Topic: Bogging! Any Ideas?

[YOguyDa]

Im at a loss. I feel like iv'e checked everything!

Needed to smog, so the weber had to go...

Rebuilt the stock carb, went for a test drive, started bucking and died 5 miles from the house as i was getting on the freeway. Started back up idled fine, wanted to die if i didn't baby it and coast, limped home.

Figured it was a sticky needle/seat, put back the original. No change.

Swapped in a combination of 4 different carbs for no change.

Found that my idle cut had lost power! Fixed it, idled ok, problem solved! NOT!! (this must have lost power sometime after the initial test drive, since it idled fine after it died getting on the on ramp)

Thats when i noticed the current symptom (which could have been the original problem rearing its head on the initial test drive and the idle cut losing power was just another stick in my spokes?)

Figured it was the egr since it leaked slightly when closed. Replaced, idled a little better, but no change to the current symptom.

Fuel level stays in the middle of the sight glass, timing is at 0*, wires ohm'd out fine, cap, rotor, plugs look fine. Advance seems to be working. Carb cleaner doesn't smooth it out when i keep it revved up in S*** mode, so i'm pretty sure it isn't a lean issue. Vacuum lines are routed correctly (c'mon now i live in CA).

Any ideas?

1986 reg cab, 22r, 5spd, federal emissions....

Here is a video of what my truck is doing:

[Steve_925]

link doesnt work for me

[tgmaul88]

me either

[nisota]

No good on the link.

[YOguyDa [OP]]

Videos should work now, sorry

[YOguyDa [OP]]

So, I tried a functional stock carb from another truck, and it confirmed that my rebuilt is fine... it ran the same as in the videos...

It runs great with the weber, s**t with the stock.... what's the difference?

Vacuum lines?

Cus pinching them one by one while its running like crap didn't change anything...

[Slolyfe]

I had an aftermarket fuel pump do the same to mine.

[YOguyDa [OP]]

What could be wrong with the fuel pump, that would make the stock carb run like that and the weber to run fine?

Does the minimum fuel pressure vary that much between the two?

[Marlin]

BigMike showed me your situation and I'd like to offer a suggestion.

My guess is that the EGR diaphragm is either opening too far or is flowing too much air.

Remove the small vacuum hose that goes to the top of the EGR valve (essentially disabling the EGR) and try it again. You wouldn't have noticed this with your webber because the webber does not provide a vacuum signal to the EGR valve.

You may be missing the orifice (a small crimped metal washer) located between the EGR and the head) and too much exhaust is entering the intake. With the EGR disabled, it should run like a top. Remove the EGR valve and replace that orifice.

You can also troubleshoot this by checking the temperature of the 90-degree elbow connecting the EGR to the intake manifold. It should be very hot due to how much exhaust is getting past it.

Let me know what happens with the vacuum source disconnected from the EGR valve, thanks.

Marlin

[YOguyDa [OP]]

Thanks for the reply marlin.

I've pulled and plugged what I believe to be every vacuum line in the engine bay, for no lead on the problem

It's going to be another hot one tomorrow,  but im going to try to make it over to where I'm storing my truck and tinker with it some more.

Ill let you know how it goes.

[BigMike]

I've pulled and plugged what I believe to be every vacuum line in the engine bay, for no lead on the problem

It still may be a ruptured EGR diaphragm which is letting exhaust bypass into the intake even with the vacuum source removed. Check the temperature of the pipe connecting the EGR valve to the intake manifold as Marlin described. If the EGR is properly closing and restricting hot exhaust gasses from passing, then the connecting pipe will more or less be the same temperature as the intake manifold.

Reading your opening post, my initial guess was an electrical issue, and I was going to mention either a bad igniter or a bad ground at the igniter (ie. as the RPMs increase so does the load/amperage through the electrical system, whereby a bad ground would handle low load levels but not high load levels). This happened on my MR2 when I had a normally aspirated engine in it, somewhere around 6,000 rpm and above the power band dropped off and it was running like crap. I added a few grounds in troubleshooting and it not only fixed the power loss but I also had a smoother idle. Ad a few misc temporary grounds: one to the block, one to the head, one to the alternator housing, and one to the body. It couldn't hurt and would be a quick way to trouble shoot a bad ground.

Good luck
BigMike

[YOguyDa [OP]]

I'll look into it.

I did replace the egr valve already, and pulling the vacuum line from the valve didn't change the condition.

The bottom line is that it runs and drives perfect, with plenty of power and a smooth idle with the weber... with the stock carb it idles smooth, revs fine, but bogs after a certain rpm...bucks while driving.

So I'm leaning towards emissions related since that's the difference between the 2 carbs.

I'll put the stock back on, plug off every vacuum line and even block off the pipe from the egr and see what happens, lol

[BigMike]

Check your PMs

[YOguyDa [OP]]

Well Marlin, you can pick up that long block whenever you want...

It passed smog

It seems to be underpowered, surgey and buckey with or without the egr functioning...its a little better without vacuum to the egr, but the weber would put the asain to shame with its power and responsiveness ... as its running right now. And that's saying something, lol.

Anyways, I bucked my truck to the smog station, warned them it bucked, laughed when I seen a guy weighing down the tailgate, and was suprised to find that it actually passed... and with good numbers too!

So, I'm still scratching my head, but at least I'm not pounding it against a wall anymore.

I can't believe the kindness you showed me and my truck today. I feel like I owe you more than an old longblock!

Hope you enjoyed the rest of your day, and make it home safe

[84toyota4x4sr5]

Have you checked the fuel level in the float bowl after it bucks and dies I had a truck that did something similar and it idled and revved up fine but when I would drive it under higher loads it would buck and die and it ended up being partially plugged fuel lines

[Kyle20r4spd]

Have you checked the fuel level in the float bowl after it bucks and dies I had a truck that did something similar and it idled and revved up fine but when I would drive it under higher loads it would buck and die and it ended up being partially plugged fuel lines

It might be the accelerator pump if it sputters and almost dies on acceleration It is definitely a weird situation. 84toyota4x4sr5 is right, check the fuel level in the sight glass as well it should only be half full, also blow out the fuel lines and check the fuel filter it could be clogged up so it is starving the engine of fuel. Have you checked the fuel tank? It could be dirty in there and is just clogging up the filter. That is what happened to mine it was full of sand