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2.3L ('83-'97) 90 2.3, lean condition, really wasn’t lean! Resolved.


corerftech

Well-Known Member
Joined
Apr 22, 2021
Messages
308
City
Memphis, TN
Vehicle Year
1987
Transmission
Automatic
Good morning folks.
Frankentruck was driven 525 miles yesterday on a road trip.
I recently replaced a bad o2 sensor causing a very lean condition.
When test driven air temp was 50-60 deg, yesterday the air temp was 15.
A big dif in performance, it was very lean until the sun rose and air temps hit about 28 or higher, then it ran substantially better but boy was it still lean.

A couple of things that were noteworthy:
I started the truck at 15 degrees and just about evey light on the dash did something, inlcuding Rear AnitLock brake light lit.
Voltmeter was at 10 volts.
Heater FAN was on but would not activate to defrost my windows.
It ran for about 3 minutes, maybe 4 and then I decided Id better test to see if it would restart.
Restart was rough, it was mad.
Second crank it lit up like it normally does, but then all lights were normal, fan ran, voltmeter was at 14 or so.

It was really pissed about running, as lean as it was. The 18-2k range was just crap.

I decided to drive it past Nashville from Memphis and go for it.

As I drove I pondered the electrical issue, decided that absolutely there is a ground problem remaining on the truck. The TACH will bounce at times, no other electrical signs, just a bounce, intermittent. The FAN gave me a clue as to the ground point that may be suspect. I intend to ground the ECU with a new wire all the way back to battery if not already completed. Ill then ensure the cab ground is replaced back to the battery.

As for the title of the thread, LEAN...... is it possible that the ECU (as seen from the 10v gauge reading likely due to high resisance ground) struggling to fire the injectors....??? If the ECU has ground switch for the injectors, is it floating or is it a common ground reference?? If the transsistor is sinking current to a floating groudn then the ground is not associated with fueling issues. If the sink is to common ground then "potentially" the injector is only opening as far as the voltage allows and maybe the pulse waveform is not true, due to the ground resistance??

The only other two items suspect are the fuel pump and the injectors themselves. I will restate the fuel rails do leak down (new regulator installed) quickly and so either could have issue. But as I have also considered that situation, if injectors are leaking fuel after shutdown, then an immediate restart should have presented enough fuel to prevent a lean POP on ignition. There should be substantial fuel in all 4 jugs and the spray should give me a clean start.

If its the fuel pump, what shoudl be the pressure at the OUTLET of the fueul filter??? Ill pull the outlet and pressure test there. I recall somethign in the mid to high 40's but not 65 like the newer pumps.... but I may be wrong.

Any thoughts?? It was a gread road test on a beautiful cold day. truck ran great. Aside from lack of pwoer and lean, on 93 octane to Woodbury, TN (all uphill grades from Memphis there) 17.3 mpg and mostly in 4th gear at 65-70 to maintain stable running. On way back I got 22.2 on 89 and droive from Woodbury to Savannah which again is mostly grades. The ECU had been reset for the fault codes and not driven much..... 22 mpg on 60% up grades (total of miles is 60%) and on country roads unliek the trip in on Interstate.... I was pretty happy.

BTW: whne air temps hit 38 degrees the truck ran very well w/o hesitation but indeed was short of power.

Last note: The INtake manifold coolant line is capped off. The metal tube was flopping around without a home (BUBBA the B-hole fixed it). I removed the tube and capped the manifold off. I will take from the above behavior that the preheat line is pretty important to maintain and have intact for the 2.3l engine to behave well. It doesnt fix lean but it sure would help with best use of fuel that is present.... seems like this enghine is cold blodded and it needs manifold heat to run best..

Aslo any thoughts on the above.

Mike
 
Had to spend a few days contemplating my 500 miles ride and what the engine did. Had to recall several times in my past, where a coil or spark plug wire had failed and caused a very specific timing to a miss that was repeatable but also intermittent. Also had to marinate on “lean” which would have raised engine temps, likely caused detonation/pinging under high load and none of that occurred, ever.

I was compelled to verify a JYD coil I procured that tested good with DVM, no cracks or defects. Car came with Duracrap spark plug wires, Use of Duracrap parts was systemic when I got the truck. I metered 4 primary side wires but found nothing alarming. Didn’t do any arc tests. In a bind due to availability, I was forced “lifetime warranty” DuraPuke wires.

I also had considered the cold fault I had experienced before the drive at 15/16 degrees and went to most of the grounds and rebuilt them, no new connectors but fresh clean meat and retorque. Both fenders, driver headlight, ECU lug on cowl wall and harness lug in same location. Simultaneously I replaced the 4 primary plug wires with new. I also removed a prior tested good radio filter cap (25uF) that was procured from JYD with the coil replacement.

In all, the truck on several test drives of 30 mins in varying temps has stabilized. The only “bucking” I can create is in 4th gear at 1100 rpm uphill on 3% grade. Yes, a complete engine lug and one that should exist. Otherwise there is zero missing in the 17-2000 rpm range where it was repeatable….. when it happened. As well my tach doesn’t bounce but once per drive and even that is maybe some of my imagination. A tiny nervous tick and it’s one bounce. I believe my crank sensor may be involved but for now, don’t care. Engine runs notably smoother and I thought it was already as smooth as the old engine could run.

A side bar: starting would almost always pop and on decel would too. When replacing a plug wire I noticed that the egr pipe had a crack and even a pinhole. After scrubbing the pipe with a scotchbrite, I found significant leaking. I could not find a replacement this week and they aren’t cheap if I did, so I tested the temperature of the pipe after a highway run and I can keep my hand on it for a bit so it’s under 250 degrees. I used a full stick of JB weld steel to create a cocoon over the entire area sealing it. Epoxy is good for 300 degrees. When doing so I realized why I had not noticed this before. It prior had been repaired similarly with opaque epoxy and poorly done. I removed the old to find the serious voids.

No leaks now. Under hood is much quieter and in cab as well.
Lastly I can’t get it to pop at all. I am hypothesizing that air was being sucked in at start up and causing the pop, and on decel, maybe some reversion altering the O2 sensor data.
Time will tell. I will be replacing a temporary muffler with a nice quiet one so that I’m not going deaf (cherry bomb/turn down). A stock muffler will allow me to hear less noise and get better feedback from the engine. I think a plug wire was the fault for the 2000 rpm issue and as well the intermittent nature of electrical crap the fault of imperfect oxidized grounds.

Interesting: I attempted a code pull on a cold truck at 25 degrees. The ECT and IAT sensors both failed pre-test due to “out of range”. That was a good learn on the obd-1 testing and it’s procedure. I think code 21 and 24. Freaked me out but I realized they popped up in pre, not as codes.

Too cold for sensors to be in range, I’d never have thought that.

Best
 
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