4bangerjp.com
General Forums => The Mess Hall => Topic started by: Desert Bob on October 01, 2007, 05:07:28 PM
-
My 1995 YJ 2.5L has issues at idle. It runs well but it idles rough (kind of pulses) and when started when it is warm it idles high (1500rpms). As soon as I drive off the idle drops down to normal (750-800 rpms). When it is cold it acts like it is going to stall out (but never does). I cleaned the throttle body, IAC and passage and ran some injector cleaner (sea foam) through it but is still acts exaclty the same. Is this the TPS or IAC that controls this circut? The Jeep has 163,000 miles and to my knowledge neither of these have been changed.
-
The IAC is what controls the idle when the engine is cold. Once it's warmed up it I believe the IAC closes. (like a choke) Does the engine idle fine when it's warmed up? The high idle would lead me to believe there is a vacuum leak someplace. Although you said it drops back to normal after a while.
I'd consider checking the PCM for stored CEL codes. Even if they don't cause a CEL there could still be codes. Here's how to do that: http://4bangerjp.com/forums/index.php?topic=3419.0
-
The engine idles OK when warm but it kind of pulses. Not a wide swing in RPM but enough that I can feel it. It is rough and stumbly (:confused:) when cold. I just replaced all of the vacuum lines and have checked for leaks on the manifold by using brake cleaner around all of the seals. No issues there. Plugs are a nice tan color. I will see if there are any codes tonight. Thanks.
-
my heep idles at 1 grand all day long :eek:
-
my heep idles at 1 grand all day long :eek:
Living with a vacuum leak? :whistle:
-
The codes were 12 and 33. The 12 makes sense as my battery was disconnected over the weekend when I replaced my lifters. I have no idea what the 33 is since my manual would lead me to believe I don't have the part effected. Any help?
-
my heep idles at 1 grand all day long :eek:
Living with a vacuum leak? :whistle:
you are correct im just too lazy to fix it, it runs so why bother?
-
Mine is ussually at around 900~1,000 RPMs (dash reading). What is the normal RPM range?
-
My past jeeps have always idled at around 700-750rpm.
-
Checked the plugs and everything look as they should. Light brown on the electrodes. Any other ideas?
-
a rough stumbling idle would lead me to believe, fuel filter is it's never been changed. maybe a possible misfire these have lots of causes, bad wires, in the ignition somewhere etc. but lets keep it simple, fuel filter change it if it hasnt been changed. and i suggest heading over to your closest jiffy lube, and have them do a fuel system cleaning, its a two step process, more than just adding stuff to the tank. and just to make sure your timing is correct stick a timing light on it and check it.
-
Wouldn't a bad filter cause issues under hard acceleration? The Jeep runs fine once off idle. I was planning on doing new plugs, wires and cap/rotor in a couple of weeks so I will replace the fuel filter then. I just got my Rubicon Express 2.5" lift kit so that will be this week-ends project.
-
I replaced the Cap, rotor, plugs, wire and fuel filter and it runs better but still idles poorly. Would an O2 sensor cause this type of behavior. BTW: Did a compression check and it goes as follows:
1st 157psi
2nd 155 psi
3rd 162 psi
4th 165 psi
Is this good for a motor with 164K miles?
Help!
-
I replaced the Cap, rotor, plugs, wire and fuel filter and it runs better but still idles poorly. Would an O2 sensor cause this type of behavior. BTW: Did a compression check and it goes as follows:
1st 157psi
2nd 155 psi
3rd 162 psi
4th 165 psi
Is this good for a motor with 164K miles?
Help!
I think your compression is pretty good for an engine with that many miles. I forget what the variance between cylinders is... gotta look that one up.
Go to the FAQ and look up Factory Service Manual and download the 94 or 95 pdf's.
-
Have you tried using propane at all of your vacuum connections? That'll help you determine wether you have a vacuum leak. If you still have the axle disconnect, don't forget to check there!!
-
I did check all of the vacuum connectors but not the quick disconnect. Will do that today. The jeep runs well and idles smooth when in the morning when cold. When it warms up it idles rough and kind of surges in a very rhythmic cycle.
-
Here is what I have done so far:
My 95 2.5l starts fine in the morning and idles smooth. Once underway it idles rough (like a miss) and rises/falls rhythmically (+/-100rpms) at stop lights. It runs fine and accelerates smoothly once off the line. When I start it when warm it idles at about 1,500rpm for about 30 seconds and then goes back down to the rough idle. I drove the Jeep to work this morning and based on a humming sound it sounds like the Fuel Pump is cycling with the rough idle. What controls this? I would have thought the fuel pump would run in a steady fashion or does it cycle based on the ECU or MAP determined by engine load.
I have done the following:
Fixed the #4 exhaust stud and replaced the intake/exhaust gasket
Replaced all vacuum hoses
Cleaned the throttle body and IAC motor and passage
Replaced the plugs (Old ones were hardly worn and were a nice light brown)
Replaced the Cap and Rotor
Sea Foamed the Intake and fuel system
Replaced the Valve Lifters
Compression: 1st=157 2nd=155 3rd=162 4th=165
Should I go for the O2 Sensor and TPS? How do you test the fuel pump? I think that is all I have left. What next? :confused:
-
Have you checked the PCM for stored codes?
-
Yes. Nothing out of the normal. I think they were 12, 33 and 55.
-
Hmm, can you still hear the fuel pump after it primes? Also have you taken a fuel pressure reading?
-
I think so. I hear a humming that cycles with the idle.
-
I think so. I hear a humming that cycles with the idle.
Hmm, mine goes quiet after it primes.
-
How do I pressure test my fuel system? I thought it either worked or didn't. It starts fine and seems to run OK. My last 2 Jeeps were 4.0 HO motors so I can't compare power delivery.
Hmmmm. I am beginning to think I should have stayed with Baja Bugs. Not much to trouble shooting an aircooled motor.
-
How do I pressure test my fuel system? I thought it either worked or didn't. It starts fine and seems to run OK. My last 2 Jeeps were 4.0 HO motors so I can't compare power delivery.
Hmmmm. I am beginning to think I should have stayed with Baja Bugs. Not much to trouble shooting an aircooled motor.
There's a tool for it but you could make one.
What RPM is it idling at when 'rough'? Have you checked the timing? You won't be able to adjust the timing but it could help diagnose the problem. Is this a manual or auto? What year is this again?
-
Jeffy,
Thanks for all the help. The engine when cold idles at around 1,000rpms. It then drops down to about 750 at the end of the block. In the morning when the air is cool it feels like it is going to stall but does not - then it idles just above 500rpms. When the engine is warm it idles at about 600rpm and misses hard then goes smooth, pulses a few times and then misses hard again. I can feel the miss through the entire chassis. It is not a completely predictable cycle like I thought before. I pulled each injector plug while the engine was running and noticed no difference except for the obvious miss fire on that cylinder.
Thank,
Bob
-
Oh and it is a 1995 YJ with the AX5 transmission. No AC. Just a basic Jeep.
-
My 1995 YJ 2.5L has issues at idle. It runs well but it idles rough (kind of pulses) and when started when it is warm it idles high (1500rpms). As soon as I drive off the idle drops down to normal (750-800 rpms). When it is cold it acts like it is going to stall out (but never does). I cleaned the throttle body, IAC and passage and ran some injector cleaner (sea foam) through it but is still acts exaclty the same. Is this the TPS or IAC that controls this circut? The Jeep has 163,000 miles and to my knowledge neither of these have been changed.
I had the same problem in my 90 yj. It turned out the EGR was slightly open because of carbon. Had it cleaned and it runs like a champ aside from the cracked exhaust manny, but the shop that replaced it the first time is going to replace it for free so I'm not that butt hurt.
-
No EGR on a 95.
-
More data. I checked the timing and it is 14* btdc which seem like way too much advance at idle. I would have expected more like 10*. Also checked my vacuum with a gauge and it is fluctuating between 15-20in./hg at idle which according to my Chilton guide is either a sticking valve or ignition miss. Right now I am leaning towards the ignition miss as my compression test checked out pretty well. Would this be the ECU or Distributor? I did notice that there was quite a bit of play in the distributor shaft when I put on the rotor last weekend. Hmmmm. I thought this was OK as I did not see any damage in the old cap/rotor. But this might be the culprit. Any way to test this as I don't want to keep buying parts hoping to find the right one. Thanks.
-
More data. I checked the timing and it is 14* btdc which seem like way too much advance at idle. I would have expected more like 10*. Also checked my vacuum with a gauge and it is fluctuating between 15-20in./hg at idle which according to my Chilton guide is either a sticking valve or ignition miss. Right now I am leaning towards the ignition miss as my compression test checked out pretty well. Would this be the ECU or Distributor? I did notice that there was quite a bit of play in the distributor shaft when I put on the rotor last weekend. Hmmmm. I thought this was OK as I did not see any damage in the old cap/rotor. But this might be the culprit. Any way to test this as I don't want to keep buying parts hoping to find the right one. Thanks.
Well the distributor can't be moved. What controls timing is the CPS which would be cheaper then replacing the PCM. Worth testing I think.
-
No EGR on a 95.
New fangled Hippy Jeeps with there codes and such, LOL :rant:
-
Well I dropped the Jeep off at my local shop that I trust and has done work for me in the past. The did a thorough check of the jeep and could find nothing wrong. He just smiled and saild I should have bought the six if I wanted a smooth running engine. I am going to keep working on it as I think it can run better. I will keep everyone posted on my journey and time will tell.
-
The shops answer to a idle problem was you have the wrong engine?
I don't think I would ever go back to that shop.
-
The shops answer to a idle problem was you have the wrong engine?
I don't think I would ever go back to that shop.
Agreed. At least it didn't cost me anything.
-
See below
-
UPDATE: Bought a Distributor off of EBay as mine seemed to have way too much play. Got it complete and shipped for $15. Good deal and it was in excellent shape. Installed it Saturday and it runs much better but still has the idle issue. The Jeep also runs quieter as well with much less ticking.
Then I replaced the O2 sensor because most likely it had never been changed as well. Still has the idle issue.
I have ordered a new IAC and TPS so if these don't do the trick what next?
-
Put in the new IAC and TPS and still idles rough. It seems to run smoother and start better but still shakes at 600rpms. So far this is what I have done:
New Plugs - Champion 4412 Gap .035
New Cap and Rotor - Goods ones with Brass connectors
New Plug Wires
New O2 Sensor
New Throttle Position Sensor
New Idle Air Control Valve
New Lifters
Cleaned the Throttle Body
Replaced all (and I mean all) vacuum lines
Replaced Distributor and Cam Position Sensor
Good compression (155-165psi)
Clean Air Filter
New Fuel Filter
Ran Sea Foam through the Engine and Fuel System
I still have a tick that I thought the lifters would fix. Maybe the cam is worn? Any other ideas?
Thanks.
-
I replaced the Power Steering Pressure Switch this weekend and still no luck. The Jeep idles at 500-600rpm when the miss starts. With the engine cold it idles really smooth at about 700rpm (IAS must be wokring) Is there someway to trouble shoot an ECM? Would a bad CPS cause a low/miss at idle? Or do they just fail outright.
Thanks.
-
Put in the new IAC and TPS and still idles rough. It seems to run smoother and start better but still shakes at 600rpms. So far this is what I have done:
New Plugs - Champion 4412 Gap .035
New Cap and Rotor - Goods ones with Brass connectors
New Plug Wires
New O2 Sensor
New Throttle Position Sensor
New Idle Air Control Valve
New Lifters
Cleaned the Throttle Body
Replaced all (and I mean all) vacuum lines
Replaced Distributor and Cam Position Sensor
Good compression (155-165psi)
Clean Air Filter
New Fuel Filter
Ran Sea Foam through the Engine and Fuel System
I still have a tick that I thought the lifters would fix. Maybe the cam is worn? Any other ideas?
Thanks.
Have you tested the coil output?
-
Would the output be different at idle? I would have thought it would be the same voltage regardless of RPM? The Jeep runs very well it just idles poorly.
-
I can't say for sure but I replaced the coil on my TJ and she fires right up and runs smooth. Had a little rough idle and hard start before.
-
I can't say for sure but I replaced the coil on my TJ and she fires right up and runs smooth. Had a little rough idle and hard start before.
Mine got better when I replace everything with the performance firepower package. New coil was part of the package. Everything works especially well when I turn the key and let the fuel pump prime before I start it. The oil guage doesn't go goofy either if I give it time to prime. I just wait a second until I hear the fuel pump stop. The other thing I did was pitch the CAI and put the stock one back on this made a difference in my opinion.
-
I still have a tick that I thought the lifters would fix. Maybe the cam is worn? Any other ideas?
Thanks.
Could the "tick" be an exhaust leak, caused by a cracked manifold? :brick:
-
I still have a tick that I thought the lifters would fix. Maybe the cam is worn? Any other ideas?
Thanks.
Could the "tick" be an exhaust leak, caused by a cracked manifold? :brick:
I just replaced the broken Exhaust Stud and the Manifold was fine. Ticked the same before and after.
Thanks.
-
I can't say for sure but I replaced the coil on my TJ and she fires right up and runs smooth. Had a little rough idle and hard start before.
Mine got better when I replace everything with the performance firepower package. New coil was part of the package. Everything works especially well when I turn the key and let the fuel pump prime before I start it. The oil guage doesn't go goofy either if I give it time to prime. I just wait a second until I hear the fuel pump stop. The other thing I did was pitch the CAI and put the stock one back on this made a difference in my opinion.
Would the Accel Coil work with new plug wires? Hate to throw away what I just bought.
-
I don't see why not! I'm using a MSD coil, with Mopar performance wires.
-
I put in a new Acel coil. No change. Arrrrg! I might as well change the CPS as this is the only thing I haven't replaced. Then at least I know I have done my best. Please any other ideas?
-
I had a similar situation, but mine eventually turned into it dying while running, especially at idle. Try checking the input wires to the coil, follow them as far as they go. On mine there was a tap comin off the power side that the person before me put on for some ungodly reason. The tap eventually broke the wire but they were close enough that it actually made contact most of the time.