Why does it take so long for my RPM's to go back to idle?

hesitation

hesitation

New plugs and wires were installed about 6 months ago. The coil packs are original with 326,000 miles on them.
 
The first thing id check is the vacuum lines and something popped off or open. Did it just start doing that or has it always been this way? If it just started then you need to find the problem that is causing the increase/hang in idle first, then tune to your liking. The EEC and IAC is doing what its supposed to do...Hold the idle steady and not stall. Something is causing the EEC to increase the IAC. Mine never took that long to come back down but it did come down slow like it was programmed to do before the chip switch. But it is programmed to go back down slow from factory. That was my pet peeve also after listening to the stangs like you said. Talk to Lonnie or your favorite local tuner, and they will hook you up with a chip.
But for where and why....It's all in the throttle decay settings. The car was programmed to slow to idle settings im assumming to lessen the chains and connecting rods from gettin jerked. From instant on then instant off torque, prolonging engine life. You need to buy a SCT chip and tell the programmer what you want or how you want it to behave. Anything in the ECM or EEC can and is able to be messed with or reset. Thats why the tuners get good money and well worth it. You can mess up an engine very quickly if you don't know what things are and go changing parameters and settings.
Not exactly sure what its called for the SCT settings because i don't have a SCT burner, but on my JET burner for my GM 5 spd truck its the throttle decay and throttle follower settings. It used to hang at 2500 RPM for like 8 seconds and not kick down till you came under about 2MPH. Reflashed it after many times of testng to figure out where i wanted it. Now it revs fast and decells fast like an indy car. Also does not hang when shifting. (again, factory programmed for ease of shifitng hydraulic clutch and life of engine with revlimit at what each gear can be shifted at with power curve still active without pulling timing or limiting fuel). I raised the RPM ceiling and killed the governors also. You can even set it to not turn on each individual trouble code if you aern't running a particular item like the EGR system. The MPH settings or ceiling can also be changed where it kicks in or turns off.
Not sure this helps, but 2 cents is better than nothing. :)
 
Thanks, that's good info to think about. I just scanned the codes and they're on my other thread about erratic shifting. I don't know how to translate them though. Anyone speek in OBD1?
 
logres said:
I am in CA, and I've never had a problem. Custom tranny, custom TC, modified shift points, modified lock-ups.

I've just never modified any of the ENGINE settings.
Click to expand...

When getting a smog check....the machine doesn't monitor any of those "mods", but lets say I wanted to turn off my EGR, or delete a smog pump(if I had one) I be able to without failing because my car doesn't have to be "plugged in". Ofcourse my smog guy is very "lenient" but when it comes to OBD2 cars...he can't do crap! If it has a check engine light, or modified(or even failed) emission system parts, engine sensors or anything that has gone bad on an OBD2 car that the machine monitors, I'm done. I can take my car in with a check engine light on, running like crap, but if it passes the sniffer....he could care less.

Take your Xcal 2 and turn off your rear 02's or modify the air/fuel mixture and than go try to pass a test.....ain't gonna happen :D I'll take my mail order tune over failing a smog test anyday, lol!

Oh....I speak OBDI :D
 
Also...the coil packs aren't going to cause a hesitation upon acceleration....they either fail completely or under load, not just normal driving...kinda like a spark plug wire. I agree with them though....300K...change those things!!

Also....get a can of SeaFoam, and do a SeaFoam treatment!

Serge....I know that, but thats not the point. The point is you can not possibly modify an OBD2 car unless its 100% smog legal(not CARB, just emission/ECU monitoring) because of the one fact that you have to plug the smog machine into the Data Link Connector. Wayne was saying I'm "behind the times", and in my defense I was just pointing out that I'd rather drive an OBD1 car vs. an OBD2 car.

And.......I can switch my chip to the factory tune WAY faster than he can reset his tune to factory. I don't have to take mine out.
 
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I forgot about the 4 bank program chips... mine is actually a 4 bank chip as well but only one of the banks is programmed, I always drive with the "race tune." Also about the coil packs, with 120k on my 95 LSC, I developed a hesitation going uphills which I thought was either fuel or ignition related. I swapped out coil packs and it went away. BTW, J, are you still running the stock fuel pump?
 
Yep, stock fuel pump. I always drive on race tune too, haha. Only when I go on long freeway trips do I change it to the econo setting.

Your hesitation up hills due to a faulty coil pack is believable, when you go up hills(expecially yours, haha) there is WAY more load than normal driving.
 
Holy crap, 160k+ plus from the stock fuel pump... forget anything else next on your list should be a Walbro 255... they are cheap too, you can get them for under $100 if you look hard enough. Plus it makes a cool whining sound at idle if you get the 255 high pressure one. I think the stock fuel pump maybe what is holding your MPH in the 1/4 mile back a bit. They start getting tired after 100k...
 
Its been on my list, but I just re-did the front suspension, and exhaust, and etc...

You may be right, but my car doesn't "feel" sluggish at the end. Who knows, haha.
 
coil packs

coil packs

Thanks to all of you who suggested I change the coil packs because of my hesitation problem. I would never have thought that would be the problem.
Thanks again.
 
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