86 GL Idle Issue

[froghatch86]

I just aquired an 86 GL hatchback from a neighbor for $50 and It is in fairly good shape. The Issue I am having is with the engine Idle. The engine idles rough and stalls. I rebuilt the carb(Hitachi) and the engine continues to exhibit the idle problem. I am a novice mechanic and was wondering where I should start in addressing this problem.

[Subaru_dude]

does it still have power when you're driving it or will it barely move under it's own power? if it will barely move... it's probably the fuel pump or filter. but before you go jumping to that, i would recommend plugs (NGK), wires (NGK), disty cap, rotor, air filter, fuel filter. check the choke too... that's the most common idle related problem causer.

[froghatch86]

I had it up to 80 mph yesterday. It runs fine except for the idle. The plugs,wires, cap, rotor, and fuel filter have been replaced recently. In reguards to the choke it starts cold and once the choke disingages the engine idles rough and stalls. The choke is not adjustable on this carb because there is a pin locking it in place which leads me to believe the problem is coming from somewhere else.

[Gloyale]

Vacuum leaks can cause poor idle too, and if no one has changed the vac hoses they probaly are all hard and cracked. IMPORTANT. if you are replacing vacuum hoses on these cars you need to know there are tiny little brass plugs with small pinholes INSIDE some of the vaccum hoses. These are important cause they send just a small amount of vacum to certain parts of the system. When you change hoses, cut the new one to length, then cut the old one up into sections small enough to look all the way through. If there is one of these plugs in there, remove it and simply push it up inside the new hose and install. These plugs are differnet sizes so make sure you go one at a time. They are identified as "orifice" on vacuum diagrams. Not all the hoses have them. But I check every hose just to make sure.

 

BTW:Also you can adjust the choke, you just have to drill out those rivets on the choke cover and tap threads for bolts. Then you can adjust the idle cam and bi metal spring. But if it's starting good and the choke opens after warm-up probably not the issue.

[froghatch86]

thank you for the warning. You just saved me from throwing out one of the vaccum line jets.

[hatchsub]

another thing you might want to check is your intake manifold gaskets. Spray some carb cleaner around them and see if the idle pics up. If it does you just found your problem. I had the same problem with my 86 gl hatch and it turned out it had vacuum leaks at the intake.

[beataru]

you can check for vaccum leaks with brake clean, if the engine raises in idle after spraying a particular hose, then youve found it, or excuse me one of them!!!

[yorab]

I had idle problems with my 85 GL carbed model. I tried EVERYTHING! Of course nothing worked. I rebuilt/replaced more parts than I care to mention. Finally, I got a FSM (not a Haynes or Chilton). It said to check the Anti-backfire device. Sure enough that was the problem. It is supposed to allow extra air into the engine during a sudden drop in RPM to prevent backfire. However, the vacuum diaphram was bad and the device was allowing extra air into the engine at all times, thus giving a poor idle. It can easily be checked by holding a piece of paper underneath the device. The paper should be sucked up against the inlet ports only when there is a sudden drop in RPM.

By the way, I got the part at a JY for about 10 bucks. Dealer wanted 160. Now the replacement is bad. Becoming hard to find a good replacement part in my area.

[beataru]

good to hear you solved it. zzzzzz now to fix it