Urgent Help Needed for a "Mystery Miss" on a 1990 Caravan 3.3

[138jbeck]

Hi all! I'm a newbie on this forum but am in need of some help with a buddies Dodge Caravan and am hoping that someone out there can help us figure this problem out.

My friend recently purchased a 1990 Dodge Caravan with a 3.3 L engine and a 4 speed automatic transmission from craigslist. He almost immediately began to have problems. He told me the engine was missing, lugging and was stuck in second gear. After a quick internet search, I told him that the van seems to be in 'limp mode' for some reason. I went over to see the van myself and to take it for a quick ride. Sure enough it was in limp mode but aside from a bit of lugging, did not notice the bad hesitation and missing that he said was going on (but at this point the engine was not fully warmed up).

Our first step was to find out why it was in limp mode. We pulled the codes and got code 12 and 25. My friend had earlier already replaced the plugs and wires and after we got code 25, the idle speed control. We reset the codes but still no fix, trans still in limp mode. An internet search led us to this very forum, to a problem with a splice of red wires near the transmission control module. Sure enough, a couple inches below the plug on the wiring harness to the TCM was a set of two red wires that ran next to each other that had been stripped bare for an inch, laying side by side, inside a shrunken heat shrink tube. There was no solder or wire nut so I cleaned the bare wires and soldered them together. We took it for a test drive and it ran great! It shifted well with no missing, lugging or hesitation. We thought all was well until the engine fully warmed up. After a couple miles of driving the engine began to hesitate badly and miss under load. Looking at the tachometer as it jumps down, it's almost like something is just killing the ignition on acceleration under load. After the engine fully cools down, everything is great. I know the splice repair fixed the transmission limp mode problem but I think the bad miss under load, when warm is a separate issue.

What he did so far was to change the plugs, wires, coil pack, crank and cam position sensors. I tested the MAP sensor and it seems ok, I tested fuel pressure (about 45 psi), I even disconnected the catalytic converter to see if it was plugged up, all with no change. Could it be an engine computer issue?

My buddy is badly in need of this van. If anyone has any ideas as to what could be going on we would love to hear it. Thank you all in advance!

[MikeCStig]

I would start with a thorough check of all the wiring. There could be more issues similar to the one that was causing the transmission issue. Stripped wires, bad grounds, loose connections and things like that can cause a lot of problems. Check all of the fuses too. If there's one particular fuse that burns out repeatedly, that might give you a clue as to where you should look for bad wiring.

[138jbeck]

Originally Posted by MikeCStig

I would start with a thorough check of all the wiring. There could be more issues similar to the one that was causing the transmission issue. Stripped wires, bad grounds, loose connections and things like that can cause a lot of problems. Check all of the fuses too. If there's one particular fuse that burns out repeatedly, that might give you a clue as to where you should look for bad wiring.

Thanks for the tip, will go over the wiring and check the fuses. I did check the injector wiring harness as it is routed over the exhaust crossover pipe and evidently has caused burned and shorted wires in other 3.3 Caravans. What I still can't wrap my head around is the fact it seems like it only starts cutting out when the engine has completely warmed up, after a few miles of driving. I know that when cold the engine is in an open loop mode, so maybe the O2 sensor is causing the bad miss.