94 YJ runs cold; sputters, misfires and dies once warmed up - Jeep Wrangler Forum
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Old 10-16-2013, 02:45 PM   #1
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94 YJ runs cold; sputters, misfires and dies once warmed up

Hey guys! I have a 1994 YJ, 4.0L Manual Trans with about 160k miles, and about a month ago I started running into problems. Someone suggested I replace the ignition pick-up as well as running seafoam throughout 3 different areas. I replaced the ignition pick up and it ran fine, and I ran the seafoam through the spots (gas tank, oil cap, and line coming from brake booster). Then while running it to clean out the seafoam, it died! It was dead for about a week and I replaced:

fuel pump
fuel filter
distributor cap
wires
plugs
Temperature sending unit
ignition coil (but my coil blows all the time for some reason, I believe its a bad mounting location)

Once I replaced the coil it started working just fine again until about a week ago, now whenever I attempt to drive it it will drive TOTALLY fine for about 20 minutes and then it sputters badly, misfires, RPMs go crazy, and eventually dies. I did the on board diagnostics and the ecm is spitting out codes: 11, 12, 22, 55.

Anyone got any ideas? It's gotten to the point where I'm ready to give up.

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Old 10-16-2013, 04:11 PM   #2
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I just had a similar issue with mine running like that. Turns out it was a stuck open thermostat. Pull the thermostat and test it.

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Old 10-17-2013, 10:22 AM   #3
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Do you know the general area that its located at? It should be right in front where those radiator hoses go right? You just put it in boiling water to test it?
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Old 10-17-2013, 10:59 AM   #4
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Do you know the general area that its located at? It should be right in front where those radiator hoses go right? You just put it in boiling water to test it?
It is located in the front of the engine where the coolant return line is. It is held by two bolts. Make sure you have a new gasket before pulling it apart. Ask me why I am recommending that.

To test it just put it in boiling water for 10 to 15 seconds and it should open. If you haven't replaced the thermostat before I would get a new one just so you know when the part was installed. Mine look really old when I pulled it out.
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Old 10-17-2013, 12:10 PM   #5
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Ok ill ask, why should I have a new gasket? and as soon as im out of class I'm going to try this, around 5 pm eastern. Thanks so much!
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Old 10-17-2013, 12:12 PM   #6
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Recommend any specific thermostat for such an old jeep? I'm seeing a bunch of options on oreillys site.
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Old 10-17-2013, 12:25 PM   #7
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One more question before I get off for class, would a broken thermostat stop my gauge from working? Because I believe my gauge is working just fine, also, what could cause it to be spitting out code 22(coolant temp sending unit) when I just replaced it yesterday?
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Old 10-17-2013, 01:27 PM   #8
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Quote:
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Ok ill ask, why should I have a new gasket? and as soon as im out of class I'm going to try this, around 5 pm eastern. Thanks so much!
As soon as you remove the thermostat & thermostat housing the old gasket will fall apart. You'll want to get the mating surface clean as well. Those old gaskets can be a pain to get completely off. Think of it this way: The coolant system is a sealed system, you need to keep everything to do with it squeeky clean. If you've ever been to a real transmission shop you'll understand. A good tranny shop looks like a hospital operating room. Very clean.

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Recommend any specific thermostat for such an old jeep? I'm seeing a bunch of options on oreillys site.
Just a factory replacement will be fine. Take your old one to the parts house & compair it to the new one before you walk out. Also make sure it has a burp hole.

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One more question before I get off for class, would a broken thermostat stop my gauge from working? Because I believe my gauge is working just fine, also, what could cause it to be spitting out code 22(coolant temp sending unit) when I just replaced it yesterday?
If the gauge is completely dead & you have a 22 code, the new sending unit you installed is DOA (dead on arrival). Replace it with a different unit. It's not uncommon for sensors/sending units to be bad right out of the box.

Hope this helps.
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Old 10-17-2013, 03:04 PM   #9
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Did you change your oil after adding the seafoam? That should've been done, I do agree the thermostat could be a problem, but seafoam can destroy an engine
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Old 10-17-2013, 03:27 PM   #10
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When it comes to the code 22, did you change the coolant temp sensor by the front of the engine or the temperature sending unit in the back? If you did the coolant one I would disconnect the battery's negative cable then see if the code comes back.
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Old 10-17-2013, 04:02 PM   #11
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If the gauge is completely dead & you have a 22 code, the new sending unit you installed is DOA (dead on arrival). Replace it with a different unit. It's not uncommon for sensors/sending units to be bad right out of the box.

Hope this helps.

My gauge DOES work, that was what confused me. I replaced the temp sending unit, in the back. I'll make sure I clean the area around the thermostat as best I can before I put it back in/replace. I was unaware at the time about what seafoam can do negatively, I asked several times if it was a good idea on a 19 year old car and heard nothing but "ohhh yeah itll do wonders"...well it did wonders all right lol

I have not changed my oil since the seafoam, I will do that first thing in the morning
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Old 10-17-2013, 04:04 PM   #12
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And as for the seafoam ruining engines, it worked for a while(2ish weeks?) after that with minimal issues, so should I still be concerned that it may have caused permanent damage to the engine block?
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Old 10-17-2013, 04:06 PM   #13
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Ill let you all know whether it starts or not once my friend gets here. It's been cooling down for about a day (which previously was more than enough time to let it cool before it decided to start again) but my battery died from trying to start it a few times over the course of the day. Does anyone have any ideas about that code 11? Could I have blown out another coil already??
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Old 10-17-2013, 04:38 PM   #14
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First thing I would do is change the oil and filter. The temp sensor you changed goes to the gauge. The one in front, should be on the thermostat housing goes to the ECM.
It supplies info that effects fuel/air mixture, ignition timing and controls EGR valve operation. I would change the CTS, disconnect the battery to clear the ECM, get it started and run for a while, then check to see if it is throwing any codes.
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Old 10-17-2013, 06:04 PM   #15
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Good news is it is still running while cold (yesterday it wouldnt start even after hours of cooling down). So i took out the thermostat and tested it with boiling water and it opened, but only a very, VERY little. I don't know if that's normal or if it should open a lot more. Also, thanks for the heads up about the gasket, the thermostat/gasket just looked like shit when I took it out, I'm gonna go over both the mating surfaces with a razor blade in the morning and replace the gasket, the coolant temp sensor, and change my oil/filter. Depending on what you guys say I may also replace the thermo.

CMIKE357 what is the CTS, what does it do and where do I find it?

Thank all of you so much, I already wish I would have made an account sooner.
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Old 10-18-2013, 09:02 AM   #16
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The CTS monitors the coolant temperature, as the temperature changes, the resistance of the sensor changes, providing a varying input voltage to the computer. The computer usese information from the CTS to adjust fuel/air mixture, ignition timing and controls EGR valve operation.

It is located on the thermostat housing.

I might add when you go to the parts store, pick up a Haynes manual. It may not have everything in it, but it is a good source of information, plus it may even have a picture of what you are working on.

Did you check to see if it is throwing any codes?

Let us know what you find.
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Old 10-18-2013, 12:27 PM   #17
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About to head out to the parts store to pick up thermostat/gasket, CTS, and some oil/filter.

CMIKE357 I have a haynes manual but unfortunately left it in IL, and I go to school in FL, I'll make sure to have my sister/brother send it to me asap.

And as for codes, yesterday it was still spitting out 11, 12, 22, and 55
I know 12 is for the battery being disconnected and 55 is the end of output.
I'm hoping the CTS will get rid of the 22 (if I'm wrong/it won't please let me know)
and I'm still looking for some guidance on that code 11. It says ignition but yesterday it was starting up just fine.
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Old 10-18-2013, 12:41 PM   #18
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Were those codes before of after disconnecting the negative cable? If they were from before go ahead and disconnect the cable, do the maintenance that you are planning to. After everything is done see if you still get the 11.
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Old 10-18-2013, 03:27 PM   #19
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Code 11 is ignition, CTS effects ignition. Purchase the parts in your last post. Disconnect the negative battery terminal while you install them. Reconnect the battery terminal and run it for a while. Then check the codes again to see if they have disappeared. Let us know how things go.
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Old 10-18-2013, 03:54 PM   #20
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Decided to start down pouring WHILE I was in the parts store, let you guys know how it goes once it lets up.
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Old 10-20-2013, 12:45 PM   #21
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I replaced the thermostat and Coolant temp sensor and it seems to be running great! I had a little hiccup (it jerked just once) while I drove it at operating temp for about 30 minutes. I honestly think it's fixed, hopefully for good (until something else needs fixing) Thank you all so much for the input! Glad to be back on the road!!
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Old 10-20-2013, 08:39 PM   #22
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Glad we were able to help and you don't have to work on it for a while. Just enjoy driving it. Thanks for updating us on what fixed it and not leaving us hanging.
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Old 10-21-2013, 12:21 PM   #23
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Well actually turns out it isn't fixed....I drove it to the grocery store and then to a friends, barely made it to my friends (only about a mile from the store) and I just left it at her house. Same symptoms, jerking, misfiring and dying after it heated up.

Are there other sensors that send temperature readings to the ECU? When I drove it from the store to my friends, whenever it starts to sputter and pull back, I would throw it into neutral and it would idle just fine. It just didnt seem like it wanted to be in gear when it was hot.

Would a video help?

I replaced the oil yesterday morning as well and the only codes coming out are 12 and 55. Could the seafoam sitting in the engine for that week(about 3 weeks ago) block something up? When I put the seafoam through, and then ran it, NO white smoke was coming out like it was on the youtube videos. There was a smell, and a light haze, but nothing like the videos where the cars are billowing out smoke.

Any help is super appreciated
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Old 10-21-2013, 03:01 PM   #24
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In your initial post you said it blows coils all the time. So that is where I would start.
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Old 10-21-2013, 04:54 PM   #25
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But usually when the coil goes out I can't run it hot or cold. I just got it home and let it idle til it died (total running time about 25-35 minutes) and I touched the plug coming from the crank position sensor and it died right then and there
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Old 10-21-2013, 05:27 PM   #26
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Also now it is giving out codes 11, 12 and 55.
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Old 10-22-2013, 05:39 PM   #27
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I tried to start it this morning after it cooled down all night, it has been raining all day too but it wouldn't even start this morning. Any ideas?
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Old 10-23-2013, 07:05 PM   #28
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Turns out it was the crankshaft position sensor! Working like new now. Thanks guys.
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Old 10-25-2013, 12:40 PM   #29
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I've been suffering from almost this EXACT problem for a month now! I've tried EVEYTHING. Is here anyway you could give me a little more info on the types of symptoms you had? Did your heat work correctly and did you idle rough after you warmed up?
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Old 11-05-2013, 12:12 PM   #30
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It would work fine when it was cold, driving perfectly for about 20 minutes, and then would sputter, misfire, die, and wouldnt work until i got it cooled down, usually about 6 hours. I'm not sure if my heat worked (I live in FL and it was nice out). And once warmed up it didnt matter whether I was idling or driving, it would die.

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