The pcm has 4 plugs , they will only plug into their respective connectors & are color coded to boot . About the only way they could be wired wrong on the coils is if all the single wires had been stripped out of the harness & run willy nilly all over the engine .
Hello All - Thank you all so much for your comments and suggestions. I really appreciate it. The one thing I forgot to mention is that the car had the same problem (starting with only three spark plugs removed) prior to having replaced the head-gaskets, timing chain, piston rings, and crankshaft sensor. The mechanic thought that replacing these parts would solve the problem. One other thing is that the car was running and once it overheated, I turned off the ignition and it has not started since. Again, thank you all so much for your help.
While off were the heads professionally checked out ? That is a confusing post , you say prior to having the work done the engine would only start with 3 plugs out & after the work was done it still will only start with 3 plugs out . You also say it overheated & hasn’t started since . Are you saying you ran it to the point of overheating with 3 plugs out ?
Hello - No, it overheated first then the problem involving starting with only three plugs was discovered when the mechanic troubleshoot for not starting. Hope that makes sense. Thanks to all.
Personally I like Tester’s idea of a plugged cat, given the new information. It doesn’t take any time at all to ruin a cat.
Creative genius? Does not start, let’s try it on 3 plugs. Never heard of that approach. CEL on? Not up enough on new car technology to hazard a guess
Not up on technology at all. I happen to be on an island in the Caribbean where mechanics does not have much knowledge. CEL is on. @ Bing - mechanic mention that he did drop exhaust from the converter back and that did not work. Thanks all.
I concur w/ @Barkydog above about how unusual it is to hear that a tech would attempt to diagnose a no-start problem by trial-and-error approach using fewer than the full set of plugs. There’s so many different combinations to try, seems like that would take forever if you didn’t have a clue which ones were the problematic ones. Perhaps what happened is the tech tried disconnecting the plugs one at a time – that’s a pretty common approach to identify which cylinder isn’t firing – and discovered the engine ran better with certain plugs disconnected, so decided to actually remove the plugs from those cylinders, which made the engine run even better.
hmmm … well for the engine to run well it has to have a steady supply of air and gas, good compression, correct ignition and valve timing, and a free flowing exhaust. So the problem is almost certainly among one of those. Your tech will just have to go through those one by one. To speed things up, maybe give a little thought to whether there anything common about those particular cylinders? For example do they use the same intake manifold routing? Or the same exhaust routing? Or use the same ECM connector for the coil firing? Likewise, the same ECM connector for the injector pulsing?
Disconnecting the exhaust behind the cat really does nothing if the cat is plugged. You’d have to disconnect the cat at the front of the cat.
OK, new theory. There’s carbon build up in those problematic cylinders, so they go “boom” as soon as the gas hits them, and refuse to wait for the spark to initiate the “boom”. This would only be a problem when the engine was at operating temperature though. But at least it’s a theory to consider if that applies.
If not that, I’m sort of leaning toward the camshaft timing as mentioned by Nevada above. But there’s problems with that theory too. Oh what a tangled web we weave … lol …
I have not worked on many Jeep liberty’s engines, but when I looked up the 2005 for parts it only showed one Gasoline engine option…the 3.7 and it does show a distributor.
Yosemite
The 3.7 does not have a distributor . It is a COP engine . I think when the Liberty was first introduced a 4 cylinder was available & maybe it had a distributor , I haven’t checked . A diesel was also available in at least some year model Liberty’s .
I have 2 Liberty’s , an 02 & an 05 , both are 3.7 V6’s & they are both COP engines with no distributor . Camshaft timing can be tricky on these engines . Lots of people get it wrong when installing timing chain kits .
The 3.7 is rather notorious for 2 things , spitting out rocker arms & dropping valve seats . I just replaced the high mileage engine in the 05 with a low mileage 05 engine .
I have no idea why the OP’s engine will only run with 3 plugs out but if I had to hazard a guess , it would be timing related . The OP said it was that way both before & after being worked on & these engines are not known to jump time but of course it could have .
...when I looked up the 2005 for parts it only showed one Gasoline engine option....the 3.7 and it does show a distributor.
Rock Auto shows coil-over-plug coils.
I don’t know where you are looking up parts, but nowhere I can find has a distibutor listed. Here’s what a coil listed for the vehicle looks like. Sure looks like C-O-P to me.
The source I’m looking at for a 2005 Liberty 2WD version shows two engines available, a V6 3.7 and an L4 2.4; neither lists a distributor. The firing order for the 3.7 is 1 6 5 4 3 2. That’s the so-called “distributor function” one of the posters above denies exists. The distributor function is done electronically on coil on plug designs rather than using a rotating dizzy. But it accomplishes the same thing, sets the correct firing order.
I continue to remain suspicious that an incorrect firing order is causing this weird symptom. The diagram I’m looking at shows cylinder 1/ coil 1 is on the drivers side towards the front of the car, cyl number 2/coil 2 is the passenger side front, so the drivers side is the odd cylinders and the passenger side is the even. Someone who knows how to use an o’scope could verify that is correct on the OP’s vehicle. There’s several ways it could be incorrect
- coils hook up to plugs wrong
- ignition coil connector to engine computer wrong
- faulty engine computer
From the excellent posts above, it sounds like the most likely among those three is the last one, faulty engine computer.
I would assume all engines with more than 1 cylinder have a firing order . If you were referring to me , I don’t recall saying otherwise . I also have never heard a pulsing signal from a pcm / computer called a distributor . In my world an engine distributor has a distributor cap with spark plug wires connected to it .
The way the wiring harness is made with wires coming out of it in various places to connect to various plugs / connectors there is not much of any way to get things all mixed up unless the wiring harness itself has been severely messed with / disassembled .
The large majority of the connectors are configured differently so they will only connect to the correct corresponding plug , sensor or whatever . The coil & injector connectors are the same but if they’re connected to the wrong one , other wires aren’t going to reach where they’re supposed to go , { UNLESS THE WIRING HARNESS HAS BEEN DISASSEMBLED } . In that case all bets are off .
Instead of saying the coil & injector connectors are the same , I should have said the coil connectors are the same & the injector connectors are the same . The coil & injector connectors aren’t interchangeable .
I wasn’t referring to your postings @Sloepoke . By “distributor function” I mean whatever it is that determines the firing order. With an actual dizzy, that is determined by the rotational sequence of the ignition rotor. With a coil-on-plug design, it is determined by the electronic and software design of the engine computer & electronic ignition system. However it is done, it is still the “distributor function”.
And if it isn’t done correctly, the OP’s symptom could be the result.
Hello - Thank you all so much for your suggestions. It is beginning to sound more like the engine computer and/or timing belt related issue might be the culprit… Again, thank you all so much. This is great.
I said that I was not familiar with the Jeep 3.7 but that is what I punched in. This is what advanced Auto showed, so I presumed it had a distributor.
http://shop.advanceautoparts.com/p/proform-chevy-hei-electronic-racing-distributor-w-coil-100-new-red-cap-polished-66941r/22740099-P?navigationPath=L114923%7CL215034%7CL3*16062#fragment-1
I stand corrected!!!
Yosemite
I wonder what the round-circle spot-light looking gadget is for on the distributor photo in @Yosemite 's link? Do you think it lights up each time a spark is made? That would be pretty cool. Light effects under the hood!