I've been having an ongoing problem... actually several problems that's driving me up the wall! It's a 91 4.3 TBI 4dr 4x4 with rebuilt engine and almost everything under the hood is new as I was/am planning to keep it for a while. Well at least I hope. New EGR, ECT, Map, distributor, plugs, wires, coil, radiator, water pump, injectors, tbi kit, delphi fuel pump, yes... you name it, it's been done as the truck has a bit over 190,000..

Anyways, it cranks up fine but will randomly shoot out a small cloud of white smoke (on start up), sometimes it will sputter black but not much. Mechanic says he doesn't think it's the intake manifold, rather it's loading up. Sometimes it will run fine although it's very slighty sluggish (perhaps timing is a bit off). Sometimes it will idle fine as if the engine isn't running at all. Down the road it drives fine, then sometimes when you come to a light it will sporadically start surging, and sometimes cutting off. When it does cut off it will crank right back up like nothing is wrong??? It may idle fine for a bit or may start bucking & surging.

As a insult to injury it has also developed an electrical issue which may or may not be related. My oil gauge used to work fine, but now will act as if I have low pressure to the point of reading very low to 0 psi at a idle causing the check engine light to come on. My voltage gauge will read a bit high, but I'm not so sure it was always accurate. Also the gas gauge is not reading correctly no matter how much you put in the tank. It will never go past half a tank even when full, then will quickly start to drop down to a quarter or less leaving me to constantly put gas in it unnecessarily. The blinkers randomly work normally as well while other times they will blink fairly fast. I have lost my reverse lights for some reason. They were new so I bothered to not even check to see if they are blown since I find it odd that both sides stop working.

I've had it at a shop that charged me $700 to get it running right, but the problem appeared again shortly. I don't drive it to work so it hasn't seen much use since the minor restoration started. I'm at a loss here and don't know where else to turn besides scrapping it, but I have much invested in it inside & out as I took pride in fixing her up. I am pleading for a solution!! Please!!

 

Pull the engine and trans gas tank and fuel pump and what ever else is salvageable.Then part out the rest and let your head ache be over.

 

I wish it was that simple to just take a loss, but I'd hate to scrap it if it's something(s) simple. But finding out what's the problem seems to more of a headache than anything else.

 

Okay... was slated to take it to the shop this morning, but I just can no longer trust these shops. At least not until I find someone who really knows the ins & outs of GM TBI. Anyways, going back to some basic diagnosis I have tracked down at least one issue which I'm sure is the culprit. She purrs a lot better, but I still want to have something checked.


The EGR was suspect although it is fairly new and is the third one. I've been wanting to try an original replacement for some time, but all that is available locally are the usual valves with the various washers. Reluctant to go back to the stealership I finally tracked down the proper numbers for the original through alldatadiy. Showing only two for this model I looked up both online and one is again supposedly the same various washer one although it say ac-delco??? The other is a bit higher, but shows some sort of plunger sticking out of the valve that goes into the intake. I'm taking it that is the proper one..... I hope anyway. Going to order that one asap. Until then the EGR has been disconnected. Already know of the bad rep the generic egr valves have so hopefully that solves that issue.

As for the other issues, I found that the P/N switch was out of adjustment. Not sure how that happened, but I have gotten the reverse lights back on. My oil gauge is still bottoming out on idle causing the check engine light. The fuel gauge and blinkers still the same issues so perhaps that is related, but unrelated to the engine issues.

Any clues?

 

Don't replace the egr. Save your money and just clean it. Sounds like its just sticking open which 99% of the time a cleaning will fix.

For the fuel level, you may wish to put a new sending unit in the tank. You can look in my build thread to see what that is. I did a tank, sender, and pump for about 350$.

Oil pressure, check the connection out at the sender again, I can't recall if its up beside the distributor or down where the oil filter lines connect to the block

 

Thanks, but the components in the tank has already been replaced when I had to replace the fuel pump not too long ago. I used delphi parts to insure I wouldn't have to go back in there too soon. The sending unit didn't fix the gauge unfortunately, but at least the pump works. I'm still wondering if there is some sort of ground issue as these problems seemed to occur at the same time. In fact the windshield wipers had stopped working and I had to attach a small ground strap to the body & frame of the wiper motor assembly in order for it to work again. Somewhere there has to be some sort of ground or connection issue. Everything used to work until the motor was rebuilt, then shortly after the issues came. I should have shot the mechanic for messing up my truck!

 

There should be 2 ground wires bolt to the back of the head,It could be on either side.As for the sending switch its right be on the distrib on top of the block.It will be a black thing about 3 inches long with a plug that goes into it.Its kinda a biatch to get to.

 

Yeah... I've replaced the oil sending unit twice.... once when it started leaking and another shortly after the rebuild because it was reading funny. This one seemed to have a short life for some reason, but then again don't most of the cheap sensors & stuff?? LOL Anyways, is there a better brand for the oil sending unit? I hate replacing that thing. It's a real pain to get to.

The fuel gauge will take some investigation. I've been looking for bad grounds but to no avail.