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okay where to begin…my 98 durango 5.2l v8 slt is having some issues. when i drive above 40mph to about 70mph my truck jerks and surges as if someone is moving the gear to neutral and back into gear over and over. it only dose this when i have the gas peddle down just enough to keep my current speed, if i let off or push in the gas to were it shifts down it stops. and during the surging the rps seem to just kinda stick the same, i have already had it in the shop for this issue, they have tried a full tune up (plugs, wires, roter and cap) also changed my transmission fluid, tps and idle air control valve with no difference at first i was thinking it must be my overdrive gear so i tried switching off o/d and it made no difference, i have also counted the gears and it seems to happen in late 3rd gear right on into 4th, oh and when it happens most of the time the check engine light will not come on, but if it dose its when it jerks pretty hard, and every time its 4 or 5 misfire codes for all different cylinders and it changes eatch time which ones are, there has also been a few times where the car just feels like a complete loss of power until i floor the car, once i do this it sometimes makes a pop sound the comes right back.
any help would be appreciated, thanks!
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you mention holding the pedal down just enough to maintain speed. how is it at idle? either way, probly best to check fuel pressure, make sure all cylinders are getting good spark. others will probly add to this. its past my bedtime. lol
at idle the rpms move quite a but if im just sitting there in drive, like 200 rpm movement or so, in park it idles perfectly, and the fuel pressure is fine as well we checked it about a month ago when this started it holds at 52 psi even left it sitting for 20 minutes no leakage at all, haven’t tested the spark though, ive just always assumed it was fine since we replaced all the plugs wires rotor and cap and coil
Given that the engine seems to run fine any other time I’d be looking to the transmission for the problem. To me it sounds like you might have a problem with 4th gear or the torque converter not locking up properly. If either one of those is happening it can cause the symptom you describe. The way to verify this is to check the pressures within the transmission to see if there is a pressure loss causing the problem. A transmission shop would be best equipped to handle this kind of work. You might consider finding a transmission shop that can do a diagnostic for you. Here’s some articles that also might help.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
http://www.ericthecarguy.com/faq/solving-transmission-problems
You really need to connect a scan tool that reads data so you can analyse all sensors and fuel trims. Like Eric mentioned it could be a transmission problem but without being able to read engine and transmission data everything is just a guess.
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