Vikesfan1974

Got a question that hopefully someone out there can answer…

My 1997 Jeep Cherokee has a problem when it starts out cold. It feels like it wants to kill when it's running down to road. It makes some popping noises and feels like its losing power. After a couple of minutes, when it's warm, it runs fine. If I let it warm up for five minutes before taking off, no issues. I have replaced the MAP sensor and cleaned the IAC Motor. Any other things that could cause this?

RTorrez1

When was the last time you gave it a complete tune up?

Vikesfan1974

Changed out plugs last summer. Other than the MAP and IAC Motor, nothing else done to the engine. This rough running issue started before the plugs were changed out.

RTorrez1

There is a lot more to a tune up then just plugs.

Vikesfan1974

Yes…of course…but more to the point of the post... I'm looking to see if anyone has had similar circumstances, and if so, what did they do to remedy the situation.

Turbo X_J

What's the fuel pressure in psi? Ever perform a compression test? How many miles and whats the general condition of this trusty steed?

tjwalker

Ever seen a check engine light? If so, you must pull codes for clues.

One engine management sensor that comes to mind is the "coolant temperature sensor". Located on the thermostat housing on your 97. If it is sending erroneous data to the computer, the computer may think that the engine is warm (or vice versa) and then your fuel/air ratio is adjusted incorrectly. So you might be getting a "lean" mixture at cold.

Not saying that is your problem but it is one thing to check out. I'd test it. They recommend you remove the sensor, place it in a beaker of hot water with a calibrated thermometer, etc. but that is a PITA so what I do is test it when it is installed. Test it cold, then test it with a hot engine. Compare your resistance readings to the chart that you'll find in any service manual.

And I agree with the other advice here. I'd recommend that you finish your tuneup by installing fresh plug wires, distributor cap and rotor. Don't want to be chasing your tail for $40 worth of parts. And putting a fuel pressure gauge on your engine when it is stone cold is also a good idea. Fuel pumps can be "marginal" and can struggle a bit when they are first called into duty, but the pump can become more efficient as they run a bit. Backfiring is often caused by a fuel/air imbalance. The fuel pressure spec for your 97 is 49 psi at idle, plus or minus 5 psi.

So I'd complete tuneup and then do some testing on fuel pump and CTS.

Good luck and keep us updated.

Vikesfan1974

Replaced CTS…all is well. XJ is running good now.

MtnHermit

Glad it runs well. Just what is a "CTS"?

Jeepin'Hubb's

Coolant Temperature Sensor

BlueRidgeMark

His answer WAS to the point of the post. Your method (ask about similar symptoms, apply whatever fixes worked for other people) is what most people come to forums like this to do.

It's not the right way to troubleshoot.

The RIGHT way is to understand how the systems work (and how they work together), and to systematically test your way to an answer. This is the long way around, but it's the right way, and, almost always, the cheapest way. It's usually the fastest way, too.

One shortcut to that which does make sense is to do basic maintenance before starting to buy parts to swap in because Joe on the forum had a similar sounding problem and a 98 dollar Wizbang fixed it for him.

So, back to the point of your post: If you don't know when the rotor, cap, & wires were last changed, it's time. And plugs a year ago? How many miles, and what kind of plugs?

Also, clean your TB and IAC. This is basic maintenance which should be done, is inexpensive, and cures a lot of problems.