Hello. I’ve had my 88 dodge B250 for a year or so. Replaced many new parts. Somewhere along the line something messed up.
Symptoms:
starts great cold. Once it warms up, if I plunge the throttle quickly it backfires(occasionally) but when I rev every time it will drop to about 4-500rpms then iac will bounce it up to 850 back down to 750. I’ve had times where it will die when surging down. Also drops down to 400 once I put in gear and goes up to 600 after.
I figure it might have to do with something electrical. I bypassed one of the wires for the coolant temp sensor(not black n blue). So when it warms up I flip a switch to turn off the coolant temp sensor. It will run beautifully, no low drops after revving, but also idles higher at about 900-1000. Feel like that makes it run slightly rich, but engine is full power.
also coolant temp is usually around the first mark after c. After a min, with engine off, key forward, it’ll show in between 1st and 2nd line. But not while running( might be separate issue)
but if I try to start after when hot WITH coolant temp, it will take a couple tries to start up. With cts OFF, starts right up at idle.

new parts: fuel pump, filter, pressure regulator, fuel temp sensor, injectors, lines. rebuilt throttle body gaskets, new coolant temp sensor, iac, map, tps, coolant temp sender, brake booster( had vacuum leak), distance sensor, 02 sensor, thermostat. Spark plugs, wires, dist. Cap and rotor. Egr, pvc valve, full exhaust
Anyway I don’t know where to start. Every time I get some time to work on it I’m stumped. Any help would be amazing
no codes other than coolant temp sensor, wondering if it could be something to do with charcoal canister or even the other evap solenoids. Thanks

 

Welcome to DF! Moving this to the Van section for ya.

 

Check and/or replace the ignition coil?

Check resistance with positive post on coil. Should read 1.34 to 1.55. Next check the resistance between the center post of the coil and either the + or - post on the coil. Should read between 8k and 12k ohms. (numbers are for 1988 b250)

If those numbers are out of range, replace. Or, just replace anyway because it's so cheap and easy

 

thanks for the reply, and already replaced that, forgot to mention. Also, i figured I’m going to replace the coolant temp sensor agin bc that is the one thing I have to bypass for it to run like a dream. When I took it out, I noticed that the threads were stripped a little bit, also the sensor threads where about at the halfway mark of how far it was in. So got new sensor, now gotta call and scrabble around to find a good tap to fix the threads. Would that cause it though???! Coolant temp sensor not all the way down in the hole? I figure coolant is definately getting to it, but maybe just the tip? Idk will replace and keep you updated. Also, will the maintenance required light go on for an 02 sensor or will that be check engine. Thanks

 

I tried new coolant sensor.. but now if my memory is working properly. I do believe I started with the thermostat, was leeking. And also pretty sure I replaced it with a thermo that was designed to open at a lower temperature range... could this be my issue?? After I replaced it, I then replaced the coolant temp sensor and temp sender bc the guage stopped working suddenly( or barely getting hot)
so could engine not reaching normal operating temperatures according to the smec,effect the coolant temp sensor and therefor the fuel air ratio??? Thanks

 

What about the engine computer, is it the original one?

 

no I don’t think so, the guy I got it from said he replaced the engine at a junkyard and went through a lot of stuff, including wires... but got wiring dialed in. Also ordered a used computer on eBay. That one made my ac on constantly but same problems. I remember it drove amazing to go get it inspected, never drove it around too much. But I’m pretty sure I swapped thermostat with I’m pretty sure was a 160degree one... right after, and that’s when I chased the other sensors. So I’m going to get a new thermostat that’s 195 like it’s supposed to be and keep y’all updated. Thanks