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Topic: engine idle (Read 1157 times) previous topic - next topic

engine idle

i need help, my 86 cougar is idling a little rough, almost like the miming is too slow, but the manual says that the idle is controled electronicly and cannot be set. would a failing ignition coil cause this? i ask because it is also taking longer to start than normal. I was on my way to Neb. this weekend and it started cutting out and "bucking" I was afraid it was my transmission, but after stopping at a gas station, i barely got her started again. once i did i headed home, grabbed the ranger and took off again. Tonight, after i got back, i replaced the plugs, wires, rotor, cap, and fuel filter ( i have had issues with filters in the past, and it was due for a mini tune up anyway) It runs better, but i'm not happy with the idle, seems rough. any ideas?
[SIGPIC][/SIGPIC]:cougarsmily:

engine idle

Reply #1 –
well for starters the first thing you always wanna check with a bad idle is what controls the idle--the IAC, Idle Air Control, motor, which is attached to the side of your throttle body. Thats why "it cant be set". If its really dirty/gunky inside clean it out WELL, i think you should also lube the stuff you can see through the two holes with 3 in 1 oil or something (wait for more replies not sure on that but i thought somehwere somebody mentioned oiling it)
 
once youre sure the IAC is functioning right, then move onto other stuff.
 
good luck!
1987 20th Anniversary Cougar, 302 "5.0" GT-40 heads (F3ZE '93 Cobra) and TMoss Ported H.O. intake, H.O. camshaft
2.5" Duals, no cats, Flowmaster 40s, Richmond 3.73s w/ Trac-Lok, maxed out Baumann shift kit, 3000 RPM Dirty Dog non-lock TC
Aside from the Mustang crinkle headers, still looks like it's only 150 HP...
1988 Black XR7 Trick Flow top end, Tremec 3550
1988 Black XR7 Procharger P600B intercooled, Edelbrock Performer non-RPM heads, GT40 intake AOD, 13 PSI @5000 RPM. 93 octane

engine idle

Reply #2 –
Quote
would a failing ignition coil cause this? i ask because it is also taking longer to start than normal.

Mmmm...that's the big clue. I sense a failing fuel pump, as longer start times is usually one of the warning signs (and sometimes there are no signs at all, so maybe you got lucky). You could try cleaning the IAC and EGR, see if that helps.

The idle is controlled by the computer, generally. This depends upon readings from a few select sensors, like the IAC/idle bypass valve, the TPS, the EVP/EGR system, and the MAP/BPS sensor. If one or more of these sensors fail then the computer reverts to a set of predetermined values. That means the car will run and try to idle, but maybe not greatly so. Therefore you need to look to those sensors first. If everything is okay and they are within operating parameters then other things have to be considered: clogged converter, clogged charcoal cannister, or fuel pressure, things like that. You can have your fuel pressure tested, too...that would probably be a wise thing to do soon.

engine idle

Reply #3 –
Run codes before you swap any more parts.
Long live the 4-eyes!  - '83 Tbird Turbo - '85 Marquis LTS - '86 LTD Wagon

engine idle

Reply #4 –
will it show codes even if the engine light isn't coming on?
[SIGPIC][/SIGPIC]:cougarsmily:

engine idle

Reply #5 –
Yes
Long live the 4-eyes!  - '83 Tbird Turbo - '85 Marquis LTS - '86 LTD Wagon

engine idle

Reply #6 –
thanks, i will try that.
[SIGPIC][/SIGPIC]:cougarsmily:

engine idle

Reply #7 –
Does a CFI have an IAC?