My daily driver is an 88 Pontiac Fiero GT. One of 6 (don’t laugh) My problem is off idle @ 2000 rpms I should have about 15 inches of vacuum but I get only 6-8 inches. After a while it trips the check engine light for an EGR code. Can you give me an idea of what to look for?
Thank you, Matt
It, obviously, has a vacuum leak. Use a bottle of propane, with a controllable nozzle. With the engine idling, open the propane nozzle a little bit and play the gas around the intake tube and intake manifold. If, at some point, the engine rpm increases, you’ve found the vacuum leak. You can, then, decide the repair.
On the four cylinder, the intake manifold bolts can come loose too. So can the carburetor. The carb gasket can be cracked in half, the carb body can be broken.
You’re incorrect if you think that you should have 15 or more inches of vacuum at 2000 RPMS.
At idle only will you have this and it will quickly drop the moment the throttle is opened.
Since you’re getting an EGR code my guess is you have a faulty EGR valve. That valve, unless it has been replaced, has a 20 year old rubber diaphragm in it and it’s a miracle it has lasted this long.
Also, the EGR valve IS a vacuum leak in one of two ways. One is controlled and the other is not.