Severe Bogging Issue

Tweekin · January 3, 2010

The truck is bogging something fierce.

Seems that the bog is at it's worse when the RPMs are between 1200 - 2200. Sometimes when the traffic lights turn green when sitting there, I will give it gas and seems that there was a blip of power then gone and comes back which results in me slamming my head into my steering wheel haha. When I'm in overdrive, I can hardly make it up a small hill, sometimes same case scenario in 3rd gear. Not sure if it's coincidence but when it's really cold out and I left it outside for the night, the bogging is at it worse. Leaving it a warm garage seems to work for a little bit then gets worse.

There are times where it works perfect for a while though. So ofcourse when I bring it into a shop, they can't always figure it out because the issue doesn't reoccur for them.

I also noticed wayyyyy to much gas in the air cleaner. Pretty bad when the gas makes my air filter stick where I almost have to pry it out.

Here is the list of stuff I have already changed or replaced:

NEW PARTS

Have the truck scanner. Nothing showed up.

Put in a new Throttle Positioning Sensor.

Fuel Pump Relay

Fuel Filter

EGR Valve

A Couple of New Hoses

Spark Plugs

Spark Plug Wires

Cap

Rotor

Full Distributor

Fuel Pressure Regulator (probably wrong name for it)

New Computer PLUS new Prom for it.

TESTED GOOD AND CLEANED

O2 Sensor Read Fine

Tested Backpresser which was fine

Tested Fuel Pressure

Test Injectors which checked out good.

Adjusted Timing so that's correct

Soaked the plug wires and no changes.

I know the Catalytic converter is getting decently bad but pretty sure that's not the issue. Otherwise that would always bog it I would think. Fuel Pump seemed fine too.

When the issue occurs the check engine light never pops on. If it did, I might have considered Map Sensor. Also when I drive down the road in overdrive, sometimes it runs fine. Not great but good enough. Then out of no where it feels like I lost 40HP. There are frequent times where im in 3rd gear or overdrive and the truck shakes like I lost am losing spark.

I'm pretty sure I missed a couple of things but if anybody else has some other ideas, that would be awesomeeeee. I dropped like 2 grand or more only because of this issue. Most of which was due to hours at the mechanics. Even brought this straight the GM thinkin they have this issue on record. Guess not. I seen a lot of the same types of issues on other forums with this truck in general but ofcourse if someone fixed theirs, they never came back to the forum to tell you what fixed it. Haha.

Oh yeah, My vehicle specs

93' Chevy Silverado

k1500 4.3L Throttle Body

4X4

Sorry for the long post, haha. Thank you!

rodram · January 5, 2010

.. after everything you have looked at and tried, I would suspect the following possible culprits:

1. fuel pressure ... get the fuel pressure actually measured .... what is it? ... these TBI engines need something like 10 to 15 psi to start and run reliably... if low, then change the fuel pump ... and if you are changing it then get a ACDelco from the dealer or a Delphi from NAPA... the other brands are far less reliable.

2. then, check the Coolant Temperature Sensor (CTS) ...you did not mention this one in your list. .. cheap part, easy to replace... this sensor tells your Engine Control Module (ECM) how much to adjust the fuel depending on the engine block temperature... it is a separate sensor from the sending unit to the truck dash temp gauge... when it fails it usually allows the truck to run OK when cold, but when the engine warms up, the sensor does not respond and it continues then to push TOO MUCH fuel into the engine injectors

3. with everything else done and the fuel pump and the CTS checked ... I would have to suspect your cat convertor...

I hope some of this might help.....

edit.... another thought.... you mention frequent shaking like you are losing spark.... this has happened to me on three different cars (I think 3 anyway) over the 40+ years that I have been driving... and each time the problem has been remedied by new spark plug wires .... but you said you have replaced yours already..... so...?

Tweekin · January 12, 2010

.. after everything you have looked at and tried, I would suspect the following possible culprits:

1. fuel pressure ... get the fuel pressure actually measured .... what is it? ... these TBI engines need something like 10 to 15 psi to start and run reliably... if low, then change the fuel pump ... and if you are changing it then get a ACDelco from the dealer or a Delphi from NAPA... the other brands are far less reliable.

2. then, check the Coolant Temperature Sensor (CTS) ...you did not mention this one in your list. .. cheap part, easy to replace... this sensor tells your Engine Control Module (ECM) how much to adjust the fuel depending on the engine block temperature... it is a separate sensor from the sending unit to the truck dash temp gauge... when it fails it usually allows the truck to run OK when cold, but when the engine warms up, the sensor does not respond and it continues then to push TOO MUCH fuel into the engine injectors

3. with everything else done and the fuel pump and the CTS checked ... I would have to suspect your cat convertor...

I hope some of this might help.....

edit.... another thought.... you mention frequent shaking like you are losing spark.... this has happened to me on three different cars (I think 3 anyway) over the 40+ years that I have been driving... and each time the problem has been remedied by new spark plug wires .... but you said you have replaced yours already..... so...?

Sorry for the extreme long reply. Guess I didn't set this to email me when there was a reply to the post.

1. Fuel pressure should be fine now that I have the new fuel pressure regulator in there. Everytime I opent hat air cleaner I have to pry the air filter off of it because of too much gas.

2. I forgot to mention the Coolant sensor, but I did put that in. That was one of the first ones I looked at. Didn't change anything.

3. This weekend I just installed a full exhaust system in started from Header Pipe to Tail Pipe. I did have a leak in my header pipe that. Seemed to kind of help the shaking but it's still there with all new exhaust.

I was possibly looking into just getting new injectors. They tested fine but some people have told me that there injectors tested good but that was only electronically.. still had some sort of clog in them though.

Another one told me that it could be a manifold vacuum leak.. but i figured i would hear something if it was annddddd the problem would ALWAYS be there. Normally when I leave a heated garage the truck runs pretty well full power int he cold for a few minutes.. then it turns to crap.

mjlimo82 · January 13, 2010

Fuel injectors could be likely - my old Dodge is TBI and it did that to me once. Ran like crap when it tried to run, and it would often shut completely down going 55 down the highway. It spent two weeks in the shop and the mechanic couldn't find anything wrong with it. Finally gave up and took it to a shop where I live that specializes in imports (Porsche, BMW, Mercedes, etc)... he had it for two hours and called back saying it's fixed. Clogged injectors. $40 to clean them. I never would have suspected the injectors, but that's exactly what it was. I'd have them cleaned, it's probably cheaper than replacing them.

Tweekin · January 13, 2010

Fuel injectors could be likely - my old Dodge is TBI and it did that to me once. Ran like crap when it tried to run, and it would often shut completely down going 55 down the highway. It spent two weeks in the shop and the mechanic couldn't find anything wrong with it. Finally gave up and took it to a shop where I live that specializes in imports (Porsche, BMW, Mercedes, etc)... he had it for two hours and called back saying it's fixed. Clogged injectors. $40 to clean them. I never would have suspected the injectors, but that's exactly what it was. I'd have them cleaned, it's probably cheaper than replacing them.

Yeah well I brought it into GM themselves and had teh injectors tested.. they checked out ok. BUT.. I heard people say that when they did their injector tests, they only did it electronically. That still didn't mean that the injectors weren't clogged. So maybe I'll hit ya up on that and bring it in. I already poured a ton of money into it, what's another 50 bucks, haha. Be cheaper than replacing the whole throttle body. I'll let you know what I come up with when I get it back and test it out.

Tweekin · January 16, 2010

Fuel injectors could be likely - my old Dodge is TBI and it did that to me once. Ran like crap when it tried to run, and it would often shut completely down going 55 down the highway. It spent two weeks in the shop and the mechanic couldn't find anything wrong with it. Finally gave up and took it to a shop where I live that specializes in imports (Porsche, BMW, Mercedes, etc)... he had it for two hours and called back saying it's fixed. Clogged injectors. $40 to clean them. I never would have suspected the injectors, but that's exactly what it was. I'd have them cleaned, it's probably cheaper than replacing them.

Yeah well I brought it into GM themselves and had teh injectors tested.. they checked out ok. BUT.. I heard people say that when they did their injector tests, they only did it electronically. That still didn't mean that the injectors weren't clogged. So maybe I'll hit ya up on that and bring it in. I already poured a ton of money into it, what's another 50 bucks, haha. Be cheaper than replacing the whole throttle body. I'll let you know what I come up with when I get it back and test it out.

I installed a new throttle body. Well it's a used one but in better shape than mine. Installed that.. idle ran high, so took that out and replaced the idle control thingy from my old throttle body and worked fine.

Just got bakck from my test drive... same crappppppp. Can't get it over 55 mph still. Seems when im in 3rd geat going about 45 mph, the truck starts shaking. Especially overdrive. Only thing I haven't changed in this truck yet is the ESC (Electronic Spark Controller). OH and never chagned the fuel pump.... wouldnt make sense to be that if im getting too much gas. But I have basically changed out EVERYTHING... I just don't get it.

Tweekin · January 16, 2010

Here's the new update on what I have installed and tested....

NEW PARTS

Had the truck scanned. Nothing showed up.

Put in a new Throttle Positioning Sensor.

Fuel Pump Relay

Fuel Filter

EGR Valve

A Couple of New Hoses

Spark Plugs

Spark Plug Wires

Cap

Rotor

Coil

MAP Sensor

Full Distributor

Fuel Pressure Regulator (probably wrong name for it)

New Computer PLUS new Prom for it.

Complete Exhaust System (Header pipe to tail pipe)

Fuel Injectors

Thermostat

Coolant Sensor

Throttle Body

Idle Sensor

New gerbils on a wheel to charge my battery....

TESTED GOOD AND CLEANED

O2 Sensor Read Fine

Tested Backpresser which was fine

Tested Fuel Pressure

Test Injectors which checked out good. (new injectors now listed above..)

Adjusted Timing so that's correct

Soaked the plug wires and no changes.

Sprayed carb cleaner around the manifold. No jump in idle. (Unless I'm spraying int he wrong spots...)

Checked all possible grounds.

gregrocks89 · January 31, 2010

did any help? another thing to check is take your spark plug leads off and grab a multimeter and meter the resistance in it. Ive done that a few times to my truck and it worked. I use to have msd leads and i dont run those anymore cuase its twice now that i got them brand new and two of them were faulty. so i just run the napa high performance line for leads. the awg is a lil bit smaller then the msd but ive had no problems for awhile.

Tweekin · January 31, 2010

Never tried that before. But wouldn't the problem be ongoing though and not just a minute or so later? Not sure what happened now but the truck has a small backfire... all of this time it seemed that it was getting too much gas because of the air cleaner being caked but doesnt it backfire when it isn't get enough gas?

Badass69 · February 1, 2010

Never tried that before. But wouldn't the problem be ongoing though and not just a minute or so later? Not sure what happened now but the truck has a small backfire... all of this time it seemed that it was getting too much gas because of the air cleaner being caked but doesnt it backfire when it isn't get enough gas?

Timing chain perhaps? You have replaced about every single thing a person can to no avail so maybe it's something mechanically internal. Try a compression test and see what comes back from that. Either that or you have the spark plug wires on wrong, but I doubt that because you only started having the issue then throwing parts at it. Gm's distributors have been prone to start cracking on the reluctor that triggers the pickup but you said you replaced the entire distributor with a new unit, so that shouldn't be it.

Tweekin · February 1, 2010

Well I checked the timing chain and seemed fine. I never did replace it though. Yeah I'm about to call it quits on this truck I think and just sell it to someone else who can figure it out. The truck is damn near all new now with what I have done... haha. I'm going to check every wire and see if they all check out fine. If they do.. I think I give up...

Mike G · February 1, 2010

Just a thought, your distributor may be shot. My truck ran like crap and wouldn't idle, these things wear out the internals. New one in and all is good.

--Mike

Tweekin · February 2, 2010

Already have a new distrubtor in there and then timed it twice.

Mike G · February 2, 2010

Wow, you do just about have everything covered. Backfire is usually associated with timing/electronics. My only other thought would be that your chain jumped a tooth. I do not have any expereince with the 4.3, so I cannot attest to longevity. Seems like a great time to go 5.7