Computer issues??

[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.

 

[kimcrwbr1]

Getting stranded is never a laughing matter. Try disconnecting the battery for 1/2 an hour and see what it does. There is no way to test the computer but resetting it might tell you if it is working, it will reset the values and then as it runs all the inputs may throw it out of wack again maybe a bad sensor engine temp, IAT, Map ect.. Clean all the connectors and intake air temp with electrical cleaner with the battery disconnected. Start it up and if it runs better the computer is likely good and after it runs and if it goes south then bad inputs or bad wiring is suspect. If you change the computer and have the same issues then you probably have two good computers chances are next to zero two computers have the same faults! Look at the wire/s going to the O2 sensor in the exhaust manifold alot of times intermittent faults are related to a wire shorting out part time and will throw the computer waco. GL

 

[kimcrwbr1]

Oh yea replace all the vacuum lines especially if they are hard or cracked or loose fitting.

 

[Spitfire1975]

MAP, IAT, ECT, IAC, O2 and all EGR but DPFE are either brand new or brand new within the last 5000 miles. I have driven this thing very little because of this dang fault issue. The wiring to all the connectors seems good, from what I can tell, not saying an internal break/ corrosion is getting me. EGR vacuum lines have been replaced, but not the lines running to the brake booster and cruise control.

The way it cycles through the running rough periods and then floods out before running good again for a while seems to be pointing towards the computer. I have reset this computer I don't know how many times and it doesn't ever make a difference. Same issue consistently. That and this most recent bout of serious running issues started after a heavy snowstorm and I had a leak where the roof connects to the A-pillar. I had a diaper collecting water that was dripping from under the glove box. I should have tried the computer a while ago.

 

[Spitfire1975]

Oh, by the way, Happy Thanksgiving.

 

[Spitfire1975]

not the computer. So I guess I am back to checking more wiring, the ignition system, etc...

watch... it winds up being a cracked distributor cap....

 

[CurtisP87]

Have you pulled the distributor and checked the stator...? Seems like a bad stator assembly could cause weird misfiring.

 

[Spitfire1975]

Have you pulled the distributor and checked the stator...? Seems like a bad stator assembly could cause weird misfiring.

That and the cap are first on the list. I thought I had changed the stator, but it may have only been on the other truck I had at the time.

 

[CurtisP87]

Sounds like that's the only thing you haven't changed already, hopefully you've zeroed in on the problem! :icon_cheers:

 

[Spitfire1975]

hopefully!