How can I determine the difference between a vacuum leak and bad air idle controll vlv?

ROBLOFLIN

MEMBER
1989 FORD TAURUS
20,000 MILES

When starting the car('89 Ford Taurus 3.0 engine) the accelerator must be depressed to keep the engine running. There are occasional pops coming from the engine. The idle will cycle from low to almost normal sounding and the engine runs roughly with occasional pops coming from it. After some time the engine may idle without keeping the accelerator depressed, but the cycling still occurs and it still runs roughly. I have attempted to check for a vacuum leaks by spraying the visible hoses and connection points with a throttle body cleaner(not sure if I got everything though). I have not heard a difference in the idling and the engine still runs rough after doing this. Is there anything else that could cause these issues?

4 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Clean out the idle air control valve and EGR valve, also test the TPS sensor-

Was this

answer

helpful?

Yes

No

+1

Tuesday, November 1st, 2011 AT 10:23 PM

JASON1969

MEMBER
8 POSTS

Popping sound?You sure this sound is not a backfire?

SPONSORED LINKS

Was this

answer

helpful?

Yes

No

Wednesday, November 2nd, 2011 AT 4:41 PM

ROBLOFLIN

MEMBER
2 POSTS

Turns out the issue was a combination of a bad Manifold Air Pressure Sensor and there is 25 degrees of slack in the timing chain that caused the distributor rotor to jump a tooth. Replaced MAP sensor, distributor cap and rotor. Engine ran fine for a day. Now the car is not getting any gas pressure. Checking the fuel pump and lines. I do have a question about the timing chain though. I understand the average lifespan for a timing chain is about 100k miles and there is 120k on the engine. How bad is 25 degrees of slack? Should I replace the timing chain?

Was this

answer

helpful?

Yes

No

Friday, November 4th, 2011 AT 5:34 PM

RASMATAZ