73mm C&L, Blue tube, 38lb injectors = black smoke rich

RichM

Registered User
Anyone have a inexpensive solution to this problem?

I have a freshly rebuilt motor, and when I put it all back together I put in the following:
73mm C&L MAF Blue sample tube
polished up the blower plenum
polished up the intake manifold
38lb/hr injectors
190 LPH fuel pump
added the Kook mid-lengh headers and a 2 1/2 to 3 to 2 1/2 inch exhaust.
I already had a 94 style blower installed from a previous "unplaned upgrade"
Everything else is stock: TB, computer, cam, fuel pressure regulator, etc.

Now at WOT I leave a small black cloud behind me. And carbon is starting to deposit on the rear bumper cover (it's a white car and is starting to look bad).

My gas milage is about 21 mpg mostly highway. The only code I get is "TPS voltage higher than expected" (sorry forgot the number) the code rairly happens and usually when the throttle is closed. No codes from the fresh O2 sensors.

When spring comes I planed on getting a chip from XR7 Dave, but till then is there anything that is quick and easy to adjust for this problem.

I did a search and at least one other person had this problem but no solution was posted. That was back in 2002. Post is HERE (members only forum)

ETA: 190 LPH fuel pump.
 
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Get a bigger throttle body? It seems like having a 73 maf and a stock TB wouldn't work well. The MAF is getting a reading from the amount of air going through it, and the TB is restricting that air from actually getting into the engine. In other words, the EEC is thinking that it is getting more air than it actually is, because of the restrictive stock TB. This sounds good anyway, although, I could be talking crazy again. It seems like the EEC would adjust thogh, after it received rich readings from the 02 sensors. :confused:
 
Darkside said:
Get a bigger throttle body? It seems like having a 73 maf and a stock TB wouldn't work well.
Maybe but I have a 76mm MAF and a stock TB in mine with no issues.
 
The TB isn't Lying to the EEC, the MAF is. It's not nice to Lie to Mother EEC. Besides, C&L MAF's are questionable, at best, to begin with.
 
maf/Tb/injectors

MarksM said:
The TB isn't Lying to the EEC, the MAF is. It's not nice to Lie to Mother EEC. Besides, C&L MAF's are questionable, at best, to begin with.
I'm really not quite sure that the problem lies in the throttle body vs MAF situation. The same amount of air thats going through the MAF is going into the TB and then into the motor. The MAF only reports how much air is going into the motor regardless of how big or small the rest of the system is.

However, correct me if i am wrong(anyone), you should have your TB calibrated for any injector change. Therefore if you upgraded injectors and didn't have your TB calibrated, thast could explain the running rich/black smoke.
 
running rich

I dont know why you guys even bother putting parts on these cars and when it comes to chips you skimp out. Get the chip right away. You need to cal your maf to injectors and need to have to data log the car to see where your rich or lean at idle and you need to see if you maf is pegging the meter. With all that said then tuner can adjust and make your car run right. Xr7 dave knows alot about these cars. If you dont have a tune someone like me will blow your doors off with a stock one. if any sc guys are in ne pa near allentown and need dyno and tune give me a shout oneqkgt@aol.com
 
It doesn't matter if the TB is smaller, the MAF just reports what the air flow is. Whatever amount goes thru the MAF is also going to go thru the TB. There is also no calibrations to be made to the TB other than the idle settings. Other than changing or adjusting the Throttle Position Sensor to get the correct voltage, the only option is to get it on a dyno with a wide band o2 and tune it.

I'm pretty sure the problem will be with the MAF transfer function. From what I've seen and read, they vary quite a bit from car to car. When I had 38s in my car it bogged very bad until I increased the static fuel pressure to about 43 psi, and I've seen other cars that ran fine at stock pressure.

David

PS: Better to be running too rich than lean.
 
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Considering mileage is decent, most likely it is within adaptive limits so you may not be in danger of ruining your cats, but running rich does have that effect. ;)

I assume you still have the stock intake on the car? Your mods list a K&N panel filter.

You need to check your TPS. It is not usual for a TPS to read high on a stock TB. You may have a bad TPS which could be causing all of your problems. Check idle voltage (should be .9-.99v) and then check for smooth transition to about 4.7v at WOT. If that checks out then your MAF readings are just too far off for the EEC to compensate.

If that is the case, best bet is to put the stock MAF and injectors back on. You are not at a mod level which would exceed the stock injectors (260rwhp max) until you can get it tuned.
 
My running "rich" problem ar WOT was a result of bad wires/plugs-- the spark wasnt strong enough for the air current coming in and would weaken, there fore only burning some of the fuel instead of full combustion.
 
David Neibert said:
It doesn't matter if the TB is smaller, the MAF just reports what the air flow is. Whatever amount goes thru the MAF is also going to go thru the TB. There is also no calibrations to be made to the TB other than the idle settings. Other than changing or adjusting the Throttle Position Sensor to get the correct voltage, the only option is to get it on a dyno with a wide band o2 and tune it.

I'm pretty sure the problem will be with the MAF transfer function. From what I've seen and read, they vary quite a bit from car to car. When I had 38s in my car it bogged very bad until I increased the static fuel pressure to about 43 psi, and I've seen other cars that ran fine at stock pressure.

David

PS: Better to be running too rich than lean.

Dave, I had the TPS set to about 0.9 vdc at idle for a while. The car hesitated quite a bit so I brought it back to about 0.8 per the factory spec and it smooted out. the black cloud at WOT also diminished a little with the TPS set to 0.8vdc while the engine is at idle.

I'm hoping to get the transfer function corrected with a chip this spring (The SC is my only car, and the weather sucks to bad to ride the motorcycle). I'm looking into getting a calibration curve for the C&L with my electronics on it, but I'm not sure how that will happen yet.

My understanding is that at WOT the computer disregards the O2 sensor input and goes strictly off the computers fuel tables and the MAF input. David Neibert and XR7 Dave, Is this true?

acb92sc, I swaped out plugs and wires when I was chasing another problem a while ago, didn't make any difference. But my plugs may be fouled now.
 
My understanding is that at WOT the computer disregards the O2 sensor input and goes strictly off the computers fuel tables and the MAF input. David Neibert and XR7 Dave, Is this true?

Rich,

While I think there are other factors besides the MAF voltage that determine how much fuel is supplied at WOT, I believe you are correct that input from the o2 sensors isn't used. However input from the o2s is used for the adaptive learning which over time could have an effect on your A/F ratio at WOT.

Since Dave Dalke (XR7 Dave) tunes these cars and has a much better understanding of how the EEC works, I'm sure he can give you a better answer.

David
 
RichM said:
Dave, I had the TPS set to about 0.9 vdc at idle for a while. I'm looking into getting a calibration curve for the C&L with my electronics on it, but I'm not sure how that will happen yet.
Most likely this issue is caused by MAF readings not matching with the expected airflow at idle. ie MAF problems.
My understanding is that at WOT the computer disregards the O2 sensor input and goes strictly off the computers fuel tables and the MAF input. David Neibert and XR7 Dave, is this true?
Yes the O2's are disregarded, but as David N said, adaptive will be adding fuel based on part throttle readings. Clearing adaptive by disconnecting the battery will temporarily reset the adaptive parameters. However there are other factors as well. Bottom line is if TPS and MAF are off then AF will be off also. Make sure the TPS transitions smoothly to 4.7v at WOT. If it does then it's probably all MAF.
 
XR7 Dave said:
Most likely this issue is caused by MAF readings not matching with the expected airflow at idle. ie MAF problems.
Yes the O2's are disregarded, but as David N said, adaptive will be adding fuel based on part throttle readings. Clearing adaptive by disconnecting the battery will temporarily reset the adaptive parameters. However there are other factors as well. Bottom line is if TPS and MAF are off then AF will be off also. Make sure the TPS transitions smoothly to 4.7v at WOT. If it does then it's probably all MAF.

David and Dave, thanks. If I survive the relatives this weekend I'll double check the TPS voltage over the full range. I did when I put a new one in about 3 months back, but better to check. I don't recall what I got for the WOT voltage reading at the TPS.
Dave, you might be getting a check from me next month. A little earlier than I had hoped but it's only money. And I'm shorter on sanity than cash right now.
 
The following is from the C&L web site: http://www.cnlperformance.com/calibration.html
Ford Thunderbird SC 73mm Unit
Std Fuel Injector (30 for 89-93), (36 for 94-95) Clear Tube (101)
36lb Injector (89-93 processor) Blue Tube (102)
42lb Injectors (89-93 processor) Red Tube (103)
(Upgrade injectors may cause computer issues with factory ECM on 1994-1995 Super Coupes)

Since your injectors are inbetween the 36lb and 42lb and running rich, a change to the Red Tube (103) should be considered, and your fuel pressure in the rail should be checked. If it is too hight to start with, that alone will cause the problem with the stock size injectors. If I've got the direction of wich tube to move to, please advise.
 
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