SwedeSpeed - Volvo Performance Forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
30 Posts
Discussion Starter · #1 ·
Hello, I have been looking for a vacuum leak for weeks. My engine runs well but idle is not what I think it should be . The engine has a miss and the sound at the tailpipe is not smooth. The car has new wires ,plugs, pertonix ignition , new cap and rotor. The engine compression is fine. I know that device to check the exhaust is used when setting the idle screw on the ECU but I have set the screw by ear. At this time I have the screw set to the full rich position at which point the engine runs best. The plugs are clean and not carbon fouled my question is, is it ok to run the ecu in the full rich position all the sensors check out well within spec with the ohm meter . I have checked all over the engine for a vacuum leak I have used carb spray , propane , and water . From time to time I have found some small leaks and repaired them but the engine has a sound unlike any other B20 I have heard there is a low whistle that can be heard at idle and when the engine is shut down almost like an in and out noise. I do not expect any answers but I am just throwing it out there maybe someone has had the same noise. Thanks in advance for ANY reply.
 

·
Registered
Joined
·
2,616 Posts
Lots of places for intake manifold leaks on a B20 E. My B20E leaked around the throttle plate shaft and around a couple of the injector holders. I found the leaks by connecting up my shop vac in reverse and jamming the hose into the intake manifold. I then used a sprayer with soapy water to check for leaks. Clamp the hoses to the MAP sensor and distributor (don't want to damage the diaphragms) and the crankcase vent. You need to rotate the crankshaft to minimize pressure loss through intake and exhaust valves that may be open simultaneously.

Because the Djet is a gamma - n (manifold pressure x engine speed) based fuel metering system, smallish air leaks in the intake manifold generally have no detrimental effect on fuel mixture. The only down side is that it will idle really fast (the air leaks are equivalent to opening the idle by-pass screw some more). If you need to crank the mixture setting screw up to the max to get it to run well, something else is likely at play. Check the fuel pressure since that determines injector flow rates and low pressure can cause it to run lean.
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #3 ·
ecu adjustment

Lots of places for intake manifold leaks on a B20 E. My B20E leaked around the throttle plate shaft and around a couple of the injector holders. I found the leaks by connecting up my shop vac in reverse and jamming the hose into the intake manifold. I then used a sprayer with soapy water to check for leaks. Clamp the hoses to the MAP sensor and distributor (don't want to damage the diaphragms) and the crankcase vent. You need to rotate the crankshaft to minimize pressure loss through intake and exhaust valves that may be open simultaneously.

Because the Djet is a gamma - n (manifold pressure x engine speed) based fuel metering system, smallish air leaks in the intake manifold generally have no detrimental effect on fuel mixture. The only down side is that it will idle really fast (the air leaks are equivalent to opening the idle by-pass screw some more). If you need to crank the mixture setting screw up to the max to get it to run well, something else is likely at play. Check the fuel pressure since that determines injector flow rates and low pressure can cause it to run lean.

Thanks for the quick answer I will give the shop vacuum a shot
 

·
Super Moderator
Joined
·
9,305 Posts
Another easy way to look for leaks is to spray starting fluid lightly at suspect areas with the engine idling. If the engine speeds up, you've found a problem.
 

·
Registered
Joined
·
79 Posts
You can make a very good vacuum leak tester with an air compressor and schrader valve- glue the valve into the end of a pcv cap and then clamp it on the throttle body with a rubber boot and hose clamps, then pressurize with a tire filler and get it to hold pressure.
 
1 - 5 of 5 Posts
Top