imloggedin

i just want a list of stuff that could make my car run rich. these ecu's are so odd i dont know what to check anymore. i did a search and read alot but theres just too much random info. if i had a list of what to check and howto check that would be great. so far ive replace the o2 sensor but not checked the voltage, ive took out all emissions, replaced all vac lines and gaskets on intake, checked for vac leaks, got a new tps and adjusted it, checked for error codes on ecu. i found out my ecu was bad so im getting a new one but i wanna know what else it might be. just want a list of things that could cause a ridiculous rich running condition.

thanks.

imloggedin

put in new ECU and does the same thing. no one has responded do this. is it that uncommon? my car runs pretty good, it backfires alot when you let off the throttle, and smells ridiculously rich. the idle adjust screw is all the way lean. have hesitation at 3800 pretty bad.

someone plz respond.

cptpain

iTrader: (1)

have you put in larger injectors?
what are your mods?

Phantomkid

i believ all our cars run rich. Did you take out the cat? Is this your t2 or na? as for checking voltage of the o2 sensor your gonna need an oscilloscop to get a real reading. Check codes check codes check codes. If you are in some kind of a fail safe mode your car is going to run rich. If your injectors are leaking you are going to run rich? if you fuel pressure regulator vacuum source fell off your gonna run rich. If you fuel pressure regulator has failed your gonna run rich. If your air filter is clogged your gonna run rich. Theres alot of possiblities. The 3800 hesistation has been covered millions of times....search and you will get answers.. Fix that first. then see if your still running rich. i think the most common cause is bad ecu grounds? not sure havnt run into the problem yet.

imloggedin

is the car in closed loop at idle? does it use the o2 at idle? air filter is not clogged. what fail safe mode do you speak of??? injectors yes maybe. this post isnt about the 3800, just mentioned it. i will ground the ecu to the bracket that the ecu mounts with via hailers recommendation in an old post.

this is on a GTU, im gonna check that the FPR is hooked up to the right nipple on the intake/tb.

Phantomkid

i think its in open loop till the temps warm up probably 5 minutes fter the car is started. It will use the o2 once it gets into closed loop. There a a few failsafe modes if the ECU is not getting a signal from a sensor example. AFM. But you would notice that one. http://www.teamfc3s.org/info/article...Signal%20Table that site will tell you how to check for codes. i understand the post isnt about the 3800 but what if the 3800 is part of the cause for the running rich.. you should check fuel pressure also. If the regualtor is faulty even if the vacuum source is good it may not let fuel back to the tank the pump will be pushing a dead head pressure probably about 60 psi, that would probably stall out the engine but if its not letting enough back you may have above normal fuel pressure.

imloggedin

ok well heres how the FPR is hooked up. i dont remember wich nipples are vacuum and wich are filtered air but im pretty sure i tested it before i hooked it up. just to make sure..



pretty sure thats right. anyway, i took the air filter off and it smells like the richness calmed down. so i guess ill get a new air filter. i will redo my grounds when i get my meter back from work. ill get a fuel pressure gauge soon and test the fuel pressure if the grounds dont fix it.

thanks guys, ill report back. finally some help!

Black91n/a

I've seen a dyno plot of a nearly stock '91 'vert and it went to about 10:1 AFR at higher RPM's. They all run rich, about the only way to "fix" it is to get some form of computer to control the mixture (anything from an SAFC to a full standalone).

imloggedin

every NA ive been in has wreaked of gas i guess. but it just seems more than it should. we'll see what happens when i reground and whatnot.

j0rd4n

ecu runs it rich for safety. no way to lean it out unless you go standalone or piggyback

pfsantos

iTrader: (1)

Yes, OP, don't worry so much about it, they all run rich with stock computers. You also mentioned you removed a lot of emmissions crap. That explains a lot of it, including the backfiring and all.

You could mess around with an adjustable FPR, but that could mess up the ratios under certain conditions. I know it's not turbo, but I'd rather have mine running rich.

HAILERS

At idle, pull the line off the FPR and make sure it's pulling a vacuum. Only takes a minute.

The car only goes into closed loop when driving. Never at idle. That's driving at a steady pace that it's in closed loop.

The 86-88 have a variable resistor near the right strut tower that can lean the mixture at IDLE and IDLE only. Turn it clockwise and it gets rich, turn counter clockwise and it gets leaner. See Fuel section of the fsm.

imloggedin

ive adjusted everything for idle including the variable resistor. it leaned out all the way, thats where it runs the best. thats another reason why i thought something was wrong. ill try the FPR thing and do the grounds once i get my dmm back. hailers you think i should cut all the ground wires the FSM specifies on the harness and ground them to the ecu bracket? anything else i should do about that? ground both ends when i cut the wire?

j0rd4n

wait, do you still think there's a problem? from what i gather from everyone else, your car is actually fine, because *everyone's* stock ecu makes the car run rich, and you can't adjust that mixture except when idling. you could get an adjustable fpr, yea, but that just sounds like you could run into a dangerous situation if it starts cutting fuel too much (ie: i wouldn't think it's what you'd wanna do with a stock computer) :/ if you really wanna lean it out correctly, shouldn't you be piggybacking w/safc or going standalone?

imloggedin

there is a hesitation problem still. thats why i wanna do the grounding. i still think it runs a bit too rich and the fact i have to turn the idle adjust screw all the way lean makes me think so. if it was meant to run that rich then the idle adjust screw would have been different. it is tested within spec too.

imloggedin

i didnt mention that emissions are removed and i have once had trouble hot starting witch never happened before i removed the emissions, and im guessing thats because of the stupid pulse width startup junk that was explained by hailers in a previous post also. ill install a switch if it keeps giving me trouble. cold starting is perfect, compression is great. overall the car is in excellent condition.

imloggedin

hey hailers could you tell me about the grounding that i asked a few posts up?

HAILERS

There is something wrong. I say that because you say the variable resistor is all the way LEAN and it runs better. ON all the cars I've seen, the car idles better at a ratio of 13/1, which means I make the variable resistor go more to the rich side from center.

Never CUT the wires at the ECU and reground them. You splice into them where they all meet. They all meet at a point about six inches from the plugs. You have to unwrap the harness some to see where they meet. Then you solder a NEW wire to where they all meet and ground the other end of the wire to a stud on the ECU bracket. I don't think this is your problem.

YOu never mention HOW you know it's rich. But if you put the variable resistor to all the way lean and it runs........it's running rich for some reason.

I sort of wish you had a meter to help out or had a wideband meter. It's hard to figure things out over a internet. And I have no want to work on someone elses car.

Remove your afm. I mean take the whole sheebang out and unbolt the afm from the asseybly. Then look carefully at the black plastic cover that covers the guts. Does it look as if someone has pried this cover off and disturbed the RTV around the edges of the black plastic cover?????

If you have a meter, idle the car hot, and go to the alternators post and measure the voltage output on the large output terminal. Should be 14vdc give/take a smidge with no lights on etc. Idle being 750-900 rpm max.

HAILERS

RX don't go into closed loop at idle, if I didn't mention that earlier. O2 is not the problem.

You have two afm now??????? As in a spare?

imloggedin

i didnt know all the grounds met, very good to know.

i thought it was running rich, cause the variable resistor and when its idle'ing it smells soooooo strong. it hesitates bad at 3800 and backfires alot.

ill check the voltage but i dont understand how that would make it go rich?

..also i dont have an extra afm but ill check the spec per fsm on it, and if the TII afm and the gtu are the same i can take it off my TII and try it.

thanks hailers!

arghx

iTrader: (3)

Check the thermosensor. The FSM has a testing procedure in the fuel and emissions section i believe.

imloggedin

tonight i got home and..

grounded the ground wires to the ecu bracket. just like hailers said. soldered a wire to where they all meet about 6 inches up the harness. worked great, hesitation problem is gone.

i checked the AFM, its all to spec. just for the heck of it i put on my TII AFM, it idled like crap with that on so i put the NA one back on and idled fine but still crazy rich.

when i drive it, it still backfires almost every time i let off the gas somewhat quick. just a tiny backfire.

i cant think of anything else that could make it run so rich at idle so i took the fuel injectors out cause maybe they are leaky. im gonna get them sent off to get cleaned and tested, only thing else i can think of is a bad FPR.

HAILERS

I mentioned the AFM because..............it may read to the checkout in the Fuel section of the manual, but that really isn't a very good check if someone has been messing with it.

If the black cover is removed you see a wheel under spring tension. The wheel has cogs on it's outer rim to hold the spring tension at a set tension. There's a STOP device that sits in the cogs. If you pry the STOP device away from the cogs, the spring tension will be relieved and the wheel will spin counter clockwise and AH SHUCKS!, all the tension on the vane is not there anymore, and now you have a piece of junk. Unless you marked the cogged wheel to a stationary place on the afm, you won't be able to get the afm's vane back to the tension required. Your lost in space if you didn't identify where the wheel was in relation to some stationary spot on the afm.

So, if Johnny Dumb Nuts got hold of that afm and *messed* with it, only God knows how close to being right/wrong the spring setting is. There is a way to overcome a messed up afm if you have a wideband. You can monitor the afr at different rpms and keep adjusting the tension till the afr's look right at idle and hard throttle.

So if you look at the plastic cover and notice that someone has cut the RTV around the black plastic covers edge...........ain't a good sign.

You almost need a wideband to tell if the thing is really running rich at idle imho. Almost.

A lot of the above will only make sense if you remove the black cover off the afm and look carefully at the wheel/spring/spring stop.

imloggedin

i dont have an a/f meter but i think because the variable resistor is how it is, and if its turned any richer it chokes, and if you smelled it you might think differently.

when i was testing the door on the afm the test just says fully open or fully closed, it was within spec there but it jumped all over when u move the door. theres no method to it on either of my TII or NA afms. the resistance was all over the place as u move the door. the AFM did look like its been opened. it looked like it had fresh silicon holding the black cap on it.

i guess if the injectors dont fix it then i will replace the afm. it never hurts to get your injectors cleaned i guess.