Older ECM's are difficult to test. The most you can do is back probe the connectors with everything plugged in and check voltages, as far as functionality goes there might be some tests you can do as per the FSM but it will be pretty limited.

 

Well I hope its not the ecm. Feels more like a component issue. The inconsistency thou makes it feel electrical...

 

Ugh.. well it didnt throw a code this morning....

 

Pretty hard to fry an ecm unless you pour water on it. or plug some high voltage into it somehow. I am leaning on a component issue as well.

 

Yea water hasnt been an issue in my truck. I saw in the fsm the fuel pump its self has a filter. Has this ever plugged up on anyone. The fuel in my filter look horrifically dirty on the entry side.

 

yes, those socks are prone to plugging up. The inside of the tank gets pretty rusty so if you go lower than 1/4 tank of fuel you can plug up that sock really easily.

 

Only done that countless times. Ill check into it.

 

I know when my tank in the 88 was full of rust i attempted to flush it out but the rust got so bad that it didnt matter how many times i flushed the tank it still plugged off the sock. Some cases its just simpler to replace the tank. If the sock is plugged it could be part of the issue with whats going on but i'm not 100% sure it will be the only problem.

 

Worth a look. And it would explain the inconsistency of the problem

 

For sure, the wife's started otu as intermittent and it is progressively getting worse. She says its pretty much everytime she drives the truck now it stutters and shakes, I really think it does have something to do with fuel delivery tho, once the truck gets to operating temps and the CSI isn't dumping that extra fuel in there is literally no smoke coming from the tailpipe when normally when its really cold like it has been there is smoke.

 

Ive noticed that as well.... mines alwayed seemed a lil smokey..... checking this tonight.

 

Have you pulled the intake air tube off and inspected the throttle body for carbon buildup? Often times, carbon will build up around that butterfly plate, and wont allow the throttle to fully close, thus throwing tps readings out of whack.

Your IAC valve could be gunked up also. With that many miles... it might be a good idea to "sea foam" it a couple times to clean up any carbon.

Guess I missed this....

YEah... if the filter is clogging due to rust in the tank, likely the sock on the pump is clogged as well, and the fuel pump has prolly overheated from not getting enough fuel to keep it cool. I'd def start by pulling the tank, and the pump, and have a look....

Its not uncommon to have a really dirty fuel filter depending on how many years since it was last replaced tho....

 

Ive cleaned the throttle body but not the plenum. Was thinking this when I seafoamed my fuel system. Where is the iac valve located?

 

Don't spend too much time on this; if the fuel tank is full of rust just replace it. RockAuto has them for $140-$175.

 

Its part of the tb.... Only way I know of to clean it is to pull the tb, which is simple, and takes about 5min.... rtv silicone works fine to seal her up again when you re-install.


Guess I missed this....

YEah... if the filter is clogging due to rust in the tank, likely the sock on the pump is clogged as well, and the fuel pump has prolly overheated from not getting enough fuel to keep it cool. I'd def start by pulling the tank, and the pump, and have a look....

Its not uncommon to have a really dirty fuel filter depending on how many years since it was last replaced tho....

 

Thanks for the info, I'll pull the tb off and give it a good cleaning. To my knowledge the pumps never been replaced. The previous owners keep super good records on the trucks maintence and left them in the glove box. Ive never seen a repair receipt for that. I thought if a pump was bad it just wouldnt work? Do they normally start acting out as they break down? Also thank you for the tank info. If its a rust bucket I'll swap it out.

 

Yeah... pumps usually work, or not.. BUT... if its getting clogged up by rust, gunk, etc... it could cause intermittent problems, and will certainly shorten the life of the pump considerably. A fuel pump needs to pump fuel consistently to keep it cool.

 

Alright. Ill report what I find

 

Just keep in mind... if you find a rust bucket of a tank, you will need to replace the tank, the pump, and the sock... NOT just the tank, else you may end up having to drop that tank all over again. Ypu MIGHT get away with just a new tank, but doubtful.... I speak in terms of experience on this one

 

Haha no doubt. Yea I was thinking I'd replace the pump regardless due to the mileage while its all apart.