Recently my jeep started having issues with the idle, and the throttle would fluctuate under constant pressure so I had a friend who is a mechanic look at it. He told me to replace the Idle Air motor because it was malfunctioning and not compensating for the right amount of air. He found this by removing vacuum seal while it was idling to see if it adjusted and it did not. I replaced the Idle Air motor and throttle position sensor with parts from Rusty's Offroad and soaked the entire throttle body in some solvent to clean it out. Now, aside from apparently blowing out my radiator it is barely running at all and stalling out frequently. I got it to Autozone (barely) to get the errors read and got the following:

P121 (Throttle position sensor shorted)
P122 (Throttle position sensor low voltage)
P123 (Throttle position sensor high voltage)
P301 (cylinder 1 misfire)
P700 (General transmission fault, Tranxaxle control system fault)
P740 (Torque converter clutch no RPM at lock-up)
P756 (Solenoid B function failure)

So now I most likely need a new radiator (engine is overheating badly even at short distances and after about 5 mins driving burning smell and lots of grey/white smoke) and have to figure out whats causing my engine to not run properly. I'm assuming that most if not all of those errors can be traced to a single malfunction. So which one is the true problem child, and are those issues enough to be considered a total loss? This is a project vehicle, its not my primary mode of transportation so I can fix a little at a time luckily, but does anybody have a good idea where to start?

 

Have the codes cleared, see what comes back.

 

Also all of the transmission codes could possibly be caused by the throttle position sensor.

The throttle position sensor control most of the transmissions function along with the TCU.

when my throttle position sensor went out my XJ bucked and lurched and was just going completely haywire, I swapped out the TPS and boom ran like a champ.

 

What's a vacuum seal?

Did you remove the MAP Sensor, IAC, and TPS from the TB when you cleaned it?

Did you remove the TB from the intake to clean it, and install a new TB gasket when it was reinstalled?

 

Ok, so the vacuum seal that he removed was just a little plastic nub that covered a line where a hose could be connected to the cylinders, its at the top of the engine near the throttle body, I have no idea what its actual purpose is but when you take it off air escapes so it was a good way to test the IAC.

When I cleaned the throttle body I did take of the IAC but forgot to take off the TPS, so when I put it back on the TPS started to malfuction, which is why when I replaced the IAC I replaced the TPS as well, so the TPS that is on there and showing errors is virtually brand new. I did not remove the MAP sensor either, or any gaskets. I'm not familiar with where the MAP sensor is.

I figured the transmission issues stemmed from the TPS, but I don't know whats causing the TPS to go haywire like that and why the replaced IAC didn't solve my original issue. I also have no idea what the solenoid B does.

 

Also would the cylinder 1 misfire be a result of the TPS/IAC issue as well? I would assume so, but I'm a relative n00b at this stuff.

 

Also, the engine tends to have a lot of trouble cranking. Battery power is fine but most times especially cold I have to pump the gas while cranking it to get it to catch. If I don't pump the gas when cranking it will turn over but not catch. This makes me think that the problem has to do with the whole fuel delivery system and not just the TPS (which is what pointed me towards the IAC first).

 

Here's a couple pics that shows the MAP sensor being tested. You can see its location on the throttle body. No doubt you know where the IAC and TPS would be. The MAP sensor is attached to the TB with two screws and is vacuum connected to the TB with an L shaped rubber tube.

Using a strong cleaner on the TB is not recommended, especially with the sensors attached. Throttle Body Cleaner is the only thing that should be used. Unfortunately the MAP sensor and p[erhaps the TPS were damaged by the cleaner you used.

I would recommend removing the TB from the manifold, Remove the sensors, clean the TB with the TB cleaner. The TPS should be a sealed unit so Your cleaner may not have damaged the TPS. The MAP sensor however may have been damaged and may need to be replaced.

When/if you remove the sensors to clean the TB, examine the pins in the sensor connectors. Verify the pins aren't bent, or damaged in any way.

Use a new gasket when reinstalling the TB.

Do this then disconnect the negative battery cable for several minutes to see if the CEL codes clear. If not you will need to take it back to Idiotzone and have them clear the codes. See if any of this helps.

You can get TPS', MAP sensors, IAC's, and TB gaskets at Advance Auto Parts, O'reilly Auto Parts, and even Idiotzone. Try and get BWD parts if possible.

I know you have other problems but try to fix the collateral damage for now.

Good luck

 

PSUmaninSC,

When you replaced the TPS did you make sure it was installed so the the tangs of the TPS were properly engaged with the throttle shaft blade? If not properly installed the TPS will have no movement when the throttle plate is opened.

If properly installed you would have to install the TPS so it was clocked a few degrees clockwise as you place it on the TB to allow the throttle shaft blade (at idle) to engage the tangs in the TPS, then rotate the TPS counter clockwise (feeling the spring tension in the TPS) until the mount holes line up. Fasten it down at this point. This will preload the TPS to approximately 18% throttle opening when the throttle is closed. 18% = approximately .90 volts, based on a 5.0 volt input from the PCM.

 

Ok so, today I was off work so I did some good maintenance on the throttle body. A few days ago I disconnected the ground, removed the throttle body. This morning, I went down to AutoZone and picked up a new TPS, MAP, and gasket along with some throttle body cleaner. I put on the new TPS with it turned slightly to the left etc and the new MAP after spraying it down with the throttle body cleaner. Then I drained the oil, replaced the throttle body, and added the new oil. Fired it up and after a few cranks (understandably considering the new equip) it fired up and sounded like it was working its way back to a good healthy idle. There was a slight tick but I'm pretty sure its just one of my lifters, so I'm pretty confident that my throttle issue is cleared up, even though I only ran it for about a minute. The check engine light is still on but that's most likely because it didn't zero out, so I'm going to run the ignition sequence to zero it out and see what comes back up.

Now, onto the overheating issue (why I only ran it for about a minute)! Some back story, I have had a crack in the heater coil for some time now (coolant tank stayed full, no loss of pressure but I would get light colored coolant smelling mist through the vents and residue on the windows) but I never addressed it because, well, its an awful process from all accounts. Its never caused any significant problems (other than being cold in the winter from lack of heater since I re-routed around it). The last two times I drove the jeep though, aside from the throttle issue, after about 5 minutes of operation I noticed a loss of power and a burning smell in the cabin combined with light grey smoke coming out of my engine compartment and apparently black smoke out of the tailpipe. The coolant reservoir is still full so I haven't lost coolant pressure, but its definitely overheating to the point that its burning oil significantly. My oil pressure is good so its not an oil leak, and when I drained the oil it had a good dark oily complexion so I don't have a warped header, there is no coolant or water in my oil. Also, none of the error codes given had anything to do with the coolant system. My friend suggested it could be a bad water pump. Other than new hoses, this jeep has had little to no coolant system maintenance done. Any ideas what could be the issue?

 

What is the current condition of the radiator fluid?
My '98 XJ acted somewhat this way, but without the smoke, when the TPS went bad. Installed two new TPS from local parts stores with no change. The local transmission mechanic said TPSs from typical parts stores aren't worth buying. When an OEM TPS was installed everything started working right.

 

Good work on the TB and sensors. Try disconnecting the battery negative cable for a few minutes to see if the CEL gets cleared. If it won't clear you should have Autozone clear the CEL with their scanner.

For some basic coolant maintenance, you should check the antifreeze level in your radiator. It's possible for the overflow reservoir antifreeze level to remain acceptable but the radiator level is low. Replace the radiator cap with a good 16 psi cap (like Stant).

You may want to flush your cooling system as well. There are checmicals available for this purpose. A good 195*F thermostat would be in order. I got mine from the dealer. It has the bleed hole/check valve in it. When installed, the bleed hole goes to the 12 o'clock position.

If/when you drain your radiator, go to O'reiily Auto Parts and get a replacement radiator drain valve before you attempt to drain it. These drain valves do break.

Moving right along....

 

Well from looking around on here etc I am pretty sure that I blew my head gasket, so it looks like I have bigger problems on my hands.

I have some friends who will probably help me with the head gasket, so once we all have some time we will hunker down and knock that out, and then I'll flush the coolant system and maybe replace the water pump and radiator.

With a new TPS, MAP, radiator, water pump, and possibly a new header I should be able to get another 100k out of the old boy though.

 

Pressure test most of the time will tell u...

 

Yeah, I'm gonna get the compression/pressure test done to confirm but based on the symptoms and everything I've read it appears that is what happened. Luckily I have no coolant in my oil so there's a chance that I just blew the gasket without warping the head, which will make the repair cheaper, it'd be nice to not have to get it re-machined at all or have to buy a new one. While I've got it off too, I might replace all the lifters since I've had lifter tick for a while now.