Transmission not shifting, Slow takeoff, TPS?, Check Gauges Light 1999 Jeep Cherokee - JeepForum.com
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Unread 12-19-2012, 12:03 PM   #1
pdxjohn
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Transmission not shifting, Slow takeoff, TPS?, Check Gauges Light 1999 Jeep Cherokee

1999 Jeep Cherokee Sport (4L 6cyl auto)

So I'm driving to work and my gauges went crazy, my radio cut out, engine lost speed for a second, then everything came back except now it's like I no longer have a first gear and I'm getting a "check engine" warning.

I have been getting an infrequent "check gauges" warning for the past few days and just went through a bad fuel episode a few weeks ago. Ended up using quite a few bottles of injector cleaner and changed out some seriously carbonized spark plugs and that issue went away, but I suspect that the carbon and junk has built up and affected sensors and such throughout the fuel delivery chain.

Tranny has had zero issues ever and I'm hoping this is really just something simple like the TPS

Again, it seems like I have no first gear and is not up or down shifting.

Idle is a little low (about 750 to 900) for vehicle since bad gas issue.
Acceleration is really slow.
Engine does not sound like it's stressing though, just really slow out of the gate.

I have tools, but no test equipment and I'm ok with replacing a few things that are probably going to need it anyway, but I'm hoping the tranny is good. It's my only vehicle, so I can't afford down time.

My questions:

What do you think is happening?
Whatever is happening, where is it located and what's the best way to handle it?

Thanks!

John

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Unread 12-19-2012, 06:34 PM   #2
CJ7-Tim
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If the Check Engine Light (CEL) is or was on, you should download the CEL trouble codes. Write them down and look them up on the Google or post them here. Your Jeep is trying to tell you what is wrong.
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Unread 12-19-2012, 08:06 PM   #3
pdxjohn
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Thanks Tim!

I just stopped at autozone and it came back with "P0715 - Input/Turbine Shaft Speed Sensor A" - I had disconnected the battery earlier today to see if it would clear up the poor thing's confusion and now it is shifting fine again, but now the idle starts off really low to stall until it warms up a little. The CEL has gone away (for now).

I'm still pretty convinced that whatever junked up my plugs had to have affected whatever sensors are in line. I did grab a new TPS and will pull the old one to see what happens.

Is there any merit to running more cleaner through the gas to clear things up?

(and yeah, I know... I should have tried to pull the codes before resetting things, but it did make it a lot easier to drive home in heavy traffic.)

Last edited by pdxjohn; 12-19-2012 at 08:38 PM..
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Unread 12-20-2012, 12:09 AM   #4
pdxjohn
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Just another thought. A couple of folks brought up electrical gremlins, so I'm wondering if I might be experiencing ground issues that are messing with my various gauges and throwing off the sensors. I did notice a lot of new corrosion on my positive battery cable this evening.

It makes sense because of the way the gauges freaked out before this latest issue happened and how if kind of corrected when I reset by removing the battery cable.

I would appreciate any wisdom. Thanks!

Last edited by pdxjohn; 12-20-2012 at 12:55 PM..
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Unread 12-20-2012, 12:29 AM   #5
mtwask01
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It never hurts to check your grounds. There should be three main ones. One branching off of the negative battery terminal to the inner fender. The second one is on the engine block near the dipstick. And the third ground is a strap attached to the back of the cylinder head and runs to the firewall on the driver's side. It is common for these grounds to get dirt and oil on them and give poor connectivity.

I definitely think that the code that autozone pulled is playing a part in this problem. The speed sensor for whatever reason (bad ground, faulty sensor, etc.) is giving the transmission erroneous data about vehicle speed and the transmission computer making shifting decisions based on that data, thus giving you inappropriate shifting and other transmission problems. One thing you ought to do first is see if the transmission will shift okay manually. Use the "1-2" position to start out in first, then progress to the "3" position for third gear, and finally move to "D" for overdrive. You will not have second gear so let the engine get enough RPMs before moving from first to third.

Hope this helps,
Matt
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Unread 12-20-2012, 10:38 AM   #6
pdxjohn
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Thank Matt!

I will be going through the wiring this weekend. I definitely have some corrosion and it looks like I need to change out the positive lead to the battery. I scraped it off and it looks like it's corroded pretty deep in, so I assume the battery is also putting out gas pretty bad now.

As far as the shifting, yes! Before I did the reset, I was able to start in 1-2 and shift up once I got going around 30 mph, so I'm confident that the tranny is ok.

Since resetting it, the shifting issue has gone away (as well as the CEL) but it's not keeping the idle up now and I have to feather the gas to keep it running when I'm braking. I bought the TPS and will put that in
along with a battery and new positive cables + I'll be looking to replace my grounds. I'll also look into the input speed sensor issue and see if that's still coming up once I do the rest.

I'm pretty sure that there is a way to pull codes with the key in a 99. I seem to remember seeing a friend do it years ago, but can't remember the sequence. If anyone know, please fill me in!

Thanks again!

John
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Unread 12-22-2012, 08:10 AM   #7
CJ7-Tim
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Quote:
Originally Posted by pdxjohn View Post
..... driving to work and my gauges went crazy, my radio cut out, engine lost speed for a second, then everything came back

I have been getting an infrequent "check gauges" warning for the past few days ......
Quote:
Originally Posted by pdxjohn View Post
....it's not keeping the idle up now and I have to feather the gas to keep it running when I'm braking. I bought the TPS and will put that in along with a battery and new positive cables + I'll be looking to replace my grounds.
These are some of the common symptoms of low battery voltage.

Perform routine maintenance of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Copper wires should be copper color, not black or green. Do the same for the grounding wires from the starter to engine block, and from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds.

Have the battery and alternator Load Tested in a test machine. Handheld tester are often inaccurate and will pass a weak battery/alternator.
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Unread 01-14-2013, 09:28 PM   #8
pdxjohn
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So just a quick update before I go out and commence to changing my freshly blown radiator (sigh) - Thanks to Tim, Matt and everyone else. I've been
going though and cleaning apparent corrosion and wear and it seems to be running fine now. The battery is definitely on it's way out so that's on my
list.

The only remaining issue is on startup. If I don't give it a pump of gas first, it will crank and sputter, but not grab idle. This is from and engine that normally turns right over on the first try and roars to life. I suspect it's related to the battery, so once I get done playing with the radiator (and that pesky lower transmission line) I'll get a chance to test the theory.
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