'91 4.9l electrical, IAC, computer?
09-24-2015, 07:40 PM
#11
For what it's worth for you to know, your system is called speed density because it measures engine speed and then takes a reading from the act because air temperature will tell it the density of the air (air will be thicker, or more dense at lower temperatures); the computer then calculates the total volume of air and decides how much fuel to add via the injectors to get the correct air/fuel mixture.
If that makes any sense. But you can see how that little tiny sensor could throw everything out of whack if it malfunctions.
If that makes any sense. But you can see how that little tiny sensor could throw everything out of whack if it malfunctions.
09-26-2015, 12:52 AM
#12
Member
Thread Starter
Thanks, Chris. That makes some sense. I can see how density and temp could be analogous with each other, even if I can't picture how these eec things really work!
You made me think of a question though. I lied that *all* of my codes are gone. I always have a code (can't remember if it's KOEO, KOER or stored) 452 "insufficient input from vehicle speed sensor." When I got this truck I put a rebuilt tranny in it and it was the wrong year for the speedometer to hook up. I've never had a speedo/odo and have always figured that code is because I don't have that hooked up. Next time I have to or have the time/money to I'll put the right tranny in so that I can hook up the speedo. Does that being unplugged affect the computer at all?
You made me think of a question though. I lied that *all* of my codes are gone. I always have a code (can't remember if it's KOEO, KOER or stored) 452 "insufficient input from vehicle speed sensor." When I got this truck I put a rebuilt tranny in it and it was the wrong year for the speedometer to hook up. I've never had a speedo/odo and have always figured that code is because I don't have that hooked up. Next time I have to or have the time/money to I'll put the right tranny in so that I can hook up the speedo. Does that being unplugged affect the computer at all?
09-29-2015, 09:20 AM
#13
Member
Thread Starter
Update: Fixed!
I think the main culprit on this was a bad Fuel Pressure Regulator. I replaced it and it immediately fixed the problems with hard starting and idles better (slower) too. After I replaced the FPR I still had some problems with missing, so I pulled all my sparkplugs to check for fouling, etc. and when I put them all back it ran perfect. Maybe I had a wire loose. Runs great now. No missing under load -- I can't get it to miss now on hills, pulling a trailer, etc.
I was planning on making a restrictor plate for the EGR valve after I got things fixed because it has always had a problem with sputtering when you let your foot off the gas and at low RPMs. After the repairs I made in the last few weeks, it doesn't even do that anymore.
Thanks for all the help.
I was planning on making a restrictor plate for the EGR valve after I got things fixed because it has always had a problem with sputtering when you let your foot off the gas and at low RPMs. After the repairs I made in the last few weeks, it doesn't even do that anymore.
Thanks for all the help.
