Stangdai

I have a 1990 Mustang 5.0L, the problem is that fuel consumption is up the roof, about 8-10 mpg. Rather rough idle and lack of power (the engine will sounds as though its producing power but no)...

I changed fuel filter, spark plugs, distributor cap and rotor, air filter, pcv valve and breather element, MAF(cleaned),also cleaned the injectors (they REALLY needed it),...

Most of these thing made a diffrence most notably the spark plugs and injector cleaning... However the change was only temporary after about 1-2 hours of crusing everything was back to normal

So there has to be some sensor that's malfunctioning... ? There are no error codes from the EEC-IV...

So currently the oxygen sensors are the next item on my list of possible problems, any thought?

Thanks!

PRO50SC

Any vacuum leaks and what's the timing set at?

Joel5.0

As PRO50SC said......check your timing and for possible vacuum leaks. Although replacing O2 sensors after 60k miles is considered maintenance, they might not necessarily be the cause. If they were off their op range, you would have failure codes showing up (or any other sensor for that matter)....after checking timing and for vacuum leaks, you might want to run a DIY KOER self-test and make sure the O2's are lean-rich switching OK (the system checks for it)........

Stangdai

Thanks guys I'll check out your suggestions!

Stangdai

I checked the timing, it's at about 12 that's an OK number... I'll try to bump it abit some other day when the car is running fine...

Regarding vacuum leaks I have found two that look like they were replaced badly(see pics)... If I pull them out while the engine is running nothing happens, it continues to idle badly... any ideas?

[IMG]local://upfiles/30450/8C361ADC963C4346B67959E6953B57CE.jpg[/IMG]

[IMG]local://upfiles/30450/848A63C53AAC4BC69B2CD9A0ACDBFAC3.jpg[/IMG]

Joel5.0

Those are the thermactor valve and EGR valve vacuum lines....you might want to check that the vauum lines are routed correctly.....use this vacuum diagram.....and run the self-tests, they will provide information to help in the id process of the causes.....

Stangdai

Wow thanks, I was just looking for a diagram of the vacuum lines, thank you!

Stangdai

Everything seems routed fine... I'm having problem with the tests, the initial Engine Off tests work perfectly just gives me 67 twice and then 11 twice...

When I turn on the engine I don't get the four flashes indicating 8 Cylinders, it just gives me a rougher idle and nothing, I waited 5-10 minutes... nothing but rougher idle...

any ideas?

Thanks!

Stangdai

OK I'm just stupid, I dono why it didn't initiate the KOER test yesterday. Today it works fine... However I'm not getting any codes, just 11 saying everythings fine... I did get 12 at first but after cleaning the IAB it worked fine...

any ideas? I'm really sick of it now, just wanna go have my vacation... seems like it'll be w/o the mustang

7upedition

heres a diagram of the vacuum system: http://www.veryuseful.com/mustang/te...uumDiagram.jpg

hope it helps