Engine tuning

[Jake Seidel]

I have a problem with my 72 1.7 914. The engine is idling high and when driven there is a spot between 3 and 4 thousand on the tach were the engine misfires and comes back to full power after 4. I heard vacum leaks could cause this? what are these? The engine also has a 75 76 air box that it had o it when I purchased it, would this have any effect on the situation?
any info would help
thanks
jake

[mr-dwight]

I think you have either improper timing or a leak in your distributor diaphram. I believe the timing is probably the problem.

[nine_one_4]

Here's a 16 mb zipped folder containing 31 jpegs of the Bosch D-Jet manual that might be useful to you for troubleshooting.

http://www.speedyshare.com/370125240.html

A few sample pics.

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[Bleyseng]

The engine is idling high, say at 2000 rpms?? Could be the AAR valve is stuck open so check the hose that goes from it to the air cleaner and plug it with your finger to see.

[Jake Seidel]

what is the AAR valve

[Bleyseng]

The Aux Air Valve when cold lets air into the plenum to raise the idle. It has a little heater in its base so when it heats up it slowly closes cutting off the air supply, idle goes down to normal.
Damn things rust inside and stick open usually. Squirt PB Blaster into it every 6 months to keep it moving freely.

[Dave at Pelican Parts]

You can also look on Brad Anders' D-jet website. It contains just about all we currently know about D-Jetronic EFI.

http://members.rennlist.com/pbanders

--DD

[RandyLok]

The misfiring between 3-4000, clearing back up above 4000 makes me think of the TPS. Look that up in Brad Anders' stuff.

[Bleyseng]

while the engine is running unplug the throttle switch and see if that stops the missing.
or it could be a timing issue as the advance is all the way in by 3500rpms so if its way advanced it misses. BTDT

[djpateman]

Check out the distributor for sticking plates and weights. Even the ground strap between the plate and body.

[Jake Seidel]

thank for the advice