5.7 TBI "slightly stinky exhaust" and not as good MPG

I wanted to post up some questions/comments/concerns to see if anyone can help me out

I am running a TBI 5.7 (350) that came out of a 1990 Caprice Classic, in my 1984 Scrambler. It also has the 700R4, 4.10 axle gears, 33" tires.

The engine always starts right up, accelerates smoothly/linearly, shuts off with no "dieseling", and has plenty of power. No bogging, stumbling, cut outs, stalls, etc. Basically, I am pretty happy with it. Runs good, very reliable.

As far as I know, the engine is bone stock. I changed the valve stem oil seals, water pump, thermostat (195 degree), some hoses, etc. The engine came with a brand new TBI unit from "Turbo City", so the injectors and all TBI mounted sensors are new. When I first started the engine up, I got a code for a bad MAP sensor. I changed this sensor, good to go. I also recently changed the coolant sensor with a new one, and mounted it directly into the stock hole in the intake manifold. Before I changed this sensor, it was mounted in a metal block extension coming off the intake, and it would only read 130 degrees with the engine warmed all the way up running at 200 degrees.

My "complaint": The first few highway trips I drove the Scrambler on, if I drove 65-70mph, I was getting between 18-19mpg!!!!!!! Now, I get 11-12. The MPG drop happened before the coolant switch change. The other issue - at idle, the exhaust is slightly stinky. It smells ever so slightly rich, but not bad. It mainly just smells "extra exhausty", if that makes sense My red Scrambler with MPI smells "clean" when idling, the tan Scrambler with TBI smells "extra exhaust" at idle. Neither Scramblers have cats.

Here is a bunch of operating data from the code reader, engine fully warmed up and idling. No MIL, no stored codes:

RPM = 525-550 (seems a bit low????)
Coolant temp = 185 -190 (when driving down the road, it stays between 200-210)
MAP = 1.74 volts at idle (that is correct I believe)
O2 Sensor = around 450 mVolts, constantly moving (below 500 is lean, which is what I am showing)(pre-convertor O2 range 100-900 mVolts)
TPS = .6 volts (0-5 volt range, low at idle, should be good)
IAC Steps = 22-23 (0-255 steps total, should be good here)
Integrator = 128 (this is what it should be if air/fuel ratio is correct, should be good here)
Block Learn = 123 (under 127, fuel being subtracted, so this shows a slight lean??)
Closed/Open Loop = it always goes into Closed Loop when running, at idle it will sometimes go back into open, then closed again
Knock Sensor = shows 18 at idle (assuming this is OK)
Clear Flood Mode = OFF (this will only show ON if key is on, engine off, gas pedal floored)
Learn Control = DISABLED (this should be off if block learn is OK???????)
Async Mode = OFF (this just shows if extra fuel added during WOT operation, out of sync with injectors??)
Rich Lean Flag = constantly alternating (I assume it should do this in closed loop when the O2 sensor constantly adjusts A/F ratio?)

When driving down the road:

TCC Status = ON (this shows the TC is getting the signal to lock up) I am POSITIVE the TC is locking. If you unplug the harness off of the transmission, the TC will not lock. You can see the RPM increase, and feel the performance difference. My TC will lock in 2, 3, and 4 (OD). You can watch it on the Scan tool, see the RPM drop, and "feel" it.
Vehicle Speed = Works (it matches the speedometer/GPS)

Other Notes:

I have an operational charcoal canister system. I am using an "early" TBI set up - canister with a line from the fuel tank, single purge line directly to ported vacuum on the TB. Works fine, no gas smell, no weird gas cap issues. My computer/harness does not support the solenoid activated purge system.

EGR system - I have the stock EGR, and the stock EGR solenoid. Everything is wired/plumbed up like it should be. I "assume" it is working correctly. The solenoid portion does not have any error codes. I will check the valve and solenoid with a vacuum gauge to verify it is working. I do not have the "typical" bad EGR symptoms, but maybe their is a problem?

Fuel Pressure - I have not checked this, it is a PIA to check on the TBI. I am pretty sure the pressure is OK. You can hear the injectors cycling back and forth, see the "cone mist" of fuel coming out. However, it "looks" like a droplet of fuel comes out of each injector, too. The throttle plates just stay "damp" at idle, no fuel puddeling, no black smoke. Spark plugs have a real nice, perfect tan color. If you pinch the return line shut, the engine starts to stumble/run rough. I will need to verify pressure to rule out regulator/fuel pump problems, but I think they are OK.

One other note - When the engine was averaging 18-19 MPG, and it was not stinky at idle, I had the heater hoses ran incorrectly, and the engine was running between 215-220 degrees. From what I researched, this is the acceptable operating range for these engines? With the heater hoses ran the way I had them, the coolant switch was reading engine operating temperature. When I re-ran the heater hoses, I don't think the sensor was submerged in coolant, so it would only read 130 degrees. I am hoping that since the new sensor is reading the correct coolant temperature, this might help fix part of my problem. I "assume" if the computer thinks the engine is only at 130 degrees, it will "rich" up the fuel mixture, like it is in a constant warm up mode?

I plan on driving the Scrambler some more, take it on a highway drive, and see if the MPG has gotten better.

I look forward to any comments/criticisms/suggestions

Did u change the injectors? And u need to find the fuel pressure out . there's a port for that on the fuel rail..

BRKLYNZ28 said:

Did u change the injectors? And u need to find the fuel pressure out . there's a port for that on the fuel rail..

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Injectors are new, good spray pattern.

I do need to verify the fuel pressure.

NO port/schrader valve on either fuel rail on this TBI. I am running the stock, factory, GM hard metal fuel rails. Their is one for supply, one for return, coming out of the back of the throttle body. The fuel regulator is inside the TB, between these two metal line ports. I "think" you have to install a "test tool" between the throttle body intake line and the TB. The problem: the threads here are super fine, everything threads in at a funny angle, very easy to strip the fitting/TB out (I already have once)

You really need to test the fuel pressure after the regulator

Is the ecu controlling the timing?

mysunnshine said:

Is the ecu controlling the timing?

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Yes

I warmed the engine up to operating temp, turned it off, unplugged brown wire, set timing to 0, turned it off, plugged brown wire back in.

Knock should be 0 if there is no knock. If you disconnect the knock sensor does it go to 0? I'd guess that the ECU is pulling 18 degrees due to knock retard of the probably 18-25 degrees commanded. So if you check the timing at idle, what do you end up getting with the SPOUT not disconnected? It sounds like it's really retarded which would cause extremely high hydrocarbons and will build heat in the engine. If you had headers, they would be glowing red.

mysunnshine said:

Knock should be 0 if there is no knock. If you disconnect the knock sensor does it go to 0? I'd guess that the ECU is pulling 18 degrees due to knock retard of the probably 18-25 degrees commanded. So if you check the timing at idle, what do you end up getting with the SPOUT not disconnected? It sounds like it's really retarded which would cause extremely high hydrocarbons and will build heat in the engine. If you had headers, they would be glowing red.

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I will re-check the timing tonight or this weekend and report back

No headers, "ram horn" style stock manifolds, the kind with the center dump.

I will also verify fuel pressure/check the regulator

If the timing is retarded that bad, I guess it would also cause the low idle RPM, or is that normal

Your IAC is pretty low so I'd guess that the desired idle speed is pretty close to 550 RPM. It's either that or your IAC is not functioning. Do the counts go up when you put it in gear? As a quick guess, I'd say that your fuel pressure is ok because the block learn is 123 which means that it's taking a little bit of fuel away for long term fuel trim. BTW, your TCC status should be normally off until commanded to be on.

mysunnshine said:

Your IAC is pretty low so I'd guess that the desired idle speed is pretty close to 550 RPM. It's either that or your IAC is not functioning. Do the counts go up when you put it in gear? As a quick guess, I'd say that your fuel pressure is ok because the block learn is 123 which means that it's taking a little bit of fuel away for long term fuel trim. BTW, your TCC status should be normally off until commanded to be on.

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Yes, IAC counts go up when I put it in gear, the engine does not bog down at all.

Fuel pressure was right around 14psi the last time I checked it, but I will check it again.

The TCC stays off in first gear all the time, no TC lock up. Reverse the same.
In second gear, TCC stays off on the initial 1-2 shift, then Locks, if speed held steady.
In third gear, TCC is off after the initial 2-3 shift, then locks if speed held steady.
In 4th gear, TCC is off after the initial 3-4 shift, but it locks up fast in 4th.

Does your scanner show mph?

mysunnshine said:

Does your scanner show mph?

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Yes

It should not lock up in 2nd gear and no lower than 40mph. There should be a 4th gear pressure switch to only allow it to lock up in 4th gear. How accurate is the scanner mph to reality?

mysunnshine said:

It should not lock up in 2nd gear and no lower than 40mph. There should be a 4th gear pressure switch to only allow it to lock up in 4th gear. How accurate is the scanner mph to reality?

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The scanner mph to reality mph is dead on. I changed the speedo gear in the Dana 300 to work with the 4.10 gears/33" tires, it is dead accurate.

As for the TC lock up, I have read/seen all different things. My engine computer controls the TC lock up, I don't have any home made switches. I have read that some 700R4's will only lock up in OD, others in 2,3, and 4. Mine locks up in 2,3, and 4. My computer/engine/transmission came out of a 1990-1991 Caprice Classic, with a 5.7, which is rare, maybe a cop car? Besides the scan tool indicating the TC lock up in 2,3,4, you can see it on the tach and feel it

You have to drive very slow/steady for it to lock in 2nd, not even sure why you would want it to lock in 2nd
The third gear TC lock up is great for towing/pulling grades.
It is hard/almost impossible to get a 4th gear TC unlock, it will down shift to 3rd, unless you are over 50mph.

I'm no 700R4 expert for sure. I haven't seen any 700R4's so far without the 4th gear pressure switch but they may have done some weird stuff with controls thru the years.

mysunnshine said:

I'm no 700R4 expert for sure. I haven't seen any 700R4's so far without the 4th gear pressure switch but they may have done some weird stuff with controls thru the years.

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I'm no expert either

IIRC, on my wiring harness, their were two wires that I could have run to the transmission:

1) a 4th gear wire only, only get TC lock up in 4th
2) the other wire, the one I used, allows TC lock up in 2,3,4

Not 100% sure on that, I will have to take a look at the pin out diagram again, I may be oversimplifying/incorrect.

I went ahead and readjusted the timing yesterday. I did not check it before I reset it because I started twisting the distributor to see if I could improve the condition by "feel"

Anyway, warmed engine up to full operating temp. Turned it off. Unplugged brown wire. Started it back up. Set the timing to 0 degrees. Turned it off. Plugged back in the brown wire.

When I restarted the engine, with the computer controlling the timing, the timing mark on the crank was just past the end of the timing scale, so I am going to say around 16 degrees at idle.

No other changes, all other info from the scanner the same.

I unplugged the knock sensor, no code or change. I plugged it back in, went for a quick drive, plugged the scan tool back in, and the count went up from the 18 it had before up to 23. I assume this number is just a counter???

The only other change: While driving, the "Learn Control" was ENABLED.

I need to buy the TBI adaptor for my fuel pressure tester this weekend and check the fuel pressure and regulator function. I "think" this stuff is OK. It does appear that both injectors have a slight droplet drip at idle.

On the last long Jeep trip highway run, my buddy behind me said he could smell the exhaust, like it was a hair rich. But, it also had a melted spark plug wire

The TC is NOT locking now, either. I need to verify my 12 volt supply/brake switch function this weekend, too

All this is chinese to me. I need to get out of the carb age and try to learn fuel injection. You can read what the sensors do but to understand the readings and what the readings should be is the hard part.

Does the timing advance when you rpm the engine?

mysunnshine said:

Does the timing advance when you rpm the engine?

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Yes

You could always TDC the #1 piston to verify the balancer hasn't spun on the rubber-