Running Lean, Poor Mileage and power

[DasBaldDog]

Okay, so over winter I replaced my LIM gasket to correct a low vacuum problem and a burning coolant problem.

I've been driving the truck (94 ranger with 4.0ohv) and the mileage is about 8-10.

Checked vacuum again, 20 inches at start up and upon warming drops to about 18/19 and I can hear and feel a popping/knocking coming from the bottom of the motor, maybe exhaust. I mean I can feel it in my feet sitting in the truck. Doesn't happen all the time.

Tried seafoaming the engine and while I was driving around after the Seafoam, I felt tons of lost acceleration. She woke up.

Next day, back to how she was.

I pulled the plugs and all of them are uniformly lean. Cleaned the plugs (autolite platinum ap105's) and put them back in.

Ran the truck abd pulled out what I am kinda sure is the SPOUT connector. ( plug by obdi test port) but the truck didn't react. I thought it was supposed to throw a code. Also, I found another similar plug up on the same side but tucked right behind the grill/drivers headlight.


Sprayed MAF cleaner all over the element and let the truck relearn. Ran the truck and unplugged the MAF, damn near stalled and did stall once.


If I had to guess, I THINK the truck is running lean for whatever reason and is knocking, so that is causing moderately white plugs and poor power.


But what could cause the truck to run lean? Vacuum is good/goodish so it's not an intake leak (I should buy stock in carb cleaner as much as I use to detect leaks). Could the oxygen sensors be reading slightly rich (falsely) and causing ab already lean motor to lean out even more?

Btw, I get no CEL and no codes either KOEO or KOER (except the code from me unplugging the maf).

 

[DasBaldDog]

And my fuel pressure is 39 psi engine off and 30 psi solid while idling.

ECT sensor is new, I cleaned out the IAC (but that should cause a vacuum issue anyways I would think)

 

[DasBaldDog]

Seafoamed the oil, ran it and changed the oil.

Also installed a new o2 sensor because one had a damaged wire.


No improvement. The knock/tap whatever seems to occur only when the truck is fully warmed and is consistent with engine speed (you rev the motor in a parking lot and you can,just barely, discern the increased tap/knock speed over the engine. So it's not the tranny, tires, wheels, etc.


Also I have noticed once the knock/tap starts, the temp on my dash gauge starts going up. Gets to about the A in Normal (maybe half way between A and L) and will then start coming down.


Any ideas anyone?

 

[Turdle]

There may be a low coolant level, or a sticking thermostat. Check the coolant level in the radiator. ( also check the reservoir level)

 

[DasBaldDog]

Levels are good, brand new thermostat. The thermostat is one of those "failsafe" models.

Thanks for the suggestions but I don't think it explains the lean plugs. If the engine is running lean, that explains just about everything, the question is WHY is it running lean?

 

[Roadrunner777]

MAF, you sprayed it down and it is to some degree operational because you unplugged it and it almost stalled the engine. I would suggest going back to the MAF with strong light and magnification, make sure the crossbars are cleand and glossy. I'm about 20% on this, but I'm mentioning it to be complete.

I have heard of cracks developing in the plastic tube between the MAF and TB. Easy to inspect.

No CEL more or less rules out the throttle position sensor.

You already cleaned the IAC.

Maybe close off some vacuum lines, see if that changes anything.

I might like to know what fuel pressures are when this is actually occurring, actually a profile of pressures at various engine speeds.

Do you see what I'm getting at? You are thinking lean. Somewhere in the chain of things, you are getting extra air or not enough fuel. That's it, that's the only two things that cause lean condition. Both can be tested for systematically.

Ignition timing could cause your overheating and pinging. I know that's not the lean category, just saying. That would be crank position sensor and the ignition module.

 

[DasBaldDog]

Well, the MaF doesn't always have a huge impact. Definitely throws a CEL when it gets unplugged but can be somewhat difficult to determine a performance difference.

The IAC, i do t know how to test if it's working. No code if I unplug it, and when I disassembled it (took the twohalves apart) the plunger moves freely but I wonder if it's stuck open or something.

Definitely no cracks in the black plastic tube. And the gaskets on both ends of the tube are good and clean.

Is there a way to test the ignition position sensor and module? I am fairly certain the coil is good. I did the old "unplug the wire from the coil and see if the spark jumps" test and the wires/plugs have less than 1,000 miles on them.

 

[DasBaldDog]

Replaced the Crank Position Sensor, IACV and MAF with known good parts and none of them helped out.

Going to pull the plugs again tomorrow to see it anything has changed.


Yeah, I got what you're saying Roadrunner. Either too much air or not enough fuel. I am starting to think not enough fuel. Holding very good vacuum, so definitely not a vacuum leak.

I removed the turned the TPS, and it had the predictable results.... The idle sped up to a certain point and then started to choke out. I tried adjusting the TPS after putting it back on the throttle body but the limits of it's adjustment are almost nonexistent.

All I can think of now is possibly the FPR but last time I checked the pressure it was good. I will go get the tool and check it again tomorrow.

 

[DasBaldDog]

Okay, update time.

Fixed the "knock", was just the new cat hitting the chassis.


However I still have the diesel sound under 2000 Rome and w general lack of power.


Last night I stuffed a rag in the tail pipe and despite having a blocked exhaust, the truck still ran. I put my hand near the passenger side exhaust manifold where most of the noise was coming from and felt a blast of really hot air coming from above the manifold but beneath the valve cover. Guessing manifold leak?


Due to the age and rust on this beast, I am guessing that the removal and installation of manifold and gasket will be difficult and probably have to install a new y pipe as the bolts on the old one may never come off.


What difficulty am I looking at here? On a 10 scale, 1 being turning the truck on and 10 is rebuild the engine blindfolded with oil change being about a 2.5?

 

[Nedwreck]

I recently put a engine in my 93 Explorer, and had lots of fights with exhaust manifold bolts.

However, that would have been the only thing I had to do to install a gasket, not the y-pipe (I never even separated it there at all).

You might want to inspect and see firstly if it has a gasket. All of mine did NOT have a gasket from the factory. So if yours has gaskets that means someone has had them off at least once already. That may help.

you'll want VERY GOOD 10mm 6 point sockets to remove the manifold with.

Remove/move ever how much stuff is in the way that you think will interfere, and remove the manifold bolts. Use a hacksaw blade or something to go in between the manifold and head if needed (cleanup/scrape), install gasket, and reassemble. A couple of the bolts can be gotten to thru the wheel well, with a wobble extension.

It's probably no more difficult than the LIM gasket, the only factor being the patience and PBlaster and time required to "talk" those exhaust manifold bolts into coming out.

Aint no shame in getting one or two loose a day and snugging them back up if you need to drive it. When they all decided to cooperate, go for it.

I live in Kentucky, not sure how much worse of a rust state PA is. (?)

Patience is the major key here, in my opinion.

 

[DasBaldDog]

Pa is much worse in rust. I used to live in Memphis and rust wasn't close to this bad.


Good and bad news. Good news is I don't think it's the manifold leaking. Bad news is that I believe it's the Manifold/YPipe fitting.

Those bolts are half gone from the rust and I have very little hope in getting them out. Prepped them last night with half a can of pb blaster always.

Worse case, I think I'll just quick steel over the whole joint and go on with my life. Lol.


Anybody know what size head those bolts are and what thread patter (on the off chance I can get then out)?

 

[DasBaldDog]

Is there a quick step by step on how to remove that wheel well? Would make this ALOT easier.

 

[Nedwreck]

I drilled a hole in my wheel well to get to one of the bolts on the passenger side. The rest were already out.

Sometimes a punch and hammer will help break them loose. just give 'em some taps, dont beat em to death, it helps dislodge rust.

I had one that was so bad I took a cold chisel and got one loose. It's hard to describe, but if you set it off center so that it "turns" the bolt as you hit the chisel, it *may* get it loose. Again, I'm not describing this well. The chisel is turned so the flat is parallel to the bolt, riding on one of the hex "bumps".

Patience young skywalker.... this job will drive you nuts.