[1992lx5.0]

im having some idle fluctuation, does anyone have suggestions on what problem might be. it has a bbk cold air intake and bbk 70mm throttle body,it has aftermarket injectors i think they might be 24lb. bbk shorty headers w/ flowmaster exhaust. it has around 93,500 miles on it. overall it runs great, except for the idle. any help would be great.
thanks, Carl

[gsalisbury]

Not that it is the problem, I had something similiar and began playing with timing for really no good reason. Found that my car '89 with 190,000 and bone stock has a little play in the timing chain. Timed the car by ear and it runs better at what comes out to be 16 degrees (which I am sure it is not) and my idle surge resolved itself along with getting a lot more bottom end power in the process.

[1992lx5.0]

sounds like a good place to start. im prettynew to wrenching on cars. but i do want to learn all i can. so this sounds like a good place to get me rollin, thanks!

[GTS 5.7]

You mentioned injectors-is the MAF calibrated for them? Since you said "I think" they are 24#,I assume you bought the car this way,try looking at the MAF electronics,it should say on there somewhere.Also try cleaning the MAF sensor..and lots of good info here...


Mustang Basic Maintenance and Technical Articles

[stangerlx]

check the O2 sensor

[1992lx5.0]

yes everything that is done to it was done before i had bought it. ive only had it for about 2 weeks

[crazyjag]

What is the computer telling you for trouble codes? Have you noticed black smoke out of the back when you floor it? Is your injectors light blue in color? If they are then they are 24lb injectors, you need to make sure that your 73mm MAF is calibrated for 24lb injectors. Also take off you Idle Air Controller (IAC), the sensor on the front of the throttle body facing the radiator, mounted at a 45 degree angle. Take the two pieces that make it up apart and use some Carb Cleaner in the mechanical section to clean the carbon out.

[towman77]

I have a 1990 5.0 i had the idle problem found it to be the mass air flow sensor.

[rickyracer]

Clean the Mass air sensor.
Replace the Idle control valve.

[Grunter]

Also check this - as i had the same problem once.

This is the inside of your throttle position sensor. Sometimes the factory grease gets old & sticky..make sure the blue part turns freely and returns to rest afterwards.

Check your voltage before removal - set it up so it's as close as can be to about 0.98 volts.

While your at it - check the other end for corrosion also maybe add a bit of dielectric grease at the connector. At the throttle position sensor you can use a silicone lubricant or very light grease(nothing too sticky)

Or buy a new one(if you want to be safe) I siliconed mine - it worked perfect afterwards - so then I bought a new TPS to get it over with!

You must realise that if the grease is dry or the TPS is sticky the seals probably got loose and let the oil out of the grease or even some water in - I didn't want to chance it - so once I found the problem I splurged for the TPS. Hope this helps you..

Also, if you clean your Mass Air use a spray electric contact cleaner.
Mass Air are vulnerable after using K&N filters as the engine sucks up the oil under high air flow conditions(WOT) and contaminates itself(small thermal spring inside).

Best Regards,

[Quadrajet]

MAF sensor, TPS voltage, or a vacuum leak are your best bet. I just had a similar problem with my 86. Someone had put a BBK intake kit on mine as well. I would check the Throttle position sensor voltage first only because it's related to the last work done to it. However the voltages change through the years.. Mine was .9 - 1.1 volts but later models were a lower voltage depending on the year. I would verify the correct voltage first before doing anything. Also on another note I had to modify my TPS to get the correct voltage. This is not for the faint hearted. At any rate the car has more than likely set a few engine codes. Those will go a long way in helping you diagnose it.

[mlgproclyde]

i just cleaned my idle air control valve and my throttle body and now my car is running at 1700 rpm. i know you can set the tps but i dont exactly remeber how,so if anyone does know how i would greatly appreciate it