Re: 1990 4.0 4wd starting
Hey there! My truck is 4 years newer so I am not familiar with your motor necessarily. Mine is also a OBD1. When I had problems with my motor running very poorly and cutting off and then back in again the motor threw a CEL. So I searched Youtube, specifically, "how to read obd1 codes for your year Ranger" and watched the videos; it is not to difficult because I was able to do it! You will just need to find your OBD1 port. I also found a website that helped me to make sure my major sensors worked (MAF, TPS, etc.) The website is called "www.easyautodiagnostics.com". Look under the Ford 4.0 section. Now I admit that I did not see anything for a 1990 but it might be a good place to see if you can use any of that information in your context. I checked my sensors and they were all good but my motor still would cut off and then back on. I found this other Youtube video, "Ford OBD-1 ECM Repair" (just Google it). This showed me how to repair my PCM. I pulled my PCM because I had nothing better to do and besides since the truck was running rough I had nothing to lose. Upon inspection one of the capacitors was shot so I did the repair and it worked!!. My truck is back in top notch health now and runs very well. Again, i know yours is a 1990 but maybe some of these suggestions might help you.
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1994 Ford Ranger XLT Extended Cab
2WD Automatic
4.0 V6 OHV
MODS: LED Dashlights, Wired for OHC (don't have the guts to cut the headliner), Lighted Visors, Auto-Dim/Mirror, Auto Headlights, other than that it's pretty much stock
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