95 4.0 OHV intermittenly running like absolute garbage at slow speeds idle, running fine the other 70 percent of the time.


New member
Mar 13, 2019
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Southern IL, USA
Vehicle Year
Make / Model
Ranger XLT 4.0
* Truck Details: 1995 Extended Cab 2WD 4.0 OHV (Engine swapped before I bought it, Explorer sourced based on the air filter type). Running 10-W40 oil for the last 6 months, runs poorly and loses power with lighter weights.

So this all started about 2 weeks ago after I noticed my coolant reservoir was low (I have a slow leak near the top of my radiator) and it being so close to winter I decided to switch from my summer/spring/fall solution of straight tap water to my normal 50/50 concentrate/water antifreeze mixture. I have no reason to believe I was ever overheating badly (though the engine has always steamed alot, and burned a little oil) but my temperature gauge has never been observed to actually move at all so take that with a grain of salt. Anyways a few days after that my truck started running crazy rough at idle and slow speeds, pretty low on power too. It also hesitated bad before revving up. No engine light or codes. I pulled the hood and the engine was visibly shaking pretty bad. It was making all the sheet metal on the truck rattle. Sometimes it will do this for about 5 minutes after I start it (even if the engine was already hot), sometimes I can drive 20+ miles with no problems at all, sometimes I get home and I'm idling in my drive way and it will drop back down into that rough idle. It clears up at about 30MPH regardless. I've never seen an issue intermittent like this. I figure it has to either correspond to an electrical circuit opening, or a mechanical valve opening. I can literally be sitting there and it will go back and forth from idling/running fine, to badly, to fine, to badly. I'm also hearing some knocking up front at low speeds that sounds like solid metal hitting sheet metal (its irregular, and seems to happen more on rougher roads) but I can't tell if it's coming from the engine or the suspension. It appears to have no bearing on how the engine runs. I'm just mentioning it because it did start at the same time.

I'm kind of tight on money right now so I don't want to start buying parts and stuff until I've gotten some advice, I did some googling and didn't find anything specificly similar to this. My current thought's are:

* Computer? I'm an I.T. professional and this is exactly the type of one off screwball behavior I would expecting from old, failing electronics. This is an expensive fix though so I don't want to replace it until I've ruled everything else out.
* Spark plugs/wires/coils? This could also cause it theoritically, though its unusual for it to be this type of on/again off again behavior.
* Sensor/Valves/Thermostat? I figure maybe the fuel flow sensor, pump, MAF, or thermostat? I'm not knowledgeable enough to speculate much beyond that.

Have any of you ever had something like this happen before? I've dealt with engines that run badly constantly before, but never one that can make up its mind.