A clogged catalytic converter can cause an engine to run very rich and foul plugs quickly but the engine should also be running very sluggish and this is something that is not going to happen overnight.
The fuel pressure regulator may have given up on it. This will allow raw fuel to pour in and kill things pretty quickly.
You’ve checked that the sensors have voltage; but, do they have the CORRECT voltages? For instance, the voltage to the CTS (Coolant Temperature Sensor) should be X value. The voltage from the CTS should be a value which will change with the temperature change of the engine. Your repair manual will tell you what voltage (and resistance) goes with what temperature. The other sensors will have different voltages with different conditions, also.
ADDED: The www.autozone.com Web site says that the 4 cylinder engine does NOT have an engine coolant temperature sensor (ECTS). Actually, I think this is strange, if true.
ADDED, again: The Point 5 Technologies wiring diagram for the Jeep Cherokee 2.5L engine, shows an ECTS. The wiring diagrams are available through your public library Web site, under Electronic Data,Reference, ARRC (Automotive Repair Research Center) Web link. Also, go to www.alldata.com at your public library (free).
Sorry but I need to push you alittle about checking the CTS. It’s my nature as a service manager… when one of my techs’ tells me he checked a component I ask him… how did you check it? What were the resistance readings?
That is my question to you… how did you check it? Did you use a DVOM? What were the resistance reading? Hot and cold?
Here are the TEMP AND RESISTANCE specs.
212 - 185 OHMS
160 - 450 OHMS
100 - 1,600 OHMS
70 - 3,400 OHMS
40 - 7,500 OHMS
20 - 13,500 OHMS
0 - 25,000 OHMS
-40 - 100,000 OHMS
Here is a description of the pressure regulator…
The fuel pressure regulator is an overflow type attached to the throttle body. The regulator is adjustable and controls the amount of fuel system pressure available to the fuel injector. Fuel pump output pressure is above that needed to operate the fuel system, and excess fuel is returned to the fuel tank through the regulator via the fuel return line. The regulator consists of a spring chamber, a calibrated spring, a diaphragm, and an adjusting screw. A lead plug seals the adjusting screw hole. When fuel under pressure enters the top of the regulator, the relief valve and spring are forced down, opening a passage to the fuel return line. A pivot on top of the diaphragm keeps the diaphragm from tipping . The amount of pressure required to force the regulator spring down determines the fuel system operating pressure. The adjustment screw allows that pressure to be set. Turning the screw in will increase the fuel pressure, and turning it out will decrease the fuel pressure. A small vent passage in the throttle body, vents the spring chamber to atmosphere, and the injector tip is also vented to atmosphere. Due to this venting process fuel system pressure bleeds rapidly to zero when the engine is not running.
If the CTS is functioning normally then I would suspect the regulator is leaking internally meaning the diaphram is ruptured.
I think Willey is right. That much extra fuel being dumped and having it happen so suddenly usually points to a bad fuel pressure regulator. Pull the vacuum line off the FPR. If there is gas in the line, you’ve found the culprit.
You make it sound as though you are hostile to new ideas, and to someone who is trying to help you.
I’m not hostile to new ideas, but give me a break. Don’t you think I’ve checked the obvious as well as the no so obvious. I’ve checked all the sensors, rebuilt the fuel pressure regulator, checked the fuel pressire, and rechecked all the sensors. … yes, with ohm meter and volt meter. Telling me to check the choke on something that has none … well, you do the math.
Disconnect the wire from the MAP sensor while running and if the situation is imiproved the MAP may need replacing.
Thanks, mine doesn’t have a CTS, at least it’s not on the thermostat housing.
I rebuilt the fuel regulator. The diaphram wasn’t damages but it was full of crud. As long as I had a new one I cleaned the housing and install it. I checked the pressure and it was exactly right.
I haven’t changed the injector modual and it’s not leaking by. I can see that it’s dry when I unclip the wire and run the fuel pump. How is it built. Could it open too far and let too much gas through?
Last night I disconnected the exhaust. This morning I re-cleaned the plugs and tried it again. Though maybe the converter was plugged. It ran for about 30 seconds and quit. Fouled plugs again. ???
OK, so maybe you are not hostile to new ideas, but I still see someone who is trying to help you receiving your sarcasm. It makes me wonder why anyone else is bothering to help you.
Um… the CTS is the coolant temp sensor. It should have one and it isn’t mounted on the thermostat housing.
You know what… you seem to have all the answers so have fun figuring out this problem. You have yet to answer my question about the temp sensor resistance readings.
I’m done with this thread.
Have you read some of the posts. I mean, come on, “maybe you didn’t index the distributor” or “try changing the air filter”.
I said I check all the sensors, I’m a pretty fair machanic. Don’t suggest I check the sensors, I’ve already don’t that. Give me some suggestions besides what I’ve already done. Obviously neither of the two Car Talk guys posts here in which case I may as well post on most any auto fix-it forum.
I asked you were it might be if it isn’t on the t-stat housing but you didn’t answer that question. My book says it’s on the housing.
I’m just tired of people assuming I’m an idiot and telling me to change the air filter.
Well… you are an idiot. Every time someone makes a suggestion you come back with I checked that already, it’s fine. Well if everything checks out fine then why are you still having the problem? You have missed something basic. That or you have to face the fact you don’t know what you’re doing.
The Auto Zone Web says that the engine coolant temperature switch is in the rear,center of the engine, mounted in the coolant by-pass hose. There are other guides (to augment your repair manual) at: http://www.autozone.com/shopping/repairGuide.htm (click on it).
It’s still not clear which 4 cylinder is in your jeep. In the 2.5L, 99% of them had TBI (Throttle Body Injection). 1% had turbos.
I’m the idiot? call the autoparts. There’s no number for the CTS in the 2.5 engine. I just called 3 parts stores and re-varified. I’m running, or attempting to run with throttle body open top so I really don’t think it’s an air filter problem. I’ve checked the MAP and TPI several times with a DC digital vom and the voltage variances are proper with vacuum and position. The Air Temp Sensor has the correct ohm reading for ambient temp and the exhaust sensor changes millivolts when I heat and cool it. The flywheel sensor works or I’d get no spark. I replaced it a few months ago. I dropped the coverter but the problem didn’t go away so I’m ruling out a clog. The TPR was rebuilt and the pressure tested. The injector pulses so I know it opening and closing and it doesn’t drip. I can see down the barrel. I’ve checked and recheck and rechecked. I don’t need people to tell me to change the airfilter.
Sooty black plugs can also be caused by things other than excessive fuel; clogged converter, weak spark, seriously retarded ignition timing, etc.
As I said before, this is a textbook case of a failed Coolant Temp Sensor. The one you can’t find, but have already checked anyway.
Because you’re so friendly and appreciative of the help you’re getting here, don’t hold your breath waiting for anyone to look up the precise location of the sensor for you.
And, yes, it almost certainly has one. If the engine is injected, it would need one. NOT the air temp sensor, the COOLANT temp sensor. NOT the one for the gauge, the one for the ECM.
You’re welcome.
Hey, thanks for the web link. I checked it out. Really cool. I’ll look tomorrow for the switch. The book doesn’t mention it. … incidently: TBI
4230 ohms and it’s about 58 - 60 outside. It’s buried on the underside of the intake manifold in the back under tubes and vacuum lines. Senses of the bypass line. One more item ruled out. Wonder why every source says it doesn’t have one?
If this temp sender is what you’re lookin’ at then that ain’t it.
http://www.lunghd.com/Tech_Articles/Cooling/BurpAirMod.htm
ECT sensors do not have one wire; they always have at least 2 to complete the circuit to the ECM and back. This is because the voltage supplied to the ECT is low and running that low voltage through the engine block instead of through a small wire to complete the circuit is going to run the resistance through the roof. I’m of the opinion your problem is not the ECT anyway. JMHO
Odd part is that the wiring schematic shows the sensor but after checking the Advance, O’Reillys, and AZ site they do not have a part listing for an ECT sensor. This is what it looks like though.
http://www.cyberjeep.com/prodinfo.asp?number=33002383&
Still think the first thing to do is conect a vacuum gauge though.