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HELP! bogs really bad and tach drops to zero.

H

hotrodford88

NAXJA Forum User
Location
jasper,al
i have a 89 cherokee 4.0 auto all stock under hood. when it is cold it bogs really bad,almost dies, and the tach drops to zero if you give it more than half throttle or go over 3 grand. if your easy on it and stay below 3000rpm it drives fine. and after you drive 10-15 miles it does fine over 3 grand and full throttle. anyone else run into this? any help is greatly appreciated.
 
CTS or MAT temp sensors may be bad (based on the cold temperature problem). They both have the same resistance versus temperature readings when new. It can be tested with an ohm meter. The temp versus ohms table is listed in a bunch of prior threads here.

TPS may be bad. Or the TPS may not be calibrated right?

But check the fuel pressure too. Is the jeep new to you?
 
Re: help! bugs really bad and tach drops to zero.

Mods, can you move this post to the other post. He has more info here, but it is a near duplicate post.

OP, this definitely sounds like the CTS Coolant Temperature Sensor, or Manifold Air Temperature, MAT sensor is bad!!! Read my reply in your other post.
 
yes its new to me. i just got it yesterday. what do all the abbreviations mean? i know tps is throttle position sensor. what are mat and cts? its wierd the way the tach drops to zero but the motor is still running just bogged bad and sputter/stuttering.
 
I just answered that in your other thread.

this definitely sounds like the CTS Coolant Temperature Sensor, or Manifold Air Temperature, MAT sensor is bad!!! Read my reply in your other post.
Click to expand...
 
where is th cts on this truck? looked it up on autozone and they said it was on the thermostat housing. its not on mine. not even a place for one.

and how do i calibrate the tps? it looks new to. PO may not have calibrated it right.
 
hotrodford88 said:
where is th cts on this truck? looked it up on autozone and they said it was on the thermostat housing. its not on mine. not even a place for one.

and how do i calibrate the tps? it looks new to. PO may not have calibrated it right.
Click to expand...

CTS was moved to the T-stat housing in 91, prior to that it was in the engine block, driver's side, under the intake and exhaust manifolds.

Lots of good info here:

http://www.naxja.org/forum/showthread.php?t=1072534

If you do not have a volt ohm multi meter, get one, and learn how to use. Diagnose the problem, then go part shopping.
 
Simply because you just got it, you Could also clean your grounds on the block at the dip stick, at the battery and block/firewall and maybe a new coil, plugs cap and rotor "look" new but mine did too when I swapped everything out for brass terminals.

I like the piece of mind that it IS new, not just looks new. Check for vacuum leaks also, mine didnt have an issue until it got cold outside.
 
souske said:
Why would you use used sensors?
sounds like a good way to get frustrated to me
Click to expand...

Agree, however, while the coolant temperature sensor is available most anywhere, the manifold air temperature sensor is OBSOLETE.

His option other than a used one is substitute a MAT with the same ranges. The one I am using is:

MAT: Air Charge Temperature Sensor Part No. 1814
Marren Fuel Injectionhttp://www.injector.com/cart/pc/viewPrd.asp?idproduct=65&idcategory=12


This is a 3/8" pipe size and will not work in the intake manifold. I purchased a 3/8" steel bung from JEGS and welded the bung into the intake tube--aftermarket Rusty's--and it works fine, in fact, I think having it out of the manifold ends up providing a slightly richer mixture to the engine.
 
joe_peters said:
Agree, however, while the coolant temperature sensor is available most anywhere, the manifold air temperature sensor is OBSOLETE.

His option other than a used one is substitute a MAT with the same ranges. The one I am using is:

MAT: Air Charge Temperature Sensor Part No. 1814
Marren Fuel Injectionhttp://www.injector.com/cart/pc/viewPrd.asp?idproduct=65&idcategory=12


This is a 3/8" pipe size and will not work in the intake manifold. I purchased a 3/8" steel bung from JEGS and welded the bung into the intake tube--aftermarket Rusty's--and it works fine, in fact, I think having it out of the manifold ends up providing a slightly richer mixture to the engine.
Click to expand...

Won't a 91 XJ MAT with an E-pigtail fix work?
 
Ecomike said:
Won't a 91 XJ MAT with an E-pigtail fix work?
Click to expand...

Could be maybe--I don't have the specs for the 91 sensor handy, and I'm not sure of the size 87-90 vs. 91+ for mounting.

Just looked up the specs, they aren't even close.
 
joe_peters said:
Could be maybe--I don't have the specs for the 91 sensor handy, and I'm not sure of the size 87-90 vs. 91+ for mounting.

Just looked up the specs, they aren't even close.
Click to expand...

Are you referring to the ohms versus temperature specs or something else?
 
Ecomike said:
Are you referring to the ohms versus temperature specs or something else?
Click to expand...

Correct.

Someone once posted on the forum that there was a common GM direct fit that matched temp/resistance, but they didn't have the part number. I think it was Jon that put me onto the Marren part.
 
Thanks, a lot of us have been looking for an answer to that for over 2 years now.
 
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