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wingman
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PostPosted: Thu Aug 21, 2014 8:27 pm    Post subject: Reply with quote

So I pulled the distributor and checked the cold start injector. It does not leak! However, the issue is getting worse as now the engine runs poorly even when warm with the following symptoms:

1. It does not idle smoothly
2. It lacks power and vibrates
3. When accelerating, it creates loud booming noises and it is getting more often

I have done the following:

1. Adjust valves
2. Check spray pattern for all the injectors
3. Replace all spark plugs, wires (except for #1 since it has the sender wire attached it), rotor and the cap
4. Replace the fuel filter

I am really out of ideas and concern there may be structure damages. Is there anything I should check before I go to the shop?

Thanks,
Michael
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raygreenwood
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PostPosted: Thu Aug 21, 2014 9:27 pm    Post subject: Reply with quote

The sender comes off...and is 100% useless anyway. It was only for dealer use as a timing input. Replace the wire.
And.....make sure they all go to the right spark plugs.
Define.....booming please.

Make sure the correct injector plugs go to the correct injector. Let me reread the whole thread and find out how this started.
Also check your compression. Ray
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raygreenwood
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PostPosted: Thu Aug 21, 2014 9:35 pm    Post subject: Reply with quote

Ok.....went back through it.

Question.....remember that long detailed list of possible vacuum leak points on the first pagd of this thread? .....did you check and verify all of that?

Now that you have replaced the bad injector and verified that the cold start valve does not leak.....do you have proper fuel pressure and proper leak down pressure?

Have you checked the copper ground braid on the breaker plate in the distributor?


If you have proper ignition and proper fuel pressure and have fixed all vacuum leaks.....then you need to verify ignition timing. .......and then you need to let us know whether its running rich or lean......and then we are going to help you adjust the mps.

Ray
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wingman
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PostPosted: Thu Aug 21, 2014 10:25 pm    Post subject: Reply with quote

Hi Ray,

Thanks. I just replaced the #1 wire and will test again tomorrow. I am pretty sure the spark plug wires are correctly connected. As for the injector plugs, the black boot plugs go with #1 and #3 and the brown (or white?) plugs go with #2 and #4, right?

The booming noise sounds like burst coming out of the exhaust. And it only did one or two during acceleration before but now it becomes more frequent. It is coming from the rear of the passenger side.

I have changed some of the vacuum tubes and statically timed it at 7.5 BTDC. I also installed pertronix ignitor and the tiny copper brown braid in distributor looks ok. How can I tell whether the engine is running rich or lean? I almost think it runs rich due to the smell of exhaust.

Thanks,
Michael
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raygreenwood
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PostPosted: Fri Aug 22, 2014 7:50 am    Post subject: Reply with quote

Typically what causes the popping in the exhaust under acceleration is either wires on the spark plugs incorrectly....and it will also cause rough running.....or an intake or exhaust valve being held open due to an adjusting issue.....or..and this is common...unburned fuel igniting in the muffler due to leaks in the muffler or exhaust system.

Are you well experienced at adjusting valves? Tell us your method please. And...have you checked them when hot? Ray
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wingman
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PostPosted: Fri Aug 22, 2014 1:05 pm    Post subject: Reply with quote

I have done several valve adjustments for type I engine in the past and I always leave it overnight before I do it.

I do have a broken tail pipe but the issue just starts recently so it may not be the cause?

Thanks,
Michael
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raygreenwood
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PostPosted: Fri Aug 22, 2014 2:41 pm    Post subject: Reply with quote

Go ahead and check the heat exchanger bolts that bolt the exhaust manifolds to the head. You will need to remove the cover plate from each side underneath. Just check to see that none are loose. Also look with a flashlight to see if there is any carbon around the outside of the header pipes where they join the head.

Also pull the distributor cap and check with a bright flashlight if there is any carbon tracking that would denote cracks that could cause cross firing. Ray
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wingman
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PostPosted: Sat Aug 23, 2014 12:31 am    Post subject: Reply with quote

I installed new distributor cap but the issue remains. I checked the old cap and the center contact to the rotor does have black residue.

I tried to remove the cover plate but had no luck with the screws. I almost stripped the screw heads but still cannot take them out. And with the tight space underneath, I had hard time to use impact screwdriver.

Thanks,
Michael
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raygreenwood
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PostPosted: Sat Aug 23, 2014 6:39 am    Post subject: Reply with quote

Ok before we get back to that......lets describe a little better exactly "when" the popping or booming happens.
1. When you are accelerating...meaning actually have your foot on the gas and rpm is increasing....is this when the popping happens?

2. Does it happen when you let your foot off the gas even if you do not fully release the pedal?

3. Does it happen at low or high rpm?

4. What gear are you in when it happens? Do you have a manual or automatic transmission?

5. Try disconnecting your vacuum advance unit and plugging the hose and see if it changes.

Ray
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wingman
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PostPosted: Sat Aug 23, 2014 4:52 pm    Post subject: Reply with quote

1. Yes, popping/booming only happens during acceleration
2. Sometimes, if it is under load like going up the hill
3. It happens in all range as soon as I start to accelerate
4. It is a 73 412 automatic sedan. Sorry I did not mention that earlier.
5. I just tried it, it makes no difference.

Thanks,
Michael
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raygreenwood
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PostPosted: Sat Aug 23, 2014 7:42 pm    Post subject: Reply with quote

Ok, I should have asked earlier anyway which engine and trans. So you are 1.7l D-jet with automatic (I knew about the D-jet part).

Ok....I think you have several things happening.

1. You are running very rich....as you already know. If fuel pressure is correct and no leaks from injectors and the CHT sensor is connected and reading in spec.....and the TPS is adjusted properly....and timing and advance are spot on......then you have a serious vacuum leak.
Did you go down the list of potential vacuum leak points I posted earlier? These are NOT optional. With D-jet....a vacuum leak is read by the MPS....as open throttle. It will run horribly and uncontrollably rich.

To add to the check list....look at the vacuum hose that goes to the transmission and make sure it is not leaking. Also....your car should have a deceleration valve. It may be vacuum operated with a small 3mm vacuum line going to the strange rubber fitting between the AAR and the center manifold. That rubber fitting is a common leak point. Also if the deceleration valve is leaking or malfunctioning.....it will cause a serious vacuum leak. Yours may also have an electrical deceleration valve. We will get to that later.

2. So we know its rich.....but the second problem is that the extra unburned fuel is combusting in the exhaust. This only really happens if you have an exhaust leak or a valve leak or valve timing problem. Valve adjustment with D-jet must be spot on.
The booming or back firing is either happening in the muffler.....meaning you have a muffler leak....or it is happening at the exhaust port meaning you have a manifold gasket leak.


Which muffler do you have? Is it the center exit pipe or the one that exits at the end of the muffler? Check the muffler for any leaks or cracks.
Also its imperative that you jack the car up and remove the cover plates to inspect for manifold leaks. This is very common.

Lastly...and this is a pre warning. There is no such thing as a "good" MPS. I have been trying to get yhe type 3 people to wrap their head around this for years....and the type 4 is more sensitive than the type 3 to this......but with all or these engines nowhere near the same kn engine vacuum parameters as they were when they left the factory. ....what appears to be an untampered with MPS may be nowhere near where it needs to be adjustment wise.

QUESTION: is the epoxy still on the large round screw on the back of your MPS...and what is the part # of your MPS and what is your ECU part #?.

Ray
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wingman
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PostPosted: Sat Aug 23, 2014 10:11 pm    Post subject: Reply with quote

Where is the transmission vacuum hose and what is its function? I accidentally pulled a hose that has similar size as the crank case breather hose at driver side and it goes through the firewall. I thought it is still connected but I may be wrong. If it is indeed the transmission vacuum hose, how can I check/connect it to the right port?

The car has the original muffler with center exit pipe and a broken tail pipe. I will try to remove the cover plate and check the manifold leaks.

Thanks,
Michael
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raygreenwood
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PostPosted: Sat Aug 23, 2014 11:17 pm    Post subject: Reply with quote

The transmission vacuum hose goes through the firewall just to the upper right of the throttle body and connects to a Y between the throttle body and the intake center section. It goes to the lower right side of the transmisson and connects to the transmission load modulator valve. It is about the same diameter as fuel hose.

The center pipe style muffler is called a damper type. It has a ceramic ring/seL where the pipe connects to the muffler body. It must not be leaking or loose.

The hose you pulled loose is most likely a fuel vapor hose to the charcoal emmisions canister.

Bear in mind.....there are no extraneous hoses in this system. There can be "0" vacuum leaks no matter how small. The fuel mixture system is vacuum controlled by the MPS.....and it is very, very sensitive. Before doing anything else.....you MUST check all of the vacuum connections in the list that I posted.

We already know you have no fuel leakage internal to the engine. You have taken care of that. There are only two possible causes of the excessive fuel usage.....vacuum leak....or MPS adjustment. You cannit adjust the MPS....until the vacuum leaks are found and corrected.
Ray
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wingman
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PostPosted: Sun Aug 24, 2014 10:54 am    Post subject: Reply with quote

I found a disconnected hose next to the transmission at the driver side. It supposed to connect to a device (which has 2 electrical wire connected to it) with a screw on connector. I also find fuel leaking onto that device Sad. Is the device transmission vacuum modulator?

Thanks,
Michael
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raygreenwood
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PostPosted: Sun Aug 24, 2014 12:15 pm    Post subject: Reply with quote

wingman wrote:
I found a disconnected hose next to the transmission at the driver side. It supposed to connect to a device (which has 2 electrical wire connected to it) with a screw on connector. I also find fuel leaking onto that device Sad. Is the device transmission vacuum modulator?

Thanks,
Michael


Ah....now we are getting somewhere. What size is the hose?
The device is the electric deceleration valve and it is close to the MPS Yes/No??

Where is the fuel leaking from? if its leaking from the drivers side of the car that is the fuel injection return line. That fuel leak alone could be responsible for poor mileage.

for the life of me I cannot remember if the transmission modulator valve is on the drivers side or passenger. Here is what it looks like
http://www.thesamba.com/vw/forum/album_page.php?pic_id=1012226

The vacuum hose should plug onto the valve and the valve screws into the transmission body. There should be on the drivers side...of the transmission...going off memory here...a switch screwed into the transmission that has 1 or 2 pins and connects to a small round or five sided vallve up near the MPS. That valve should have two 8mm hoses and a 3mm hose attached.
Let me look iin my books and report back. Ray
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wingman
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PostPosted: Sun Aug 24, 2014 5:59 pm    Post subject: Reply with quote

I think it's the electronic decel valve and it should be the root cause of my issue. I hooked up the hose and now I have less popping and much better power! And somehow I cannot find fuel leakage anymore. Thank you so much for the help.

The engine still vibrates quite a bit at idle and makes popping noise from time to time. But I am at least able to drive the car while sorting out other vacuum leaks.

Thanks,
Michael
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wingman
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PostPosted: Sat Aug 30, 2014 12:58 am    Post subject: Reply with quote

Hi Ray,

I still have idle, power and vibration problems even it is a bit better when the engine is hot. The idle is low and unstable, and adjusting the screw next to TB does not affect much. I would like to try adjusting the ECU but I cannot find where it is located in my 412 4doors sedan.

Thanks,
Michael
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raygreenwood
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PostPosted: Sat Aug 30, 2014 4:01 am    Post subject: Reply with quote

This is still a vacuum leak problem....most probably. If the idle adjusting screw on the throttle has no effect in adding rpm....it is because the system is already getting too much air somewhere else.
If rpm is high and the idle adjusting screw cannot lower rpm then the vacuum leak is larger than the idle screw orifice or is likely on or near the center manifold.

Only "E" models of the ecu are adjustable.....but that is the last thing to do. The ecu in variant/wagons is behind the armrest panel on the passenger side of the back seat. In sedans its on the left side of the engjne compartment behknd the black oval panel.

Again. ...a couple pages back I left you a list of vacuum leak points that must be addressed before adjusting the ecu.
Also..... could you answer please the questions regarding what vacuum leaks you have checked on the list, the pcv valve and the rear screw/plug on the mps. Ray
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wingman
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PostPosted: Mon Sep 01, 2014 11:05 am    Post subject: Reply with quote

Thanks. I found the ECU and the screw was maxed out. But adjusting it seems has no effect to my problem. The idle is still low (<700) and unstable. So I tried to check the vacuum leak this weekend. I hooked up a vacuum gauge before MPS and blocked the following ports on plenum but it does not have any effect either:

1. 2 ports to dizzy
2. port to oil breather chimney
3. port to auto tranny and TB

I cannot find the port that connect to decel valve so I guess that may be the cause. Can you please let me know where I can find it on my 73 412 sedan?

Thanks,
Michael
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raygreenwood
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PostPosted: Mon Sep 01, 2014 11:33 am    Post subject: Reply with quote

A vacuum gauge is not useful for finding vacuum leaks. It takes a much more subtle level of vacuum than the gauge can read. Also the vacuum at the port you are checking may be perfect but you are only reading the vacuum at that port location. The vacuum in different areas of the manifold is totally different.

The deceleration valve feeds clean air from the plastic "Y" fitting that is near the throttle body. The Y feeds clean air from the intake boot between the air cleaner and the throttle body.
The left leg of the Y feeds the AAR valve and the right which is smaller in diameter than the left feeds through a long hose that leads to the deceleration valve. From the deceleration valve a hose leads to the left side of the center intake plenum right next to where the MPS hose plugs into the plenum.

Ok.....I am going to give you some advice. You will do this for months and never get this engine runnjng properly. You cannot look for vacuum leaks a singular item at a time or by aimply inspecting the parts.

There is not one single hose, gasket or seal or connection in a D-jet system that is not 100%
Important too proper running.
The sealw and connections in normal running will not sray tight for more than two years. If the car has sat still for any lengthy period of time....every connection in the system WILL BE LEAKING to some extent. You cannot move from one component to another suspecting and hoping that will be it.

Here is the primary rule with D-jet:
If you have not Peronsally and recently replaced a seal, gasket, hose or clamped connection.....and I mean within the a year.....it is suspected to be leaking.

The proper way to check all of this is to stop running and adjusting the engine. Take the manifolds off and replace the gaskets, replace the tb o-ring, and definately replace the runner boots and injector o rings. Replace the gasket on the oil chimney, check the pcv for leaking.
All hoses must be new or at least fresh. Trim each end off the hose to get to fresh rubber...and CLAMP every single hose in the system and use zip ties on the small hoses. The small angled boots at the AAR and the pcv hose to the manifold must be clamped.

Devices like the MPS and the advance can must be leak free.

After you have don2 this.........only then......can you start tuning the fuel mixture.
Set the knob on the ecu at the middle....about 12 clicks. It is for idle only.

Check the connection quality of every connection in yhe system. Use circuit cleaner and blowcthem dry. Take a male pin from an old broken component like an injector or temp sensor 1...and use it to test the fit of every connector in the system. It it fits loosely....you need to remove the connector from the plug and either squeeze it tighter with pliers or replace it.

The ground connectors under the intake center section must be PERFECT.

Only after you have checked all of this will you be able to tune this properly.
It requires about 5 hours maximum to do this.

Also...check the voltage at idle to the coil and efi system. It must be stable at idle and prefrably above 11.5 volts. Ray
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