Skipping and misfires

[Tex06]

OK, will give that a try. The hard line is still there, looked over it twice and it looks solid. I've also used a whole can of ether checking for vacuum leaks to no avail.

 

That a 98+ intake? Looks good!

[HOrnbrod]

It's an 00 intake, and thanks!

[MJ_Milam]

Have you tried backprobing the MAP signal at the ecm? Maybe you have a wiring issue or possibly loose terminal. Also check the grounding splice for the sensor for corrosion.

[Tex06]

Hadn't solved the issue yet, cold weather, rain, and a torn ACL have hindered progress somewhat. Will update when I continue to TS issue.  Does anyone have a wiring diagram of the ECU with wire colors?  I don't really want to undo all the factory wiring looms to chase this signal, although I know that's probably what I'll have to end of doing....

[Tex06]

Update time.  Talked with an old timer about what a crapshoot these computer-aided troubleshooting systems are (OBD 1 for the rest of y'all).  He suggested a leaky fuel injector causing the stutter so I grabbed my junkyard set of Bosch 703 injectors and threw them on.  Jeep ran like a top!  For a day.  Now, I'm getting the stutter again but not nearly as bad.  I'm thinking he was on to something so I picked up a set of reman 703s on FleaBay and they should arrive Monday.  

 

Man, and I was so close to liking my Comanche again.  SO CLOSE!!!

[Tex06]

Newest update, the jeep isn't dead.....yet.

 

New 703s installed.  Look good, ran great.....for a day.  Now back to same issue.  Pulled fuel regulator even though it tested good (was full of rust and crap) and swapped for another from the JY in much better shape.  Also swapped out relays for fuel pump and auto-shutdown.  No change.

 

I did start logging when the issues are happening though.  Everytime the temperature is below about 70* F the jeep acts up.  So the issue is definitely temperature related and intermittent when it does happen.  I finally pulled out the stops and bought an A/F Ratio gauge as well as an electric oil pressure gauge I'm rigging up to read fuel pressure.  This way I can positively ID the issue when it does happen.  Also bought a new fuel pump to swap in if this is the issue although I haven't yet.  

 

Tested the cat today (IR thermometer method) and it clearly wasn't doing much so I gutted it.  Gonna go for a test drive although it's well over 75 today, I doubt I'll have any issues at all....but if I do, the fuel pump is going next.

 

At this point I have a new crank position sensor, new MAP sensor, cleaned throttlebody, new Idle air sensor, new air filter (K&N from the junkyard for $2!!!), new fuel filter, new pressure regulator, upgraded injectors (cleaned and bench tested), new distributor, new spark plugs, new spark plug wires, new ignition coil..........any other ideas??? 

[Tanner]

Newest update, the jeep isn't dead.....yet.

 

New 703s installed.  Look good, ran great.....for a day.  Now back to same issue.  Pulled fuel regulator even though it tested good (was full of rust and crap) and swapped for another from the JY in much better shape.  Also swapped out relays for fuel pump and auto-shutdown.  No change.

 

I did start logging when the issues are happening though.  Everytime the temperature is below about 70* F the jeep acts up.  So the issue is definitely temperature related and intermittent when it does happen.  I finally pulled out the stops and bought an A/F Ratio gauge as well as an electric oil pressure gauge I'm rigging up to read fuel pressure.  This way I can positively ID the issue when it does happen.  Also bought a new fuel pump to swap in if this is the issue although I haven't yet.  

 

Tested the cat today (IR thermometer method) and it clearly wasn't doing much so I gutted it.  Gonna go for a test drive although it's well over 75 today, I doubt I'll have any issues at all....but if I do, the fuel pump is going next.

 

At this point I have a new crank position sensor, new MAP sensor, cleaned throttlebody, new Idle air sensor, new air filter (K&N from the junkyard for $2!!!), new fuel filter, new pressure regulator, upgraded injectors (cleaned and bench tested), new distributor, new spark plugs, new spark plug wires, new ignition coil..........any other ideas??? 

I'm anxious to see if you find out what the deal is using your A/F ratio gauge. I have the EXACT same issue with my truck and have yet to find the issue. 

[HOrnbrod]

Did you get a wide or narrow band A/F meter? With either one you will be able to clearly see the open-to-closed loop transition, which I think is at least p/o your problem. Also, I've never had any luck running anything other than NTK or Mopar (made by NTK) O2 sensors in OBD1 or 2 Jeep engines. Don't cheap out on the O2 sensor............

[Tex06]

Purchased an AEM Wideband....just need to find a decent exhaust shop this week to punch me a hole since my welder is in Atlanta at the moment:

 

http://www.amazon.com/AEM-30-4110-UEGO-Ratio-Gauge/dp/B00N3VGPYS/ref=sr_1_1?ie=UTF8&qid=1459873315&sr=8-1&keywords=AEM+wideband

 

I'll just mount the 2nd O2 sensor in the pipe between the (now hollow) cat and the manifold.  Comes with the kit, so no needing to match it to the Jeep computer. :D

[Tex06]

I'm anxious to see if you find out what the deal is using your A/F ratio gauge. I have the EXACT same issue with my truck and have yet to find the issue. 

 

 

 

What have you done so far to troubleshoot?

[HOrnbrod]

New injectors, sensors, etc. try doing the ECU "hard reset" procedure below. It clears the codes back to factory and starts from scratch with the ECU:

 

Clearing error codes and removing residual memory

1. Disconnect the POSITIVE battery terminal and touch it to ground for 30 seconds. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.
2. Reconnect the Battery Cable
3. Turn Ignition Switch to the "ON" position but DO NOT start the engine
4. Turn Headlight "ON"
5. Turn Headlights "OFF"
6. Turn Ignition Key "OFF"

The PCM Adaptive memory has now been flashed, or erased from the PCM.

[Tex06]

New injectors, sensors, etc. try doing the ECU "hard reset" procedure below. It clears the codes back to factory and starts from scratch with the ECU:

 

Clearing error codes and removing residual memory

1. Disconnect the POSITIVE battery terminal and touch it to ground for 30 seconds. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.

2. Reconnect the Battery Cable

3. Turn Ignition Switch to the "ON" position but DO NOT start the engine

4. Turn Headlight "ON"

5. Turn Headlights "OFF"

6. Turn Ignition Key "OFF"

 

The PCM Adaptive memory has now been flashed, or erased from the PCM.

At this point I'd do a rain dance.....I'll try it when I get home tonight and take the truck to rugby practice. 

 

Also, the cat wasn't the problem although throttle response is MUCH better now.  Went to replace fuel pump, the original (I think it is anyway) was in there with no strainer....bought another strainer and installed thinking the old one could be in the tank blocking and unblocking the pump.  NOPE.  Same issues, now waiting for my bosch strainer to arrive since the Advance Auto Parts one didn't fit properly on the New Bosch Fuel Pump.

 

Good news, I would be willing to bet money I can change that fuel pump now faster than anyone else on the forum! :D  3 times Sunday and I'll be doing it again as soon as the new strainer arrives. 

 

Another question: When you first turn the key on, does you fuel pump come on then cut off automatically after about 2-3 seconds?  Without starting the motor.  Just curious.

[HOrnbrod]

 

New injectors, sensors, etc. try doing the ECU "hard reset" procedure below. It clears the codes back to factory and starts from scratch with

 

Another question: When you first turn the key on, does you fuel pump come on then cut off automatically after about 2-3 seconds?  Without starting the motor.  Just curious.

 

Yep - that's normal.

[Tanner]

 

I'm anxious to see if you find out what the deal is using your A/F ratio gauge. I have the EXACT same issue with my truck and have yet to find the issue. 

 

 

 

What have you done so far to troubleshoot?

 

 

tested and replaced bad cps, Have new plugs wires and distributor because I replaced all of that after I rebuilt my motor. tested and replaced fuel regulator, new fuel filter. tested ignition coil. also tested the MAP. My next step is the A/F gauge just don't have the funds or time to mess with it right this second. 

[Tex06]

But idles fine and revs ok as long as the motor isn't under load?

 

Reason I ask is the T/S method I did was if I disconnect the MAP sensor my issue goes away (ECU reads "No Vacuum" and therefore runs the motor rich but won't idle for crap).  I'd try disconnecting the MAP sensor and see if it changes the problem....if so you're probably looking at fuel injectors or fuel pump.....hence why I'm going this direction with the AFR gauge.  

 

I'll keep you updated as to where I end up, I found an exhaust shop near me I just have to get time off work to take the thing over to him now. 

[Tanner]

But idles fine and revs ok as long as the motor isn't under load?

 

Reason I ask is the T/S method I did was if I disconnect the MAP sensor my issue goes away (ECU reads "No Vacuum" and therefore runs the motor rich but won't idle for crap).  I'd try disconnecting the MAP sensor and see if it changes the problem....if so you're probably looking at fuel injectors or fuel pump.....hence why I'm going this direction with the AFR gauge.  

 

I'll keep you updated as to where I end up, I found an exhaust shop near me I just have to get time off work to take the thing over to him now. 

yes that is correct.

I will try that. 

I have new (refurb) ford 5.0 injectors in it. I have not however replaced (or tested) the fuel pump. but again this only happens when it is below 70 here and ONLY until the truck warms up.

 

okay cool.

[Tex06]

OK, did the PCM hard reset this morning and got my electric fuel pressure gauge hooked up.  Didn't get to test drive yet, but I did notice that my fuel pressure sits at about 26psi while idling according to the electric gauge...goes up to about 32-33 upon hitting the throttle, but is very low the rest of the time.  I'm not sure if my gauge is out of calibration or if this is actual pressure....my mechanical gauges (two of them) are showing higher pressures (32 on one, 38 on the other IIRC).  When I get a chance I'm going to run all three within a few minutes of each other or if I can find the plumbing parts for it, hook them all up and see what the deal is.  

 

I'm wondering if the mechanical gauges have some sort of built-in check valve, but I am using an electronic oil pressure gauge for fuel pressure....this just got really interesting and I haven't even installed the AFR gauge yet!

[Tex06]

Another baby step forward and then a few more back:

 

Got the jeep ready for a test and was watching my new electronic fuel pressure gauge, it's reading a solid 32-33 psi. Pop the hood to make sure no leaks, etc and notice I had left the fuel press regulator unhooked from earlier so I plug it back in and the fuell pressure reading just go all over the place, just crazy up and down at idle and even when blipping the throttle. Verify that disconnected the reading is steady, even drops slightly upon hitting gas.  Ok, bad fuel regulator.  SHouldn't have swapped in one from the JY but hey, I at least had ordered a new Standard unit and I pop it in (Really I fight with the damn thing for 10 minutes before soaking it in 15W-40 and then popping it in).

 

Fuel pressure now holds steady, slightly increases with throttle (less vacuum....more fuel press.)  Idle pressure reads 25psi.  Go to back up and I notice that the "pressure" drops to 12 psi when I apply the brakes.  So now my question is, where is the best place to measure system voltage?  The brake lights shouldn't have enough amp pull to draw down my gauge I would think.  Or could this be a bad ground issue?  I guess my next step will be to wire my pressure gauge to the battery directly and see if that eliminates the draw down unless I have a voltmeter I can pop in my new dual gauge pod.

[cruiser54]

You know your fuel pump is grounded very poorly in a piss poor spot don't you? Behind the left taillamp....

 

http://cruiser54.com/?p=249

[Tex06]

You know your fuel pump is grounded very poorly in a piss poor spot don't you? Behind the left taillamp....

 

http://cruiser54.com/?p=249

I had read that....I think I'll be cleaning all of my grounds this weekend and redoing others if I can track down my electrical stuff.  

[cruiser54]

 

You know your fuel pump is grounded very poorly in a piss poor spot don't you? Behind the left taillamp....

 

http://cruiser54.com/?p=249

I had read that....I think I'll be cleaning all of my grounds this weekend and redoing others if I can track down my electrical stuff.  

 

Those things in the Tips could BE your "electrical stuff". 

[Tex06]

 

 

You know your fuel pump is grounded very poorly in a piss poor spot don't you? Behind the left taillamp....

 

http://cruiser54.com/?p=249

I had read that....I think I'll be cleaning all of my grounds this weekend and redoing others if I can track down my electrical stuff.  

 

Those things in the Tips could BE your "electrical stuff". 

 

Electrical stuff was wire, crimpers, heat shrink, terminal ends, et. al.  Basically all my electrical tools except my multimeter because that stays in my toolbox.

 

Went to clean all my grounds (Big thanks to Cruiser54 for pointing me in this direction!) and while getting to the one on the firewall-cylinder head, discovered my temperature switch was broken.  Like fell apart broken.  Don't know how in the hell I missed that.  Test drove down to auto parts store with cleaned grounds (fuel tank and aforementioned cylinder head) and it was still acting up on me.  Got back to the house, pulled everything apart again and put in the new coolant temp switch and she runs like a champ (for now).  Idle isn't quite right, it kicks up and down like the A/C compressor is switching on (It's not connected currently) so I'm going to replace a few more vacuum lines and hunt for leaks but I was able to drive to work today without issues.  

 

 

Tanner, I'd check your temperature switch (cost me $20 from Carquest/Advance).  The white epoxy that acts as a thermistor gets old and cracks with age.  It's a PITA to get to but that would explain the temperature related aspects of the issue.  While you're back there (I removed my fuel rail to get to the switch), CLEAN THAT GROUND!  11/16" Wrench, PB'laster, and a wire brush.

[cruiser54]

I'm to the point that I just add a good cable ground to the system as described in Tip 1 and clean the connection at the firewall. That versus getting to the braided cable at the head. 

[Tex06]

I'm to the point that I just add a good cable ground to the system as described in Tip 1 and clean the connection at the firewall. That versus getting to the braided cable at the head. 

 

I contacted John from KellysWIP on a cable set for some old heads and other 4.0 H.O. parts I've got, he's swamped right now but is going to get back to me when things slow down.  The lack of grounding on these things is almost laughable.  Makes me wonder how many jeeps were scrapped because of a little corrosion in the wrong place.  Literally a free fix if you have a few tools.

[cruiser54]

 

I'm to the point that I just add a good cable ground to the system as described in Tip 1 and clean the connection at the firewall. That versus getting to the braided cable at the head. 

 

I contacted John from KellysWIP on a cable set for some old heads and other 4.0 H.O. parts I've got, he's swamped right now but is going to get back to me when things slow down.  The lack of grounding on these things is almost laughable.  Makes me wonder how many jeeps were scrapped because of a little corrosion in the wrong place.  Literally a free fix if you have a few tools.

 

exactly. In a pinch, add the cables outlined in tip 1 in the meantime.