buddies 94 grand cherokee issue

[XJ4IV]

ok my buddy went out to his jeep the other day to head to work went to start the jeep and it would crank strong but no fire...'
after quick diagnosis I came to the conclusion that the problem was STILL no fire all the way back to the coil, I called matt to see if there was a way to check a coil or not and he asked if I had checked the codes... NOOOO anyhow I really fast checked and based on this site
http://www.jeepforum.com/wiki/index.php/OBDI_Error/Check_Engine_Codes
I found that it was a code 32... so that being shown could that in fact give me a no fire issue?
mind you this jeep has a handfull of issues that need to be addressed but NONE of which actually kick on the engine light, I am not positive that the code that Im reading is even the cause for his no start but MIGHT be a code from last month when he had a severe loss of power issue but that has been rectified.
the reason I say im not sure is cause I cant get his jeep fired up to see if the light stays on!
Please help!
Thanks

[xj4life2]

Sounds like the ill fated crank position sensor to me !! And yes you can test a coil , heres a link :
http://autorepair.about.com/od/troubleshooting/ss/coil-test-ohm.htm

[XJ4IV]

well CRAP... cause IM the guy who is gonna do the labor... I REALLLLLLYYYYY dont wanna do this, Its such a PITA
so my next question is what up with the EGR failure code?

[msmoorenburg]

Quick search the GC has a EGR valve just a fyi

[XJ4IV]

HUH!?!? odd guess one of those hoses actually DOES have an EGR in it! wonder if mine should?

[XJ4IV]

So why is there no spark coming from the coil? I removed a plug and plugged it into the coil wire and grounded the plug but nothing... still sensor?

[XJ4IV]

OK so I changed the CPS... YAYA it worked but NOW back to an initial problem
earlier it had a code 32 which is a power loss or EGR issue, this is a 4.0 motor with NO EGR ... YES it does have a significant power loss on about 2 or 3rd gear very hesitant and sputters... could this be a MAP sensor? or something else? I checked his cap n rotor the other day and they were a little dirty but Ive seen MUCH worse and perform better i did a seafoam treatment on it last month because of the same complaint however at THAT time I couldnt duplicate the issue but tonight after installing the new CPS I took it for a good hard run on the high way and about 45 MPH it starts to sputter a bit and it feels like a loss of fuel.. I guess it could be injectors but wouldnt that then be ALL the time rather than under heavy acceleration and also not until 45 MPH...

[XJ4IV]

Quick search the GC has a EGR valve just a fyi

V8's only had em not the 4.0

[msmoorenburg]

Any backfires? Here is a quick search with fixes more info would help


1. Engine has a lack of power. No trouble codes....
1994 Jeep Grand Cherokee Laredo 4.0L, Vin S, Eng Cfg L6
Test Details... Confirmed Fix Details...

Tests/Procedures: 1. Monitor the upstream and the downstream Oxygen (O2) sensors while driving, they should both switch between 0.1 volt and 0.9 volt. As the vehicle goes into heavy acceleration, the O2 sensors should...

8 Confirmed fixes

Restricted Exhaust System
Fuel System


4 - Catalytic Converter(s)
1 - Fuel Pump
1 - Timing Chain
1 - Ignition Coil Assembly
1 - Spark Plug(s)
2. Intermittently loses power to the point that it backfires....
1994 Jeep Grand Cherokee Laredo 4.0L, Vin S, Eng Cfg L6
Test Details... Confirmed Fix Details...

Tests/Procedures: 1. Monitor the Crankshaft Position (CKP) sensor and the Camshaft Position (CMP) sensor on a lab scope. Compare them to a normal pattern, overlapping patterns indicates a sync problem, caused by a loo...

6 Confirmed fixes

Cam Angle (CMP) Sensor
Crank Angle Sensor (CKP)
Exhaust System
Fuel Pump
Throttle Position Sensor (TPS)
Wiring Harness


3 - Fuel Pump
1 - Front Fuel Pump/Module Assembly
1 - Powertrain Control Module (PCM)
1 - Crankshaft Position (CKP) Sensor
3. Won't get above 2,000 RPM once warmed up. Before that it is fine. RPM reading on scanner was giving random readings when it acts up. It is worse with a load on it. Popping back like crossfire. Timing...
1994 Jeep Grand Cherokee Laredo 4.0L, Vin S, Eng Cfg L6
Test Details... Confirmed Fix Details...

Tests/Procedures: It sounds like spark is occuring at incorrect times. That may be because the CKP signal is giving erratic info to the PCM. Scope check the CKP pattern when not acting up so you know what normal is, t...


Crankshaft Position (CKP) Sensor


4. The engine idles and runs really sluggish. Also, when you try to start it, it will not start until you let off the key. Then it just barely starts. Off of idle and at cruise speeds, it runs fine....
1994 Jeep Cherokee Sport 4.0L *
Test Details... Confirmed Fix Details...

Tests/Procedures: Try adding alternate fuel and check spark kv when cranking. Check spark plug condition. Check fuel quality....


Insufficient Fuel Delivery
Weak Spark

[msmoorenburg]

:D and more info

Description Potential Causes
Confirmed Fix
1. Engine has a lack of power. No trouble codes....
1996 Jeep Grand Cherokee Laredo 4.0L, Vin S, Eng Cfg L6 *
Test Details... Confirmed Fix Details...

Tests/Procedures: 1. Monitor the upstream Oxygen (O2) sensors while driving, they should all switch between 0.1 volt and 0.9 volt. As the vehicle goes into heavy acceleration, the O2 sensors should go high 0.8 to 0.9 ...

28 Confirmed fixes

Restricted Exhaust System
Fuel System


15 - Catalytic Converter(s)
4 - Fuel Pump
2 - All Oxygen (O2) Sensors
1 - Fuel Filter
1 - Catalytic Converter(s), Downstream Oxygen (O2) Sensor
1 - Catalytic Converter(s), Spark Plug(s)
1 - Powertrain Control Module (PCM)
1 - Crankshaft Position (CKP) Sensor
1 - Engine Air Filter
1 - Exhaust Gas Recirculation (EGR) Valve
2. Loss of power one minute after starting the vehicle, feels like it is running out of fuel. Runs like this for a few minutes, then starts running good. There are no codes set. Gets a few backfires out...
1996 Jeep Cherokee Classic 4.0L *
Test Details... Confirmed Fix Details...

Tests/Procedures: 1. Monitor the O2 sensor(s) for activity. Normally, these sensors should be switching between 0 and 1 volt about one minute after starting. If the sensor is slow or lazy, the system will go into clos...

26 Confirmed fixes

Fuel Pump
Oxygen Sensor


8 - Oxygen (O2) Sensor
6 - Upstream Oxygen (O2) Sensor
5 - Heated Oxygen Sensor (HO2S) Bank 1 Sensor 1 (B1S1)
2 - Heated Oxygen Sensor (HO2S) Bank 1 Sensor 1 (B1S1), Heated Oxygen Sensor (HO2S) Bank 1 Sensor 2 (B1S2)
1 - Heated Oxygen Sensor (HO2S) Bank 1 Sensor 1 (B1S1), Heated Oxygen Sensor (HO2S) Bank 2 Sensor 1 (B2S1)
1 - Lower Intake Plenum Cover Gasket, Upstream Oxygen (O2) Sensor
1 - Heated Oxygen Sensor
1 - Fuel Pump
1 - Downstream Oxygen (O2) Sensor
3. Intermittent stalling and rough run. Code 11 is stored. The engine idles rough, then fine, then rough. The crankshaft sensor has been replaced once so far....
1993 Jeep Grand Cherokee Laredo 4.0L, Vin S, Eng Cfg L6 *
Test Details... Confirmed Fix Details...

Tests/Procedures: 1. Lab scope the camshaft and crankshaft signals to verify there has not been damage to the sensors or the pulse rings on the engine. Check the wiring and harness for visual damage. Check the connec...

4 Confirmed fixes

Camshaft Position Sensor (CMP)
Crankshaft Position (CKP) Sensor
Wiring


4 - Crankshaft Position (CKP) Sensor
4. The engine runs like it's late in timing. When scanned, the ignition timing goes up and down. Has good compression. Checked the MAP sensor, crank and cam sensors. Checked the coolant temp and that wa...
1993 Jeep Grand Cherokee Laredo 4.0L, Vin S, Eng Cfg L6 *
Test Details... Confirmed Fix Details...

Tests/Procedures: Advised to check the fuel quality. Is it contaminated? Yes. Replace the fuel. It is discolored and doesn't smell like fuel....

3 Confirmed fixes

Plugged Exhaust
Poor Fuel


2 - Catalytic Converter(s)
1 - Fuel Pump
5. Loss of power cold, hesitates. This only happens once during the warm up cycle and then it is gone....
1996 Jeep Cherokee Classic 4.0L *
Test Details... Confirmed Fix Details...

Tests/Procedures: Check the O2 Sensor operation at "closed loop"....

2 Confirmed fixes

Upstream Oxygen (O2) Sensor


1 - Upstream Oxygen (O2) Sensor
1 - Oxygen (O2) Sensor Heated, Oxygen (O2) Sensor(s)
6. Surges at idle, misfires and dies at lower RPMs....
1996 Jeep Grand Cherokee Laredo 4.0L, Vin S, Eng Cfg L6 *
Test Details... Confirmed Fix Details...

Tests/Procedures: 1. Turn the balancer clockwise to Top Dead Center (TDC). The rotor will be turning clockwise also. The trailing edge of the metal part of the rotor needs to be 0.020" past the #1 terminal in the cap...

2 Confirmed fixes

Camshaft Position (CMP) Sensor
Crankshaft Position (CKP) Sensor
Distributor Sync
Ignition Coil
Oxygen (O2) Sensor, Bank 1 Sensor 1


1 - Oxygen (O2) Sensor, Bank 1 Sensor 1
1 - Distributor Sync
7. Engine barely runs after new Crankshaft Position (CKP) sensor was installed....
1995 Jeep Grand Cherokee Laredo 4.0L, Vin S, Eng Cfg L6 *
Test Details... Confirmed Fix Details...

Tests/Procedures: 1. Scope the CKP sensor. It should output a 0-5 volts square wave type pattern....

2 Confirmed fixes

Defective Crankshaft Position (CKP) Sensor — Faulty new CKP sensor.


2 - Crankshaft Position (CKP) Sensor
8. Once 6 to 8 miles is reached, the vehicle backfires, misses, and has loss of power....
1995 Jeep Grand Cherokee SE 4.0L, Vin S, Eng Cfg L6 *
Test Details... Confirmed Fix Details...

Tests/Procedures: 1. Check the Crank Position Sensor (CKP) and Cam Position Sensor (CMP) signals and sync with a dual trace lab scope. The patterns are 5 volt square waves and should look consistent while the motor is...

1 Confirmed fix

Camshaft Position Sensor (CMP)
Crankshaft Position Sensor (CKP)
Flywheel
Powertrain Control Module (PCM)
Timing Chain
Wiring


1 - Distributor Timing
9. Missing, shuddering and code P0171. Fuel pressure is at 24 lbs ....
1996 Jeep Cherokee SE 4.0L, Vin S, Eng Cfg L6 *
Test Details... Confirmed Fix Details...

Tests/Procedures: Check the fuel pressure with the motor running, then deadhead the fuel pump. Fuel pressure should be no less than 46 psi....

1 Confirmed fix

Filter
Fuel Line
Fuel Pump
Wiring Harness


1 - Fuel Pump
10. Loss of power at highway speeds. Fuel pressure is dropping off while driving....
1996 Jeep Grand Cherokee Laredo 4.0L, Vin S, Eng Cfg L6 *
Test Details... Confirmed Fix Details...

Tests/Procedures: 1. Verify the power (Dark/Green and White) and ground (Black) to the fuel pump is stable when the pressure drop occurs. If they are, then the problem is a weak fuel pump. 2. Take a fuel sample to...


Fuel Pump Assembly
Fuel Pump Ground
Fuel Pump Power Supply

[XJ4IV]

nope No backfires, Im thinking it MIGHT just be the cat... we live in a non emmissions county... should he just remove it and straight pipe it? there is no O2 behind the cat...

[4.3LXJ]

It will run better with a high flow cat than no cat at all.

[XJ4IV]

Hmmmmmm high flow??? can this be purchased at an auto parts store like carquest or orielly or autozone? Im thinking about it and I don't recall a SINGLE muffler shop here in marble falls.

[4.3LXJ]

Best place to get those is Summit Racing. Very fast and reasonable shipping. I have had two, absolutely no complaints on either. Still running the last one. A 3" in and out. Hardly know it is there.

[bigjim350]

Why would it run better with a high flow cat than no cat at all?

[4.3LXJ]

Why would it run better with a high flow cat than no cat at all?

Because the ECM is programed to have a little back pressure. The programming is set for those conditions. The same is true of a good set of headers or a rough cam shaft. The ECM needs to be reprogrammed for those parameters to run right. You would think it is not the case, that the little mind in there would compensate for it, but it doesn't do it very well sometimes. I have heard of many fellas on other forums take their cats off and have their Jeeps run rich or rough. Chevys are the same way. Summit Racing has a service where they provide reprogramming for modified smog engines.

[XJ4IV]

Because the ECM is programed to have a little back pressure. The programming is set for those conditions. The same is true of a good set of headers or a rough cam shaft. The ECM needs to be reprogrammed for those parameters to run right. You would think it is not the case, that the little mind in there would compensate for it, but it doesn't do it very well sometimes. I have heard of many fellas on other forums take their cats off and have their Jeeps run rich or rough. Chevys are the same way. Summit Racing has a service where they provide reprogramming for modified smog engines.

:shocker::shocker::shocker: WHO WOULD DO SUCH A FEAT? That kind of activity should get you BANNED from a website....:D

[xj4life2]

As for high flow cats , they are a hoax !! a cat is a cat we have actually opened several "high flow" cat boxes and found regular cats inside with the regular part number on them. Although we can no longer legally use them here, I will still state that they are a hoax , just get a regular cat at NAPA and be done with it !!!