Skip to main content
Topic: 1986 Cougar 3.8 L won't idle. (Read 5939 times) previous topic - next topic

1986 Cougar 3.8 L won't idle.

My 1986 Cougar 3.8 L V6 won't idle on its own. The milage is 135,000, which is relatively low for the age. If I manually spray starter fluid down into the throttle body the car starts right up and runs great until the fuel is burned off. I have replaced or done the following:
1. replaced the fuel pressure regulator
2. replaced the fuel injectors
3. replaced the control module
4. replaced the pick up coil
5. replaced the fuel filter
6. replaced the computer
7. replaced the battery cables
8. fuel pump is ok and fuel pressure is good
9. Bought a tune up kit for the throttle body and did that

After doing all of this there is no change and the car will not idle on its own. ANY ideas on how to get this car running again???


1986 Cougar 3.8 L won't idle.

Reply #2
Yes, same car - and very frustrating. And now it's over at a car repair shop and they say it's not showing any codes. Maybe this could be because the battery was disconnected over the winter therefore all codes would have been lost? Also, since they put a new computer in it would it show codes without being driven? The car hasn't been driven any distance since the "it won't idle" problem started last summer. The mechanic said the only thing they can think of doing is to replace the throttle body…this doesn't make sense to me since the throttle body has already been rebuilt/cleaned when I installed the new injectors. What do you think?

Also, I never did pull a spark plug to see if they could be the problem.  Could new plugs solve this?  I am lost…

1986 Cougar 3.8 L won't idle.

Reply #3
Did they actually check the codes or just look to see if the check engine light was on? These cars can still have fault codes with the check engine light off.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

1986 Cougar 3.8 L won't idle.

Reply #4
Quote from: thunderjet302;465347
Did they actually check the codes or just look to see if the check engine light was on? These cars can still have fault codes with the check engine light off.
The check engine light hasn't worked in the car for years. The mechanic I had the car towed to has the diagnostic equipment to check for codes even if the light isn't working or so I am told. He said it was throwing no codes. Besides, wouldn't the car need to be driven for a certain amount of time (miles) before it would show codes after the battery was disconnected for months (during the this past winter)?

1986 Cougar 3.8 L won't idle.

Reply #5
Won't run or won't idle?

1986 Cougar 3.8 L won't idle.

Reply #6
Quote from: softtouch;465351
Won't run or won't idle?

If I spray starter fluid (or pour in gasoline) directly into the throttle body the car runs great until it burns the fuel off. Also, I replaced the throttle body sensor (TPS) as well but it hasn't made any difference. Any ideas?

1986 Cougar 3.8 L won't idle.

Reply #7
Well it sounds like a fuel delivery problem.
You said (maybe in your other thread) that you had good fuel pressure.
Was this checked at the Schrader valve test point in the CFI (throttle body)?
If you have pressure at the fuel filter and not at the CFI, check for a crushed fuel line between the two.

If you have pressure at the CFI, check if the injectors are spraying fuel while cranking. Look, smell. dangle something in there to see if it gets gas on it.

If the injectors are spraying you may have a vacuum leak that is making the fuel/air mixture too lean to run.

"Good" fuel pressure is 39 psi.

1986 Cougar 3.8 L won't idle.

Reply #8
Parts artillery, Ready, Aim, FIRE!
or
You could try testing.  You've got lots of really technical guys here, who understand the product deeply and have very valuable insights and advice.
You were asked if it doesn't run, or runs but doesn't idle.  Translation: If you DON'T give it alternative fuel, will it start and remain running with throttle applied?
This is a critical distinction, because if it runs with your foot on the gas, you could have one set of problems (such as a failed idle speed control motor or a large vacuum leak), but if it doesn't run at all, you could have a DIFFERENT set of problems (like no injector pulse, poor fuel volume, a failed MAP sensor, etc).

1986 Cougar 3.8 L won't idle.

Reply #9
Thanks to all trying to help me with my Cougar. I am not a mechanic so please forgive my ignorance. To be clear, it will not start with the throttle applied. It will only start if fuel is manually sprayed or poured directly into the TBI.

1986 Cougar 3.8 L won't idle.

Reply #10
The backbone of the diagnostic process it SSCC, or Symptom, System, Component, Cause.
Symptom - crank/no-start
System - fuel system.  When alternate fuel is introduced, the symptom is temporarily resolved
Component - ?
Cause - ?

This is where you are in the process.  Here are the questions to ask: what are the components in the fuel delivery system?, which ones are working? 
Your other posts, talk about fuel pressure.  You have roughly 40 psi? if that's the case, you can rule out the pump, it's wiring, and it's command, as well as the lines.  You have a new regulator, so lets assume it's good.  That leaves injectors (2) and wiring.  Test: with key on, the injectors should have power, but not ground.  Disconnect the injector connectors and check for power with a multi-meter. If you don't have one, a test light will do for now. If there's power, you'll want to see if the EEC is pulsing them on (by grounding them).  To do that, you'll want to get what's called a "noid" light. If you plug in the noid light to the injector connector, and it flashes while you're cranking the engine (on both) your injectors are being fired.  Are they actually spraying fuel? If yes, something got missed, if no, you have Component

1986 Cougar 3.8 L won't idle.

Reply #11
Thanks for the suggestion! I think the mechanic already tried this test but I will pass this on to him - I am heading over there now. I miss my car!

1986 Cougar 3.8 L won't idle.

Reply #12
Quote from: TheFoeYouKnow;465367
The backbone of the diagnostic process it SSCC, or Symptom, System, Component, Cause.
Symptom - crank/no-start
System - fuel system.  When alternate fuel is introduced, the symptom is temporarily resolved
Component - ?
Cause - ?
This is where you are in the process.  Here are the questions to ask: what are the components in the fuel delivery system?, which ones are working? 
Your other posts, talk about fuel pressure.  You have roughly 40 psi? if that's the case, you can rule out the pump, it's wiring, and it's command, as well as the lines.  You have a new regulator, so lets assume it's good.  That leaves injectors (2) and wiring.  Test: with key on, the injectors should have power, but not ground.  Disconnect the injector connectors and check for power with a multi-meter. If you don't have one, a test light will do for now. If there's power, you'll want to see if the EEC is pulsing them on (by grounding them).  To do that, you'll want to get what's called a "noid" light. If you plug in the noid light to the injector connector, and it flashes while you're cranking the engine (on both) your injectors are being fired.  Are they actually spraying fuel? If yes, something got missed, if no, you have Component

The mechanic has done the noir test and the injectors are firing as they normally should. However, they aren't getting any fuel. When starter fluid is sprayed into the TBI the car starts right up and the only way to keep it running is my pressing the gas pedal repeatedly. The car isn't drivable currently. My mechanic had a question: How does this car normally at start up get fuel to the injectors?


1986 Cougar 3.8 L won't idle.

Reply #14
Quote from: TheFoeYouKnow;465388
You have fuel pressure? Roughly 40 psi?  Can fuel be seen spraying when the engine is cranking?


I do know the fuel pressure is good. The psi is 35 or more which according to the shop manual is correct for a 1986 model. I will check with the mechanic to see if fuel is spraying when the engine is cranking. I don't think it is because if it was wouldn't the car start? The only way this car starts now is when starter fluid (or carb. cleaner) is sprayed directly into the TDI.