another stumbling idle thread

[cerberusaardvark]

my 94 explorer just started getting really bad with its idle and stumbling under throttle. i think ive replaced almost every component besides the injectors themselves and this problem continues to plague me.

things replaced new: fuel purge canister, fuel pressure regulator, fuel pump (bosch), fuel filter (motorcraft), injector o rings
things cleaned and reassembled: a full top end rebuild from the short block up

i have about 7k miles on the rebuild and have not recurringly had this problem till the past few weeks. i have no CEL and no codes.

ive replaced quite a few engine sensors like the maf, tps and pcm with junkyard stuff, and they all seemed to mitigate the problem but only temporarily.

 

[236PR]

What's your fuel pressure?

 

[Gadget X]

Have you checked\cleaned the iac valve?

 

[malohnes]

I second the IAC and encourage checking MAS and O2.

 

[cerberusaardvark]

yea its the third maf, iac and tps all together. but they are all junkyard pickups. i cleaned them all before i put them in. my 02 sensors are about 18 months old, and helped me pass my smog a few months ago.

the stumbling was a problem i had rarely enough to forget after each time it happened for a few years but its just gotten so frequent.

i havent tested my fuel pressure but bc it can also run great with no problems for a week straight before the stumbling happens. i suppose i should try to see if i can cause it so stumble while testing.

i wonder if its worth buying new electronics straight up?

 

[cerberusaardvark]

replacedd the IAC and TPS with new sensors, now engine wont even start. no cel, but i checked the codes and i get a 111, followed by a 10, followed by a 157. so im thinking its the maf, as i have the original and a junkyard find. i guess they could both be bad. my autozone sells duralast brand mafs for 90 bucks, the only kind they carry. i think ill pick up a new one to see if that is the source. ive cleaned both the old mafs multiple times but maybe it was no use.

 

[cerberusaardvark]

just swapped in the new MAF but im getting the same code, 157, and it wont start and run. im going to check the fuel pressure next.

 

[Gadget X]

Check your coil pack, too. It could be the source of your issue.

 

[vq5speed]

Have you checked all vacuum connections to make sure no cracked or harden hoses not getting a good vacuum seal check the intake tube for spits and cracks. Also make sure the MAF connector is not backing out. I had this happen with mine had to zip tie to hold the coonector on. My stumbling issue was fixed with a new TPS. Unfortunately its a lot of process of elimination with this truck but you have to replace all with new parts. Used parts does not eliminate that part. It be nice to pin point the problem but my experience there could be a multiple of issues going on.

 

[cerberusaardvark]

so the issue ended up being a shorted out tps circuit on the pcm. fixed with a new pcm, had to set the idle on the new tps and its good and running smooth. sorry for the long wait