rickjeep42

My 1998 4wd Jeep Grand Cherokee Laredo 4.0 was having, what started out as, some shifting problems. Was not shifting smoothly, started to get worse. Then it began to have some idle issues. when put into reverse or drive, the jeep's rpm's would dive down to the point of nearly killing it, but it always recovered. Check engine light went on and the code P0123 (TPS). So I.....
-Cleaned throttle body
-cleaned IAC valve
-Changed TPS
-Adjusted kickdown
-unpluged clock spring
-transmission flush (changed filter and flushed only what was in pan)

.....and nothing. As a matter of fact, now the jeep wont even turn on! Please help! I am out of ideas. Could it be the Crankshaft position sensor? Is it the PCM?!?!

rickjeep42

Also, now that the jeep wont start, while trying to start it I can hear the fuel pump, the lights and everything work, can hear it cranking, but not starting....

rickjeep42

Alright, Ill give this another shot. Went to turn on the jeep today to see what was up and start working on it. The battery (fairly new) is now completely dead, which made me think it could possibly be the alternator causing the problems. I'm not sure if it is possible for the alternator to cause shifting and idling problems and I'm not sure why the car was throwing out a TPS code, but that's really all I can think of now. Does ANYONE have any knowledge on this and could I be heading in the right direction? I really cant afford to take it in and i'm getting desperate!!

Kingfisher

Something drained battery. (dome light or something?)
Get battery fully charged and see what happens.
Could what you thought was a shifting problem have been caused by a poorly running engine?
Check fuel pressure

dave1123

Why did you unplug the clockspring?

rickjeep42

I unplugged the clock spring because I was told that it shared the same ground as the TPS and sometimes if you clock spring goes bad it can trigger the TPS code. Not sure if thats true, but i decided to check anyhow. Gonna give it a jump and check fuel pressure later tonight. Will update.

czettlera

Hi I would say you should start checking things in an order. If it doesn't start, fuel or spark is missing. Start it from the easier side, check the spark in all 6 cylinders. If it's not OK or week but the plugs look good, move on to the distributor cap, rotor, wires or the coil. If they seem to be fine, the next step could be the pcm, first the connectors (clean connection, check if they are loose). If you have proper spark in every cylinder, then measure the fuel pressure. If it's OK then you are back at a pcm or sensor related failure. Than it's time for checking for new codes, and measure the related sensors one by one (I like it more than starting to change good sensors).
I hope this will help you a little.

rickjeep42

Well got her to start up today. Distributer good and proper sparks on all plugs. Had let the glove compartment partially open and that's what drained the battery. Checked the fuel pressure was about 41 without the car running and 49 with it running. Is that a correct pressure? still having same problems, still throwing out the same code, and still not sure what it is.

czettlera

I would say that this fuel pressure should be enough. Are you sure the new tps is good, what brand is it? You can measure it working properly, just with an ohm meter. I have a short description about it, if you need it, I can send it to you.

rickjeep42

Its a BWD and I am not sure if its good I just assumed it was. Would love for the short description on how to do it with an OHM. Thank you! Wont be able to get to it for a few days I work multiple days in a row in the backcountry. Will let you know what happens with it when I return.

czettlera

This was written for RE transmission diagnostic, but I think it fits your problem. I hope it helps. I was wrong with ohm measuring, actually it's voltage measurement, but it shouldn't make difference. Also gives you the answer why to check the clock spring. Let me know how it turned out.