99' XJ Problems

[customcreationsllc]

Just went to harbor freight, and bought a fuel pressure gauge.

My fuel pump is working up to par. It stays at about 50PSI at idle, and about the same when i rev the engine.

I also drove to CVS today, and it ran fine, except for when i got to CVS, i put it in park and let it idle, and the second i took my foot off the gas, the engine stalled out.

*****EDIT***** Left the fuel pressure gauge on for about 30-45 minutes, and the pressure dropped from like 45-46(where it started) to 30. Normal?

I don't know what the specs are off hand but it sounds good.
after you shut the engine it drops? that is normal if it drops too much it is usually the check valve but that just leads to long cranks to start.

when checking the fuel pressure. good trick is to pinch off the return line if it spikes the pump is definitely good if it is low when driving it could be the filter.

The timing light to check the spark is good when driving around just through it on the passenger floor if it stops flashing you lost your spark.

Some times you can position a spark plug so you can see it under the hood while cranking it is hard to do it yourself but it can be done.
you don't need the plug on it you can just stick a screw driver in the wire and hold it away from metal just a short cut.

Buy a manual you can figure out how to test everything. Most you can do with just an ohm meter graphing ones are just better.

[Hudson]

I don't know what the specs are off hand but it sounds good.
after you shut the engine it drops? that is normal if it drops too much it is usually the check valve but that just leads to long cranks to start.

when checking the fuel pressure. good trick is to pinch off the return line if it spikes the pump is definitely good if it is low when driving it could be the filter.

The timing light to check the spark is good when driving around just through it on the passenger floor if it stops flashing you lost your spark.

Some times you can position a spark plug so you can see it under the hood while cranking it is hard to do it yourself but it can be done.
you don't need the plug on it you can just stick a screw driver in the wire and hold it away from metal just a short cut.

Buy a manual you can figure out how to test everything. Most you can do with just an ohm meter graphing ones are just better.

The spec is 49PSI at idle +/- 5. No, when i turn the engine off the pressure normally remains the same for a pretty long while before dropping.

Where even is a fuel filter on an XJ? Is it easily accessible?

I think i might pick up a cheap timing light to see if i am loosing spark. Normally when i'm driving, the thing just stalls. No signs or anything, just BAM dead.

Currently testing the TPS, and i think i might have a problem that someone might be able to clarify.

Before you have to read everything on that Pastebin, i'll give you the shorter version of it for clarification. One wire should have 5 volts. One of the other wires should show .26V (or so). The other wire will be the ground and should show no voltage.

I did the procedure as described (http://pastebin.com/jc8XfCUY) with a digital multimeter. I turned the key to the position right before the engine begins cranking, unplugged the harness from the TPS, grounded my meter on the ground terminal of the battery, put the meter on Volts DC, and began probing the three prongs of the TPS with my postive multimeter lead.

Anyways the ground prong reads .010 volts, the middle prong reads 4.74 volts, and the far prong reads 5.20 volts. Is this a problem? Was i suppose to unplug the harness from the TPS?

Here is a video in case you're unclear of what i did. Video might need like 20 minutes to be live though.

[customcreationsllc]

That link is blocked at work.
You leave it plugged in you should just need to measure voltage at the signal.
So one wire on the signal the other to ground.
Back probe the sensor us a paperclip or something thought the back of the connector or punch a hole in the wire.

You shouldn't need to start it just turn the key to on and rotate the throttle.

[jeepkid03]

Sounds like a TPS problem to me. The TPS is directly related to how the AW4 shifts. When you feel you have a tranny issue, always try the TPS first.

[Hudson]

Just got to looking at things.

Went out and drove the thing about a mile and back home, and it ran perfect. Went to WOT and the RPMs went way over 3,000. Started fine too.

Got it home, and let it sit for about ~10 minutes, and when i went to start it again, it just cranked and cranked and cranked. I stopped cranking, and started re-cranking, and it fired right over. (With no assistance of the gas pedal.)

Popped the hood, left the key in the postilion right before the jeep starts cranking, stuck a needle into the tps middle wire, grabbed my analog meter, grounded one side of it, touched the other side to the needle, and it read like nothing on my analog volt meter. It did move slightly up, under 1, but it wasn't much. Moved the throttle to WOT and the meter did a nice slow sweep that was in proportion to how much i opened the throttle. Didn't fluctuate at all. I think the TPS is good.

Not sure if this still sounds like a sensor issue or what. Wold the CPS cause this problem?

[Hudson]

Just went out and spent some $$ to try to figure it out. Never changed the ignition coil, so i figured i'd start there as the one in it was probably the original one.

Bought another coil, antifreeze (was running straight water during the summer shun me i know), and some seafoam.

Got the new coil in, and i must say, i'm feeling more confident already. I think this might of fixed the problem. Maybe it was just a bad coil. Also went to a Jeep dealer (Heard aftermarket CPS's are hit and miss being mostly miss) and got one priced out for like 75$ just in case i need to buy one.)

After i got the coil in i flushed the system and did a 50/50 mix of antifreeze/water. Let it get up to operating temperature and sea-foamed it.

Feel more confident about driving it already. If it continues, the CPS is next.

Oh, and on another note those fucking advanced auto discount codes are addicting. I kept adding more to my cart to get more money off essentially trying to get "Free stuff".

[Hudson]

Drove about 50 miles since replacing the coil. Thought all was solved then ... stall.

Going to buy a CPS tomorrow and report back. I think the old coil was bad as well as the CPS.

[Hudson]

If anyone has been following this thread i've fixed it.

The problem was; A dead battery, A bad CPS & A bad ignition coil. Thing is up and running again. Drove it for about 100 miles today and it worked flawlessly. I guess you could call it all basic maintenance, but it ended up costing me around 200$.

I also flushed the radiator/heater core and put in a 50/50 mix of antifreeze/water. I also spliced the vacuum line together that went to the vacuum canister. Did some other misc stuff as well. Feel free to ask if interested.

Thanks for all the help.