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Old 07-30-2019, 07:51 PM   #10
78F350
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Join Date: Jul 2014
Location: Oklahoma
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I'm still debating if I want to keep the 2.5L engine in the '01, or go ahead and swap the Audi engine into it rather than the '99. I've had two problems develop:
  • When the car is driven hard, the the coolant tank over-pressurizes and vents coolant. The engine still runs in the normal temperature range, but the coolant level drops. I actually had a guy in a Mustang wave me down because he though I had a fuel leak (coolant draining out by the right rear wheel).
  • I got a check engine light with codes P1128 and P1130, which from my understanding means that the O2 sensor is detecting a lean condition that cannot be compensated for.
Water punp that I removed when I first got the engine:

This engine had a failure of the water pump that put debris from the composite impeller into the cooling system. It was like that when I bought it in a cheap Boxster S and I eventually removed the engine because of it. I was hoping that a thorough flush of the engine would clear it. My theory is that a piece of debris is either causing a hot-spot in the engine making steam or keeping an air pocket in the system, which expands. My next (last?) attempt to resolve the cooling will be to replace the oil cooler.

Venturi tube removed from intake:

At first, I thought that the 1128 and 1130 DTCs were from using the intake and DME for the 2.7L engine with a 2.5L engine – too much air for the 2.5. Some reading showed that there are a variety of causes and cures for those codes, so I checked a few things. Oil cap and crank case vacuum were good. Next I looked for intake leaks. I found that the brake booster venturi line was starting to separate from the intake just before the throttle body allowing unmetered air in. I'm planning to remove the intake tubing and fix it or replace it. For the moment, I have the venturi hose and hole in the intake 'patched' with Gorilla Tape. I'll see if the codes come back. It takes about 50 miles of driving to get the codes to trigger.

I really want to get moving on the Audi swap. I don't need have the actual swap car ready to get started. For fitting the engine, I have a parts car already that I can use to develop the engine support with. For wiring, I have charts and pin-outs for most of it already worked out. This week I plan to pull the harness off of the ABZ (1998 32-valve Audi V8) and splice on harness connections from a 2001 car that I stripped. That should allow me to work on the harness in air conditioned comfort, then just plug it in when I install the engine in the car.
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Last edited by 78F350; 07-31-2019 at 09:37 AM. Reason: deleted, a few, extra commas,,,
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