Engine Cutting out under Acceleration

I did a bit of searching, but couldn't find the exact symptoms. Basically my 1994 4.0l XJ runs perfect most of the time. No rough idle, no sputtering, but occasionaly when I'm accelerating the engine darn near appears to shut off completely for one or 2 seconds and then returns to normal.

And no, it's nothing silly like hitting a rev limiter, this is just regular acceleration from a stop light, or when clmbing a long steep grade.

02 sensor. same problem i had, couldnt press the gas over about 10%. But its weird what these lil' sensors will do.

Wouldn't the O2 sensor be a bit more consistent? I can stop and go with normal or rapid accelaration, and it only happens maybe once every 10 times.

I'd say it could somehow be intermittent, although it doesnt make sense.

My jeep has made me drive home at 10% throttle, topping out at 28 mph, 3 times now.

Yet ive been driving it for 4 months...

Maybe I'm not being clear, but it cuts out only momentarily. so when it does happen it's a maximum of one second before everything returns to normal... It's almost like the computer for some reason shuts down the entire ignition system for a second.

Make sure the CPS cable isn't melted and shorting to the exhaust manifold.

old_man said:

Make sure the CPS cable isn't melted and shorting to the exhaust manifold.

Click to expand...

Agree, but it could also simply be a bad CPS.
Fuel delivery problems usually cause the engine to cough and splutter before it cuts out. If the engine cuts out suddenly without any prior spluttering, it's likely to be something electrical like the CPS.

Watch the tach when it happens. When this was happening to my old Grand, the tach would fly back to 0 and then bounce back up to the rpm level. That is assuming that it did cut back on.. sometimes it would just stall. So yes, I'd lean towards the CPS.

i had a 2500 gmc that did that too, we replaced the injectors and the O2 sensor and it ran like a champ.

check the fuel filter, fuel pump psi (should be around 38-41psi), throw some injector cleaner in there.

if you have access to a scaner, hook it up and moniter the 02 voltage. if it spikes or dips, you know that there could be a short or the o2 sensor is bad.

i would also search around the under the dash and under the hood to see if there are any shorts or bear wires there. expecially by the o2 sensor. if it has an 02 sensor in the cat check back there too.

is it throwing a code? (check engine light) if so go to a local autozone or w/e and have them scan it. if its the o2 sensor it will thow the code.

you might want to check the plugs and all that also considering it might be spark or timeing related

you also should check ALL your vacuume lines and make sure those are good, but considering you have a good idle i would rule that out.

normally when you have a cps go out the vehicle will run fine but wont start back up. (check for shorts there also)

conclusion:
with the problem that intermitent, i would lean toward a short in the electrical system or dirt particals in the fuel system.

DonkRado said:

Watch the tach when it happens. When this was happening to my old Grand, the tach would fly back to 0 and then bounce back up to the rpm level. That is assuming that it did cut back on.. sometimes it would just stall. So yes, I'd lean towards the CPS.

Click to expand...

this is exactly what happened last week (1990 w 2.5L) but after 10 miles it died.... cranked but no start... came back later... same thing... had it towed home.... dc'ed the battery, then started to unplug all the molex connectors.... cleaned them (CPS 1st.... Coil second).... reconnected the battery... cranked and it started right up....

the cps is very sensitive to poor ground and dirty connectors....

I have not taken it for a longer drive... but it has faithfully started in the driveway, i am waiting to have a spare CPS before going on the road for a test drive

Michel
90wranwran
74 wagoneer