Hi
I have a 91 with a 5.8 efi with a e4od tranni. the problem is that after starting the engine after about a minute the engine hiccups then goes to high idle then settles down.then about every 20 to 30 seconds it does it again and again while in park. when it is drivin the engine hiccups more often making the tranni down shift and up shift. also while this is happening the check engine light flashes for half second to one second.
could it the problem be some kind of sensor? I don't think any sensors have ever been changed. is it worth it to get a code reader to save alot of guessing. if I have left out any info please ask thanks in advance

 

there could be one or more sensors causing that or a vacuum leak. go to the sticky at the top of the forum about reading codes. i took a video of how to hook up the jumper wire to test them.

 

thanks Bman
the video was helpfull.the codes I get are 44 no hego switching 36 can't find anything on that and 66 maf sensor. can't figure out what or where
MAF sensor is. posted pictures of engine hope that helps. can you point me in the right direction to find info.

 

i could be wrong, but the maf stands for mass air flow, i am not sure but i dont think yours has the maf sensor.

 

I have a 91 F-150 having similar problems except my code reader will not read the codes. My engine cuts out at speeds above 45mph for a few seconds, the light comes on and when I slow down it runs great. I have not been able to retreive the codes because the "Check Engine" light needs to be on when I hook up the reader and it is not. I will try the volt meter method and see if that works and if not I will relace the MAF sensor. You can get them at Rockauto.com. Thanks for having the same symptons as I do.

 

did you or a previous owner do a MAF conversion on the truck? if not then i'm pretty sure they only did MAP engines in '91. do you have a pic of how yours is setup?

 

That is most definitely a speed density system....I can tell by looking at it. 36 is EGR solenoid not opening.....What kinda hiccup.....

 

thanks Buddhaman:

My Bad as they say nowadays, I was looking in my Chilton when I made that statement and not under the hood. Now that I checked under the hood I see I do not have a MAF sensor. I also got my code reader to start working, seems that I had it plugged in upside down. I got a mess of codes KOEO: 23, 34, 41, 63, 81 AND KOER: 12, 13, 44, 65, 74, 77
AND 2 codes that arent in any book a 10 KOEO AND A 40 KOER.

Looks like I need new O2 sensor, Throttle Pos Sensor and Thermactor Air system and EVP further diagnostics.

I will start with the O2 sensor and work my way down the list until the symptons stop. I would appreciate any Ideas or constructive critizism.

thanks for your input.

 

Mine did that. When I got my '91 (5.8l) all of the vacuum hoses were disintegrated. After I replaced all of them, new EGR solenoid, new o2 sensor, etc.

It takes time, but it is possible to get it all corrected and you can do most of it yourself. Mine just passed emissions testing with great numbers.

 

Forget all the KOER's until you deal w/ the KOEO first.
What code reader do you have?

See link: https://www.f150forum.com/f10/heads-...05/#post623219