so i've got an 89 f150 with the 302 and it's only got 122k on it. love the truck but can't figure out what's wrong with it.
symptoms...inconsistant idle (jumps between 700-900 rpms every couple seconds), shifts too soon so it bogs way down and chugs a lot, and it's a little chuggy when going down the road at a constant speed. almost seems like i'm running off 7 cylinders.
i know there's no vacuum leaks which was my first guess. and i changed the plugs and wires. next up is a compression test i suppose.
anyone heard of or experienced these symptoms before or have any advice? my next guess would be the throttle position sensor but i don't want to just start buying and replacing things if i don't have to.
thanks guys!

 

Inconsistent idle - this model year series had problems with carbon fouling of the Idle Air Control (IAC) solenoid. Suggest to pull it and clean any deposits out with carb cleaner.

IMO - have to remember what the late 80s were like - fuel injection was relatively new, and many manufacturers resorted to seriously detuning the engines and programming fast up-shifts in the trannies to meet then-current regulations. One story I've heard, but can't validate, is that Ford actually gave away the 351s on a few trucks to meet fleet average requirements - apparently they were having trouble getting the 302 cleaned up. Another true story, although I don't know when it first happened - was the manual tranny lockout on the Corvette - where if the driver didn't 'get on it' - he would be forced to shift from 1st to 4th, or something like that.

As far as other 'chuggy' issues - suggest to pull the codes from the computer to see if anything shows up. O2 sensor problems, lean problems, rich problems, etc. should be flagged by the computer - saving a lot of troubleshooting and head-scratching time. Also, a timing check is not out of the question.

Verify that your cat is not plugged - one way is to punch it and see whether it has trouble getting into the higher RPM range - a plugged cat will make things seem like the truck is really loaded down and the RPMs likely will not approach redline due to flow issues.

Good luck, and keep us posted.

 

i know what you're talking about with the "skip shift" in the corvettes. i've got a 2001 camaro ss and that does it too. it was really annoying so i had it deleted when i got the car retuned.
i'm running a catless exhaust due to lack of emissions in michigan and i've got hooker headers.
i checked all the sensors with a volt-ohmmeter and got no reading when i tested the idle air sensor itself and same thing when i tested the plug running from the pcm. not sure where that leaves me. i don't have a port to plug in a diagnostics program or anything to see why i'm not getting signals from the pcm.
i consider myself pretty mechanical when it comes to working on vehicles because i grew up doing it but i'm stumped on this. i've been at it for a couple hours a day for a couple weeks and am coming up with the same 'lack' of results. most irritating thing ever.
any ideas?

 

Check the computer for codes and post them here. This will tell you how:
https://www.f150forum.com/f10/how-retrieve-trouble-codes-obdi-10907/

 

well it threw 41 and 33. i know one of them has to do with the egr, though i don't know exactly what it has to do with the egr. i took it off and cleaned the carbon out of it but she runs the same. i'm not sure what the other code was for. i couldn't find it in my book.

 

Sounds like you're on the same path as me...

The 33 is for "EGR movement not detected"
The 41 is for either "HEGO sensor indicates lean condition" or "HEGO sensor not switching"

The 41 seems to come along with the EGR mess, so based on what I've learned so far (thanks to a few helpful folks around here), I'd sort through the EGR system first.

You cleaned the EGR valve, right? Did you clean the orifice at the bottom where the larger tube runs to the exhaust manifold? I'd check for movement - apply vacuum at the top of the valve, either with a pump or with a vac hose attached and you sucking on the open end - you'll see/hear it moving if it's moving. If it won't move, you might try to clean it more, or replace it.

From there, it could be a vacuum leak - check the vac lines between the valve and the solenoid on the other side of the motor. There are some connectors right behind the intake plenum too check too.

If that checks out, check the vacuum into the solenoid - you'll just have to have the engine running and feel the vac line that goes into the solenoid - should have a good constant vacuum. Plug that back in, and check the line coming out of the solenoid. If you have the engine temps up to normal, open the throttle a bit and you should feel vacuum coming out of the solenoid. If there's no vacuum, the solenoid could be your issue.

You might as well check out the IAC while you're playing around - I cleaned mine out and it helped the idle a lot. I sprayed mine with some carb cleaner and a black river poured out! Spray that out good and let it dry - spray a touch of WD40 in there (I did - others might say not to) and try it out. This smoothed things out, probably because it was needed, but didn't solve the problem on my truck.

Mine has pulled the HEGO code before too, but the EGR code is consistent. Consensus of the forum seems to be that the HEGO code comes from the computer thinking that the EGR is working, then struggling because it doesn't work.

Hopefully this will get you started - be sure to let us know what you find out. I'm currently waiting on a new EGR solenoid to come in on Monday - I'm somewhat convinced that it has been causing my issues.

 

O2 sensor will give you some of those problems also. If it hasn't been changed in a while, couldn't hurt.

 

so i had replaced the wires before and it ran better but ended up running like crap. i'm an idiot and didn't check the wires again until today. yup, melted on the headers again (probably about the time it started running like junk again). didn't wanna spend 80 bucks on the bosch wires that you cut to length yourself (considered it because the head of the plug that slides onto the plug was smaller) so i bought the cheap wires and put the small part of the wire that is supposed to go on the distributer on the plug and vice verca. runs like a champ and have zero clearance issues with the wires and headers.
still shifts early and i still need to pull off the egr and clean it or replace it but the idle has steadied and it's back to running real strong.
i'll let you guys know the results of the egr thing but i just wanted to say that i appreciate all the help fellas!

 

You can pick up some plug wire guides at the auto parts store to get those wires where you want 'em. Cheap and easy, and cleans up your engine bay.

 

good call. i'll probably do that today. this thing is runnin like brand new... reminded me of why i bought the truck in the first place! i made my own intake hopin to get some better gas mileage too so we'll see how that goes.