Anyone have experience working on foxbody 5.0 fuel injected Mustangs?

[Damon23]

I'm chasing something that I don't know if should really worry about. I've asked questions on a couple Mustang boards but not getting any help. I have a '89 with a automatic. It has zero modifications done to it. Earlier I was chasing a cold start issue where it ran like crap cold but shut it down and try again and it was like new. I cleaned the IAC and the throttle body and installed a new oxygen sensor in the passenger bank and that is all good. Another code popped up 94 and 44 which are telling me the air management system is inoperative which means the smog pump. I pulled the pump out and it is very noisy but when it spins it puts out air. There are two valves in the loop, one that diverts air to the atmosphere and then to the second valve which dumps the air to the heads or to the cats. I have all of that apart. I've made sure that the valves are functioning by giving it my own vacuum so I guess that would lead me to believe that the car is not giving vacuum to the valves in order for the system to function? Am I thinking correctly here? I need to swap out the pump cause it is dreadfully noisy but was thinking of coming up with a way to bypass the valves and just have it pump air all the time. Would that be a bad thing to do?

[Beagle]

Check the crossover pipe in the back that goes to both heads? It's probably carboned up either in the pipe or in the passage in the heads. The codes are for both sides so my thought would be the air is not getting to the heads or the tubing down to the cats is wasted. Permanently diverting it one way or another (or removing it) is likely going to throw a code because it is checking for diluted exhaust when it's diverted to the heads / cats by expecting more 02 at the 02 sensor. You wind up having to disable with something like a Tweecer or living with the codes. Did it have any other codes besides the 94/44 ?

[Beagle]

http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

I think if the solenoids aren't switching on / off the codes will get thrown too.

[Damon23]

Thanks. No other codes. I had a 42 before that. Replaced the O2 then these popped up. Frustrating. It has not thrown a CEL for the 94 and 44 yet anyway. Going to test the regulators today but if all that checks out then I'm just not going to worry about it and pass the car on.

[tedly]

No idea if this is the problem or not, but it's fairly simple and easy so worth checking out.

The PCV valve is on the back of the intake, right? Well there's a metal mesh filter underneath it (in the intake) that hardly anyone checks and it's real common for it to get clogged up. Use a hook pick to pull it out, bend the cage open to get the filter out, unroll the filter element, and clean it with brake cleaner. When it's de-scuzzed, cut about 1 1/2" off the end with tin snips, roll it back up, put it back in the cage, and pop it back into place.

Again, I have no idea if this is the problem, but it will only cost about 15 minutes of time and half a buck in brake cleaner to find out.

[Damon23]

Oh wow, I was looking for the darn thing. Great picture, I will get on that this afternoon. Why in the world did they put a change out part like a PCV in the back like that? I guess the same reason they used two different sensors for engine temp. Thanks again guys.

Edit: So far all I've been able to get out is the top of the screen stuff. That thing is buried in there. I'm going to run over to harbor freight and see if they have a long skinny pair of needle nose pliers.

[Barry Donovan]

I see there is a vacuum reservoir aiding in an after shutdown use, or cold start before vacuum.
goofy as the 80s, that stuff.

coolant temp reading and an ecm that understands, a map sensor.. alot of thing to upgrade to. The mustang ought to be a very easy..respecting that original stuff gets tiresome.

[Damon23]

Check this out. How much you wanna bet that passage in the intake is plugged up? I poked around with a pick and didn't get anything out. We'll see.

[tedly]

That's it, and believe it or not that's in fairly typical shape. Nobody ever bothers to clean them and it can lead to all kinds of minor driveability issues. Generally once that is cleaned up you'll see a little difference, especially if you already cleaned the MAF and IAC. Spread the cage from the top just far enough to get the element out and it should unroll fairly easily.

When you cleaned the IAC, how did you do it? Best way I've found was to spray carb cleaner into the opening and let it soak for a bit, dump it out, and move the plunger back and forth with needlenose pliers. Repeat until the plunger moves freely and the cleaner that's dumped out is relatively clear.

It's been a long time, but if I remember right there was a connection between that screen getting clogged and the IAC getting gummed up, as well as (I think) the throttle body.Something like the circulation was forced into a different route that wasn't filtered and you'd get the oil and crap that was normally caught by that screen getting piped into the manifold right by the throttle body/IAC? Don't remember for sure, but pull off the throttle body and and look at the vacuum/air lines around it. If there is a trail from one of them, then this was probably the culprit. I'd have to actually poke around in a 5.0's engine bay to work my way through it again, so that's the best I can do for you right now.

Also don't remember if Seafoam will help clear the gunk out, but it probably wouldn't hurt.

[tedly]

Oh, for future reference, the easiest way to get those screens out is to snag one of those 3 bent tabs on the top with a hook pick and wiggle till it's free.

Check back in and let me know if this helped. If not I'll wrack my brain and see what else I can think of.

[tedly]

Also, why the hell are you even bothering to put the smog pump back on??? Chunk it and cap off the lines going to the exhaust. Only difference you'll notice is the CEL comes on and throws a code, but you can have that taken care of fairly easily. I think the only other thing you'll need is a shorter serpentine belt. I guess if you're wanting to keep it stock then that's one thing, but tossing those smog pumps was the first thing everyone did to get better performance.

[Huskinhano]

Reminds me of my 04, 4.2 I6 Trailblazer. It was the day of our house closing when we sold our house. Car full of crap along with a two axle trailer from U haul. Car was running fine but the battery went dead. Bought a new battery and everything was fine. 150 miles later at night dead tired it will not idle when stopped at stop signs or red lights. It keeps stalling out. Next day google the problem. Of all things the throttle body needs to be cleaned. Turns out it's a common problem on them when you change the battery. What happens is the throttle body gets sooted up put the ECU learns this and makes corrections. When you disconnect the old battery the ECU forgets what it learned and goes back to default. Clean the TB and the ECU re-learns.

[Damon23]

Got everything buttoned up and it runs better. So far so good with codes but I have not fully jumped on it yet and have driven no more than about 5 miles. Going to get it out today and see if a CEL comes on but it runs smooth and strong so I'm calling it done. I used a pair of 11in angled needle nose to pull it out. And as far as the IAC I did just that, carb cleaner and moved the plunger. I fully cleaned the throttle body and replaced the gaskets as well. Hopefully that is all. Thanks for the info.

[tedly]

No problem, glad I could help. From the symptoms you were describing, that should fix it. If you have any more issues, yell and maybe I can help out again.