I have a 97 Dodge van with an odd problem. Once it is driven for several miles, it will only run at idle and wide open. In between these 2 throttle positions it hesitates, backfires thru intake and exhaust. It has had 2 fuelpump/filters,distributor,throttle postion sensor,distributor cap and rotor button,computor changed by 2 different mechanics. Does anyone have any suggestions. THANKS
Check timing and do a compression check. Did the mechanics have any suggestions besides playing darts with replacement parts?
I am guessing that it starts running like crap after reaching a certain engine temperature? If so sounds like it all goes to heck when the computer goes closed loop, look at sensors that provide feedback to the computer for closed loop operation, how many miles on it and has the O2 sensor ever been replaced?
All this is assuming of course that it runs well when cold as you imply.
good luck
nate
also what codes is it showing?
nate
It could be the oxygen sensor. Wide-open-throttle and during warm-up are two of the conditions in which the engine runs "open loop", that is it ignores the O2 sensor, and thus would work right, in spite of bad sensor data. I am not sure about warmed-up idle; it seems like that would be a closed loop mode, but maybe the the O2 sensor is sending a value that makes sense for idle.
Idiot.
Yes, here's a suggestion: Stop going to self-proclaimed "mechanics" who are nothing but parts changers. What is needed here is not more randomly-specified parts that do nothing to solve the problem but cost you plenty of money. What is needed is systematic, proper diagnosis. It's clear from your description that once the van's engine reaches operating temperature and the SBEC (computer) goes into closed-loop mode, it is getting wildly incorrect or nonexistent information from one or more sensors. Top suspect is the O2 sensor, closely followed by the MAP sensor, but this isn't diagnosis, just a guess. Your van is equipped with sophisticated onboard diagnostics which, when accessed via a "scan tool" used knowledgeably and correctly, can tell a competent and smart mechanic where the trouble(s) are coming from.
Fuel pumps? TPS? Computer? None of those were likely faulty, given your symptoms.
As others have suggested, you need a competent diagnosis, not continued parts changes.
I went through my manual and besides sensors, it recommends you look for vacuum leaks and EGR system problems, but there are lots of other contributing possibilities.
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