1985 3.8 questions

[tbirdscott]

I just picked this car up on thursday and am trying to get it roadworthy, I need something to drive for the next couple weeks till I get my regular DD going again.

Recently been replaced: Water pump, plugs, wires, cap, rotor, timing chain, fuel filter. Not sure wether it was done at a shop or a "handyman" (i'm leaning towards the latter as he took it fir a test drive with the hood unlatched.... i'll be pounding dents out of the cowl later..)

The bad: Exhaust rotted off after cat (fixin today) battery cables corroded to hell (replaced) battery toasted (replaced) 245K k/m, engine is a big ball of grease from leaking v/c.

When its started up cold it will idle at 1500 rpm but occasionally it will fall to about 500, catch itself, then keep idling at 1500 rpm, when you rev it up it will rev fine but when you let off the gas it will almost stall (like someones cut spark) then once again catch itself and keep idling fine.


I'm getting codes 12, 23, 31... I think, was reading with my voltmeter.

So the TPS and EGR are out of whack but wtf does code 12 mean?
Also noticed the antifreze is a bit low which means hg's are probabally on there way out.

I'll try cleaning the egr valve and if I can find the specs adjust the tps.

Anything else I should look at?

 

[v8only]

two websites that may be better for this.

www.foureyedpride.com

www.3.8mustang.com

 

[tbirdscott]

Yeah i've been to 3.8 but they only seem to deal with the newer 3.8's there and all my searches returned info regarding them..

I just signed up at FEP, just gotta wait for them to let me in, thanks

 

[TheRedBlur]

could code 12 be your MAF? or is it speed density?
maybe your ignition timing is off, I highly doubt the timing chain would be off considering being one tooth off is usually enough to marry pistons w/ valves. another thing, 5-sp or auto?

 

[tbirdscott]

Its an auto, and the woman mentioned something about the timing too, gotta find my timing light, havnt sen it in quite a while here.

 

[TheRedBlur]

Its an auto, and the woman mentioned something about the timing too, gotta find my timing light, havnt sen it in quite a while here.

yarr, I'd get a new balancer for good measure, that thing is probably like 20 years old and has likely shifted, timing could vary. Now, I'm not so sure how your harness works, but it should have a SpOUT connector (spark output) if it electronically adjusts advance curve. That SpOUT connecter needs to be disconnected, otherwise the computer will adjust the timing while you twist the distributor, prohibiting you from getting the real base timing.

 

[tbirdscott]

BUMP

Any other suggestions? I took it for another drive (30km) and either i'm getting used to it or its getting better, probabally just adapting

And yeah, I know I gotta lose the hubcaps

 

[tbirdscott]

*bump*

Anyone know what the tps voltage should be? I went to three places today looking for a manual and everyones out.

 

[JChalfan]

*bump*

Anyone know what the tps voltage should be? I went to three places today looking for a manual and everyones out.

I don't know for the 3.8 specifically, but for a 5.0 it should be just under 1 volt, like .98. I think anything between .90 and 1 is ok. It's probably the same for the 3.8, but maybe someone here knows for sure.

Jeff

 

[tbirdscott]

Thanks, i figured as much but I just put a new TPS in, the old one was reading 1.9@750rpm as the trottle went to WOT (engine off, ignition on) it got up ti 3.4 then dropped down to 1.3 for the last 1/4 of movement, it now doesnt die on you when you floor it but its still sucked down, gonna check the cats as soon as it cools down and delete them if theyre still there, hopefully that'll clear things up a bit.

Scott

 

[tbirdscott]

Cats were already gone, its very slow to rev in park or neutral, any ideas on what else could cause this?

 

[jslatts]

tbirdscott, i own a 1986 Mustang 3.8L and i have the same rev. problem, when i start it runs at about 1500 then drops down to about 500

 

[TheRedBlur]

do the timing man. read the codes too. also, when you put in the new tps, you have to set it and the throttle stop screw.

 

[tbirdscott]

when i start it runs at about 1500 then drops down to about 500

That sounds about normal, what mine was doing was idling at 1500, dropping to 500 rpm like someone just turned it off then going back up to 1500rmp then repeating itself every few seconds-minute

do the timing man. read the codes too. also, when you put in the new tps, you have to set it and the throttle stop screw.

Will do, the timing should be at 10 ̊ correct? I just tossed the tps on and left it since theres only about .3v of adjustment without ovaling out the holes and I had to be somewhere but i'll re check that, whats involved in setting the throttle stop screw? is it just to a certain RPM?

Also any tips on how and what your supposed to adjust the ISC to?

Thanks
Scott

 

[TheRedBlur]

well, pull the stop scew untill the plate is soo closed that it dies, then do about a full turn to open it just a bit. The proper way to set the trhottle plate is to close it all the way and disconnect the idle control motor. When you reach a point to where it has enough air to idle, then you're good. then calibrate the tps, it's normal to oval out the holes on the tps for better adjustment. If your engine ignites on proper timing, then you should be easy street on the throttle body/tps/idle motor. can you dig?

anyways try this
start ignition timing at 10 degrees (SpOUT disconnected)
adjust throttle plate (IAC motor disconnected)
Test TPS voltage
if tps is in within range (not sure which range and domain the 3.8 uses) then reconnect everything and let the computer cycle, meaning, let the ****er idle and run for about a gas tank.

Once she begins to behave like a mustang, bump the timing up to 12 degrees and see if the 3.8 likes that. Also, consider the possibility that your airflow meter could be grimey and inacurate. clean out your EGR as well. that device is known for regulating airflow too, actually, it recycles exhaust gasses into the engine, by nature, spent engine gasses are inert, meaning that recycling them makes the fuel behave like it has a higher octane rating. It reduces ping.

God I love engines, sorry for my drunken rambnling.

 

[stykthyn]

sweet car, ditch the rims

 

[tbirdscott]

anyways try this
start ignition timing at 10 degrees (SpOUT disconnected)

Also, consider the possibility that your airflow meter could be grimey and inacurate. clean out your EGR as well.

To see the timing marks do you gotta lay under the car? looks like the pointer points off to the side, if thats the case looks lik its a beotch to adjust by yourself.

I believe the tps should ve around .80-.90 correct me if i'm wrong

Where is the airflow meter located? is it under the throttle body?

The egr looks brand new, shiny and silver, maybe i'll pull it off anyway just to check its not stuck.

Thanks for the help RedBlur

 

[TheRedBlur]

Well, you adjust the timing by twisting the distributor, but you use the timing marks as reference, point the timing light at it from above.

no problem scott!

I think that the tps should be higher, in the .9's

The airflow meter is between the throttle body and the air filter, it reads how much air goes into the engine at any given time, the computer takes this reference and puts a certain amount of fuel/timing into the motor. I forget what type of cleaner you use on it, most people say don't clean it at all, but I think electrical parts cleaner should work, since it doesn't leave residues.

 

[tbirdscott]

Well, you adjust the timing by twisting the distributor, but you use the timing marks as reference, point the timing light at it from above.

Ok, the reason I asked is because the only pointer I noticed on the engine was pointing off to the passenger side.

The airflow meter is between the throttle body and the air filter,

umm yeah not on this thing, you must be thinking of a different type of injection.

I forget what type of cleaner you use on it, most people say don't clean it at all, but I think electrical parts cleaner should work, since it doesn't leave residues.

I used WD-40 to clean the MAF flapper and IAT on my sprint against what everyone said and I havnt had a problem, just sprayed it on a rag and wiped it down.

 

[tbirdscott]

sweet car, ditch the rims

Yeah the hubcaps are teh suck but $4.50 for a can of tremclad and they are presentable, I have since sprayed the wheels and whitewalls with flat black.