93 running lean

rathr-b-cruisin · Oct 3, 2014

Been working on this truck for a while, new coil, plugs wires, MAF sensor, TPS, O2 sensors. just had a new muffler put on, i had to wait for the front pipe to come in, so i just got it back from the shop and he tells me that it is running lean. showed me the new muffler and it was grey, like ashy looking he said it was probably glowing and it must be running lean. I'll be playing again tomorrow. changing T-Stat, looking for vacuum leaks. probably check the fuel pressure.

any more ideas as to what causes it to run lean? It was running ok, then i put a new battery in it and it ran good, then on my way to work it started chugging and could hardly run unless it was floored. then it ran smooth, this would make me think fuel pressure regulator.

94RoadkillRanger · Oct 3, 2014

Besides what you already mentioned...
Fuel filter clogged or fuel line.
Fuel Pump weak.
Strainer on fuel pump clogged.
Corroded wire to fuel pump not giving enough amps (current) to pump.
Junk in the injectors (fuel filter failed).

black_demon69 · Oct 3, 2014

check your catalytic converter (would cause chugging low power if plugged also could possibly get red hot usually caused by rich condition. rich condition could plug converter)

what engine?

RonD · Oct 3, 2014

Yes.............what engine?

If you are running lean engine will ping/knock under load.

Mufflers don't "run hot", Cat Converters do and that is from running rich not lean.

Check your MPG.

rathr-b-cruisin · Oct 3, 2014

4.0 5 speed, 136,000 miles. i did replace the fuel filter too, father-in-law replaced fuel pump before i took the truck from him. fuel mileage is anywhere from 12.5 to 14. exhaust shop said he could see through the cat. i had both rich and lean codes before, but have not driven enough today to have the cel come on again. it's a lot quieter and smoother than when i first got it, but it's not quite there yet.

Andy D · Oct 4, 2014

The symptoms you described are caused by running rich in my experience, not lean. When it happened to me it was caused by a weak coil.

RonD · Oct 4, 2014

MPG seems a little low if you are not running bigger tires and running around with empty bed.
I get about that but have canopy and full load of tools 24/7

T-stat needs to be 192 or 195degF, 180 will lower MPG

Easy test for intake manifold fuel leak:
Warmed up engine test is best, but can be done cold
turn key on
press gas pedal to the floor and hold it down all the way
turn key to START, crank engine
it should NOT start, or fire at all
Fuel injectors are shut off but spark is still on

If engine does not fire then no fuel pressure regulator leak or fuel injector leak
If it does then you have a leak

release gas pedal at anytime to restart fuel injectors

You didn't mention CEL before, do you have the exact code numbers from those incidents.
The Computers are pretty good at setting the correct codes but people are very bad at interpreting them, I am including myself in this and pretty much the rest of the people on the planet.

rathr-b-cruisin · Oct 4, 2014

replaced the t-stat this morning with a 195, then cleared all the codes then went for a ride. the temp on the gage is closer to normal but not straight up however it used to only come off of the base line, i also replaced both coolant temp sensors. at idle it was pretty rough, then it would clear up and run smooth. if i revved it up it would idle down and run rough, then smooth again. during the ride it started off good, but still sluggish as always, but smoother. then it happened again. chugging, choking, could only go 35 mph. then it cleared up again and i made it home like nothing happened, however its always sluggish unless i really push it. got home and checked the codes. i'm getting 173, and 176 now. new O2 sensors no exhaust leaks.

rathr-b-cruisin · Oct 4, 2014

i'm taking the plugs out tomorrow maybe that will give me a better idea of whats going on. I started looking at injectors tonight after i checked the fuel pressure regulator. that appears to be working fine. i did notice that at idle, it ran the smoothest at 30psi. when it went to 33 psi it was really rough. when i unplugged the vacuum hose to the regulator the pressure went up to 39 as my haynes book says it should go up. i noticed while digging around that some of the injectors have a very noticeable tick while some were faint. cylinder 1 was barely making a noise, but 2 was pretty loud. when touching the #1 injector i couldnt even feel it tick but then it ticked faintly. i put in some fuel injector cleaner and seafoam in the vacuum hose, let it sit and then went for a drive. at first i thought success! but no. after i got back i had codes 10, 121,173, 176. so how hard is it to remove the intake and change the injectors. thinking if i do it i should replace them all while i'm in there

rathr-b-cruisin · Oct 5, 2014

i pulled the plugs this morning, all of the plugs on bank 1 (passenger side) look like this:

all of the plugs on bank 2 look like this:

so not sure where that takes me now.

RonD · Oct 5, 2014

You have a sticking injector on bank 2 or O2 sensor is reporting lean on bank 2 when it isn't.

Often overlooked is an exhaust manifold leak.
Headers(manifold) are tuned to create a negative pressure at the exhaust valves while engine is running, if there is an exhaust leak you hear the "psssst"when the closest cylinders exhaust valve opens, but in between the "psssst's" it is sucking air in.
This air causes O2 sensor on that bank to see Lean exhaust, i.e. high Oxygen level, so computer adds more fuel.
I know you said no exhaust leaks but still worth mentioning.

Because it is Batch Fire one injector will effect the whole bank but I would expect the spark plug in the closest cylinder to the sticking injector to show more carbon build up.
If you have the engine idling and it is a bit rough use a socket extension or similar and a hammer to lightly tap on each fuel injector on Bank 2.
These are made of plastic so be gentle but make taps firm.
Fuel injectors rarely fail electrically, it is more common for them to fail mechanically, i.e. stick open now and then, tapping on them can free them up temporarily, or dislodge some debris that is causing the issue.
If tapping on one injector causes idle to smooth out then replace that injector.

rathr-b-cruisin · Oct 5, 2014

OK, heres where it stands as of right now. I put in 2 bottles of techron yesterday. since i have narrowed it down to the injectors i was about to bite the bullet and order a set and i thought i really havent given the techron a chance to work. so, since i could tell the Lions were going to let this game slip away, i thought l'd put some miles on it. things started out with chugging, hesitation, not running well at all. so i just kept pushing it. basically had to drive with it floored a lot of the time. then slowly it started getting better so i drove it in 4th gear at 60-65 to keep the rpms up. i went and bought some more techron for my next tank because it's on sale at advance. i was pretty pleased with how it was running when i got home. I cleared the codes so i'll see what happens tomorrow on my way to work. I'll let you know. hopefully this is does the trick.

rathr-b-cruisin · Oct 6, 2014

so i started off to work this morning and everything was fine...until half way there it started acting up again. coming home it was horrendous. barely go 40, sputter, sputter, then hold on there she goes, then sputter. it was terrible. so when i got home i pulled the intake off. I decided that with the symptoms i'm having now, it has to be the injectors, not much left.

RonD · Oct 6, 2014

I know it is probably not this but..................almost reads like water in the fuel tank.

rathr-b-cruisin · Oct 8, 2014

I pulled the intake off and i am replacing the injectors. I got them out last night and cleaned the old gasket off. I'm not so sure the gasket wasnt leaking, so i may be getting 2 problems taken care of here. So i should be getting the injectors today, advance auto had a 15% off of online orders for bwd injectors. The only thing now is i cant find a 93 4.0 intake torque pattern. my haynes manual says the torque for the studs, then the nuts, but nothing about what order to bolt these in. Anybody know what order these should be torqued down in?

93 running lean

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