I just bought a 1992 4x4 Ford Ranger and I knew what the issues were before I bought it and thought I might get lucky and replace something simple. But I think I've got a bad cat or low compression I'll test the compression tomorrow morning, so it's very gutless and it tops out around 50-60 mph in fourth gear. I've replaced the MAF, AIC and the O2 sensor for free which didn't fix anything but I'm also now getting the code P0172 after replacing the O2 sensor any ideas if the compression test doesn't result in anything tomorrow? Also, one more thing the low range light is on and it wont turn off not sure if the light is bad but idk anything about 4x4 since this is my first truck.

 

Welcome to the forum

You can test compression with vacuum gauge and also if exhaust is clogged, great tool to have for $25
18-21" of vacuum at warm idle is expected at sea level, means good compression, less is OK above 2,000ft elevation
REV engine and hold at about 2,000rpm if vacuum is slowing dropping then exhaust is partially blocked

Expected compression is 150psi on a 4.0l OHV engine, all spark plugs removed, good battery and throttle wide open when testing

Hard to tell from ad and your description if its a manual or automatic, I am guessing manual since you said "4th gear" and not OD(which is 4th in an A4LD automatic)

If manual trans there is a clutch switch that tells computer when clutch pedal is down, this tells computer to limit RPMs to 3,000, called a REV limiter, if this switch is broken or bypassed then engine RPMs would be limited to around 3,000
Bypassing the clutch switch was done to get starter motor activation when part of this switch failed, there are actually 3 switches inside this one switch, starter motor switch, neutral switch(REV Limiter), cruise switch(shuts off cruise)
Automatics have similar switch for Park and Neutral but on the transmission


4low light could mean a few things
Does the transfer case have a manual shift lever in the cab or is it electric shift, so buttons on the dash?

 

Thanks for getting replying to me so I've got the compression results 1. 180, 2. 190, 3. 190, 4. 165, 5. 160, 6. 165 not consistent but it shouldn't be so gutless right? I never held the throttle wide open tho is that a problem? The reason I said 4th gear is because when I shifted up to OD 5th gear it doesn't have enough power to even stay at 55 mph. And 4low light is dim not as bright as the 4x4 light when I activate it also yes its an electric shift it has only two buttons 4x4 and low range on the dash. Just did a vacuum test at idle it sits around 15-14 (maybe a leak?) when I give it throttle it sits around 18-15 then when I let off the throttle it jumps up to 23 then falls back down really fast I did this in the dark so I'll test it again in the morning.

 

Yes, vacuum is pretty low at idle but compression seems OK, which is odd

Whats your elevation above sea level?

Will the engine REV above 3,000rpm?
4.0l OHV makes best torque/power at 2,500rpm, and best horse power at 4,200rpm, so should be no issue holding RPMs above 4,000rpms


The 4x4 lights both get 12volts with key on, the 4x4 controller uses each bulb's ground wire to light the bulb up
So if 4low light is on with key on it could be a short to ground on that bulbs wire, assuming transfer case is NOT in 4low of course, lol

 

The engine will rev just fine without a load but in gear I cant get much above 2500-3000rpm in fourth gear around 55 mph and I cant really gain anymore speed. I haven't tried it in any other gear but I'm pretty sure it would go above 3k since I've got power in first for the most part also, I'm 20' above sea level.

 

None of it reads correctly, we are missing something

The low vacuum could be blocked exhaust but the REV test says "no"

I like these tests with vacuum gauge: https://www.gregsengine.com/using-a-vacuum-gauge.html

I assume the vehicle rolls OK in neutral, brakes are not rubbing, lol, have to ask?
Running out of ideas

Could possibly be a fuel pressure issue, 30-35psi is expected at all engine loads
There are 2 fuel lines attached to the engine
One goes directly to the fuel rail on drivers side of intake, this is the IN from filter/pump
The other line goes to the FPR(fuel pressure regulator) on passenger side front, this is the Return line back to gas tank
The FPR will also have a vacuum hose attached, check that hose for gasoline, shouldn't be any of course

 

That's why I'm kind of of stumped myself, it rolls fine plus if the brakes were rubbing that bad I would imagine I would be able to smell and feel it fairly quickly. Now ill test the fuel pressure this Monday unless I'm busy, I'll let you know what results I get as soon as possible thanks.

 

Well I basically got 40 psi but I noticed two wire plugins that were unplugged which I noticed earlier but I didn't realize they went to #1 and #2 injectors, plugged them in and didn't notice a difference. So I tested both injectors and one came back with 72.0 ohms that's got to be the issue but wouldn't that cause a misfire code with them being unplugged?

 

No misfire codes on OBD1, oh they are there but unless there is a Cam sensor you won't get misfire codes

1992 uses Batch fire fuel injection, so on a V6 the computer opens 3 injectors at the same time then opens the other 3 next time, usually 1, 2, 3 and then 2, 4, 6
So 1 and 2 being unplugged would effect power and I would think you would feel some misfires under load

Yes, the injectors should be 11-18 ohms

 

Okay just put the new injector in and it ran good, right before I took it out for a test drive it did seem to idle a little off. now while on the drive I noticed no difference in the power but about a mile or three down the road whenever I came to a stop it dropped to 500-700 rpms and sounded pretty rough even died once while racing back to the house it sounds rough at idle now. I bet when some debris got inside and, clogged one or multiple up since the intake was oil fouled from the bad valve cover gaskets. I'll mess with it again tomorrow but now I've got 3 different obd1 codes 172, 185 and 186 if that's helps you.

 

185 and 186 are but MAF sensor codes in a 1992 4.0l, but indicate lower voltage from MAF sensor than expected for throttle position and RPM
Clean MAF sensor, if you haven't and check connector for corrosion

172 is probably a result of the above 2 codes

 

MAF is new also got the same type of code once or twice for IAC and O2 sensor which are also brand new but haven't seen one of those codes since I reset it until obviously now.

 

Okay just took all the injectors off again and now the last one it took out had the green nozzle split in half nothing fell into the motor when taking it out. But I had a spare one from the bad injector so I popped that off and put it on this one. So while I was cleaning it I notice it was cracked once again the arrows show where the spilt starts and ends would this cause any issues? sorry for the crappy image my camera sucks I'll probably have everything put back together before I see your msg.

 

It's called a pintle cap, there are a few designs for them: https://g4y9a3e2.rocketcdn.me/wp-con...Boschmpi04.jpg

Cracks can cause them to drip instead of spray

But should cause low power at speed, just maybe misfire at lower RPM

 

Just replaced the bad injector it started up like normal sitting around 1000rpms 5-10 minutes later it finally warms up and drops to around 800 and starts to idles a little off maybe a small misfire it sounds like when I first bought it. And it still has no power and I got the code 172 once again.

 

And no other codes now?

Just 172 Lean on passenger side of engine

 

Yeah just 172 I'll take it out again tomorrow maybe I can get another code to show up. But I thought 172 was fuel rich not lean?

 

Okay I tried testing the injector plugs again now I'm getting .01 volts on all the passenger side I could only access the two on the driver side and it's showing around 2-.4 volts if that on #4 and #5 last time I check it I swear I saw almost 12 volts must have missed something. the passenger side injector plugs don't do anything if unplugged while running maybe a bad ECM? I checked the EEC relay and that was fine find but I cant find the ECM relay any ideas?

 

Yes, sorry,
P0172 System too Rich (Bank 1)

In a 1992 the EEC relay might be under the fuse box, drawing here: https://www.justanswer.com/uploads/L...pump_relay.gif

But engine wouldn't run at all if injectors had no power
And engine wouldn't run if 3 injectors on one bank/side were unplugged either

 

I already thought about this idk why its still running I've unplugged #2 and #3 and it didn't run any different so idk what the full issue is. I might just send it into the shop and have them fix it.

 

Well it was the computer finally got the replacement tonight and it sounded so much better and it actually has power now. But it is idling a bit off so I got 2 codes 41, 95 idk if 95 is that big of an issue but 41 means it running lean correct? and if so where should I start looking for that issue?

 

OK, something is wrong

You can have 4 digit codes(1995 and up OBD2)
1994 and older use OBD1 and 3 digit codes or 2 digit codes but not BOTH

So decide, what are we working on here???

Lean code usually means there is a vacuum leak(90%) or low fuel pressure(5%) in any year
Other 5% is old O2 sensor or failing MAF sensor