ccdguy

Hey guys... I'm running out of ideas. I used the search function, and read up on everything I can get my hands on to try, but I'm not getting anywhere. I have a stock 87 GT, 5 speed, speed density car. I've replaced and installed (2) new O2 sensors, intake air charge temp sensor, coolant temp sensor, new IAC. Cleaned TB, started the car when it was at operating temp with IAC disconnected. I had to turn the idle screw in one full turn to get the car to start and idle without the IAC at the lowest steady RPM of 650-700. Idles nicely. Turned the engine off with IAC still disconnected, key on-engine off set TPS to .98v between green and black wires. Disconnected battery, turned all lights on and off, tapped brakes, left negative terminal off for about half hour. Came back, reconnected IAC, reconnected battery. So that is pretty much (as I know it) base idle reset, right? Now, I get in, start the car, and the damn thing starts up at 650-700 rpm and hunts for about 1 minute between 400-1000rpm until it settles down bouncing at around 800 rpm... Also, when the car is stone cold in the morning, I start it, and it's as if it does not want to pick up rpms until it warms up. It just tries to idle at the base rpm on 650-700 and pretty much dies on me, unless I rev up wit the gas pedal for a while... WTF???? It used to start up on cold mornings, engine rpm would go up to like 1000-1200 until it warmed up and then it would come down to about 800 or so and stay there. It no longer does that? There are no CELs and no codes come up when tested. All sensors are plugged in. To my knowledge there is no vacume leaks. What gives? can you guys give me some ideas? Ohh, and I had tested the fuel pressure and the pump is fine, no fuel issues.... Sorry about the long post, but just wanted to give some detailed info on my problem,....

AdderMk2

you need to wrm the car up before performing a base idle reset.

also, the car should be idling around 500-575 before the IAC is connected.

you did it wrong, try again

ccdguy

Well, that's just the thing,... The car was warm and at operating temp, and the IAC was disconnected before I started the engine. Then I turned the screw on the TB to get it to run steadily at 600-700. Could not go lower as it would be too low for the alternator to run properly (lights and bulbs would flicker a bit) and it would not idle any lower. Turned it off, set TPS to .98v with key on, engine off. Then disconnected the battery for 1/2 hour, reconnected IAC, then battery, then started it... I still think that is the correct order, is it not?

AdderMk2

if ti wont idle any lower, there is a good chance that you have a vac leak... get searching.

Common area.. under the intake manifold.

and stop with the .98v bull****. set it close to .8 and leave it the hell alone.

ccdguy

I agree with that .98v crap. I've read too much into it. Just plopped down a new TPS and it came up with .74v close enough. I've turned the idle screw a bit higher and got .80 on TPS and 4.71 at WOT. Just waiting for my new IAC to be delivered today to Autozone, since I think the last one was bad. will give that a try, and then start looking at vac problems. About time I replace the PCV anyway. Good place to start. Will let you know if anything changes..

AdderMk2

Stop adjusting the throttle open. the more you open it up, the less your vac can compensate. search for and repair,any vac leaks. then adjust the idle around 575 rpm when you plug the Iac in, you should be around 675. No higher.

ccdguy

Thanks for all of the suggestions guys.... Sorry for the long reply,. I really appreciate your input and advice. I have figured it out!!! I've tested for all possible vacuum leaks. Around TB, upper intakes, EGR, vac tree, hoses, etc. No change at all - no effect from the carb spray. Decided to purchase ODB-1 scan tool and just ran it last night. KOEO codes 23 and 54. My TPS was at .64v before. I had reversed it, so that the three wires can clear the edge of TB/spacer, set it to .98vdc and no more 23 code. Then, I took out the "new" Autozone SU203 ACT sensor which I've put in a few weeks ago. Brand new when I bought it, but looked different that the OEM that I took out. When I took the "new" one out, it was missing the sensor wire on the tip!! Burned off, broke off, just plain ol' missing. Off to Autozone, and got the correct one this time. Looked just like OEM did. Screwed it in, ran KOEO test again. Got code 11, which is all clear. Started the car and what a great feeling. Idles perfectly, and when warm goes down to 700 or so and is nice and smooth. Throttle response is better too with the darn TPS working in range now !! Now onto timing. Marked the balancer, and tested with spout out. Looks to be at 8 degrees, and not the 10 I thought these Mustangs were set with. It was late at night, so I've decided to leave that for another day. Will try to bump it up to 10-12 range and go with 89 octane to see it it likes it. If so, why not? ) Might get some extra free ponies under the hood.... Will watch out for any signs of detonation, of course. Thank you for all the ideas and help, guys. )

AdderMk2

shouldnt need 89 octane with only +2° additional advance over stock...