New here and need help

[Shaggy]

Hello I'm new here I have a 93 ford ranger with a 3.0 engine that I rebuilt about 7k miles ago. I have a couple problems with it I can't figure out I have an undercooling problem have replaced the thermostat 3 times, maf sensor, temperature sensors, and my heater core. I also have a reving problem when I let go of my gas my truck wants to keep speeding up unless I press my clutch in to let the engine rev to 3k then it droppes back down I have replaced my iac motor and nothing changed. Both problems have been going on since I bought the truck way before I rebuilt the motor. If anyone can help me figure out what else could causing these problems I would be grateful. Thanks

 

[Dirtman]

Welcome to the forum!

I'm sure one of the resident geniuses will be along soon to give you much better help than me but in the meantime a couple questions.

First and foremost have you checked the computer for any codes? Your truck is OBD1 and just because the check engine light isn't on doesn't mean there's no codes in there. Codes are valuable info...

When you say "undercooling" I assume you mean overheating, are you using the OEM temp thermostat? Have you verified the temperature outside of relying on the instrument cluster guage? Im assuming the water pump was replaced when you rebuilt the engine? At 7k miles the engine should have "burped" but it's worth asking if you are sure all the air was removed from the system?

As for the reving issue. Check your TPS sensor. If you have a multimeter you can do a sweep test. Pretty good video on how to do this below.

 

[Shaggy]

Thanks for the reply but no it really is an under cooling problem. I'll take a picture and add it my heater is actually pretty cold it heats up just a little enough to keep me from freezing lol. My thermostat is OEM and I did check for codes and I don't have any codes.
I'll test my TPS sensor and let you know

 

[rumblecloud]

When you say it's under cooling, to me, that means it is not getting cool enough. Nevertheless, screw the terminology.
Since you replaced the heater core, can we assume you're not getting any heat? Have you felt the radiator hoses? Is the gauge frockled?

Keep posting, someone will be able to help.

 

[Uncle Gump]

I've been messing with vehicles for many years... can't say I ever heard the term until now.

From what I see on your temp gauge (cold) and description of minimal heat from the heater... it would be better to say the engine won't reach operating temperature. That could also be considered over-cooling I guess but certainly not under-cooling.

How about you forget that term and tell us what is actually happening with the engine temperature. Does it run cold... doesn't heat up?

 

[Shaggy]

Right it's not heating up all the way. I felt my hoses and there warm but not like any of my other cars and I'm sorry if I was using the wrong term I'm still learning

 

[Shadowrider6661]

It could be the size of your radiator. I have the same problem with my 97, it doesn't get to operating temperature. It runs cold because I have the biggest radiator made for it, the only time the temp goes above 100° is when I'm pulling a trailer, even then it only gets to 130° but drops back down constantly. I don't know if this helps, just food for thought !

 

[rumblecloud]

Right it's not heating up all the way. I felt my hoses and there warm but not like any of my other cars and I'm sorry if I was using the wrong term I'm still learning

Ha! We're all still learning! Don't worry about the terminology...let's talk about fixing your truck.

 

[Uncle Gump]

I've owned a few 4.0L engines... I've never had any heat issues. They will typically cook you right out of the cab. I say this because it's not like the in-line 4cyl engines that just don't heat up well.

So you've replaced the thermostat three times? Are you buying the cheapest stats you can find? Have you tested any of them?

My mind says it's the thermostat. To me I think it opens to soon and once it does... it doesn't offer enough of a restriction to let the coolant heat up. Put a pot on the stove with water and your old stat with a thermometer. Do a little testing.

There are a ton of junk parts these days... see if you can find a Motorcraft Thermostat.

 

[Dirtman]

Are you sure the guage is working? If the needle never moves at all I'd be inclined to say the guage is not functioning.

You say you replaced the sensor. There are two temperature sensors, one two wire used by the computer and 1 singe wire used just for the guage. You can also obviously have a problem with the wiring/connector being broken.

 

[Shaggy]

I tested my tps sensor and it's good. I'll have to test the thermostat. I did put a peice of cardboard in front on my radiator and it did heat up more I was getting better heat out of my heater and my temperature gauge went up as well just above the cold line

 

[Dirtman]

Another issue with the reving could be a dirty throttle body not closing properly, try cleaning it with throttle body cleaner (NOT CARB CLEANER!). If you use carb cleaner it can remove the coating and cause the throttle body to stick. Most ford throttle bodies have a teflon coating on them. Some even have a warning sticker on them about this.

Or someone messed with the anti-deisel screw that people mistake for an idle screw. If you mess with that screw it messes up the TPS sensor.

 

[Shaggy]

Ok i will look at those

 

[19Walt93]

What brand of thermostat are you using and does it seal well in the housing? If coolant can pass around the thermostat it isn't going to work. I'd fix the temp problem before getting involved with the running issue. When you get that far, check the voltage at the signal return wire coming out of the TP, you want as close to 1 volt as you can get by moving the TP back and forth on the screws.

 

[Alan_nc]

How long have you run the engine. My 94, 3.0 takes forever to heat up and even after 10 miles of driving the needle will only be maybe up to 1/4. I do have good heat after maybe 5 miles.
The thermostate shouldn't make any difference (unless it's stuck shut) as at some point they all are open and the coolant is running freely.