Having engine(?) problems whenever I drive through water, please help!
05-11-2018, 11:18 AM
#1
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Location: New Brunswick
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0l Renix
Having engine(?) problems whenever I drive through water, please help!
It’s a 98 sport edition, 6 cyl 4.0, 220000 kms. Automatic transmission. Not lifted or anything. Only purchased it last September, everything ran perfect until December, when this issue started coming up. I lived in the woods and had to use old logging roads and wheeler trails to get in and out everyday, and there are some pretty deep puddles (never above bumper-level, but usually touches the rockers panels). So I couldn’t avoid water at all.
If I drive really slow and manage to not splash anything up, it’s usually okay, but there are a couple rough spots where I just can’t avoid a bit of splash. It has never happened in the rain or anything, only in the woods through puddles, mud or slush. I will try my best to describe the symptoms:
-the engine revs on its own, and rpms fluctuate between 250 and 1000 (normal idle is 750).
-if I take my foot off the gas completely, the jeep still jerks forward with every rev, I have to keep my foot on the brake if I want to stop moving.
-when my foot is on the gas, it doesn’t matter how much I give it, it still fluctuates and the rpms still dip way down like it’s not getting any gas and almost wants to stall (hasn’t happened yet). Sometimes it will fluctuate fast enough that it’s almost like a stutter, and I can feel the gas pedal “clicking” under my foot.
-when I switch it into neutral while it’s freaking out, it will instantly go back to normal but only for a few seconds, then starts revving again. It’s usually not quite as bad as when it’s in gear though.
-I’ve lifted the hood while it’s been doing this, the whole engine moves when it revs. I’ve pulled on the cable to manually give it gas but it’s the same result, it will fluctuate between enough gas and what sounds like none at all, even though the throttle is open.
-the only thing that fixes it is waiting for it to dry out (I’m assuming), which can take anywhere from 10-25 minutes. I don’t necessarily have to shut it off, it’s usually dried out enough by the time I get out of the woods and reach the highway, but a couple weeks ago it took way longer and I had to pull over, shut it off and just wait.
That’s all I can put into words, I’m really hoping someone here might have had the same issue at some point, as it seems pretty specific! I’ve been able to ignore it for so long because there are no puddles in the winter, but now that it’s spring and I’m back on those roads I need to deal with it! I will be meeting up with my mechanic at some point, but from the descriptions alone he doesn’t have an immediate idea.
I assume it’s something electrical because I don’t know what else would be so immediately but briefly affected by water in that way!
Thanks for taking the time to read, any ideas/advice will be greatly appreciated!
If I drive really slow and manage to not splash anything up, it’s usually okay, but there are a couple rough spots where I just can’t avoid a bit of splash. It has never happened in the rain or anything, only in the woods through puddles, mud or slush. I will try my best to describe the symptoms:
-the engine revs on its own, and rpms fluctuate between 250 and 1000 (normal idle is 750).
-if I take my foot off the gas completely, the jeep still jerks forward with every rev, I have to keep my foot on the brake if I want to stop moving.
-when my foot is on the gas, it doesn’t matter how much I give it, it still fluctuates and the rpms still dip way down like it’s not getting any gas and almost wants to stall (hasn’t happened yet). Sometimes it will fluctuate fast enough that it’s almost like a stutter, and I can feel the gas pedal “clicking” under my foot.
-when I switch it into neutral while it’s freaking out, it will instantly go back to normal but only for a few seconds, then starts revving again. It’s usually not quite as bad as when it’s in gear though.
-I’ve lifted the hood while it’s been doing this, the whole engine moves when it revs. I’ve pulled on the cable to manually give it gas but it’s the same result, it will fluctuate between enough gas and what sounds like none at all, even though the throttle is open.
-the only thing that fixes it is waiting for it to dry out (I’m assuming), which can take anywhere from 10-25 minutes. I don’t necessarily have to shut it off, it’s usually dried out enough by the time I get out of the woods and reach the highway, but a couple weeks ago it took way longer and I had to pull over, shut it off and just wait.
That’s all I can put into words, I’m really hoping someone here might have had the same issue at some point, as it seems pretty specific! I’ve been able to ignore it for so long because there are no puddles in the winter, but now that it’s spring and I’m back on those roads I need to deal with it! I will be meeting up with my mechanic at some point, but from the descriptions alone he doesn’t have an immediate idea.
I assume it’s something electrical because I don’t know what else would be so immediately but briefly affected by water in that way!
Thanks for taking the time to read, any ideas/advice will be greatly appreciated!
05-11-2018, 11:40 AM
#2
CF Veteran
This could get a little complicated. So I'll start with just a couple things to do even before diagnostics.
1. Clean up all electrical connections. Particularly your ground locations. To ensure that the water isn't causing a temporary failure of components to have a good ground.
2. Inspect your wiring in general, especially anything that is low enough to see contact with that water. (Did water splash as high as the throttle body?...its important to know).
Now I'll get into some of the symptoms and components to consider.
In order to rev higher on its own, the motor must get more air. So if the revs are going up and down, then that means that the air that the motor is getting is going up and down. From the behavior you mentioned, it almost sounds like the IAC (idle air controller) is actuating and opening up additional airflow when it shouldn't. Typically it would only open up when your foot is off the pedal, and the computer is managing the idle RPM of the motor (via the IAC position). But, the TPS (Throttle position sensor) is where the computer gets its information regarding whether your foot is on the pedal or not. So there could be a TPS problem where the TPS is occasionally saying that the pedal is not being depressed and the computer will start messing with the IAC to begin managing idle because it things you are off the pedal. The IAC and TPS are on the throttle body, which is quite high up in the engine compartment. But they ultimately connect to the PCM which is a bit lower, and more up front (driver side). So perhaps the connectors on the PCM are getting wet and messing with its ability to know what is going on. Look for evidence of water getting to the PCM, then look for evidence of water getting as high as the throttle body. If you can confidently say that those are remaining dry, then wiring between the components and the PCM might be suspect. Most of the wiring for those sensors runs high in the compartment as well. So I don't see what water in the lower areas would cause a problem, unless the water is generally messing with important ground connections (like the engine block grounds down by the coil).
Btw, if you get a OBD2 scanner that can do real time data (i recommend BAFX bluetooth adapter) you can see a few data points (like throttle position, and engine rpm) it can be useful because you are seeing what the computer thinks its seeing, and this can help troubleshoot (for example, you might see the throttle position drop to 0 when you have your foot on the pedal, which would indicate a problem between the TPS and the PCM).
1. Clean up all electrical connections. Particularly your ground locations. To ensure that the water isn't causing a temporary failure of components to have a good ground.
2. Inspect your wiring in general, especially anything that is low enough to see contact with that water. (Did water splash as high as the throttle body?...its important to know).
Now I'll get into some of the symptoms and components to consider.
In order to rev higher on its own, the motor must get more air. So if the revs are going up and down, then that means that the air that the motor is getting is going up and down. From the behavior you mentioned, it almost sounds like the IAC (idle air controller) is actuating and opening up additional airflow when it shouldn't. Typically it would only open up when your foot is off the pedal, and the computer is managing the idle RPM of the motor (via the IAC position). But, the TPS (Throttle position sensor) is where the computer gets its information regarding whether your foot is on the pedal or not. So there could be a TPS problem where the TPS is occasionally saying that the pedal is not being depressed and the computer will start messing with the IAC to begin managing idle because it things you are off the pedal. The IAC and TPS are on the throttle body, which is quite high up in the engine compartment. But they ultimately connect to the PCM which is a bit lower, and more up front (driver side). So perhaps the connectors on the PCM are getting wet and messing with its ability to know what is going on. Look for evidence of water getting to the PCM, then look for evidence of water getting as high as the throttle body. If you can confidently say that those are remaining dry, then wiring between the components and the PCM might be suspect. Most of the wiring for those sensors runs high in the compartment as well. So I don't see what water in the lower areas would cause a problem, unless the water is generally messing with important ground connections (like the engine block grounds down by the coil).
Btw, if you get a OBD2 scanner that can do real time data (i recommend BAFX bluetooth adapter) you can see a few data points (like throttle position, and engine rpm) it can be useful because you are seeing what the computer thinks its seeing, and this can help troubleshoot (for example, you might see the throttle position drop to 0 when you have your foot on the pedal, which would indicate a problem between the TPS and the PCM).
05-11-2018, 07:29 PM
#3
CF Veteran
X2 there Jordan... that's what I'd check first as well. And as mentioned, wouldn't get water up to the level of the IAC or TPS without submarining the whole vehicle practically. And then you'd have worse issues like soaking the ECM.
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