Computer issues??

[adsm08]

A head or gasket would be very very unlikely to cause that kind of issue. Not without more serious issues going along with it. A compression test would show the problem if it is in the heads or gasket though.

 

[Spitfire1975]

A head or gasket would be very very unlikely to cause that kind of issue. Not without more serious issues going along with it. A compression test would show the problem if it is in the heads or gasket though.

That's kind of what I figured, but wasn't really sure.

I let it cool all night and am about to restart it. If the idle is good and then goes bad while hot, I will run the compression check and if it comes out good I will start looking for a manifold.

Ebay has a couple. Is this an item I should be buying new? If so, where is a good place to find one? Rockauto doesn't seem to carry them.

Thanks for your help on this.

 

[Spitfire1975]

Finally just changed the manifold and it seems to be doing ok. We'll see how it holds up.

 

[baggedcereals]

Has the new Intake fixed your problem? After reading your postes this is almost how my truck acts!

 

[Spitfire1975]

nah.

It did solve the intake leak problem, but it still runs weird. One day it is great, the next it is bucking and jerking with an inconsistent idle. Seems to be missing a cylinder pretty regularly. I am starting to think it is just a messed up ground somewhere, or the in tank fuel pump going bad. It seems to act up more when it is warm outside, but all of the temperature related sensors have been changed.

It is still a big mystery.

 

[baggedcereals]

thats just crazy man!

Check the negative battery ground wire that runs to the block.

 

[kimcrwbr1]

Intermittent faults are usually wiring connector related. Sand all the grounds you can find metal to metal even under the dash. Clean all electrical connectors with elect cleaner and use dielecric grease to put them back together. Look for any bare cracked broken wires and repair as necessary. Solder with shrink tube works best. Pull the connector off the computer and clean it good also especially look around the exhaust manifolds for shorting wires. Get the wiring all up to snuff reset the computer and erase the memory and see if it throws any codes. I prefer to erase the memory first then disconnect the battery for 1/2 an hour to reset the computer then you can start with a clean slate.

 

[Spitfire1975]

thats just crazy man!

Check the negative battery ground wire that runs to the block.

Yeah, I am not even going to mess with checking it. It's fairly old, so I am going to just replace it.

 

[Spitfire1975]

Intermittent faults are usually wiring connector related. Sand all the grounds you can find metal to metal even under the dash. Clean all electrical connectors with elect cleaner and use dielecric grease to put them back together. Look for any bare cracked broken wires and repair as necessary. Solder with shrink tube works best. Pull the connector off the computer and clean it good also especially look around the exhaust manifolds for shorting wires. Get the wiring all up to snuff reset the computer and erase the memory and see if it throws any codes. I prefer to erase the memory first then disconnect the battery for 1/2 an hour to reset the computer then you can start with a clean slate.

Any good way to locate all the grounds? I don't seem to be able to read the electrical charts all that well.

 

[kimcrwbr1]

Look for any wire that is bolted to ground. engine to chassis, battery neg to chassis, Adding a ground to the alternator housing from batt neg is a good upgrade. Anywhere you see a connector without a wire to it just follow the harness you should see all the grounds. I think there is a ground by the computer also pull the passenger side kick panel, like on mine there was a smaal water leak and it dripped down on the computer connector. Go through with a comb and look close at everything if it dont look right it probably aint.

 

[Spitfire1975]

Look for any wire that is bolted to ground. engine to chassis, battery neg to chassis, Adding a ground to the alternator housing from batt neg is a good upgrade. Anywhere you see a connector without a wire to it just follow the harness you should see all the grounds. I think there is a ground by the computer also pull the passenger side kick panel, like on mine there was a smaal water leak and it dripped down on the computer connector. Go through with a comb and look close at everything if it dont look right it probably aint.

Thanks!

 

[CurtisP87]

I had a similar problem a while back, and it was just as kimcrwbr1 suggested, some water had dripped in and gotten on the CPU, engine was doing all manner of weird stuff, some of it similar to what you've described. After trying everything I could think of, I swapped in a rebuilt ecu (can't trust one from a junkyard...) and it fixed the prob right up. You mentioned you've replaced yours before though, so you right be having s different problem...good luck to ya.

 

[Spitfire1975]

I had a similar problem a while back, and it was just as kimcrwbr1 suggested, some water had dripped in and gotten on the CPU, engine was doing all manner of weird stuff, some of it similar to what you've described. After trying everything I could think of, I swapped in a rebuilt ecu (can't trust one from a junkyard...) and it fixed the prob right up. You mentioned you've replaced yours before though, so you right be having s different problem...good luck to ya.

I did have a leak in that area, and I can find absolutely nothing else wrong with the truck, so I think I am back to biting the bullet on a new computer. New MAP (wasn't testing right)....no real change. Swapped TFI's (I have a collection)...no change. Fuel pressure is rock solid through the stumbling and dying.....vacuum is doing exactly as it should.

It either has to be computer or dizzy. I don't know what else to look for.

I think at this point I will be just taking it to one of you mechanic types.

 

[Spitfire1975]

lol.

Drove the truck 800 miles from Utah to Willamette Valley. At times it drove great. At times, not so much so. Bucking and jerking, then smoothing out. Anyway, made it to my destination and when I went out to start it this morning......nada. Cranked, but no catch.

SO.........I guess start with fire, fuel then air???? If I have those items, what could I possibly be looking at....toasted head/cylinders, etc.? Is there any way to take the computer out and have it tested at Autozone, etc.?

The truck is about to leave me actually stranded for the first time. 800 miles from home.

How can you not laugh?

 

[Spitfire1975]

No fire problem was the fuel pump relay. Changed it out and I still have the bucking/jerking/stumbling/studdering issue, so I am ordering a computer tomorrow. Let's see if that is it. Diagnosing is going nowhere, so I am into just buying parts. I guess I am also going to start hunting down wiring harnesses in good shape. Dang it.