b1k3r1d3r

Hey guys,
I've been using this forum the past week or so since i bought my 2000 Cherokee. I bought this thing with no research because some realiable auto resources (relatives and mechs alike) all said the 4.0 is bomb proof and they're good vehicles. Now 10 days into ownership I've already replaced the imfamous 0331 head due to a coolant leak between cyl 3 and 4 down the side of the engine. worst part is i pointed it out before purchase but my resources all shook it off as a valve cover leak. Anyways everything is assembled now and it runs pretty good when it runs. but here's my issue:

first start after about 10-15 minutes it starts, runs for 5-10 minutes depending on how long it sat. the longer it sits the longer it runs. but the idle is really low and then the engine stalls out. Then i can restart it but it takes a few on/offs with the ignition before i can turn it over.

Here's what i've done:
-checked grounds
-vacuum hoses
-cleaned iac
-and drove for about 20 minutes just keeping the idle around 800-1000 at stop signs.
-replaced battery

I'm lost now. did a bunch of searching and you guys have been great so now i'm here asking for a little more help. any ideas?

my next guess is something to do with the fuel system. Everything is hooked up correctly. however the priming situation leaves me with this guess. also when it stalls for the third time in a set of consecutive starts (starting it right after it stalls) I cant even get it to start. cranks fine. but no start.

Any guesses, suggestions?

update:
So before I did any testing this morning I took it out for another 15 miles in hopes the computer would relearn idle. And what i came to realize is since i had it running for about 5 minutes and shut it off on my own about 1/2 hour before i made the trip is that it only stalls when the engine is up to temperature. not sure if that would make a difference to any of the things im testing but just wanted to throw that out there.

fishtaconc

You "rent" a fuel pressure gauge from the big box auto parts stores, you buy then they give you a full refund. There is a schrader valve on the fuel rail, this is where you test should be 49PSI +/-5 PSI. Turn the key on should within spec, also check while idling. Check spark by pulling the plugs one by one and grounding them to the side of the block, have someone crank the engine, should be a blue spark, yellow/orange is a weak spark. http://www.jeepforum.com/forum/f11/h...-4-0-a-803463/ For testing Crank Sensor.

b1k3r1d3r

Alright i'll check fuel pressure tomorrow already have a pressure gauge.

Checking spark is quite difficult with the coil pack, that this model year 2000 has. Instead i triple checked all the connections and the plugs that were going into it worked before and were relatively new. any suggestions for the coil pack set up and testing?


and as for the cps, I've been through that before on my uncles cherokee and his just wouldnt start. it would turn over for ever but no start. mine starts just what seems like to me, once the fuel rail is up to pressure. no smell of fuel so no leaks, but who knows. plus the fuel line into the fuel rail is the the last connection i took on/off during the head swap that i have rechecked. I didnt know we had a pressure gauge at the house.

fishtaconc

The poormans prime, turn the key to run for 2-3 secs. repeat 2x and it starts, sounds like beginning of fuel pump failing. Possibly fuel filter, these models, it only gets replaced if troubleshooting points to it being suspect, as its part of the fuel pump module.

b1k3r1d3r

hopefully not. im going to check all the fuel lines first thing. hoping theres a kink. don't feel like putting any more money into this thing.

b1k3r1d3r

So after doing some thinking. is there any chence the cps connection isn't located at the back on the intake. took a look under the truck and it looks like it goes to the passengers side and the connections on the intake were for the 3, o2 sensors (2 before cat, 1 after).


edit, i should have actually read that instead of looking at images. its where i thought it was, not on the intake. anyways might as well replace that as its a cheap part if my fuel pressure is good.

cherokee104

I have a 00 jeep cherokee and it is giving me p0353 primary and secondary coil malfunction i tried the coilpacks cam sensor and no luck any body have a clue on what it might be?

b1k3r1d3r

also i want to throw it out there, before i swapped the head, the car didnt seem to have any of these issues.

tjwalker

Start a new thread. You'll get more accurate replies and it won't be confusing for the ones that are trying to help on this one.

tjwalker

I think you need to get some test data here.

1. I know you said you checked grounds, but specifically...did you remember to hook up the ground wire from the back of the head to the firewall when you swapped in the new head? This is a very important ground point.

2. Fuel pressure data. You have the gauge.

3. Test your "throttle position sensor". More on that below.
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The throttle position sensor is connected to the throttle shaft on the throttle body. It sends throttle valve angle information to the PCM. The PCM uses this information to determine how much fuel the engine needs. The TPS is really just a simple potentiometer with one end connected to 5 volts from the PCM and the other to ground. A third wire is connected to the PCM. As you move the accelerator pedal with your foot, the output of the TPS changes. At a closed throttle position, the output of the TPS is low, about a half a volt. As the throttle valve opens, the output increases so that, at wide open throttle, the output voltage should be above 3.9 volts. Testing can be performed with an electrical meter. Analog meter is best. You are looking for a smooth sweep of voltage throughout the entire throttle band. While slowly opening and closing the throttle, take note to the movement of the voltmeter needle. There should be a direct relationship between the needle motion to the motion of the throttle. If at anytime the needle moves abruptly or inconsistently with the movement of the throttle, the TPS is bad

You should have 5 volts going into the TPS. At idle, TPS output voltage must be greater than 200 millivolts. At wide open throttle (WOT), TPS output voltage must be less than 4.8 volts.. The best is to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. One of the other wires should show .26V (or so). The other wire will be the ground and should show no voltage. Move the throttle and look for smooth meter response up to the 4.49 at WOT.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.

The TPS is sensitive to heat, moisture and vibration leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following: -

NOTE: The throttle position sensor is also DIRECTLY involved with transmission shifting characteristics! It should be verified early in the troubleshooting process, when a transmission issue is suspected!

• Poor idle control: The TPS is used by the ECU to determine if the throttle is closed and the car should be using the Idle Air Control Valve exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".
• High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction with a slow engine return to idle speed symptom.
• Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.
• Engine Hesitation on Throttle Application: The TPS is also used by the ECU to determine if the driver has applied the throttle quicker than the Manifold Air Pressure sensor can read. The fueling is adjusted acordingly to cope with the sudden increase in air volume, however a faulty sensor can cause the ECU to ignore this data and the engine will "hesitate" when applying the throttle. In extreme cases with the engine at idle, a sudden application of full throttle can stall the engine.
• Engine Misfire: A fault TPS can report values outside the deined acceptable range causing the ECU to incorrectly fuel the engine. This is noticable as a slight misfire and can trigger the misfire detection software and/or Malfunction Indicator Lamp (MIL) light on the dashboard. Extreme cases can cause excessing misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.

fishtaconc

Buy it from Jeep, lots of aftermarket sensors are failing in short order.

b1k3r1d3r

thanks!

I'm planning on testing the cps first thing. thinking back the odessa head has a coolant opening right infront of the #14 head bolt which i didn't know of and when i filled it with coolant, a small amount (1/2 a cup) leak down the back of the engine and thats right where the connection is for the CPS. going to disconnect it, clean, and still run the test and hopefully that sensor is good. then i'll go test the throttle position sensor. I've done quite a bit with electronics and engines in college (set up data collecting devices, and programmed/calibrated acquisition devices for collecting and studying diesel fuel particulate emissions on a consumer diesel engine, VW 1.8. and several rebuilds of that engine). I'm definitely capable of tackling all of this and just want to thank you guys again for pointing me in the right directions!

b1k3r1d3r

replaced the ckp and now its all good!