What could be wrong

[silver87]

I just bought an 87 gt with 77,000 miles on the car. Just recently I have noticed it idle's extremley high around 1,500 rpm. It then drops down to around 800 rpm. This happens periodicly jumping in rpm's at idle. Also when I am shifting there is no rumbling form the exhaust when I let of the gas, it sounds like I never take my foot off the gas. Does anyone know what could cause this. I have never had a major tune up since I bought the vehicle, could it be a bad distributer or maybe could it be out of timing? Does anyone have any suggestions?
Thanks

 

[shttygtstang]

hows the voltage from your tb did you test it

 

[silver87]

I have not run that test yet? I dont want to sound like a complete idiot, but do you just use a voltage meter to test it?

 

[shttygtstang]

yes ground on the black wire not the bat- and green if its wrong then loosen one bolt anslightly twist it it should go up an down ideal setting is .92-1.00

 

[Quick5pnt0]

Yes you need a volt meter to set the tps. Clean your IAC, and TB, then set the TPS, and clean the MAF
It's all here...
http://www.muscularmustangs.com/iac.html

 

[silver87]

Thanks, I will try that. Would an electric fan cause any problems like this?

 

[shttygtstang]

that might not be it though do a tune up first show your car some love

 

[silver87]

I've noticed that the distributer rotor needs to be replaced and I will be rplacing plugs and wires soon.

 

[HISSIN50]

really check out the IAB, as said. as long as the TPS is under 1.3 volts, static, the puter will zero it out. i would not sweat that too much, right now.

check for vac leaks. a stock-ish motor should have 15-20 inches at idle.

on an aside, i would hit all the maintenance items, as it sounds like you are preparing to. spend some cash and do the plugs, wires (if necessary), fuel, air, all other filters. cap, rotor, as you said. PCV, grommet, screen and all that kind of stuff. no one item may make a big difference, but commulatively, it can make a difference.
if unsure what all to check/replace, get a repair manual and check the schedule of maintenance intervals and chapter one (maintenance items, normally). mow it all down, IMHO.

oh yeah, pull codes for fun, so you know what gives (either a clean slate or you will know other things to fix down the line). sorry, im all over the place - tired.
good luck.

 

[silver87]

Thanks, I really appreciate the help.