Jeep died/won't start

[rwat96]

I have had about 50 out of 60 parts fail in months if not right out of the box from AZ the last 3 years.

Get a code scanner and check the codes and post them up. AZ will check them for free.

Oh and yes they scanned it and it was giving a code for a bad tps. They told me it was the wiring harness potentially, but after thinking about it I later realized that was wrong based off what I said in my other reply.

 

[Ecomike]

If this is true it screams of a wiring problem, (thus not a TPS problem) or a problem somewhere else, like the no air supply when cranking from the IAC, which can flood the engine in 5-10 seconds of cranking.

"And it isn't a wiring problem thankfully as it runs better unplugged/with this sensor than it did with the old one which shows the tps is able to send a signal, but what is odd is that there is literally no difference between the autozone sensor being plugged in and completely unplugging it, and both sensors I tried literally did nothing at all"

Do you have and know how to use volt-ohm digital multi meter?
Check the ground from the TPS wiring harness side ground wire to the battery negative post. It should be less than one ohm. The other wire should read 5 volts DC if it is the same as the Renix years.

 

[rwat96]

If this is true it screams of a wiring problem, (thus not a TPS problem) or a problem somewhere else, like the no air supply when cranking from the IAC, which can flood the engine in 5-10 seconds of cranking.

"And it isn't a wiring problem thankfully as it runs better unplugged/with this sensor than it did with the old one which shows the tps is able to send a signal, but what is odd is that there is literally no difference between the autozone sensor being plugged in and completely unplugging it, and both sensors I tried literally did nothing at all"

Do you have and know how to use volt-ohm digital multi meter?
Check the ground from the TPS wiring harness side ground wire to the battery negative post. It should be less than one ohm. The other wire should read 5 volts DC if it is the same as the Renix years.

Yes I feel that wiring could be a problem, what is strange is that when I reset the CEL it instantly comes on with no delay when I crank it over. And this morning it wouldn't start at all, which is odd because it ran ok last night just not very well. I am suspicious of the autozone cps I put in it 2 days ago so I will swap it for the factory one to see if that is why it won't start today and I will also do the multi meter test for the tps. I really hope that there isn't a wiring problem, if so we will just have a shop sort it out because I am tired of guessing and putting money into things that aren't the problem. I will give an update tomorrow.

 

[Runnin'OnEmpty]

I agree with the wiring problem, but it might be something
as simple as a pin pulled loose in one of the connectors.

I'd check the TPS plug first, since it gets the most use and
is easy to reach. Of the three wires, one is a ground, one
should show 4.5-5v, and the third signal wire varies v as the throttle moves.

 

[rwat96]

I agree with the wiring problem, but it might be something
as simple as a pin pulled loose in one of the connectors.

I'd check the TPS plug first, since it gets the most use and
is easy to reach. Of the three wires, one is a ground, one
should show 4.5-5v, and the third signal wire varies v as the throttle moves.

The plug looks ok, and having the old sensor was worse than unplugging it or using the autozone sensor (when it ran for me lol) which seems to me the plug and wiring is ok, but I could be wrong. Hopefully I can figure it out tomorrow.

 

[rwat96]

It's been a while but I thought I would give an update. So we took it to a shop and it took them a few days to find the problen, but turns out it was a $3 throttle body gasket that needed to be repacked I guess air leaking behind the mad was really screwing with the ecm. I can't believe it was something so simple, and I never heard this mentioned once in all of research, but I'm glad it's running again.

 

[old_man]

Ok so yesterday I went to start my jeep and it was cranking over with nothing happening after a minute or two of attempts it sputtered to life and it ran fine the rest of the night and this morning. While on my way to work this afternoon, it suddenly died at a stop light and it took a few minutes of cranking for it it start again, and it made it a good ways but when I let off the gas the engine rpms didn't return to idle but instead it idled high and was somewhat erratic (i cleaned my idle air control valve a few months ago so I doubt that's it). It died once again at the turn into the parking lot, and this time it wouldn't start and a good Samaritan in a truck pulled me into the lot. I haven't had much time to do any trouble shooting but I feel it is either the CPS or a fuel delivery problem. Does the inconsistency usually mean a fuel delivery problem or the CPS? I originally thought the CPS but when I think about it now it may be fuel related as both times it didn't die while idling but instead when I just started to accelerate from a stop. Any thoughts?

Before throwing parts at it or randomly testing sensors, take a look at the basics. Spray some ether or carb cleaner down the intake and try and crank it. If it starts/sputters, you have a fuel problem.

Pull a spark plug and see if you have a nice fat spark.

If you have fuel and spark, the only thing normally left would be air. If you get to this point and you really have verified these things, my bet would be a clogged CAT. If you can get it to run a bit, a manifold vacuum gauge would verify this.

 

[Ecomike]

I am not buying the throttle body gasket story for an "It will not start", and dies story here. They may have accidentally unshorted something moving the harness and connector wires, or improved contacts at the TPS or IAC on the throttle body when they changed the gasket. It may have needed replacement but it would be no different than a disconnected vacuum hose to the intake which I have had many times and those just caused a high idle and sucking sound-noise.

 

[rwat96]

I am not buying the throttle body gasket story for a won't start story here.

Ya honestly I don't know why that would make it run as poorly as it did/not start, i would agree that iy doesn't make sense, but then nothing has since this whole ordeal started. it probobly didn't help that I reset the ecm multiple times while replacing sensors and trying to clear the cel. If anything they would say it was something really expensive to sicker money out of us. So if they were lying it would be counter intuitive to say it was the throttle body gasket. But I honestly don't care because it's running again, whether they changed the blinker fluid or muffler bearings it doesn't matter now.

 

[rwat96]

I am not buying the throttle body gasket story for an "It will not start", and dies story here. They may have accidentally unshorted something moving the harness and connector wires, or improved contacts at the TPS or IAC on the throttle body when they changed the gasket. It may have needed replacement but it would be no different than a disconnected vacuum hose to the intake which I have had many times and those just caused a high idle and sucking sound-noise.

Ya that's a good point, so Idk what happened. They could have accidentally restored a bad electrical connection when they did a run through of the system or something like that.

 

[rwat96]

I am not buying the throttle body gasket story for an "It will not start", and dies story here. They may have accidentally unshorted something moving the harness and connector wires, or improved contacts at the TPS or IAC on the throttle body when they changed the gasket. It may have needed replacement but it would be no different than a disconnected vacuum hose to the intake which I have had many times and those just caused a high idle and sucking sound-noise.

Just sitting here thinking I came of with a potential theory for how a bad gasket could cause these problems, could a leak directly under the MAP sensor cause the sensor to not work properly by disturbing the airflow over it? Will a jeep start or run with a bad or malfunctioning MAP sensor?

 

[Ecomike]

Just sitting here thinking I came of with a potential theory for how a bad gasket could cause these problems, could a leak directly under the MAP sensor cause the sensor to not work properly by disturbing the airflow over it? Will a jeep start or run with a bad or malfunctioning MAP sensor?

Yes, but only if the map sensor vacuum source is close enough to the leak location and if the leak is large enough, in theory. I would have to grab a 96 throttle body and maybe dissect it too see if it is close enough to the gasket area, but only a defective staged gasket test would confirm it.

I have never heard of a no start/dying issue from that gasket. But if the MAP sensor vacuum line cracks or comes loose from the throttle body to leak enough then yes, it will cause it die when you hit the throttle, but not at idle. Not sure the Map sensor vacuum is even critical for starting the engine, in fact I think it is not critical at all for starting, IIRC. Maybe some one else can confirm that.

 

[rwat96]

Hmm, well when it did run it would die when I hit the throttle, but that went away when I put a defective autozone TPS in it which laybe changed something enough for it to run thsat day? but then the next morning it wouldn't start at all for whatever reason, maybe the gasket got worse? So maybe it was a combination of the two? It would start after sitting but when warm it would get worse until giving it a little throttle would kill it, so maybe temperature variation changed the size of the leak?

 

[rwat96]

Yes, but only if the map sensor vacuum source is close enough to the leak location and if the leak is large enough, in theory. I would have to grab a 96 throttle body and maybe dissect it too see if it is close enough to the gasket area, but only a defective staged gasket test would confirm it.

I have never heard of a no start/dying issue from that gasket. But if the MAP sensor vacuum line cracks or comes loose from the throttle body to leak enough then yes, it will cause it die when you hit the throttle, but not at idle. Not sure the Map sensor vacuum is even critical for starting the engine, in fact I think it is not critical at all for starting, IIRC. Maybe some one else can confirm that.

Oops I didn't quote you there, my response is what I just posted.

 

[rwat96]

Well guess what, it looks like ecomike is right. I was driving my jeep around my neighborhood testing something else and it suddenly died on me without warning. Since I don't have the crappy autozone tps confusing the troubleshooting process anymore, here is a current update on what it is doing. So it wont start unless I floor it (something is causing it to flood on start I believe), and it takes a few seconds to start, once it does it runs very rough for a few seconds until the idle smooths out, it idles normally and coasts in gear without throttle just fine, but when I give it gas in park or in drive, it sputters pretty bad, almost like its running on a few cylinders, and when in drive when I give it gas, it usually dies. When I floor it while running in park it bogs and sputters really badly until the engine revs above 3k rpm when it clears up and runs smoothly. These are very similar to the symptoms I had before I started replacing stuff and took it to the shop, except it isn't quite as bad (maybe because I cleaned the IAC for the heck of it tonight). I would suspect the IAC but there seems to be more to this than that.

So to surmise here is what I need to know:

- What can cause a jeep to flood on start?

- Why would this issue be intermittent?
(has randomly come and gone, and gotten better/worse and somehow self healed at the repair shop until now)

- Why will it idle fine but run horribly rough below 3k rpm and above idle?

 

[rwat96]

I just tried something else to troubleshoot more, I unplugged the IAC to see what that would do and it didn't change anything at all, it it sticking or something? Because i realized that of I gave it throttle gently it wouldn't sputter and would run smooth above idle at any rpm, but if I give it throttle it too abruptly it wont until 3k. I believe it's getting too much fuel and I can certianly smell it in the exhaust. Is the IAC stuck in a position that floods the engine with too much fuel at low rpm/idle/start? Maybe the IAC is stuck/sticky and the problen has been intermittent? If you guys think the IAC is the problen I may drive down to FNJEEP and grab a Mopar IAC (not autozone lol). It's a 30 min drive, it's finals week, and I don't want to buy a part I don't need so I would like to be pretty certian before I do.

Thoughts asap would be great as I would be awesome to confirm I could fix this easily before we tow it to the shop again tomorrow to have them do it right if neccecery.

 

[old_man]

Well guess what, it looks like ecomike is right. I was driving my jeep around my neighborhood testing something else and it suddenly died on me without warning. Since I don't have the crappy autozone tps confusing the troubleshooting process anymore, here is a current update on what it is doing. So it wont start unless I floor it (something is causing it to flood on start I believe), and it takes a few seconds to start, once it does it runs very rough for a few seconds until the idle smooths out, it idles normally and coasts in gear without throttle just fine, but when I give it gas in park or in drive, it sputters pretty bad, almost like its running on a few cylinders, and when in drive when I give it gas, it usually dies. When I floor it while running in park it bogs and sputters really badly until the engine revs above 3k rpm when it clears up and runs smoothly. These are very similar to the symptoms I had before I started replacing stuff and took it to the shop, except it isn't quite as bad (maybe because I cleaned the IAC for the heck of it tonight). I would suspect the IAC but there seems to be more to this than that.

So to surmise here is what I need to know:

- What can cause a jeep to flood on start?

- Why would this issue be intermittent?
(has randomly come and gone, and gotten better/worse and somehow self healed at the repair shop until now)

- Why will it idle fine but run horribly rough below 3k rpm and above idle?

Starting with the pedal fully depressed actually turns off the injectors. So it does sound like you are flooding. I would pull the plugs and see if they are wet when this happens. If it is only one or maybe two, you may have gotten some crud in the fuel and those injectors may be stuck open. Either way, I would run a can of BG44K through it to clean out the injectors and carbon.

All of this can also be explained by a clogged CAT. Hook up a vacuum gauge and when you get it started, check the vacuum and make sure it is nice and high at an idle. If it drops a ton when you bring up the rpm's with the tranny in neutral, I say it is the CAT.

 

[rwat96]

Starting with the pedal fully depressed actually turns off the injectors. So it does sound like you are flooding. I would pull the plugs and see if they are wet when this happens. If it is only one or maybe two, you may have gotten some crud in the fuel and those injectors may be stuck open. Either way, I would run a can of BG44K through it to clean out the injectors and carbon.

All of this can also be explained by a clogged CAT. Hook up a vacuum gauge and when you get it started, check the vacuum and make sure it is nice and high at an idle. If it drops a ton when you bring up the rpm's with the tranny in neutral, I say it is the CAT.

Ya that would make sense, I will look into that, and I doubt it it's the cat, it's a month old walker stock replacement cat, but I will check that too.

 

[Ecomike]

It is definitely not the IAC.

It only controls Idle air flow rates and only affects idle speed.

It has nothing to with what happens when you press the gas.

All your signs are classic of a vacuum leak on the MAP sensor tube/hose from the throttle body to the MAP sensor, with a possible leaking injector or two causing the flooding at start up, or a bad TPS, my money is on the MAP vacuum line or vacuum line connector at the throttle body. Mine use to loose and was easy to knock off loose enough to cause your exact symptoms and still look connected.

Inspect the MAP sensor wiring and especially the vacuum line.

Do a leak down test with a gas pressure gauge to see if the fuel pressure holds after the engine is shut off, If it drops over a 30 minute period significantly it may be a leaking injector or 2.

A new Cat can go bad (burn up and beak up/melt and block the exhaust) fast if the engine is running very rich (flooding) for a long enough time. So do not right off what old_man said. You may have two problems.

 

[rwat96]

It is definitely not the IAC.

It only controls Idle air flow rates and only affects idle speed.

It has nothing to with what happens when you press the gas.

All your signs are classic of a vacuum leak on the MAP sensor tube/hose from the throttle body to the MAP sensor, with a possible leaking injector or two causing the flooding at start up, or a bad TPS, my money is on the MAP vacuum line or vacuum line connector at the throttle body. Mine use to loose and was easy to knock off loose enough to cause your exact symptoms and still look connected.

Inspect the MAP sensor wiring and especially the vacuum line.

Do a leak down test with a gas pressure gauge to see if the fuel pressure holds after the engine is shut off, If it drops over a 30 minute period significantly it may be a leaking injector or 2.

A new Cat can go bad (burn up and beak up/melt and block the exhaust) fast if the engine is running very rich (flooding) for a long enough time. So do not right off what old_man said. You may have two problems.

Hmm that's interesting, that could be the problem, but it doesn't explain the starting and flooding problem, as the problem occurs when you shutoff and start the engine right after, which would give no time for a slowly leaking injector to cause the problem. When I tested my fuel pressure a week or two ago the pressure seemed to drop very slowly, so I could have a check valve with a slow leak, or like you said the injectors could be leaking, but the leak seems way too slow to flood the engine in a few seconds. And I didn't disregard that idea about the cat, it is just that I was saying it was very unlikely it was the current problem, but yes it could certianly happen if I kept trying to drive it like it is.