I did a search and it seems like some people are having a similar problem, but not exactly...
1997 se wrangler...103xxx miles, basically stock, runs like a peach most of the time, except...
95% of the time when I start it, starts up fine then within 30 seconds or so it will start to lope real bad and the idle will drop to about 500. If I try to drive it during this time it will backfire, sputter and actually lose power the more throttle I give it. It almost feels like a cylinder is missing. So I sit there, wherever I am, blipping the throttle and wait about 30 more seconds and it smooths out and runs great.
This only happens upon startup, has never presented itself any other time.
Everyone elses problems seem to be more random and can occur at anytime...
It also sometimes feels more powerful (relatively speaking) than other times, like the parking brake is partially engaged, or fuel is lacking, but its still smooth. Don't know if thats related?
Does this sound like a sensor problem? As far as know, none have been replaced. Id like to get some insight before I start throwing money at it.
And I dont need the advice "your lack of power stems from your lack of two cylinders", as it seems like someone is always ready to throw that one out there. When its happy, I'm more than satisfied with the power.
That was me, man, the original poster. Just wasnt sure if you were being sarcastic or not. If you weren't, then I apoligize for the kinda sarcastic response-seriously. No offense on this end. I'm not trying to start some bickering match, just looking for suggestions. I'm married, I get all the bickering I can handle at home. Anyone else have this problem, though?
This may be a longshot, but you may need to replace your coolant temperature sensor. In the Saturn S-series cars, they were resin-tipped and prone to cracking, causing the coolant to mess to enter the sensor itself and send a bad signal to the ECU. The coolant temperature of the engine tells the ECU what operating temperature the engine is at, and it adjusts fuel trim for that specific temperature. I don't know how many sensors the Jeeps have, but your gauge may or may not be fritzy during this time. Might be something to look into.
You may also need to clean out your idle control solenoid too. It wouldn't hurt to remove it and check it out though.
2015 JKU Rubicon Hard Rock on order...
try priming the fuel pump a few times before you start it. turn the key to on and wait till you dont hear the fuel pump any more, about 5 sec, then off then on again for 5 sec then start. wranglers have a check valve in the fuel system thats known to fail and let the fuel drain out of the lines back into the tank. if you prime it and it never does it again then its the valve, some people just live with it some fix it, the vavle is in the tank.
You said you "checked the plugs and wires etc.." How, visually?
It sounds like an ignition problem, like the high tension is getting to ground. Not a direct short, but it's jumping somewhere.
You cannot tell if an ignition wire is broken inside by looking, it may look good but be bad.
Try replacing the coil wire - cheap easy - just that one, not all of them.
Look close at all the wires - if you see any small places that look grey or discolored, it may have been shorting to ground. Same with the coil - look real close.
If everything looks OK, try spraying a liquid - water - window cleaner - 409 etc -- NOT FLAMMABLE - on the distributor and the plug wires. Position the wires away from vacuum lines - the black coloring in them is carbon - conductive.
Let us know.
If that doesn't help, tell us:
Does it always do it or just when it's a cold start?
It's no wonder the country is falling apart - stupidity abounds!
Thanks for the suggestions guys. Rrich, it does it hot or cold, and not everytime, but when it does, its exactly the same time after startup, and lasts the same amount of time. Its the opposite of random. Thats what got me thinking its a sensor and the ecu after startup is getting a bad signal. It def. wouldnt hurt to check wiring again though, a little closer. Flashing the ecu probably couldnt hurt either, doesnt that just bring everything back to factory settings?
Thanks for all the responses, it could be a lot of things, I guess.
Damn fuel injected vehicles. This is why I prefer vehicles made before 1970.
No carburated jeep is gonna get 20 mpg though either, so I guess it's a trade off.
I'll post up when I fix this...
The "flashing the ECU" described here would only clear codes, it's not long enough to return everything to default. Disconnected overnight does.
--- Cold or hot, sometimes, acts the same each time it does it. ---
Still sounds like ignition problem to me.
Since it happens almost immediately after start-up - before the computer really comes on line, it could be a vacuum leak. When the computer comes on line it compensates for it. But - it's seldom a vacuum leak is intermittant, it's usually always there (broken hose, gasket etc.)
If it was a sensor it wouldn't be just for those first few moments, a bad sensor stays bad. During those first few moments most of the sensors aren't doing much anyway.
But - a defective coil wire, or coil can certainly do it. They are often intermittant. Your comment about sometimes lacks power supports that too.
Try 2 things - set it up for the test - unplug a plug wire, start it, hold the plug wire near ground so the spark jumps to ground. Observe the COLOR of the spark. Do it when it's acting up. (Good way to hold the disconnected plug wire - slip the end on a Phillips head screwdriver, you hold the insulated handle and hold the shank near ground.)
The spark should be a thin crisp BLUE spark.
If it's orange or any color other than BLUE - replace the coil wire and coil.
If you can't get it to "do it's thing" when you want, start it, then try dousing the coil and coil wire with a spray bottle of water, window cleaner, 409 etc. If the engine falters, it's an insulation problem - usually requiring replacement. Very common with that mileage Jeeps. I may be wrong, but it seems like Jeep coils are only good for 100k miles or so. They aren't expensive.
Let us know.
It's no wonder the country is falling apart - stupidity abounds!
Just went threw a similar issue with my 2000 toyota tundra. I had a clogged fuel filter. I replaced the fuel filter and would still have it studder and I would see a drop in rpms. It seemed random and I was getting ready to replace the $250 pump but read my book first. The first thing toyota wanted was to clean the butterfly valve for the air intake. It's the flapper where the intake meets the engine. I also cleaned the vent tubing from the crank case to the top of the intake. I think its called the AIC cant remember. Next would be to clean and check the psi"s of the fuel lines including the vent return to the fuel tank. The butterfly valve was the second and final issue to the filter. After cleaning it restored my cold idle to about 1200-1300 rpm and would rest warm at 500 rpm. 3 weeks later and running smooth. Did not have to spend the $250 on a new fuel pump.
I hope this helps. She was thirsty and choking but happy and strong now.
Check one other thing. If your heater blower is going to defrost, no matter whether you have it on floor, dash or defrost, start looking for a vacuum leak. Good chance it might be around the intake manifold. I ran into much of the same symptoms you have and it was vacuum.
FYI the vacuum lines are the very thin black lines, about 1/8 inch think, though the connectors are obviously larger.
As for the battery question earlier, YES, an old battery that is not providing expected amps will cause the ECU to lose its little brain and get stupid.