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Discussion Starter · #1 ·
1996 Passat TDI, 1Z motor code.

Car has been sitting for two or three years.
Ran fine before sitting in the driveway a few years..
Motor only uses a liter of oil between oil changes,
such that the exhaust is essentially clear...

Can't get motor rpm to exceed 3300 rpm.
Starts easily and revs up to 3300 rpm, then
will rise no further.
Changed air filter.
Haven't checked or changed fuel filter yet.
Like to think the injection pump is working ok.
Is my catalytic converter plugged...?
If so, I was going to drill three or four, quarter inch
holes in the ceramic to see if that will allow more
exhaust to pass through.

Anyone's thoughts?
gary
 

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I would assume that this is a fuel issue or the car is in limp mode.
Do you have bubbles in your fuel line? Did you have a diesel additive for storage in the tank? You may just have bad fuel and a clogged fuel line intake or fuel filter.

Check all vacuum hoses in the engine compartment. Rats or mice may have chewed through some hoses, or wires, or into an intake duct. You may be in limp mode from a vacuum leak.

I recently revived my '97 TDI 1Z after an 8 year outside side of the house storage. I had diesel kleen in it for storage but I topped off the tank with fresh diesel. I had to drive it a few dozen miles before it felt like it had all its power back. I did start the car every month or so during this storage and tried to keep the battree charged.
 

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Couple thoughts here. If you have an ir temp gun take readings before cat, at cat, after cat. Id catalyst is working temp should be higher comparing before and after. Do this at idle and 2 to 2.5k. Not conclusive or don't have ir gun? Disconnect downpipe and see see it motor revs freely.
 

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Discussion Starter · #5 ·
No bubbles travelling along in the fuel line. I'll try a little Seafoam fuel treatment to the fuel tank.
I have never replaced the fuel filter/water separator in the twelve years I have owned the car. If
that is the culprit, then, of course I'd replace it. I think it's a 1H0 127 401E Volkswagen part.

I have thought of disconnecting the fuel line right at the inlet to the injection pump, then connecting
a hose leading to a bottle of clean diesel fuel. If the rpm is uninhibited, then I'd know for sure the
blockage is between the fuel tank and the injection pump...

I don't know if there is a small fuel pump in the fuel tank sending fuel up to the fuel filter, then to
the injection pump. Should I push a little compressed air down the fuel line, say from the fuel filter
back down to the fuel tank? Would this compressed air harm the fuel pump in the fuel tank if there
is a pump inside the fuel tank?

Thanks for the advice.


gary
 

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Discussion Starter · #6 ·
Couple thoughts here. If you have an ir temp gun take readings before cat, at cat, after cat. Id catalyst is working temp should be higher comparing before and after. Do this at idle and 2 to 2.5k. Not conclusive or don't have ir gun? Disconnect downpipe and see see it motor revs freely.
If I understand you correctly, if I get a temperature at the cat inlet of x* F, (x degrees Fahrenheit) therefore, the
temperature at the cat outlet should be >x* F (greater than x degrees Fahrenheit) if the cat is working ? ?

...because the operation/reaction within the ceramic of the cat of combusting the unburned fuel components in
the exhaust, is exothermic, thus raising the temperature at the outlet above the temperature of the exhaust when
it enters the cat ? ?

...providing that the heat losses through the body of the cat don't lower the temperature at the outlet back to
somewhere around x*F (x degrees Fahrenheit) ? ?

I have a couple of infrared temperature guns, so I will measure the temperatures at inlet and outlet, at approximately
the rpm that you have suggested.

Thanks for your thoughts on the matter.


gary
 

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Discussion Starter · #7 ·
Couple thoughts here. If you have an ir temp gun take readings before cat, at cat, after cat. Id catalyst is working temp should be higher comparing before and after. Do this at idle and 2 to 2.5k. Not conclusive or don't have ir gun? Disconnect downpipe and see see it motor revs freely.


I just checked the temperatures of the inlet and outlet pipe for the cat when the Passat TDI was warmed up and rpm was set at around 2500 rpm.

The inlet temperature was 535* F and the outlet temperature was 610* F, thus confirming my exothermic theory, so I am concluding that the cat is working fine...

I am also assuming that if this test was performed at 2500 rpm under load of pushing the car along, that both temperatures would be higher, because of the
extra fuel necessary to push the car along while maintaining the test rpm of 2500.

Thanks for the suggestions.

Now I will apply myself to determining where there is a restriction in the fuel supply.

gary
 
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