My 89 crewcab dropped about 6 mpg over night. I just installed my rebuilt 454 and was averaging about 12mpg now I'm down to a little over 6mpg. It dumps way too much fuel at idle especially when cold. It dumps so much fuel it fills up the throttle bores. I tried buying an aldl cable and using win aldl but can only pull up maw/ip, prom a and the iac. The iac is jumping from 7 to 256. Would like to be able to see O2 and map at least. Any suggestions?
Was the drop in mileage right after fresh installation of the engine? If so, did you change the camshaft? What other engine mods were performed if any? Could be a temp sensor issue. You should download Tunerpro for datalogging and viewing the data stream, it is a much more capable and powerful tool in so many ways. The iac counts are likely because the excess fuel is affecting the idle and the iac is trying to control it, albeit wildly.
Double check all the ground connections, the temp sensor and get back to us.
Buddrow
If it don't fit force it, if it don't force fit f&%@ it!
I couldn't get tuner pro to show anything I don't think I set it up right. I had about 400 miles at around 12 mpg then the last 200 have been at 6 that's all the miles on this engine. The O2 injectors and coolant temperature sensors have about 800 miles on them. As far as mods I had a good valve job done stainless valves installed, pocket ported intake full ported exhaust, mild rv cam and edelbrock intake. Around the time milage dropped it started hesitating and stumbling right off idle. Now it's lost idle control too.
got tuner pro working now im so confused
You are still in open loop so theres not really much feedback. The blm and int are locked until closed loop. Did you by chance install a new fuel pump, injectors, or modify any part of the fuel system? It really shouldn't be "filling the bores" with fuel. By chance is your check engine light flashing rapidly? What, if any, changes have you made to the calibration?
If it don't fit force it, if it don't force fit f&%@ it!
Made no changes to calibration no changes to anything since drop in mpg. I un plugged the map sensor first electric side no change then the vacuum side then and the truck died. I plugged vacuum line back started the truck and it is still rich but no longer filling the bores with fuel. Also it's still in open loop but the ecm sees coolant temp at 174f what else is needed to go to closed loop?
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