1999 Jeep wrangler 2.5l

348tripower · March 14, 2014, 11:24:58 AM

I been trying to sort this one out. Idles perfectly. All new ignition parts including the coil.
This thing looses power from time to time. Seems to be worse when it is warmed up. If I lay onto it full throttle it misses and bucks. I can let off the throttle and it will pickup rpm and speed and run right along. Map seems to be functioning properly, new TPS . Testes show the ignition advancing. Running along at 50 mph I can't get anymore speed out of it. Cat plugging up? Fuel pump failing? Suggestions?

enjenjo · March 14, 2014, 12:42:37 PM

Check the wires to the VSS.I have had several that had frayed or corroded wires at the sensor that would cause an intermittent loss of power and engine miss.

348tripower · March 14, 2014, 04:29:10 PM

Quote from: "enjenjo"Check the wires to the VSS.I have had several that had frayed or corroded wires at the sensor that would cause an intermittent loss of power and engine miss.

Will do. Had the trans out about 3 weeks ago to put a new clutch in. Didn't see any thing and we had the problem before the repair.

zzebby · March 14, 2014, 06:20:33 PM

Plugged muffler with mice nests? Frank knows about that.

kb426 · March 14, 2014, 06:23:17 PM

I hadn't heard of a vss problem. I'll try to put that in my memory bank. My vote is for a restriction in exhaust, fuel delivery or air intake. The last thing on my list is weak ignition for whatever reason.

UGLY OLDS · March 14, 2014, 08:01:42 PM

Try hooking up a vacuum gauge to the engine ...Tape it to the windshield & go for a spin ... Carburetor / fuel injection / dribble system .....
The magic gauge never lies .....

Bob.......

enjenjo · March 14, 2014, 09:16:52 PM

Quote from: "kb426"I hadn't heard of a vss problem. I'll try to put that in my memory bank. My vote is for a restriction in exhaust, fuel delivery or air intake. The last thing on my list is weak ignition for whatever reason.

This is linked to the anti lock brakes, and traction control. It compares wheel speed, VSS speed, and throttle position, If the wheel speed, and VSS don't match, it limits power levels.

rooster · March 15, 2014, 08:09:11 PM

If you have a scan toll , see if its running in closed and open loop during the good and bad times!

Maybe it will set a code, to narrow things down.

papastoyss · March 16, 2014, 12:38:55 PM

Not familiar w/ jeeps at all but have seen crud build-up on crank angle & cam position sensors on other vehicles (imports) cause weird problems.

grazza · March 17, 2014, 07:51:18 AM

You know guys, I just read all this and realised I have a problem.

I have not one idea about what ever it is you're talking about. I would have been looking for a bit of dirt in one of the carby jets. I have to go get some lessons on this new junk I think. :?

Being the other side of 60 sux sometimes.

wayne petty · March 17, 2014, 10:53:53 AM

first step is a voltage drop test..

i would also run a test from the alternator output terminal to the battery positive post.. 0.07 volts is kinda expected.. but because there is significant current flowing thru that circuit you may get up to 0.7 volts.. thats 7/10ths of a volt on some cars with LONG LONG wiring between the alternator and the battery positive..

post the results..

this is not quite right..

you should also find the location of where the computer is grounded at..

check or take that apart and clean it. i can look that up that location.. if you cannot spot it..

the voltage drop test will prove that the electrical connectors are mostly properly grounded.. since electrons flow from negative to positive.. its important..

spend the 5 or 7 minutes and PROVE it.. with this test..

UGLY OLDS · March 17, 2014, 05:00:31 PM

Quote from: "grazza"You know guys, I just read all this and realised I have a problem.
I have not one idea about what ever it is you're talking about. I would have been looking for a bit of dirt in one of the carby jets. I have to go get some lessons on this new junk I think. :?
QuoteBeing the other side of 60 sux sometimes.

We're on the "other side of 60"

When did that happen

? :? :oops:

Bob.....

348tripower · March 20, 2014, 01:58:52 PM

Soooooooooo,
I finally got away from the customer cars and fixing the brakes on my Silverado and checked fuel pressure on this. Book says 45 to 54lbs at idle.
25lbs

I'll put a pump in it.

wayne petty · March 20, 2014, 07:51:18 PM

please find some strong magnets and drop them into the fuel tank away from where the sending unit lever lands..

so it will pull all the ferris material to them..

just leave them there..

you also might want to verify the voltages to the fuel pump and the ground side of the circuit..

make sure there is no voltage drop happening also.