so i originally i had terribly leaky valve cover gaskets on my 90 f150 i pulled off the upper intake to get at the passenger side bank (god bless whatever engineer designed the 5.0 upper manifold) anyways needless to say i replaced both valve cover gaskets with some felpros from the local auto store i also picked up a felpro manifold gasket set to replaced the upper one. also picked up a new EGR gasket for good measure. Well after putting everything back together i had a terrible intake leak and it was running like ***** with a huge sucking noise. so i pulled off the upper again and siliconed the gasket. still same problem. went back to auto store and bought new felpro gasket set and was a bit more liberal in my use of silicone. so i fire up after waiting a 24hr period to let the silicone dry i dont hear anymore vacuum leaks however whenever its at low idle it sounds like its about to die. Also it will die when sitting at a stop sign but fires right back up again i sprayed carb cleaner around the base of the manifold and it doesnt bog down or anthing i also replaced plugs an wires and the same time when i had the upper manifold off. All vacuum lines are plugged in nothing isnt where it was when i started the repair. needless to say im outta ideas.. HELP?

 

so its idling low? does it bog when your driving? any cel? have codes checked? unhook the vacuum line to the egr valve while its idling and see if it changes. what brand plugs and wires did you use? what rpm does it idle at?

 

well it will idle at about 550-1000 (thats what it sounds like no tach.. its in the mail from summit) then it will just run really rough and die it doent really bog awhole lot when driving just it sounds like its missing somehow.. i have taylor wires with acdelco plugs nothing comes up far as codes wise.. however when i remove the vacuum line from the EGR nothing happens...

 

i know absolutely nothing about those wires. did you replace the distributor cap and rotor? at night i would open the hood and look at the wires in the dark. if you see the wires or anything arcing then check it out. or you could spray soapy water on the wires, cap and rotor and look for arcing. did you hook the wires up in the right locations? you could also throw a bottle of techron fuel system cleaner in the fuel tank to see if it helps. could also be bad gas.

 

The original vacuum lines can become very brittle over time, and you may not see the cracks if the split loom covering is still on them. Don't spray flammables on a running engine - use a 3' section of garden hose as a stethoscope, or buy a mechanic's steth. (~$12 from Snap-On) & remove the hard probe. Listen ALL over the engine at idle; any leaks (exh. or vac.) will be obvious & easy to pinpoint. Also check under the dash where the brake pushrod goes thru the firewall, and around the cruise servo.

Click my black Bronco in my sig, scroll to the bottom of the list, & read all the TSBs that apply to your truck. There are several about the IAC, so check the captions, too.

 

Double check the firing order 1-5-4-2-6-3-7-8 counterclockwise on the distributor.

 

thanks for all the advice so far i removed all the looms over the vacuum lines and found one broken (a yellow one on the passanger side ((guessing)) going to something to do with the smog pump) i used some wire shrinkrap for a temporally fix to see if thats the problem. even though the line is fully sealed it still does the same thing.. i know its not gas its half tank 93 oct premium and the firing oder isnt off cause it will run and idle at around norm rpm but then it just chokes and dies i also heard from a buddy about the garden hose trick and i tried it i just cant seem to locate anything..

 

Have you checked to see that the IAC is plugged in correctly? I'd also check voltage there to make sure it is getting signal. You might also consider cleaning it as it is prone to carbon. There is also a port just inside the upper manifold just in back of the throttle body, make sure this port is clean and not carboned up. This port allows for air to the other side of the manifold at idle.

 

What's your fuel pressure? If this problem appeared immediately after changing the plug wires, then you could have them routed wrong. Study this & then double-check yours:


Labnerd
The IAC only affects idle, and that's where his engine runs well.

 

Say what, Steve83?

 

I guess I picked the wrong week to spray-paint my eyeballs.



Dunno how I missed that...

 

So that's the problem I have all of the time! And here I thought it was my dyslexia. You might also have dyslexia. Folks with IQs over 135 seem to have more of it than others. Have you ever been tested for IQ or dyslexia? Anyway, as my stepdad used to say "only the folks doing something are prone to make mistakes. Folks that don't do anything never make mistakes". I screw up constantly. I guess I'll go lock up the spray paint.

 

Yes, I've been tested for both. So far, I haven't caught either one!



Seriously, though: back when I was in the GPGC, it was ~130-150, but that was MANY years ago, so I'm sure it's much lower now. But I've never had dyslexia severe enough to diagnose - I'm a very good spleler.

 

haha speleing has been an issue im sure most of us are terriable with sorry i havent gotten back on here been busy so i replaced the IAC and it no longer dies when at a light or stopsign however it still does run at like 1000-1350 rpm when at idle. It trys to go down to back around 500 and will run at that rpm for a short while but just picks back up after about 5-10 secs no idea whats wrong with it yes i used a gasket on the iac and a new one on the throttle body itself any one got any other ideas?