Bizarre intermittent engine sputtering/stalling/misfire on 1995 YJ 2.5L Automatic - JeepForum.com
Reply
 
LinkBack Thread Tools
post #1 of 24 Old 05-09-2017, 02:38 PM Thread Starter
IROCZman15
Registered User
1995 YJ Wrangler 
 
Join Date: Nov 2013
Location: New Jersey
Posts: 45
STRANGE Bizarre intermittent engine sputtering/stalling/misfire 1995 YJ 2.5L Auto

Hey there fellow Jeep guys ... I have quite an interesting problem that randomly rears its head with my 1995 YJ 2.5L auto Rio Grande 157,000 miles on it, (but about 4,000 on the top end engine rebuild).

The issue first arose a few years ago out of nowhere. Over the years, it has become more frequent but still at totally random times, speeds, environmental conditions. It happened again this morning and caused me to be late to work, whih is fine, but it is getting me mentally to the point where I am too concerned to enjoy driving the jeep and instead typically drive another vehicle so I don't have to deal with the possibility of it acting up again.

In simple terms, the problem is basically the engine will be performing normally (revving, idling upshifting, downshifting, etc) and then out of nowhere the whole engine begins to sputter, stall, spit, backfire, and it sounds like it is mixing up the firing order. Not like just one cylinder is a problem.. but all of them in an instant. If I can work the throttle enough I can usually limp it to the side of the road or a parking lot, but sometimes I can't. It truly sounds like the firing order went haywire and the engine is still rotating independent of the ignition sequence. (see below for what I have done in attempts to remedy this)

Here is where it gets wacky.... If the engine does wind up stalling or I get the jeep to a safe spot, I'll shut it down and take the key out. When trying to restart it, it will crank, and SOMETIMES, sputter and backfire, but then have no power/momentum and will stall. HOWEVER, if I let the engine sit a good 15-20 mins, it will fire back up and idle normally and run normally again! WTF is that. It's almost like it just needed a "break" and after 20 mins, it is ready to go again. This is what is wacky because it can eliminate MANY of the thoughts I had about defective parts...since if they were defective or off, the engine would not go back to running normally after its issues 20 mins earlier.

Over the years, I have:
-replaced two Crankshaft position sensors,
-replaced several cap and rotors
-replaced ignition coil
-replaced stator (cam position sensor under distributer cap)
-replaced plugs
-replaced wires
-tested and retested fuel pressure regulator (40psi with vac hose off)
-tried spraying starting fluid in it directly after misfiring, still no start
-replaced fuel filter
-fixed rotted out sections of fuel vapor line with fuel rated rubber hose,
-checked and rechecked timing
-checked for vacum leaks by letting engine idle and spraying vac hose areas with starter fluid to see if engine RPMs rise up
-cheked for codes using CEL flashes, I only get the first and ending one along with the one for Air Conditiioning (i have no AC)
-(rebuilt the entire top end 2.5 years ago) but mechanically i don't think this would be a cause


what I can think of to still do is:
-replace oxygen sensor
-clean throttle body
-clean IAC (still wouldnt be a cause would it?)
-clean Throttle position sensor (same as above)
-clean connections at ECm computer
-replace crank position sensor with a Dodge one and not one from Autozone?
-replace cap and rotor again??!


Here is why I am questionable about some of the above things...

if the o2 sensor or cap/rotor/stator was bad or the ECM was defective, why would it be only randomly intermittent and why would the engine come back to life normally after a 15-20 min rest period? what is that about?!! Thats why i can leave some things off the list, like that maybe the timing jumped.. because, why would it jump back after just sitting left alone?

The jeep has done this at cruising speeds 30-45 mph as well as at lower speeds, and once while idling at a traffic light. There is no noise/vibration warning, it just happens in an instant so When it does I try to work the throttle to keep it alive enought to find a good spot to pull over and shut it down. it is becoming a pain in the butt because it seems to happen more frequently in the past 4 months or so. again, no CEL codes get thrown, dash gauges are all reading properly before/as it happens as well. spark plugs arent greasy oily or white, just the normal brownish burnt color.

I did some google searhes using this forum and other wrangler forums as parameters and learned a lot about stalling issues, but NONE that matched the ones I am having. Any ideas you guys have for me to investigate? I love driving the jeep but it can be mentally a pain to wonder if I take it anywhere should I plan on getting stuck or not. Thanks in advance

IROCZman15 is offline  
Sponsored Links
Advertisement
 
post #2 of 24 Old 05-10-2017, 10:56 AM Thread Starter
IROCZman15
Registered User
1995 YJ Wrangler 
 
Join Date: Nov 2013
Location: New Jersey
Posts: 45
So yesterday I drove the jeep home from work after the morning mishap. I made it 22 of the 25 mins without a problem and I stopped at a store to grab some food for a total of about 10 mins. I came out and started the jeep, after a few moments of idling and pulling up to the exit, it went into the haphazard running condition described above. I had begun to pull out, and fortunately there is a long steep hill for a good half mile in the direction i was going. I put it in neutral, shut the engine off and coasted along the shoulder with my hazards on. this took a couple of minutes , and then I figured I'd try to start the engine while rolling. Welp, it fired right up and ran normal, so I rev matched it as best as i could guess to and put it into drive, and drove the last bit of roadway home.

Why would that happen? Why would coasting in neutral help?


Overall seems to be a fuel issue? too much fuel and it needs to evaporate out? yet why would everything be fine on the drive home yet as soon as I go to start it after letting it sit for 10 mins, it goes back into weird mode. it can't be mechanical right? fuel or iginition/computer related.. but what exactly?

anyone have any idea about any of this !?!?
IROCZman15 is offline  
post #3 of 24 Old 05-10-2017, 11:10 AM
S8NNG8
Web Wheeler
 
S8NNG8's Avatar
1995 XJ Cherokee 
 
Join Date: Feb 2012
Location: Helena
Posts: 9,568
Maybe the cat is getting plugged. When it gets hot from being partially plugged, your issue occurs. When it has a chance to cool down, it works till it gets hot again.

D3<!L!>3D
S8NNG8 is offline  
 
post #4 of 24 Old 05-10-2017, 11:38 AM
mike134
Registered User
1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland
Posts: 5,693
I can think of a couple possibilites.

First, this sounds like classic coil problems. You stop the engine, the coil heat soaks, you start driving again and it overheats and stops firing. cool it off and its fine again.

Alternators can also do the above.

As far as fuel goes, this is an easy one to diagnose. Carry around a fuel pressure gauge with you, and when it acts up, measure fuel pressure. On the 95, it couldn't be any easier to measure pressure. You literally just plug the gauge into the fuel rail.

I know you switched the coil before. These usually last a long time. However, what brand fuel pump did you buy? the ONLY fuel pumps that I think the forum would recommend are OEM from the dealership or Bosch (or hesco, which doesn't apply to you). The other ones break after about 2 years. Not to say the autozone fuel pump is a bad deal with a lifetime warranty, you just need to cut the access door out of the cargo area, always carry a spare, and be ready to change the fuel pump at any time on the side of the road when you're late for your unprecedented combination wedding and job interview.
mike134 is offline  
post #5 of 24 Old 05-10-2017, 12:16 PM Thread Starter
IROCZman15
Registered User
1995 YJ Wrangler 
 
Join Date: Nov 2013
Location: New Jersey
Posts: 45
thanks for getting back to me guys!

I had previously thought o the cat as a potential problem, since it is about 6 years old. I do not need to pass emissions anymore due to the vehicles age in NJ is is EXEMPT from emissions/inspection testing, so I can simply get rid of the cat(or hollow it out)...
.... however, the one thing that gets me hung up on this is that this winter, january I got in the jeep, let it warm up 30 seconds, drove 1 minute down the road, and it went into funk mode.. so the cat/coil/components couldnt have been that hot...right? hmm


as for a fuel pump, I have never replaced it. I didnt mention anything about it above (i dont think i did), but i did replace sections of the small diameter fuel vapor line as they rusted out. the pump is still stock (or at least has not been replaced since I have owned the jeep since 2005). i would be happy if this was the culprit, and I would simply replace it. just mechanically i don't know why it would happen so intermittently in the above mentioned conditions, yet still have 40 psi at the rail. i do have a fuel pressure gauge and have checked pressure when the engine is running normally, but I'll keep one with me so that the next time it starts running awful, I can check it hopefully before the engine stalls out.

this issue is driving me nuts because it doesn't seem to have a clear routine/cause ...but the solution is to let it sit for 20 mins untouched. baffles me

haha that was funny though 'change the pump roadside when late for wedding/job interview" !!! ya never know!
IROCZman15 is offline  
post #6 of 24 Old 05-10-2017, 12:22 PM
mike134
Registered User
1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland
Posts: 5,693
Sorry, I must have confused you with a different thread on the fuel pump. The pump can definitely fail under load and/or when it gets hot or just fail all together. It should give you 30 psi at the rail at idle, and 40 psi with the vacuum hose disconnected from the fuel pressure regulator. that 10 psi makes a big difference in these old FI systems. When you say you have 40 psi, is that all the time?

Also, when it dies, does the tachometer go right to zero? bounce around? drop slowly? you said you replaced the CPS twice, but dropping right to zero would indicate a CPS problem or a CPS wiring issue.
mike134 is offline  
post #7 of 24 Old 05-10-2017, 12:29 PM Thread Starter
IROCZman15
Registered User
1995 YJ Wrangler 
 
Join Date: Nov 2013
Location: New Jersey
Posts: 45
definitely 40 psi with vac hose off and I can check exact numbers later today but I do know that it drops down a bit when vac hose is reattached. for sure


if it is inexpensive to just put a new regulator on it, i'll do so. just kinda hate throwing parts at it if the current ones appear to be doing their job (hah like the many crank sensors, plug wires, etc) any brands to avoid?




I would love for this to be a fuel issue because that is all simple components I can replace, as opposed to troubleshooting an ignition/ESC issue.

next time it happens ill whip out my phone and get some audio/video of it happening but I think ill surely gut or remove the catylitic converter setup. i was thinking to do an O2 sensor if I can get the old one out without too much of a problem..but then again, thats just throwing more parts and hopeful wishes at it
IROCZman15 is offline  
post #8 of 24 Old 05-10-2017, 01:19 PM
mike134
Registered User
1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland
Posts: 5,693
The regulator doesn't break very often, and it is relatively expensive. The more common cause of high fuel pressure is an obstructed fuel line back to the tank or leaking vacuum hose to the regulator. A few years ago there was a long series of multiple people with regulator failure, it was very weird. check the pressure with the vacuum hose disconnected and report back. There are some other tests to do to make sure the regulator is working correctly even if you have high pressure. Namely, disconnecting the return line and sending it to a jerry can. 30-32 psi is where you want to be at idle.


Keep the cat if its working. It's good for the environment, and you don't really gain any power advantage by removing it. The trees will hug you as you drive by. If it is in fact bad, then you can make your own decision on whether you want to buy a ~$85 replacement. I wouldn't go for the 50 state $400 OEM one unless absolutely mandatory in your state though. Basically you'd be deciding between a $10 pipe or a $100 new converter.

Before messing with the exhaust I'd install a vacuum gauge in the cabin. It will tell you if the exhaust is clogged.
You would see a slow steady decline to 0 vacuum as the cat starts to get blocked. http://www.jeepforum.com/forum/f12/b...ealth-2841418/
mike134 is offline  
post #9 of 24 Old 05-12-2017, 10:18 AM Thread Starter
IROCZman15
Registered User
1995 YJ Wrangler 
 
Join Date: Nov 2013
Location: New Jersey
Posts: 45
ok, cool. I should do that vacum gauge setup in the cabin. that could certainly prove worth while


Tested the fuel psi 40 with vac hose off 32 vac line on. see video

and it holds fuel pressure overnight actually, so I can assume the inectors aren't bad or leaky. so thats all goood stuff fuel system wise.


I am going to do what i can to clean up the terminals on the ECM and related components. apply some di-electric grease to them too. might hold off on doing the O2 sensor fornow

running out of ideas for possible causes is making me more confused than I was initially. Thank you for the help so far!
IROCZman15 is offline  
post #10 of 24 Old 05-12-2017, 10:38 AM
mike134
Registered User
1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland
Posts: 5,693
fuel pressure definitely looks good then. fuel pressure regulator is good, injectors aren't leaking. The fuel pump CAN still fail under high load, but that usually only happens for a little while before failing at idle.
mike134 is offline  
post #11 of 24 Old 05-12-2017, 01:06 PM
mike134
Registered User
1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland
Posts: 5,693
Still thinking about your issue. I don't really have any more suggestion than what was listed. You can try replacing the gas cap and see if it was a pressure buildup problem. But other than that.... It will probably come down to wiring. I would jiggle the F out of the wiring harnesses and hope for a full break. 100% failure is much easier to diagnose than intermittent problems.
mike134 is offline  
post #12 of 24 Old 07-20-2017, 06:57 AM Thread Starter
IROCZman15
Registered User
1995 YJ Wrangler 
 
Join Date: Nov 2013
Location: New Jersey
Posts: 45
Sorry I let this thread go so long without updating. I did have an update, and it is a BAD one. I parked the jeep and focused on some house projects and camaro projects over the last two months. Once in a while in May and early June I would go out and start the jeep, let it run, to see if it stalled out as I was not driving. I took it around the block a few times but didn't venture too far since I didn't have the time to deal with a roadside breakdown. About 3 weeks ago I went to fire the jeep up and it will crank but not fire. I did the usual checks, fuel pressure at the rail is good, compression is good, starting fluid doesn't work, etc. I traced the electrical ignition system as best as I could at the time but put everything away to do some research.

Came out yesterday and attempted to fire it up. Still cranks healthy but no start. Noticed no spark coming from plugs. Pulled wires off the dist cap and no spark there. Pulled wire from coil to cap, no spark. pulled out the ignition coil and ran the OHM test on it, and as per my service manual, the primary and secondary resistance ohms ARE within the proper specs. tested for DC voltage at the coil output and was getting around 10.6 *(battery is getting drained from attempting to start it). Came out at night to check for blue spark in the darkness and was not getting any spark from coil wire to a metal ground when using a screwdriver inside the plug wire in place of a spark plug.

Curious about if this could possibly be a computer ECM issue?!?! I did jiggle the wiring mentioned above quite a bit too. nothing seems to change.


Before I go buying a ECM for this thing, does anyone have any thoughts, input, etc? I think I can rule out it being a distributor issue, since I am not getting blue spark prior? I can go buy another ignition coil from Advance or Autozone.. or if you recommend ... order one direct through Chrysler/Jeep?

ANY help is much appreciated! Thanks!!!
IROCZman15 is offline  
post #13 of 24 Old 07-20-2017, 07:26 AM
mike134
Registered User
1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland
Posts: 5,693
Probably not ECM. The ECM has only one specific common issue. There are two symptoms: 1.) The check engine light doesn't illuminate when turning the key from OFF to ON. 2.) The fuel pump doesn't prime (no fuel pressure). You don't have either of those.

Check your new check engine codes.

If nothing pops up, I would swap the crankshaft position sensor. Its good to have a spare anyway. If you disconnect the battery and then reconnect it and it fires right up, CPS is a very very attractive attempt, since these are the textbook symptoms, and it has a relatively high failure rate.

The other possibility is that the coil is failing when energized, but since your resistances look good, I'd wait on this one.
mike134 is offline  
post #14 of 24 Old 07-20-2017, 08:16 AM Thread Starter
IROCZman15
Registered User
1995 YJ Wrangler 
 
Join Date: Nov 2013
Location: New Jersey
Posts: 45
ok, yea. I can easily do the CPS again. I have done 3 of them over the past 6 or so years. All bought from autozone, so mayyybe is there somewhere else i should go to for a quality CPS less likely to fail? Genuine chrysler part I can order instead ? I do actually keep an old one in the toolbox i keep in the jeep.

through this whole endeavor, not once have I had a check engine light go on to display a code! I sure wish I had, so that I could pinpoint the issue better!

I agree with you about the lack of the two symptoms you mentioned above BUT
I'll recheck and see if the check engine light does come on when turning key. If I recall correctly, it does, and then would go off after a few seconds.. along with the audible buzzer. I do certainly have proper fuel pressure
IROCZman15 is offline  
post #15 of 24 Old 07-20-2017, 09:52 AM
mike134
Registered User
1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland
Posts: 5,693
Sometimes the CEL doesn't illuminate but can still have some codes stored. Go here to check:

If you replaced the CPS 6 times, I might start suspecting the wiring harness has a chaffing issue, or you don't have the distance correct. HESCO still has a quality CPS, but with the autzone one, if you have a free warranty just grab another.
mike134 is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome