1998 Jeep cher classic 4x4

DesertSkyeNovember 18, 2005

Car has been in shop all day due to losing power

My reg mechanic did not have the means to run a diagnostic

Happens full tank or not

Usually on turns but sometimes on straight stretch

My Mech testd the fuel pump said its pumping fine but maybe going out

Suggested sending to a repair shop specializes in jeeps

They couldn't all day find anything when running tests and diff diagnostics

Decided to take it on a longer test drive and bingo started losing power

Brought back to shop hooke dit up....did it again

said the oxygen sensors were shutting down

but need to do further testing now that they have actually had it happen there

want to keep it until monday

Any ideas on what causes this?

It happened once last week then no more so I thought nothing of it

then Wed of this week kept happening

scared me to death as it was happening right in the middle of the intersection and I have 3 kids in the car

so between the house and dropping them off at school and getting it back home happened about 12 times in 20 min

but i was always able to start it right back up

Am a single mom and I know nothing about this kind of stuff( I can change a tire change oil etc but not this!)

Thanks in advance!

no engine light coming on either

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jemdandy

If the shop reported that the oxygen sensors are shuting down, this can affect performance, but I not certain just how much. Usually, when an out-of-range reading is sensed from the oxygen sensors, the system automatically reverts to default settings which normally results in increased fuel consumption. Replacing the oxygen sensors should correct this situation (if that is all that is the matter).

How many miles do you have on your oxygen sensors? These are supposed to be changed about every 80,000 miles or so. But these can fail before this. So, for example, if you have 50,000 miles on them, they could fail.

Could you possibly be experiencing "pinging". The knock sensor, when triggered, retards the timing and that will cause momentary reduction in power. However, as soon as the ping goes away, the system will recover in a short period unless another ping is heard.

You may have a temperature related sensor failure. The cam position sensor, or crank position sensor may be failing when hot, but returns to normal upon cooling. Suspect these items if the car starts ok when cold and operates well until fully warmed or under load such as crusing at 65 mph. These parts can heat soak while waiting at a stop light, or in slow traffic.

One more unusual thing is faulty plug wires (leads). These are not metallic wires these days, but carbon like resistor materials. The plug leads should measure no more than about 3000 ohms per foot of length. (Consult your repair manual for the recommended ohmic value.) I've had these fail in this manner: Starts ok when cold. Runs ok until the engine get hot, maybe 10 miles of cruising at 50 mph over country roads with stops every 2 miles or so. Then, suddently, on an uphill or when pulling away from a stop, the engine misfires and stumbles and does not run well until the load is reduced (back the foot off the gas pedal). The diagnostic for this condition is that the plug leads will measure too high in resistance particularily when these are hot. This item may not show a trouble diagnostic code.

One more item that can cause the problem you descibed is the throttle position sensor. This is a key item for setting the fuel mixture and spark timing.

    Bookmark   November 19, 2005 at 4:55AM
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