Occasional high idle
06-17-2003, 12:52 AM
#1
Three Wheelin'
Thread Starter
Occasional high idle
I just got my car back on the road.. I'll post pictures tomorrow.. it's INCREDIBLE 
Anyway, I noticed that occasionally, the car will idle at like 1500-2000 RPMs. I didn't clean the ISV when I had it apart, since I'd cleaned it back in december (like 500 miles ago) when I had it apart. It's not the TPS sensor (well it was at first, as the car heated up, everything expanded and pulled the throttle cable so it was off idle, but I fixed that.)
When I had the trouble with the ISV, there was nothing I could do to persaude the car to come back down to a reasonable idle, but now when it decides to idle high, I can blip the throttle until she decides to calm herself down.
So, besides the ISV, what could be causing this occasional high idle?
BTW: The car is back from a fresh top end rebuild. 3-angle valve job, new headgasket (stock, not widefire like I'd originally planned), and a set of GURU chips. (The chips have made a big difference as well, now it REALLY pulls between 5 and 6k RPM).
Anyway, I noticed that occasionally, the car will idle at like 1500-2000 RPMs. I didn't clean the ISV when I had it apart, since I'd cleaned it back in december (like 500 miles ago) when I had it apart. It's not the TPS sensor (well it was at first, as the car heated up, everything expanded and pulled the throttle cable so it was off idle, but I fixed that.)
When I had the trouble with the ISV, there was nothing I could do to persaude the car to come back down to a reasonable idle, but now when it decides to idle high, I can blip the throttle until she decides to calm herself down.
So, besides the ISV, what could be causing this occasional high idle?
BTW: The car is back from a fresh top end rebuild. 3-angle valve job, new headgasket (stock, not widefire like I'd originally planned), and a set of GURU chips. (The chips have made a big difference as well, now it REALLY pulls between 5 and 6k RPM).
06-17-2003, 07:13 AM
#2
Race Director
The most likely is a vacuum leak in the big hoses under your intake-manifold. One of the most common sources is the 180-degree bent hose. It has a fitting that goes into the Y-shaped venturi that generated vacuum for the brake-booster. This end of the venturi has an O-ring that typically degrades over time and leaks air past it. This extra air is what causes the idle to get stuck on the high side. Try turning in the idle-adjustment screw on top of the throttle-body by about 1 to 2 turns.
06-17-2003, 12:28 PM
#3
Racer
Join Date: Apr 2002
Location: Denver Colorado
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You might check your TPS to see if it is closing. I had the same problem after installing the intake manifold. I was going to start through the vacuum system but thought of the TPS first. I checked it and it was not closing. Adjusted the cable and the engine idled at 800.
06-17-2003, 06:14 PM
#6
Three Wheelin'
Thread Starter
Danno: That crazy bent hose has a spear type fitting on it that plugs into a hose that leads to the ISV. When I pulled out the ISV and all the attached hoses, I just pulled the spear out of the plastic tube thing it was attached to.
Do you think that I need to replace the spear or plastic tube thing, or that might be the cause of the problem?
Do you think that I need to replace the spear or plastic tube thing, or that might be the cause of the problem?
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06-17-2003, 07:31 PM
#8
Race Director
"Do you think that I need to replace the spear or plastic tube thing, or that might be the cause of the problem?"
When you pull that spear out of the venturi tube, you'll notice that there's an O-ring on it. Try to find a new O-ring to seal the assembly. I usually just seal it in with some Yamabond-4.
Also all the stock hoses in that area use cheap strap-type hose-clamps. The problem is the rubber hoses shrink with time and no longer holds tightly. If you can spin any of those hoses on the venturi or idle-stabilizer motor, cut off the strap and install a real hose-clamp.
When you pull that spear out of the venturi tube, you'll notice that there's an O-ring on it. Try to find a new O-ring to seal the assembly. I usually just seal it in with some Yamabond-4.
Also all the stock hoses in that area use cheap strap-type hose-clamps. The problem is the rubber hoses shrink with time and no longer holds tightly. If you can spin any of those hoses on the venturi or idle-stabilizer motor, cut off the strap and install a real hose-clamp.
