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Rpm drop at higher speeds

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Rpm drop at higher speeds

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Old 12-05-2018, 08:49 AM
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Default Rpm drop at higher speeds

So I just bought my XJ about a month ago. Itís a inline 6, 4.0. Had some minor problems. Cylinder 4/5 misfire which I found it to be the injectors. So I just replaced all of them. But what I have been noticing which is most concerning to me. Which Iím not sure is a normal issue. That when I get to about 60-70mph, first it is kind of wobbly. Which might just be a alignment issue or an arm issue. Which I plan to check both. But when I am at those speeds Iím at about 2300-2500 rpm. Which I have never owned a automatic whith 5 gears. So Iím sure that is probably normal. But when I let go of the accelerator it drops to about 1400-1500rpm. Now I have worked on my fair share of transmissions on my old dodge truck. I know that itís not slipping or dropping gears when I let off the gas. But it will go right back up to its 2300-2500 rpms when I get back on it. Any ideas on what it could be or if it is even an issue.

on another topic, when I get on the gas hard the check engine light will flash. But never stays on. It only does this when I really rev it up to get up to speed. When I do it gradually there is no issue.
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Old 12-05-2018, 12:13 PM
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Originally Posted by Dylan King View Post
So I just bought my XJ about a month ago. Itís a inline 6, 4.0. Had some minor problems. Cylinder 4/5 misfire which I found it to be the injectors. So I just replaced all of them. But what I have been noticing which is most concerning to me. Which Iím not sure is a normal issue. That when I get to about 60-70mph, first it is kind of wobbly. Which might just be a alignment issue or an arm issue. Which I plan to check both. But when I am at those speeds Iím at about 2300-2500 rpm. Which I have never owned a automatic whith 5 gears. So Iím sure that is probably normal. But when I let go of the accelerator it drops to about 1400-1500rpm. Now I have worked on my fair share of transmissions on my old dodge truck. I know that itís not slipping or dropping gears when I let off the gas. But it will go right back up to its 2300-2500 rpms when I get back on it. Any ideas on what it could be or if it is even an issue.

on another topic, when I get on the gas hard the check engine light will flash. But never stays on. It only does this when I really rev it up to get up to speed. When I do it gradually there is no issue.
What year is it?

Aw4 trans is an automatic, it's a 4spd. You may think it's 5, because the torque converter locks up in od (this is normal) and the rpms drop, just like when it shifts. The rpm drop when you let off the gas sounds normal to me too. Flashing check engine light means misfires are happening.
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Old 12-05-2018, 12:27 PM
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The torque converter will normally lock in 3rd gear then it shifts to 4th with the converter locked.
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Old 12-05-2018, 05:53 PM
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Originally Posted by foxmxrcer View Post
What year is it?

Aw4 trans is an automatic, it's a 4spd. You may think it's 5, because the torque converter locks up in od (this is normal) and the rpms drop, just like when it shifts. The rpm drop when you let off the gas sounds normal to me too. Flashing check engine light means misfires are happening.

its a 1998. So your your saying that the rpm drop is fine. And I just had the check engine light come on on the way home but nothing is popping up when I scan it. But my scanner is junk. So Iíll be getting a new one tomorrow.
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Old 12-05-2018, 05:57 PM
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Originally Posted by Dylan King View Post
its a 1998. So your your saying that the rpm drop is fine. And I just had the check engine light come on on the way home but nothing is popping up when I scan it. But my scanner is junk. So Iíll be getting a new one tomorrow.
From what you explained, yes, sounds normal. Not sure what size tire you're on, but the rpm's at cruising speed sound right too. Post up the fault coffee when you scan it if you're not sure where to go with it.

What part of pa are you from anyways? We've got a bunch all over that may be willing to give a hand if you ever need it. Check into the pa Cherokee club thread up in the stickies section if you want to too.
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Old 12-08-2018, 08:41 AM
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Originally Posted by foxmxrcer View Post
From what you explained, yes, sounds normal. Not sure what size tire you're on, but the rpm's at cruising speed sound right too. Post up the fault coffee when you scan it if you're not sure where to go with it.

What part of pa are you from anyways? We've got a bunch all over that may be willing to give a hand if you ever need it. Check into the pa Cherokee club thread up in the stickies section if you want to too.

Iím right above Harrisburg Pa, and as for the tires they are not any bigger then the stock size. I have alloy rims on it though. And got the new scanner and it came up with cylinder 4,5 misfire again. But Iím thinking it might be a fuel issue. Every time I put fuel cleaner fluid in it, it will take about a quarter tank for it to take. But after that the check engine light will go out. And will run great until I fill it up again and get on the gas. I got a new filter for the bottom of the pump. But if Iím wrong. I donít think the fuel lines will corrode from the inside, right? And Iíll look into that other thread, thanks for all the help guys.
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Old 12-08-2018, 04:26 PM
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If you decide the transmission shifting is not the cause, check the catalytic converter for plugged up. just a thought.
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