,

trust all is well? I have a problem which has been mind boggling. allow me to give you a brief history. remember I am running a 2LT carb for a number of years with no issues.
about 2 months ago I decided to take the car for a good spin and to be truthful, I opened her up on the freeway running flat out. NO PROBLEMS.
returning home, I noticed the idling very erratic and the engine very hot including the battery terminal. now understandable with the ambient temperature being so hot and driving hard the fan will stay on drawing a lot of current as my fan on second stage is very audible. the battery terminal was so hot that I actually burnt my hand by just touching the positive terminal. so that is not my concern as I can expect that since the fan running high all the time.
IDLING like it has a performance cam! removed the plugs(BP6ES) and found the gaping to be big. :eek: next day fitted a new set of plugs(BPR7ES). CHECKED THE CARB base plate, whilst busy with the carb decided to give a good clean as I have done this many times prior.
THIS IS VERY IMPORTANT TO NOTE! REV counter idles at about 1000 but steady. the idling is erratic like I mentioned. when driving about 120km/h and coming to a stop, it will idle at about 1.4k and drop to 1k after about 15 seconds. taking off, driving slowly. coming to a stop. it will IDLE at 1k. another encounter, if I am in 3rd gear and suddenly put foot, it will first give abit of a kick back. I have adjusted the timing by advancing and retarding but the pinging still remains under load. :bang:

in my experience, I have now ruled out the carb as the cause of this puzzling problem. I apologies for the essay and hope for some feedback please?

TIA
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Re: Jetta2 IDLING ISSUES

Post by PapaJo » Tue Jun 05, 2018 9:19 am

You have checked the carb base plate and seems to be fine. Have you checked the second stage butterfly and the acceleration pump in the carb. The second stage butterfly some times get sticky. In my case this caused the second stage to not close completely and motor died when getting to a stop. Also check that the choke plate stats fully open.
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Re: Jetta2 IDLING ISSUES

Post by jetta786 » Tue Jun 05, 2018 12:17 pm

PapaJo wrote:
Tue Jun 05, 2018 9:19 am
You have checked the carb base plate and seems to be fine. Have you checked the second stage butterfly and the acceleration pump in the carb. The second stage butterfly some times get sticky. In my case this caused the second stage to not close completely and motor died when getting to a stop. Also check that the choke plate stats fully open.
thank you for the prompt response. I have checked everything on the carb including the acceleration pump. I have changed the diaphragm as well. the car does not stall. :crazy:

remember I also have the pinging issue. I am thinking more towards the lifters that could be an issue. just my thoughts.
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Re: Jetta2 IDLING ISSUES

Post by Jetta2 » Tue Jun 05, 2018 12:23 pm

Pinging will be caused by the ignition timing being too far advanced, or running too lean, or a combination of both.
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Re: Jetta2 IDLING ISSUES

Post by VAG Fan » Tue Jun 05, 2018 1:20 pm

If these problems were only a result of your highway run, then I'd start by checking engine timing (camshaft and distributor vs. crankshaft). Perhaps you were running on a slightly loose timing belt, and the high revs caused it to jump a few teeth.

I once had a case where a timing belt had jumped a few teeth and one of the resulting problems was severe pinging.
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Re: Jetta2 IDLING ISSUES

Post by PapaJo » Tue Jun 05, 2018 4:16 pm

Check also that vacuum advance unit on distributoris functioning correctly and are either not stuck in advanced position after burning it on the highway or worse case vacuum advance unit leaking through and not pulling any timing.
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Re: Jetta2 IDLING ISSUES

Post by jetta786 » Tue Jun 05, 2018 5:33 pm

PapaJo wrote:
Tue Jun 05, 2018 4:16 pm
Check also that vacuum advance unit on distributoris functioning correctly and are either not stuck in advanced position after burning it on the highway or worse case vacuum advance unit leaking through and not pulling any timing.
Abit confused with this one. Not stuck in advance position? Could you elaborate please?
VAG Fan wrote:
Tue Jun 05, 2018 1:20 pm
If these problems were only a result of your highway run, then I'd start by checking engine timing (camshaft and distributor vs. crankshaft). Perhaps you were running on a slightly loose timing belt, and the high revs caused it to jump a few teeth.

I once had a case where a timing belt had jumped a few teeth and one of the resulting problems was severe pinging.
Thank you. Will surely check this as I do suspect.
Jetta2 wrote:
Tue Jun 05, 2018 12:23 pm
Pinging will be caused by the ignition timing being too far advanced, or running too lean, or a combination of both.
Will check on this after checking what jetta 2 suggested.

Thank you gents
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Re: Jetta2 IDLING ISSUES

Post by PapaJo » Tue Jun 05, 2018 5:57 pm

The vacuum advance unit on distributor is linked to a sliding plate inside the distributor to advance or retard the timing as it is moving the Hall sensor to advance or retard timing depending on the amount of vacuum it receives from the motor. What you can do is remove the pipe on motor side (sits normally on the rear of carb or on one of the small pipes on the non return valve connected to the booster) and then you suck on this to check if timing changes during idle when motor is idling. You can also test this with motor not running and then remove dissy cap and check if you can see the plate moving inside dissy. Easier to observe the timing change when motor is idling.
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Re: Jetta2 IDLING ISSUES

Post by jetta786 » Tue Jun 05, 2018 6:40 pm

PapaJo wrote:
Tue Jun 05, 2018 5:57 pm
The vacuum advance unit on distributor is linked to a sliding plate inside the distributor to advance or retard the timing as it is moving the Hall sensor to advance or retard timing depending on the amount of vacuum it receives from the motor. What you can do is remove the pipe on motor side (sits normally on the rear of carb or on one of the small pipes on the non return valve connected to the booster) and then you suck on this to check if timing changes during idle when motor is idling. You can also test this with motor not running and then remove dissy cap and check if you can see the plate moving inside dissy. Easier to observe the timing change when motor is idling.
Brilliant. I know exactly what you referring to. Yes the plate moves in dizzy when car not idling. Never knew you can check this whilst idling. Never to old to learn. :thumbup:
I thank you Sir!
Will provide feedback over the weekend.
God bless to all who responded.
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Re: Jetta2 IDLING ISSUES

Post by jetta786 » Mon Jul 16, 2018 1:28 pm

Hi Folks,

apologies for the delay on feedback. I did what all members suggested. timing is spot on. vacuum advance works perfectly. carb base plate is new as mentioned. idling is steady, yet from the exhaust you get that splutter if that is the correct word to use. any other suggestions?
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Re: Jetta2 IDLING ISSUES

Post by PapaJo » Mon Jul 16, 2018 2:43 pm

Have you done a compression test to check that all valves are sealing?
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Re: Jetta2 IDLING ISSUES

Post by panic-mechanic » Mon Jul 16, 2018 7:20 pm

yup sounds like a burnt valve.
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Re: Jetta2 IDLING ISSUES

Post by jetta786 » Fri Jul 27, 2018 5:22 pm

PapaJo wrote:
Mon Jul 16, 2018 2:43 pm
Have you done a compression test to check that all valves are sealing?
Not yet! Will get it done as I get some time. Things have just been very hectic recently. Thanks for the replies gents.
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