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View Full Version : 90 sc running pig rich need help



Ninja38
05-17-2017, 07:34 PM
I have a 1990 3.8l sc and it is running pig rich at idle and almost seems lean at wot. Had a breakout box and checked the mass airflow was reading a bit hight, replaced, no change. Coolant temp sensor for computer readings were ok, replaced anyways, no change. I scoped the cam and crank sigs and have a nice square wave on both. Changed plugs because by now they were black as sin still no help. Changed coil pack even though i had good looking spark still no help. Have put 12 gals of 93 octane in it and it is still running rich. Also checked computer power grounds ect all checked out fine. Fuel pressure is dead on. Fuel pressure regulator is not leaking and has vac at idle. I know alot of reasons for a car to run lean but not many more for a rich condition in open loop and closed loop. Any advice would be verry helpfull.

XR7 Dave
05-17-2017, 10:36 PM
You didn't mention 02 sensor waveform. That would have been my first check.

Ninja38
05-18-2017, 07:37 AM
In open loop o2 has no effect

XR7 Dave
05-18-2017, 02:14 PM
In open loop o2 has no effect

Not exactly true. If it learns bad data in closed loop, it will be applied to open loop as well. You can verify this by disconnecting the battery to clear memory.

Ninja38
05-19-2017, 05:14 PM
Have all ready done a battery reset, still no change. Will a bad computer do this? Also does anyone know what the octane adjust plug is for?

davec73
05-19-2017, 07:20 PM
O2s are probably shot anyway i would replace them.

XR7 Dave
05-20-2017, 08:12 AM
Did it always run this way or did it start doing this at some point? If it started at some point, go back over that happened or what you did. Give us a little more detailed background on how it got to the point of running rich.

Ninja38
05-20-2017, 11:52 AM
No it had been sitting for about a year, would only start with starting fluid. So i drained all the gas, put 12 gallons of 93 in it. Still running verry rich at idle, cuts out and falls on its face under load and rpm. Got a breakout box and started checking sensors. As i said the mass was a little high, but other than that i could not find anything else out of spec. Got out the scope and did both cam and crank. Both looked nice and clean. O2s are pegged as you can imagine. I would have to check but the injectors were in spec at around i want to say 3.6 ms, all the readings ect are at work but was in spec (all this according to alldata) The one thing we could not check is the baro sensor as in this year depending on who you ask it also acts like a map but i do not know. Also had to change plugs and oil as both were loaded up with gas. Being i dont get a chance to work on it i always disconnect the battery as the battery is pretty ~~~~ but i use a jump box when i do start it and all voltages are good.

davec73
05-20-2017, 12:09 PM
No it had been sitting for about a year, would only start with starting fluid. So i drained all the gas, put 12 gallons of 93 in it. Still running verry rich at idle, cuts out and falls on its face under load and rpm. Got a breakout box and started checking sensors. As i said the mass was a little high, but other than that i could not find anything else out of spec. Got out the scope and did both cam and crank. Both looked nice and clean. O2s are pegged as you can imagine. I would have to check but the injectors were in spec at around i want to say 3.6 ms, all the readings ect are at work but was in spec (all this according to alldata) The one thing we could not check is the baro sensor as in this year depending on who you ask it also acts like a map but i do not know. Also had to change plugs and oil as both were loaded up with gas. Being i dont get a chance to work on it i always disconnect the battery as the battery is pretty ~~~~ but i use a jump box when i do start it and all voltages are good.


When i took my care to the shootout last year i thought my 02s were ok too but when we looked at them they were switching very slowly. Its just a pretty safe bet to start there. Then again i would do whatever xr7dave tells you to do, he knows a little bit more about this than most of us or well, pretty much all of us lol.

Ninja38
05-20-2017, 01:59 PM
well i disconected them and still running into the same problem, if im correct it should go to a factory baseline once it sets the o2 code. and they are not switching just staying rich as the car is just dumping fuel.

Ninja38
05-20-2017, 02:00 PM
like i said this is not an easy one, alot of reasons to run lean but not many to run rich.

KMT
05-20-2017, 02:47 PM
when we looked at them they were switching very slowly.

Happen to recall what brand they were, and what brand you replaced them with?

RalphP
05-20-2017, 03:58 PM
Something I've not seen yet, and probably a silly question.

Are these the factory fuel injectors, or have they ever been replaced with a larger set?

RwP

Ninja38
05-20-2017, 04:39 PM
as far i know it is a stock engine

XR7 Dave
05-20-2017, 10:43 PM
Does it hold fuel pressure after you shut it off? I rarely see problems with injectors on these even after sitting for years with old gas in them, but one has to wonder if maybe you have sticking injectors. I assume the engine runs smooth, not like it's misfiring or anything like that?

How high is the MAF voltage over spec? I think normally a stock SC will see around 1v at idle but I have not checked that in a long time.

If the 02's are working (you did say they read high all the time) then the most likely cause of a rich condition will be an artificially high MAF signal voltage or injector malfunction.

BAP does not affect AFR, the fuel command comes pretty much directly from MAF signal modified by ECT. It's really pretty much that simple.

The 02's come into play when the EEC tries to close loop, but that takes around 1 minute to 3 minutes or sometimes more depending on a variety of conditions. When the EEC attempts to go closed loop it will first look for a high 02 signal. You indicated that this exists, so then the next thing the EEC will do is begin to remove fuel until the 02's drop and then will begin it's switching routine. So if it's rich on startup, the first reaction you can observe is when the 02 begins to drop. This will be kind of hard to observe because you don't know exactly when it's going to happen. After a fixed amount of time with the trims maxed out (25%), if a lean condition doesn't result during that time, the EEC will "give up" and not attempt to correct again until there is a key cycle. So what I'm getting at is if in your observations you do not detect this happening, you may miss the event entirely and it may never (to your knowledge) even appear try to go into closed loop.

I did notice that you said it seemed lean at WOT, which is puzzling. How did you determine this? Did 02 sensor voltage drop under boost? I know you said you checked fuel pressure, but I wonder if you could have a fuel deliver problem. Does pressure drop under boost? It should rise # for # under boost. So basically 48-52psi depending on rpm (at WOT). It would be pretty typical for you to have a bad fuel pump after sitting, etc., but that doesn't explain your rich idle condition. It may be you have two separate problems going.

Oh, did you say whether you ever verified TPS voltage and sensor output? It's a quick check with the BO box and will eliminate that as a contributing issue.

Ninja38
05-21-2017, 01:56 PM
I did check tps and it was fine, along with fuel pressure after shut off also check fuel pressure regulator and it is not leaking. I will have to get my notes on monday to give actual readings from the bo box. Will reply with more info then

Ninja38
05-25-2017, 08:17 PM
xr7 dave can you give me some info on ford computer failure and how to check them. Can you give me some info on what to look at and or for.

XR7 Dave
05-25-2017, 08:54 PM
xr7 dave can you give me some info on ford computer failure and how to check them. Can you give me some info on what to look at and or for.

The easiest test is to run all codes. You should be able to perform all tests and receive "all clear" signals on all routines. If the EEC will perform the tests and give you either all clear or trouble codes, then 99% says it's fine. Other than that a known good EEC is your best resource.

Ninja38
05-25-2017, 11:07 PM
can we post vids on this forum and if so what kind of kb/gb

Ninja38
05-25-2017, 11:14 PM
well we dont have a obd 1 scanner at our shop, now if it was a vw benz bmw id be fine but we dont do the domestic stuff here, and running codes its the really crappy obd1 ford junk, eng off enging running but i never got verry far hence the break out box, again verry fun to find. But we had a 3000gt vr4 that was kinda doing same thing. Run rich lean ect and even though the ecm had all the inputs, grounds, power ect. It would just not control fuel for some reason and it was about the same year. If the ecm is bad will it just dump fuel if the inj drivers are well screwed? and again on a fresh boot with no learned fuel trims.

james5275
05-26-2017, 12:57 AM
Very odd if it's only been sitting for a year. I've had one case where an injector stuck open, but it was from a used set that I purchased, lord only knows their history. If shutdown FP is holding, rule that out.

I'm just learning the basics of tuning, but here's some ideas:

1. Would a misfire on 2 cylinders create a supposed rich condition? I'm thinking I witnessed rich on my narrow Bands when I (as many others have) connected 2 spark plug wires backwards at the coil pack.

2. With engine idling, kill power to the fuel pump. If rich, Rpm's should momentarily increase. Just to confirm mixture state.

3. Once found a beetle bug in the MAF sample tube, caused all sorts of havoc.

4. Weak spark?

5. Is this a customers car or new purchase? Any number of things could have been messed up. If rich at idle but lean at wot, almost sounds like MAF is unplugged? Unplug MAF while running and see what happens?

6. Are you sure you checked the ecm coolant sensor? Right side, near ac compressor.

Sounds like your more inclined than me, sometimes fresh ideas go a long way.

Best luck,
JJ

XR7 Dave
05-26-2017, 07:43 AM
With the ECM anything is possible, but these are pretty robust so unless someone did something (like connect the battery cables backward) it's pretty rare that they would fail. Temporarily swapping in a known good ECM is about the only way to verify this. I guess one could put a noid light in to see if they are pulsing, but 99% says they are.

Without a code reader you can use the paperclip method (lots of online instructions for that). You'll also need the user instructions too (when to goose the throttle, etc.) and how to read the results. But I think this is an important test. If the ECM is fried, it likely won't initiate the tests. The code test also checks for response to change in commanded AFR vs. 02 sensors and things like that so again, passing or at least performing this test will rule out a lot of guessing. The engine running code test also includes a cylinder balance test that will pinpoint weak cylinders.

I've never had an ECM with bad injector drivers, so I can't say for sure how that would act, but if the ECM is fubar, the car will run super rich. In fact it will barely run at all.

davec73
05-26-2017, 05:23 PM
How much vacuum is the car making at idle?

Ninja38
06-22-2017, 06:41 PM
So i got my hands on a ford obd1 scan tool and it looks like the computer is trashed. When i try to run any of the programs it just crashes. But i need help now getting the proper computer i have a pic of mine but it does not seem to match up to the ones for a 1990 sc.

Ninja38
06-22-2017, 06:43 PM
these are the choices that rockauto has

A-1 CARDONE 784857 {#F0SF12A650MA, F0SZ12A650MA} Reman. Engine Control Computer Info
4 speed trans.; Units are pre-programmed at the factory.; Correct VIN and OE Number Required When Ordering.; with Federal Emissions (Only 3 Remaining)
Previous Image

Next Image
$86.89 $20.00 $106.89
Add to Cart
A-1 CARDONE 784763 {#E9SF12A650JC, E9SZ12A650J2C, E9SZ12A650JC} Reman. Engine Control Computer Info
5 speed trans.; Units are pre-programmed at the factory.; Correct VIN and OE Number Required When Ordering.; I.D. #(s) E9SF-JC; with Federal Emissions (Only 3 Remaining)
Previous Image

Next Image
$75.79 $60.00 $135.79
Add to Cart
A-1 CARDONE 784405 {#F0SF12A650LA, F0SZ12A650LA} Reman. Engine Control Computer Info
5 speed trans.; Units are pre-programmed at the factory.; Correct VIN and OE Number Required When Ordering.; I.D. #(s) F0SF-LA; with Federal Emissions (Only 2 Remaining)
Previous Image

Next Image
$75.79 $70.00 $145.79
Add to Cart
A-1 CARDONE 784856 {#F0PZ12A650ALA, F0SF12A650LB, F0SZ12A650LB} Reman. Engine Control Computer Info
5 speed trans.; Units are pre-programmed at the factory.; Correct VIN and OE Number Required When Ordering.; I.D. #(s) F0SF-LB; with Federal Emissions
1 Day Delay
Previous Image

Next Image
$99.79 $70.00 $169.79

james5275
06-22-2017, 09:27 PM
Need more answers or you'll have your hands full.

What's the story on the car?

Mine is also a 90, but different numbers on the ecm. Is yours a 5 speed?

JJ

Ninja38
06-23-2017, 04:48 PM
Yes it is a 5 speed

Tim Groth
06-23-2017, 11:22 PM
I have a good 90 five speed EEC from a parts car if interested PM me.

-Tim