My truck has just developed this strange problem. It is an 86 F150 with EFI 302 and a 3 speed +OD manual trans.

This happens when going at speed or accelerating, it dosn't matter, and it dosn't do it all the time either. Basically you can feel when your driving down the road a bog, the truck will hold speed, but if you give it more gas you just get a slight shudder and you don't gain any speed. You can put your foot to the floor and it dosn't matter. Usually after a few seconds it will clear itself up and get going again.

Sometimes it does it while your accelerating, and it just dosn't build up the RPMs like it should. It usually pulls hard in 2nd gear. It will still speed up, just not like it usually does. And again, sometimes it will clear itself out and get going like normal.

I should add that if your at speed and you feel the bog, if you dump the clutch and rev it, it revs right up like normal, it's just under load. The truck is always empty. I wish I could describe the problem better in words.

This just started on my way to work during the week. The front fuel filter has about 5K on it, but I never changed the one in the plastic can by the tank (if there is even a filter in there? I hear they didn't have a filter in that if they had the front filter?) Maybe I just got some bad gas? It has a recent tune up and all. I don't know what to do. Thanks!

 

What does the codes say? Have you pulled any codes?

 

I pulled the codes but none seem to relate to my problem.

I always get egr code 31, but it has a new egr and sensor and has been running fine even with that code for some time now, I don't let codes bother me if it's running ok. With the engine running I got O2 sensor lean, but I've gotten that before, I have a new o2 sensor, and it wasn't totaly warmed up when I did the test, so maybe that's why.

But basically no, I didn't get any new or relevant codes.

 

That sounds like an egr or oxygen sensor problem or possibly the solenoid that operates the EGR valve. This solenoid can be found on the passenger side wheel well.

I have the same problem with my 86 intermittently.
EGR is for pollution control, but it can cause driveability problems if it is not opening and closing at the correct times.

 

Imadore may be right, I'm also getting the same problems an have replaced everything except the Oxygen sensor, if that doesn't cure it then the egr relay is next...my 86 will run excellant without a miss of any kind while running 55, but when I go an slow down to around 30 it shugs along unless I press alittle more on the gas, or give it time to adjust to the speed I'm going. I am also getting a code 31 with a 11 (pass) on the koeo stage of the test. After replacing it, will reboot the computer so it can relearn everything.

 

Hi Guys

My '86 is still doing the shudder thing too. New Engine, Dist. body, cap, rotor, wires, O2 sensor, EGR, Injectors, and cleaned out TB. Still has the shakes!
Is the EGR rely on the passenger side inner fender?

There's 3 or 4 in a row. How do ya test?

Thanks

Reamer

 

Reamer...you have 3 or 4 relays? I only have two of em, one is going to the egr cannister then to the egr sensor on the egr, have already replaced the egr and sensor thats on top of it...still getting the code 31, have ordered the Oxygen Sensor, so will perhaps change it out tommorrow to see if I have to go futher with the egr relay, theres a way to check it, but rather replace it if thats the problem too....may have to anyway later on. I know I don't have any vaccum leaks, cause the motor been rebuilt, and I've checked the hoses and even put sealant around the ends to make sure there no leaks anywhere...now if I can just get rid of the shutters.

 

Yep, three relays, with one of them having two sets of wires that plug into it.
How do I test the EGR relay?
I will easily trace from the EGR vac line to one of them.

 

I'd also like to know how to test the EGR and other relays. Anyway, my truck has a new o2 sensor, new egr valve, and a new egr sensor. I've been getting that code 31 for a while now and the truck has been running fine with it.

Today I replaced the front fuel filter (only had about 5K on it) and I also replaced the one inside of the can by the gas tank, that one was black and never changed. We'll see how it does.

 

Here's some information I found about the EGR:

Code 31 .....EGR position sensor fails to open

If there is too much EGR, or if the EGR comes on at the wrong time, the symptoms will be poor engine performance. The symptoms include:
* poor idle
* stalling, especially when starting after cold soak
* hesitation, stumble and rough running during or slow driving and during warm-up
* hesitation or stumble
* surgeing at cruise
* slow stumble acceleration
Symptoms of EGR malfunction
The EGR system is often misdiagnosed or blamed for problems that may
not be its fault including hard starting, stalling and hesitation
during warm-up, rough idle, missing, spark knock, backfiring and loss
of power. Sure, the EGR system can cause these symptoms, but so can
other components and systems. Don't jump to any conclusions until you
have checked the basics. Don't overlook carbon buildup in the
combustion chamber for spark knock, for instance. Also, don't overlook
vacuum leaks for hard starting and hesitation. Don't overlook the
ignition or fuel systems as the cause of missing.
The EGR system can malfunction in four ways:
* problems with the passages
* problems with the EGR valve
* problems with the vacuum control system
* problems with the computer control system.
EGR Control Solenoid.... Red-Yel.... More than 30 ohms
EGR Vent Solenoid.... Red-Dk Grn.... More than 30 ohms
TAB Solenoid.... Red-Wht/Red.... 45-90 ohms
TAD Solenoid.... Red-Lt Grn/Blk.... 45-90 ohms

 

Hi Locknkey

The ohms readings, Are these what they should be when running?

Higher is bad or lower is bad?

thanks


Reamer

 

More is good, less is bad.

 

i had the same problem in my 86. i had replaced basically everything under the hood including the motor but was still having the same problem listed. from previous repairs i have removed all smog and emission stuff. i disconnected the ECM from under the dash and the thing has never done it since. just to make sure i also re-plugged the ECM back in and it immediately began to do it again. i may worth a try

 

Hi Pistol Pete

What is the ECM and where do I find it?

Thanks

Reamer

 

pretty sure it stands for electronic control module. it is located under the dash between the steering column and the ash tray. it should have one bolt that you can back out and pull the thing apart. i was told by a mechanic to try it he had a lot of experience working on fords. by the way, my truck has an in-line six and a manual 4-speed tranny, i think i forgot to mention that eariler.