shoggoth80

Odd question...
is there any way to adjust the fuel/air mix on the fuel rail? There are some small, elongated knurled ***** on there that look like they would control some kind of air/fuel mix. I ask, because a)nothing is mentioned in the manual, and b)I had an Audi once that you could alter the air/fuel mix on/to the injector rail.

If this is possible, does backing it out increase air, or fuel?

trans_am7935

no there is no adjustment unless you have an aftermarket adjustable fuel pressure regulator. also there is no reason to adjust your air/fuel ratio, as the computer does it for u. the only reason to do it yourself is if you put a cam in it, turbo, or blower on it. if you are having problems with it, i would look at your O2 sensors first, MAP sensor and IAC sensor

shoggoth80

Lol... Yeah, I ran outside and checked it... it's just some kind of valve. Probably a pressure blow off or something. Or it's a hook-up for some gauge tool or something.
MAP sensor is new. Got a new O2 sensor waiting to be installed, though I hadn't thought about the IAC sensor... it's easy to get to.

Sensors...I don't trust them too much. Lol. Replaced a bunch recently, and replacing more over the weekend (crankshaft, and 02).
I'm worried that I might be running a little lean. I occasionally get a little pinging here and there... but I am also chasing down some sort of harmonic vibration, which makes it harder to hear exactly what is going on during ignition.

I'll check the price on the IAC... if it isn't too expensive, I'll pitch the old one for good measure.

Slick761

U are correct! That **** comes off to reveal (ready for this) the fuel pressure relief valve. Doubles as a port for your fuel pressure gauge.... not nearly as exciting as an adjustable regulator (to adjust your a/f ratio) would be.:-( ... and yes these engines tend to run lean from the factory. Emissions. If your pinging its probably due to carbon buildup in your cylinders. I could tell you a way to clean it free but no one would believe me.

shoggoth80

Lol... mist water into the manifold? Some guys do it on their motorbikes to avoid tearing down the top end. If I could find the spare time, I'd pull the head and look... but it isn't exactly a fast process in my experience.
Still, I am temped to do lifters and pushrods... as they aren't very expensive. If I got that deep, I'd of course do the head gasket as well. Maybe I could get away with just a good cleaning on the valvetrain components, one set at a time or something. Maintenance like this gets tough when you only have two days in a row off a week to do something about it. If I can get a gauge to test fuel pressure, I know where it goes now. Would be a good thing to verify. I am going to pop my filter out over my weekend to inspect the pick up screen. IF it is dirty (my fuel filter was), that might be causing some of the cutting out/missing/backfire issues I have been having. Eliminating suspects at this point.... this all rolls into some level of neglected maintenance...so I am playing catch up... quite a bit.

Slick761

You called it. Most people look at me like I'm crazy when I tell them to mist water into the throttle body.... oooold mechanic trick.... I proceed to tell those people that look at me like that "ok.you got me.... the real trick is to put a garden hose in your throttle body" heh heh heh..... seriously though if you do that a little here and there it will be spic n span in no time. Also though check your knock sensor on the driver side of your block almost midway back..near where the oil pan bolts up.. they're kinda fragile. I just replaced mine.... think it was around 40$...

P.S. I don't trust those old sensors either

SNIDELYWHIPLASH

They did away with the knock sensor on the HO motor...

Slick761

What year is the jeep? See I have no idea....could be renix or h.o. guess I assumed due to his talk of distrust and seeming mild distaste for sensors that it was a renix.

SNIDELYWHIPLASH

His profile says he has a '93 with a 2.5 4 cylinder. I guess it's not an HO or a Renix, LOL.

shoggoth80

1993 with a 2.5L... from what I gather that is the first year for the multi-point injection system. Pretty sure it is the AMC 2.5L, as I think that is all that was supplied for the 2.5L. I *wish* I had the 6cylinder in any flavor... though the 2.5 is supposed to be the AMC 6 with 2 cylinders lopped off... so I guess that doesn't speak ill of the 2.5's reliability. A straight 6 of almost any variety is a notoriously strong motor in terms of longevity.

I've got my fair share of sensors... none of which I trust to do their jobs right at this point. I have replaced:
Throttle Position, Manifold Absolute Pressure, going to replace the Cranskshaft sensor, as well as the 02 soon ( I have them, need to put them in), I have also replaced the coil, pick up coil, plugs, wires, rotor cap... replaced some lines that were iffy. I can't find a knock sensor part number for my engine, so I think it's not there. Thinking I might do the MAT and IAC sensors as well. Even if I have to get to them 2 weeks from now. If I wanted to get fancy on removing carbon, I'd pull the head, scrape and sand, and clean... drop the crank and rods out the bottom and do the same to the pistons. Though you can probably get away with just cleaning off the crowns.

It *is* possible that a torched valve or a out of spec timing chain could cause these problems... but those would manifest themselves in worse ways than a little noise and misfires I think.

Slick761

I'm on the app.... I can't seem to view profiles.