Help! Fixed HGs and now no Idle!

Berserk

Registered User
So after two and a half months being apart, I got the SC back together. Put the fluids in, reattached the battery, and she started right up. Sorta.

Ok, here's the symptoms:
The car won't hold idle, or anything close to it. If you keep off the throttle pedal completely the car just dies. If you put it down to about where it would normally hold at 2K rpm, she'll just ramp up to about 3K rpm, cut and die off to about 500 rpm, then ramp back up in a loop. You can start to hold higher rpms, starting around 3 or 4 thousand. While the car is surging, the supercharger bypass is cycling open and closed. Once the engine was warm, it ran a little better, but still not good. It would never hold idle at all.

She's so close to being ok again, I need your help! Any hints or requests for troubleshooting info is very very appreciated.
 
Check all the usual stuff, make sure the plug wires all go to the correct plugs, check for vacuum leaks with some carb cleaner or propane. Mine did the same thing. Wouldn't idle unless I put pressure on pedal. But it fixed itself after I drove it a while. It now idles perfect, the tach needle doesn't even move at idle. I still have boost problems though and missing at boost. Sometimes I think the computer just needs to relearn to get it running right.
 
Thanks - sounds like good advice thus far. Tomorrow I'll do those checks, and hopefully it'll even itself out.
 
Sounds like a vacuum leak. Recheck every IC tube connection, SC top, and every vacuum fitting. That's usuually what's wrong in this situation.

Jerry
 
I agree the symptoms all point to a vacuum leak someplace.....hose, intake manifold, throttle body??..... Also if your headgaskets failed your Oxygen Sensors should be replaced, but run it for a little while (30 min) first to burn all the cooland residue out of the exhaust system. Cooland residue will destroy oxygen sensors, but they do not affect idle until in closed loop, so if the wierd idle is on initial cold start i dont think it's an oxygen sensor problem. The computer does have to 're-learn' it's parameters after an extended period with the battery disconnected, but i don't believe it would be to the point of not idling at all....just a little erratic...until it 're-learns'.. but i could be wrong on that one...

Good luck....definitely look for vacuum leaks
 
Well, I've scanned for vacuum leaks and seen none. No clue what the problem is. Disconnected the MAF, just to check, and it doesn't run any better or worse. I'm getting some kind of a coolant leak that drips onto the passenger side exhaust manifold and I can't tell where its from. Doesn't seem to do it all the time - only once the engine warms up a little right after starting... maybe 30 seconds of runtime. There also seems to be an oil leak at the back side of the same valve cover gasket. Any hints on finding those? At this point I'm pretty sure I could make it to a shop, with some work and luck, think I should take it in for professional help?
 
How did you re-seal the IC tubes and other parts of the intake system ? When checking for vacuum leaks, did you spray all the connections from the Throttle body to the Intake manifold with carb cleaner while the engine was running ?

Are all the vacuum hoses on the back of the inlet and return plenums secured ?

David
 
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When I resealed the supercharger tubes, it was with the remaining RTV sealant from the head gasket fix. I was definitely trying to spray the connections with carb cleaner, but I can't be sure if I got them well enough or all of them thus far. All of the vacuum hoses that I can find are secured. I'm pretty sure that I got all of them, but we'll see. I'm planning on going after them all with propane or carb cleaner again later. Its rather hard to do, after all, since it won't idle properly, its hard to tell what's due to the carb cleaner and what's just due to the natural surges of the engine.

On another note, it seems the coolant leak was a false alarm, and the oil leak seems to be just the back lower edge of the passenger side valve cover gasket. I've tightened that guy up a little more, and hopefully that'll take care of that and I can just focus on the vacuum problem.

Could this be a sensor or electrical problem? I'm not getting any codes, except when I pulled the MAF. (well, the Check Engine light isn't coming on anyway)
 
Update: fixed oil leaking and sealed the only vacuum leak we could hear - the EGR. Right now there are no other obvious vacuum leaks. What could be leaking enough air so that at a steady 1500 rpm I'm only holding 10 in Hg of vacuum? We've checked pretty much everything. Wouldn't it, whatever it is, be making one heck of a lot of noise? Hints or help local to Gaithersburg, MD would be highly appreciated.
 
Hopefully my last update - Fixed the vacuum leak, it was the lower intercooler tube. Loosened both ends, retightened them, it was fine. So now its time to get the fluids set up right and drive it a bit, make sure its running happily.

Thanks for the help everyone.
 
Hope it worked

Cause that sounded like a definite IC tube leak to me....it's best to get that tape and use it to seal them with....JMO

Rick in FL :cool:
 
sealing IC tubest

What's the best to use for this? I had to tear my SC down to the heads this weekend, and am not sure what's best to use. I used RTV and the o-rings that came with the FelPro Gasket kit, when I did it last time, but the sealing job looks sloppy at best...

Ideas appreciated.

Chris
 
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