Going to fix drop-to-idle Problem

As most of you know I've had weird idle issues for along time. If you want to see what I'm talking about, goto my myspace (http://www.myspace.com/davetalon) you may have to add me, and check out my videos section. At the end of the one, I pull the throttle open. Now, it should (once closed) drop back to base idle at 850rpm. But it just hangs there and takes a while to drop down.

When I'm driving, it takes even longer. And doesn't fully drop off until I come to a complete stop.


So what have I checked...

-The front of the car is open; no a/c core, better radiator, no grill, no fog lights. The filter sits basically right in front of front bumper opening, right behind the cooling fan. Could the extra air (while driving) be causing a problem?

-The TPS and IAC are fine. Just checked those, both have the right Ohms or whatever. Did it according to the book.

-Cleaned the TB. Butterfly was sticking so I cleaned and even sanded the edges just a wee bit and it fits much better now. Throttle feels better too now. I'm going to loosen the throttle cable just a little. It's as tight as it can be. The SAFC doesn't show the throttle being open at all when car is heated up and everything.

-Vacuum lines are good. All hooked up right, no leaks as far as I can tell, no openings. One question, when I took off the cruise control, I just plugged the one vacuum line with a screw. Should I reroute that somewhere? It was a sucking vacuum IIRC.

-Plugs are newer. Was going to change in the next month or so. But I ran a same set of plugs for a year and a half before I changed them with no problems. Properly gapped also.

-I do have the Crower cams and the intake inside is advanced (IIRC) by very little. Shouldn't cause problems.

-EGR is fine and clean

-SAFC at 1000rpm is set to -10%

When I reset the ECU, the car runs like it should with the idle drop, but once it reprograms itself, it's no good then. I know I'm wasting a ton of gas with this problem. This needs to get resolved soon.

As most of you know I've had weird idle issues for along time. If you want to see what I'm talking about, goto my myspace (http://www.myspace.com/davetalon) you may have to add me, and check out my videos section. At the end of the one, I pull the throttle open. Now, it should (once closed) drop back to base idle at 850rpm. But it just hangs there and takes a while to drop down.

When I'm driving, it takes even longer. And doesn't fully drop off until I come to a complete stop.


So what have I checked...

-The front of the car is open; no a/c core, better radiator, no grill, no fog lights. The filter sits basically right in front of front bumper opening, right behind the cooling fan. Could the extra air (while driving) be causing a problem?

-The TPS and IAC are fine. Just checked those, both have the right Ohms or whatever. Did it according to the book.

-Cleaned the TB. Butterfly was sticking so I cleaned and even sanded the edges just a wee bit and it fits much better now. Throttle feels better too now. I'm going to loosen the throttle cable just a little. It's as tight as it can be. The SAFC doesn't show the throttle being open at all when car is heated up and everything.

-Vacuum lines are good. All hooked up right, no leaks as far as I can tell, no openings. One question, when I took off the cruise control, I just plugged the one vacuum line with a screw. Should I reroute that somewhere? It was a sucking vacuum IIRC.

-Plugs are newer. Was going to change in the next month or so. But I ran a same set of plugs for a year and a half before I changed them with no problems. Properly gapped also.

-I do have the Crower cams and the intake inside is advanced (IIRC) by very little. Shouldn't cause problems.

-EGR is fine and clean

-SAFC at 1000rpm is set to -10%

When I reset the ECU, the car runs like it should with the idle drop, but once it reprograms itself, it's no good then. I know I'm wasting a ton of gas with this problem. This needs to get resolved soon.

i dont have a myspace nor will i get one, so I couldnt watch your vid. from the sound of it though, maybe your BISS is open too much? Also, does the condition change depending onthe outside temp and/or engine temp? how does the car idle? It almost sounds like a vaccuum problem, even though you said you checked everything. I'm sorry I can't help you very well, I hope you figure out the problem.

Also, I have had a lot of weird idle issues too. From having a messed up throttle body, throttle cable issues(I have a 91 non-cc cable now), bad tps, bad IAC, TPS wiring not spliced into the safc properly, safc not spliced into the ecu properly, etc.

Now my problem is 272/272 cams, NO iac, NO map sensor, cyclone intake manifold with the dual runners, and gm-maft, and my dsmlink isnt hooked up because there was a problem with the chip(in the meantime i'm tuning with safc). When I'm slowing down, if I put it in neutral and let the rpms drop in 65-70 degree weather, car fully warmed up, they drop to about 2k and slooooowwllyyy drop to 1500, then when I come to a stop, they slowly drop to 1000, and then bounce between 800-1300 rpms. I'm just mentioning the problem I have, because maybe it might help you figure out something. good luck

Pretty sure the 420A dosn't have a BISS, but if he had a 4g63 that would have been a good suggestion. I wish I had something to suggest, but it looks like you covered all the bases Dave. Don't loosen the throttle cable too much...you want it nice and snug. The extra air shouldn't be causing the problem either.

Pretty sure the 420A dosn't have a BISS, but if he had a 4g63 that would have been a good suggestion. I wish I had something to suggest, but it looks like you covered all the bases Dave. Don't loosen the throttle cable too much...you want it nice and snug. The extra air shouldn't be causing the problem either.

oh sorry lol i didnt look at the sig, I just assumed he had a 4g63.

well, for any car, like you said the extra air wouldnt be a problem. before I had all the mods I listed, I used to have a little ram-air duct going though the hole that the stock side-mount pipe went through and pointing at the air-filter. I'm sure it got a lot or air in there, but I never had Idle drop-down problems with it. now I have an open turbo, so i dont need the duct.

Try this:
http://vids.myspace.com/index.cfm?fuseaction=vids.individual&VideoID=21584807

If that doesn't work I'll post it someplace else tomorrow. It's at then end when I open the throttle.


No BISS on the 420a. I'm lost. I've got nothing else to look at. SAFC is wired right. Everything is good as far as I can tell.

Im still betting on a vacumm leak.

But where? lol.

I would start by disconnecting each vac line, plugging the intake and testing each line 1 by 1. If everything checks out, could be TB gasket, or either gasket on the intake manifold runners.

TB gasket is good for sure. I've replaced and sealed twice already.

I had the problem (as far as I can remember) since before the head swap too, which means I've redone every line up top. I'll go over them all again. Disconnect, clean, and replace.

what about the gaskets on the intake manifold? Where those replaced with the head swap?

Sure were. Replaced and sealed.

I dont know what to tell you man. But it sure sounds like an air leak somewhere. What about the EGR system. Could it be leaking somewhere?

Perhaps an intermittent short in one of the sensor wiring? Maybe one of the many signal wires? If you have replaced everything else this would be something else to check. Wiring in general as well.

Perhaps an intermittent short in one of the sensor wiring? Maybe one of the many signal wires? If you have replaced everything else this would be something else to check. Wiring in general as well.

That's what caused some problems after the head swap. The loom for the TPS and IAC caught on the EGR pipe and melted the loom and the insulation. THe wires pressed on it, and was basically shorting something out. Threw a CEL but I fixed it. Moved the wires, checked the sensors, and they test good. I double checked them.

EGR is good. It's a newer valve & solenoid, and pipes are clean.

Have you tried swapping out the ECU with a known working one? It has to be something electrical. You've checked and double checked everything else. This has got to be one of the weirdest problems I've seen in a long time. I bet its going to turn out to be something so simple and stupid.