1994 2.3 very low rpms at idle and when driving

cmattina · Jul 20, 2012

I just bought this truck and I really love it, beats the old s10 for sure. But it's rough...

anyways, it starts up great and idles relatively smooth, though it idles at about 350... When i am driving, i shift around 1000 and then it drops to about 6 and i am driving at around 800rpm. I can't even get it about 1000 without it sounding like I am red lining...

The thing is: all of this is happening with the check engine light (reader will be in the mail tomorrow), but one day, after running some errands I got in and the light DIDN'T come on, and it ran great: idled at 650 and ran at about 1500rpm while driving. since the light went out and it ran properly, i feel it is a electronic or sticky sensor...???

i'll post the codes soon

cmattina · Jul 20, 2012

thanks for any input, and i will be an avid visitor now on!

Insanejughead · Jul 20, 2012

My 2.3s (the turbo and normally aspirated) will NOT run below 800 rpm.

If your engine starts up and sounds fine without a lot of wiggling, then your engine is fine. A better indication of how your engine is running can be seen with a vacuum gauge. If the needle hovers between 18-20 inches of mercury, then it's golden.

I would guess that someone, at some time, swapped out a gauge cluster in your truck. The '94 2.3 rangers did not come with tachometers, but some people think that swapping out the gauge cluster from an '89-'92 2.3 will work, but they don't. I know because I've been one to try that.

I recommend that you take out your gauge cluster and check the Ford part number on it. You may find out that it's several years older than your ranger. If it's stamped (or stickered) with a F2****** or lower number sequence, the cluster is from a '92 or older ranger.

Welcome to The Ranger Station.

cmattina · Jul 20, 2012

Thanks a lot. I've been beginning to suspect that it may be a false reading.

Still, the odd thing is that every once in a while after driving around town all of a sudden the check engine light will go off and I will be getting a "proper" reading, with 1500rpm being the sweet spot for cruising and 650 being my stop light idle. Though, i do not think i hear or feel a big difference in performance, it is kind of hard to tell. SO, by your explanation, the swapped instrument panel malfunctioning is causing my check engine light to go on, and when the truck warms, it the panel works properly and the check engine light doesn't get confused by the rpms...???

I did pull the codes and they were 157 low volatage MAF

and 224 (haynes says SPOUT circuit open) the everyone says it means the coil pack...

I put in two brand new (aftermarket) coil packs as the others were cracked and the made zero difference. Wires and connections look good.

The truck may have been sitting for a while, so I put half a tank of fuel in and half a bottle of seafoam, and will be changing the filter this weekend. Airfilter was done already (i found some peanut shells that a squirll left behind n the box...

cmattina · Jul 20, 2012

but anyways, the light going out on its own and rpms going back to normal has happened twice now

--weezl-- · Jul 21, 2012

here's the bottom line, i do not know of a single motor that can idle at 350rpm without stalling, my work trucks, which consist of powerstrokes, e series gas, escapes, international (full size diesels) and freightliner trucks, not a single one of them would be able to idle at 350 regardless, let alone smoothly, and these include vehicles (freightliner fl-50) that has a rev limiter, or fuel shutoff, or some similar system, that won't let the engine go past 2500rpm, i know this because i put it into 2nd instead of D by accident, and had it floored, and when it stopped accelerating, i looked at the gauges (60km/h 2500rpm, 2nd gear)

Insanejughead · Jul 21, 2012

cmattina said:
1500rpm being the sweet spot for cruising and 650 being my stop light idle.

SO, by your explanation, the swapped instrument panel malfunctioning is causing my check engine light to go on, and when the truck warms, it the panel works properly and the check engine light doesn't get confused by the rpms...???

I did pull the codes and they were 157 low volatage MAF

and 224 (haynes says SPOUT circuit open) the everyone says it means the coil pack...

What speed are you going while cruising? 1500 Rpm doesn't mean anything to us unless you can tell us how fast you were going. (Also, what size of tire do you have and the gear you were cruising will help us figure out your true RPMs.)

The computer cares not about your gauge cluster. The check engine light is by itself among the gauges. The two codes you pulled will be there no matter what gauge cluster you have installed.

Code 224 deals with your Ignition Module. If your gas mileage isn't hurt, and you don't mind the CEL being on, then I wouldn't worry about that code. I had it the entire time my pickup had the stock motor, but I always got 22-24 mpg.

My conjecture is that your tachometer is configured for a v6, which often came equipped with tachometers. If that's the case, then you can do some simple math and get a close approximation of what your RPMs should be (and most likely, are).

650 is what your gauge is showing you, but if you divide that by 2/3rds (.66) then that number comes to 985. Right under 1000 RPM is what the 2.3L loves to idle at.

1500 divided by 2/3 = 2275. Now, if you have stock sized tires and a 3.45-to-1 differential and in 5th gear, that is pretty much exactly what RPM you can expect while going around 55 mph. If you have a 3.73 ratio differential, your engine RPMs would be roughly 150 higher than that, at that speed.

wr250rdr · Jul 21, 2012

Not to poke holes but I Did do a tach swap into my cluster and it reads accurately. When it's hooked up to smog Equiptment the smog comp reads identical to the tach. And I have a 94, that was swapped with an exp tach. It works...

cmattina · Jul 21, 2012

1500 rpm would be at 60km/hr. On the highway at 90 km/hr I am around 1800 or 1900rpm. However, in the back I have 15's and in the front I have 14's. The read tires are probably 29 or 30 inches...

The weird thing still remains... why is the light going out after warming? It could be a temperature thing, or it could be enough bouncing around is jiggling something back into place... And why is the check engine ligh and false tach readings connected...

As for 224, i guess i should check all my wires and plugs, as i've checked my coil packs already, is there anything else to check?

and 157, would cleaning or getting a new MAF help?

Insanejughead · Jul 22, 2012

wr250rdr said:
Not to poke holes but I Did do a tach swap into my cluster and it reads accurately. When it's hooked up to smog Equiptment the smog comp reads identical to the tach. And I have a 94, that was swapped with an exp tach. It works...

I know nothing about the Explorer tachometers. What engine did the explorer have in it?

cmattina said:
1500 rpm would be at 60km/hr. On the highway at 90 km/hr I am around 1800 or 1900rpm. However, in the back I have 15's and in the front I have 14's. The read tires are probably 29 or 30 inches...

The weird thing still remains... why is the light going out after warming? It could be a temperature thing, or it could be enough bouncing around is jiggling something back into place... And why is the check engine ligh and false tach readings connected...

As for 224, i guess i should check all my wires and plugs, as i've checked my coil packs already, is there anything else to check?

and 157, would cleaning or getting a new MAF help?

Work on figuring out the reason for the codes. Once they're fixed and those two errors aren't affecting engine performance, then you'll have a better idea of what your RPM should be. I've had code 224, but not 157.

Code 224 deals with the ignition module. Plugs and wires won't matter, as far as I know, but it's worth checking them anyways, just to be sure they're fine. I honestly never had any issues with my motor's performance with that code, though.

Code 157 could be a completely different story. Cleaning the MAF might work, as it could be dirty and causing an erratic reading. If it says it has low voltage, then look up the specs for the voltage requirements for your MAF and then check the ground that comes out of the MAF. An iffy ground can impede voltage and subsequently cause the MAF to not read 100% as it should.

cmattina · Jul 22, 2012

I am curious if anyone knows if the tachometer is connected to the ignition module??

cmattina · Jul 22, 2012

Or even more so, if there is some sort of voltage issue from the addition of the tach. Though I cannot clearly see how this tach would be connected to the ignition coil as aftermarket tachs are???

scotts90ranger · Jul 23, 2012

It's not the tach, it could be the ignition module though if you take it to an auto parts store they should be able to test it.

a '94 explorer only came with one engine, a 4.0L, same tach and shouldn't be an issue

Thed · Jul 23, 2012

Insanejughead said:
My 2.3s (the turbo and normally aspirated) will NOT run below 800 rpm.

I set mine to idle at 780... I rescued her at 450 one time, too. :icon_confused:

cmattina · Jul 23, 2012

mine sits at 400 without needing to be rescued. So i don't think it is actually idling at 400.

All logic says that the tack and codes are seperate issues, that is clear. HOWEVER, the light goes out and the tach funnctions properly at the same time after the engine warms, that is a fact. I don't know if i want to spend 100+ on an ICM, though i can clean the MAF, or get another from the wreckers. I havn't even changed the fuel filter, coolant, fan belt, or tanny fluid, which all need to be done. I havnt had a chance to check my actual mileage yet, so, i will wait to see what i get on a full tank.

Think a cracked fan belt could cause water pump issues?

1994 2.3 very low rpms at idle and when driving

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