cokenz

My girlfriends car is a 1986 5.0 mustang with 180,000 miles ,bone stock motor and it has a surging idle that eventually led to the car not starting at all.The fuel pump is recent as well as the injectors,new spark plugs,cap and rotor,and wires.For the life of me I cannot figure out how to get this thing going.The surging idle has been going on for a while and I never could figure out how to fix it.I bumped the timing up a little from the stock 10 degrees to a 12 degrees which helped out the idle problem a little bit but it struck back again with a vengence.Heres the situation the engine turns over and sounds like it wants to startand as soon as the enigne sounds like it is going to start it does.Any advice would be appreciated thanks!

88stangaruu

Clean the IAC valve, and it probably wouldnt hurt to replace the 02's, but the 02s have nothing to do with idle.

But clean the IAC then clean the MAF.

cokenz

The 02's were replaced about a year ago,and this car is not equipped with mass air,it has speed density fuel injection.One question where is the IAC sensor?

94gtmax50

the iac is on the side of the throttle body ,it looks like a small cylinder with a plug going into it and it has 2 bolts holding it in place .

88stangaruu

See...once again..just goes to show what i know about speed density...i totally forgot all pre-88 cars were speed density.

Stupid me.

cokenz

Actually now that you described it I did replace the IAC valve with one from another 5.0 thinking that it would solve the problem but it still won't start.

Lysawy

check map sensor w/o Map sensor engine will turn over but wont start....

Lysawy

oh and forgot to add map sensor is located on the firewall right after the manifold somewhere in the middle i think!!

cokenz

Thanks if i remember right it has a vaccum hose that goes to the intake manifold right?How much are they?And can they be cleaned?

Lysawy

No idea man how much but don't just buy it yet have a fellow 5.0 friend close to you help you out by swaping ..... the part....


but it looks like map sensor is your problem ... check the vacuum line no vac no start...