Help please !

[BOB MARLIN]

This is my first post on the site , please be easy on me!

I have an issue with my truck-1996 ranger, 4cyl,5 speed, 4x4 single cab.
135,000 miles.

Runs fine untill the temp gets aroung 165 deg. Then I lose alot of power. Truck still runs smooth, idles fine, starts up fine when hot. Just as soon as it warms up I can hardly get it going from a stop sign. I've had this truck for 6 years and it's never had alot of power but this is something new. New air cleaner, timing belt about a year and a half ago. Fuel pressure is about 32 psi at idle. At no time does it spit, spudder or stall. Also cleaned maf. It's like something that is supposed to switch off or on when it reaches operating temp is't switching. It drives like its always in too high of a gear.

 

[BOB MARLIN]

I'v also replaced the coolant temp sensor, plugs and cat. and no codes are thrown.

 

[Mark_88]

I'm no expert on this model year and I'm sure someone will respond who actually knows what they are talking about, but apparently the IAC can stop working once it reaches a certain temp...not even sure if yours has one...but you can also do a search on the forum for IAC and read up a bit till your answer comes...

Oh, and welcome to TRS...you will get the right answer...

 

[BOB MARLIN]

I cleaned that too!.

 

[escort_gts]

Maybe the engine temp switch. Maybe injectors?

 

[escort_gts]

Have you checked the fuel filter?

 

[BOB MARLIN]

Picked up a fuel filter yesterday, gona install it tomorrow. It needs to be done anyway.
Would a bad O2 sens. cause this type of problem?.
Can't figure out why it wouldn't throw a code if it was the O2.

 

[escort_gts]

It is possible for it to go bad and not give any codes. But it is rare. Try the filter and check into changing the engine temp switch. I had an 89 escort lx that i swapped in an 87 gt motor and spliced in the wireing to the original harness. During the swap i forgot to run the wires for the engine temp switch and for months couldn't figure why it was running like crap. Hooked up that sensor and ran like a champ...

 

[BOB MARLIN]

I changed the cts last week, if that is the "switch" you are referring too. It made no difference. Whats odd about the whole thing is the truck doesn't spudder or mis or backfire or idle rough. It does not stall and starts right up, just like nothing is wrong. But as soon as it get above 165 on the temp gage it acts as if you are going against a 60 mph head wind. I can hardly leave a stop sign.

 

[Earl43P]

Here is a pretty good explanation of what goes on:

http://www.fordfuelinjection.com/?p=64

In your case, the computer is going into closed loop at that coolant temp (165). That causes the computer to use whatever values the sensor's are reporting. Can a bad O2 sensor cause problems and not throw a code? Absolutely. So can an ECT, IAT, MAF, TPS, etc. Over time, the computer will "recognize" a bad signal as good and make the engine run poorly as a result.

Your best bet is to TEST each of those sensors:
http://www.fordfuelinjection.com/?p=28
http://www.fordfuelinjection.com/?p=29
etc.

If your O2 sensor is over 60k miles old, replace it.

I have a ScangageII that shows each of those sensors as a gage reading. Many scaners can do that.
I suggest you ask around and beg/borrow/buy one or troubleshoot the good old fashioned way, with a meter.

 

[BOB MARLIN]

I was unaware of the "act". I need to check that. Where is it located.?
I am assuming that the O2 sensors are originals. But thay aren't cheap. I am trying to kinda peck around replacing them untill I am sure it's the problem. Some of the things needed replacing anyway. I did read a bit on how to check the O2 with a volt meter. I'm just not sure if mine meter will read less than a volt.

 

[Earl43P]

IAT should be on the intake tube. Has GY and GY/RD wires.

 

[BOB MARLIN]

Would the fan clutch cause this much drag?. About the temp that this is hapening I notice is about the sametime as the fan clutch is kicking in.

 

[escort_gts]

Possible but I doubt it is the problem. Could be wrong though....