2000 caravan, sluggish acceleration

[wvcab]

2000 dodge 3.0, idles  good, slowly accelerate, it will hit the rev limiter, but if you punch it, it backfires.  driving, it sounds runs good in gear, accelerate slowly runs good till about 30 mph, then stumbles. put your foot into it, and it stumbles and back fires.

has a new timing belt, and it is dead on the marks on the lower pulley and the cam pulleys.

[Crosley.In.AZ]

fuel problem...  fuel pressure check?

fuel pump bad , weak...  

fuel filter clogged?

check engine lite on?

[wvcab]

no engine codes, or lights.

i drove it all day friday no problems, night driver drove it 70 miles, said it was running good, he went around a corner and accelerated ( punched it) and it started backfiring, and stumbling.

i found the rear cam was 1 tooth off, replaced the timing belt, set it dead on the marks, and it fired right up, but still has the stumbling back firing.

no i have not checked the fuel pressure, yet.

[wayne petty]

does your scan tool display live data stream.?? so you can see what the sensors are doing??

can you see if the sensors are putting out the right signals..

i have a gm chart that will help...

if your scan tool will display live data.. look at the map sensor voltage with the key on.. engine off...     it should be at one end of the range.. when you start it.. it will drop to about half......     then in park.. slowly bring the engine rpms up...  the vacuum should increase.. or stay stable..  NOT decrease toward where the reading was with the engine off..

the chrysler OBD2 sensors will display very close to this ...  look at one line at a time... compare it.. looking at the whole chart is TOO MUCH info at one time...



that would indicate a blocked exhaust system...

are all the spark plug wires pushed in...

do you have the 8 buck coil output tester... i have had those coils fail to put out enough spark that it will barely run...  you might inspect the coil for burn marks also..



the lamp type coil spark testers just don't work for weak spark...

how about the cap and rotor..  those caps usually have a lot of cross bars molded inside the cap... and they can leak high voltage to each other...

[enjenjo]

I had a Caravan that had an intermittent problem like this. It was the wiring to the VSS. It could not reconcile the TPS and VSS signals.

[wvcab]

the follow up, sensors looked good, no codes.

the motor in this sob, is the dirtiest, oiliest mess you would ever want to see,  it had some seals that were leaking, which i changed while doing the timing belt, I pulled the wires, and plugs today, the wires on the radiator side were dripping with oil, the drivers evidently don't use a funnel when adding oil, and must only get a half a quart in when they add a quart

and the plugs on the 2 and 4 cyl showed arcing along the base of the plug, the boots on those plugs felt soft, and looked larger than other wires(swelled due to the oil?).

change out all the plus and wires runs like a new van, ... ok it runs good for a van having 272k on it.

thank you for the ideas.