Mechanics

CHEVY BOGGING SEVERELY

1993 Chevrolet Silverado

Engine Performance problem
1993 Chevy Silverado 6 cyl Four Wheel Drive Manual 97,700 miles

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 (Truck doesn't shut off). When I'm in overdrive, I can hardly make it up a small hill, sometimes same case scenario in 3rd gear. When in 3rd or overdrive, the truck would shake bad. Now that I have a new exhaust system in, it doesn't shake as bad. Probably ran harder because of the header pipe leak. 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. In that case, is there some gaskets to look at?

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
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
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)
New MAP Sensor

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.
Ground to Fuel Pump
Ground under Thermostat

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!
Avatar
Tweekage
January 11, 2010.



The first thing I thought was a plugged catylatic converter, but you replaced that. My next thoughts are the mass air flow sensor or the temp sensor. However, they should have kicked a check engine light. I didn't see either on your list. Did you replace them?

Well my truck doesn't have a MAS considering it's throttle body. I checked into that in one of the books I got for the truck when I was trying to locate one.

I did change the coolant sensor, which was one of the first things I looked at but didn't fix the issue then. That was about a year ago.

This has been a long issue, haha.

Some other asked about my manifold maybe having a vacuum issue. But I would think that the truck would be decently loud and the issue would be constant even at idle. Seems that the truck is fine when it was in a warm garage. But getting outside in the cold for a couple minutes changes everything. Usually starting in the cold has the issue almost right away also. Could also just be coincidence.

Tiny
Tweekage
Jan 12, 2010.
I looked at the year and read it as 98. The 4.3L in the early 90's had a common issue with intake gaskets. I would spend some time rechecking that.

When I brought it into GM they said they checked for vacuum leaks and all. They never did mention gaskets or anything. I suppose I could recheck the gaskets then. Do you know which ones had the most common problems maybe?

Tiny
Tweekage
Jan 12, 2010.
The rear of the intake gasket. Do you have a vacuum gauge? If so, check manifold vacuum from any of the intake ports.

Let me know what you find.

Joe

Well I got a little daring and just sprayed some carb cleaner around the gaskets to see if I could get a burst of idle. Nothing.

Sooooo I just bought a full throttle body. Was noly about 65 bucks and looks to be in better shape than mine. So this weekend I'm going to work on installing that.

Honestly after this I can't see it being anything else haha. The last few days I couldnt even my truck over 55mph and it shakes quite a bit. So I don't think it's anything electrical (ground wise). Still cant see it being a fuel pump since it's pumping too much gas out. Figured the new fuel pressure regulator would hand that issue if it was one.

So when I have that installed. I'll let you know if it fixed it or not : )

Tiny
Tweekage
Jan 14, 2010.
Still a no go. Still has that terrible shaking bog at 45 mph on 3rd gear. Overdrive is even worse. Sometimes when it hits that bog now, it stays. Even at a stop.

Here I will update everything I have changed.

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.

The one thing I haven't checked yet is the ESC (Electronic Spark Controller I believe). Honestly, I couldn't tell you what else could be doing this. The issue seems to get worse and worse slowly.

I did spray the manifold with carb cleaner to see if the engine's idle would kick up. Nothing.

Tiny
Tweekage
Jan 15, 2010.
Someone from another forum mentioned if the timing chain was lose but it isn't.

The only thing I haven't tried yet was maybe getting new o-rings for the fuel lines that go into the throttle body and possibly getting a new ESC (Electronic spark control I believe)

Tiny
Tweekage
Jan 16, 2010.
Okay, it sounds like you have rebuilt the car. The ESC could be a problem, but I would think it would have set and engine code. I, like you, am really starting to get confused and I've done this for nearly 30 years.

I am going to ask for the recommendations of another tech that is excellent. AS far as the timing chain, it could be loose and having an affect on the timing, but why doesn't it do it all of the time (In all of the gears)?

Let me ask and see what he says before you spend anymore time or money.
Have you checked the crank sensor? I just read through your list before I sent this. Make sure it is clean and tight if you haven't already.
I'll be in touch.

Joe

Well it bogs all of the time. There are times where it runs good though. When all of this first started it wasn't really that bad. You could feel it but eh. That was about a year ago. Just sees that the longer I have this issue, the worse it's become.

Don't think I have checked a crank sensor. Not really sure this truck actually has this sensor. I suppose I could check and see. I'll hold off and see what you come up with. Thank you for your patients : ).

Tiny
Tweekage
Jan 17, 2010.
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