TTurner

Well I pulled the ECM and not to my surprise I had the same blown/discharged capacitors that other people have had fail. Ordered a new ECM and should have it in the truck tomorrow. I will update if that changes anything. Thank yall so much for the help I really appreciate the "second set of eyes" so to speak.

vjsimone

Not surprising, the capacitors have reached their lifespan after 30 years. Depending on environmental conditions they can last +/- some years, mine are still ok in my 85 & 88.

That Code #15 is usually one of the signs.

Be sure to capture all the Numbers and such from your original computer if you are surrendering your old one as a core. You may need that information down the road, or next month..... Photo it & print it, or even post it.......

TTurner

Update..... Got the new ECM/PCM in the truck. It fired up and ran amazing... ran the truck for 15-20 min with zero problems... then I shut it off


About 3 hours later went outside to see if it was a fluke deal and sure enough it was. Started the truck and it immediately start missing and stumbling. I'm really starting to get pissed off now lol


Pulled some engine codes and from what I can tell it brought up an IAT and O2 sensor problem. The 15 "PCM code" is gone now. So I'm confident the old computer definitely had some issues. I metered the IAT prior to doing the code retrieval and from what I could tell from the chiltons manual it was good. But the computer is saying its bad. Also is there a way to check an O2 sensor??


Any help will be great.

vjsimone

When you are dealing with a potentially bad computer, you never know for sure what else is wrong, troubleshooting kind of starts from scratch again when replacing.

Engines are easier to diagnose over the internet when all the codes are listed, and in order of test.
KOEO - (O) Self-Test Codes =
KOEO - (C) Continuous Codes =
KOER - (R) Self-Test Codes =

Make sure your A/C, Heat, Radio, etc. are turned off when testing.
The "10" appears on a digital code reader during KOEO to indicate the start of Continuous Memory Codes.
The "10" appears on a digital code reader during KOER to indicate the start of the WOT test.

Same goes for any measurements you take, list/post the actual reading so everyone can evaluate.

When power is disconnected from a computer, or a replacement is installed, if possible, it is recommended that you put a few miles on it up to 55 mph prior to running the KOER Self-Test. If the truck is not drivable, then you can imitate a ride by varying the engine rpm up high then back to idle, do this a few times and add a few WOTs in the process.

Engine needs to be fully warm before starting KOEO & KOER test. I usually rev the engine few more times just prior to starting the KOER test to heat up the O2 sensor.

You can check an O2 by putting a meter on the output/signal line to measure the dc voltage output. It is a small voltage between 0.0 and 1.0 vdc. During warm cruising, this voltage oscillates above and below 0.5vdc. What O2 code are you getting?

The O2 is a regular scheduled maintenance item, it wears out and fails, and falls under; "Do All Scheduled Maintenance Prior to Troubleshooting"

When you get a chance, add; 1988 F150 5.0L Dual Tank, to your signature block.

TTurner

OK new update on signature to help people help me LOL!

Got home today and pulled the IAT Sensor and compared it to the new one. While the readings were close the old IAT sensor took much much longer to react than the new one so for the $15 it cost me I put the new one in.

I took the truck for a drive and for the most part had no issues. Drove the truck for about 15-20 min anywhere from 30 MPH in town-65 MPH on the highway.

Got home and pulled codes:

KOEO (O)- 34
KOEO (C)- 34
KOER (R)- 34, 42, 13

34- EGR Related but not exactly sure the details
42- HEGO (HO2S) sensor voltage high/system rich
13- RPM at idle out of range/low

So thats where I'm at.... I know in my first post I said EGR delete...... well its not fully deleted. Im sorry for the confusion there, the valve is still there and the pipe but the pipe is not running to the exhaust due to my current exhaust setup not allowing it to be possible. Hopefully I have done a little better this time. Thanks for taking the time to read this.

Truck currently is running good only thing now is right off the start (getting up to speed) it seems to kinda bog down just a little bit.

Also there is NO check engine light on while driving.

wde3477

Suggest the 34 code relates to the EGR valve not being positioned where it's supposed to be. This could be due to the valve mechanically sticking/stuck, the position sensor on top of the valve failed or a wiring issue, or the vacuum control solenoid on top of the driver-side intake manifold not working or a vacuum line issue (just follow the vacuum line from the valve back).

Opinions vary, but mine is that the EGR system needs to work for proper engine management controls. Others report they have deleted it without issue. At any rate, want to make sure that air cannot leak through the valve into the engine, causing potential idle speed and fuel mixture (lean/rich) faults due to this unexpected air input.

TTurner

OK gonna try and verify that.... update on the truck just went outside and started it after letting it cool down and it is back to spitting, sputtering, cutting out etc whatever you want to call it.

FYI the vacuum line is not attached to the valve i disconnected it after i changed the exhaust out.

vjsimone

Hopefully you have plugged the disconnected ERG-V vacuum line...

Take heed to what wde3477 says about a leaking EGR-V, I suggest you make a block-off plate/gasket to install between the EGR-V and the intake if not already done. This will insure you are not leaking anything in via the EGR-V.

The protocol used to be to work the lowest Code #s first, don’t remember where I read that.

To be sure you are not chasing your tail, I would verify repeatability with respect to your Codes.

So, I have seen where the old carb guys will try to adjust the throttle plate stop screw to adjust the Idle, they usually fail, but they don’t get the screw back to where it was, that is where the Throttle plates are all the way closed, but not sticking/stuck. This failed attempt sometimes causes the Code #13.

Sometimes you can tell if the screw has been tampered with. And sometimes it's just the new EECM struggling to learn to set the proper idle.

Also a vacuum leak will cause a Code #13.... But then you don't usually get a Code #42 with a vacuum leak...

See attached procedure. I have successfully solved the Code #13 using this procedure on mid to late 80’s motors.
You might have to do this procedure a few times to get it right, took me a few.

Do you have a Tachometer ?
Question; What is your current Warm Idle RPM ?

I see you have replaced the TPS, most likely with an aftermarket one. Might be a good idea to measure the output signal to see if it is below 1.0 vdc.

TTurner

I started the truck a little while ago and let it run to warm up. The vacuum port that supplies the egr and the egr itself are capped. Now for the cap on the intake side when i touched it it fell apart. So at this time I took it upon myself to hook the egr back up just you know to see what happens. Well that was not the right direction while the truck did run it ran like pure crap and when i would disconnect the vacuum line from the egr it would run much smoother. While it was hot with the egr still hooked up i ran check engine codes and got the same ones as listed above plus 22 on KOER. Other than that all were the same.

The only thing that is building any consistency is once the truck is warm/hot it seems to run ok. When i shut it off than let it sit for maybe 15 min abd restart it than it runs like crap.

Some people were talking about the pickup sensor in the distributor having issues when it gets warm could that be the problem? or would that give me issues no matter what the condition.

I will say i cant guarantee the EGR isnt leaking by. there is no block off plate installed. currently the only thing done to the EGR is the valve and the vacuum line on the intake are both plugged.

Checked timing just for fun and its good 11-12 degrees

Even though im getting code 13 the idle is not low. I do have a tach but it doesnt work properly... when i checked timing the idle was 950-1000

Checked the TPS the other day and at idle or closed its like 1.1ish on the lower side of ish lol

Im running out of ideas.

vjsimone

For clarification, the Self-Test is looking for the low Idle and does not sense it. Code #13 is not that you have a low idle, it means your idle is not low enough.

975 is to high..... See if you can adjust your TPS to less than 1volt, sometimes it matters, sometimes it doesn't. I prefer .85 v.

Then use the Throttle Screw procedure.

What was your Idle with your old EECM ?