Running LEAN-What common suspects?

[monte87]

hey Guys-

Car was runnign LEAN!!!! On the A/F ratio monitor., What causes mass air cars to run LEAN??? The usual suspects????.. Remember-I had complete F/P throughout the entire spisode. When it starts its ****, spntaneously, comes and goes-Its in a LEAN condition. Shakes, stumbels, wants to stall, it drops 500rpms, like running on 4 cylinders. Then miraculously- It clears up and the A/F ratio goes back to normal-then everything is fine and normal. Until the next time... Please help,
Thanks Ant

 

[monte87]

P.S. Replaced, IAC, TFI, COIL, plus and wires, TPS, WTF!!!!!!!

 

[HISSIN50]

A bad PIP can do what you're seeing.

 

[jrichker]

What type of A/F gauge are you using? The ones that use the stock O2 sensors are useless except to make a pretty light display.

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Equus - Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

 

[monte87]

Thanks Hissin for the 411, and Jrickter, i have been reading,m and re-reading your sticky for days now. Thanks for the 411. I have to get myself a scanner, thats the prob. I have the bull**** Autometer A/F, i know its a lightshow, Just took notice-At the time the cars acts up, The gauge is pegged on LEAN and will not do the rainbow dance, at that point- The symptoms are as follws-
The car goes from idling and acting normal to, car shakes, stumbles and wants to stall, But doesnt-it maintains a real crappy idle of 500 from about 1000rpms. It seems liek the car is running on 4 cylinders. The exhaust gets real queit and low and slow, from the normal cammed up style, loud, fats and rumpity. very weird.
Its seems to happen at start up, then when depressing the gas-it normalizes out and when on the highway-runs like a champ, idles good to-when coming down from highway speeds, doesnt die, BUT-if you shut it off and restart it after a few minutes-its possessed again. same story. Throughout this entire dilemma, it maintains FUEL PRESSURE....
Now for the visual, after watching that crappy A/F do the rainbow dance, when this happens-It gets pegged on LEAN and the first red LED, and will not move, even when depressing the gas @ idle, it will clear up after driving-Once it clears up-the rainbow show goes back to normal.
Any suggestions on what sensors can cause this behhavior, besides the PIP sensor???

Thanks for any and all rpelies and help.
Ciao Anthony

 

[mineralgsvt]

A bad PIP can do what you're seeing.

PIP = ?

 

[monte87]

DISTRIBUTOR IGNITION PICK-UP.
SEE- Manufacturer Info

 

[Gearbanger 101]

I would also check for intake leaks after the MAF meter. A bad seal between the meter and the intake hose, or a plenum/throttle body gasket sucking air can throw things into array.

 

[mineralgsvt]

DISTRIBUTOR IGNITION PICK-UP.
SEE- Manufacturer Info

Cool, thanks. Never heard of one going bad.

 

[monte87]

Ok-Thanks gearbanger,
Could a bad MAF cause these symptoms?
i am not getting a check engine light at all.

Thanks Ant

 

[Gearbanger 101]

Ok-Thanks gearbanger,
Could a bad MAF cause these symptoms?
i am not getting a check engine light at all.

Thanks Ant

A bad meter could cause it, yes. The elements do sometimes go bad with contamination unfortunatley

 

[monte87]

Thanks bud, gotta check into this...
Later Ant

P.S. how about bad 02's??? would they cause the symptoms or not? being the A/F ratio gauges is pegged in lean mode, i thought-myabe one was bugging out erratically-spontanouesly.

Hit me back, thank Ant

 

[Gearbanger 101]

Bad O2's should set off a different code. What kind of mileage is on them?

 

[monte87]

about 114,00 original miles. I never chnaged them ya htink-they may cause this crap?

 

[Gearbanger 101]

Can't say for sure, but for what it costs to replace them, it couldn't hurt to instal a set of new ones into the mix.

 

[monte87]

Yeah, I hear ya.... Thanks 4 ur help bud.
Later Ant

 

[jrichker]

Go back and dump the codes. Codes may be present without the Check Engine Light being on. Throwing parts at an undiagnosed problem just makes you poorer and frustrated.

 

[strtrcr50]

A bad meter could cause it, yes. The elements do sometimes go bad with contamination unfortunatley

Or if you have a K&N filter which is oiled.. Oil hits the MAF and you have problems.

Go back and dump the codes. Codes may be present without the Check Engine Light being on. Throwing parts at an undiagnosed problem just makes you poorer and frustrated.

Exactly.

 

[monte87]

Just wanted some thoughts on the main culrpits that would cause a lean condition, Obviously it isnt a fuel related problem.. Air + Fuel = Combustion. So if we eliminate fule from the equation, we are down to AIR. Sometimes withour cars, they usually have the same prb's, Just thought i would get some feedback on some other guys, probs' regarding these issues. Its obvious, Im gonn ahave to dump the codes, in the time being-Just wanted to brainstorm.

 

[monte87]

Swapped a new MAF sensor, nothing, same ****.... swappd in 2 new 02's sensors-got a little better, But still get the SURGE that really close to stalling out car. Idle is adjusted to 950-1000rpm for cam car, Dont understand it. it runs fine once going, Its just when coming to a stop-thats when the problems happen, Anyone???
P.S. I visually inspected the PIP sensor and lower dizzy, no arcing or marks of any kind.......