Bogged down While In Gear And Sputtered During Acceleration

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seabee

seabee

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Hello All,

Yesterday while driving I lost 50% of power and experienced a sputtered acceleration-giving it gas from stop it lurches forward then quickly sputtered and "coughed" but still moves. Everything has been running fine for 8 months and this is a daily driver.

When I put it in gear (a904) the manifold vacuum drops from 16 to about 7 and feels bogged down. While in park or neutral the engine idles and revs great.

To make sure it wasn't a carb (Eddy 1406) problem I pulled it and ran it through an ultrasonic cleaner, rebuilt and replaced the gaskets. Same thing. Idles and revs great but in gear it falls on it's face.

I also:
Disconnected the vacuum advance
adjusted the kick-down linkage
replaced the tranny filter and fluid
swapped plugs
Checked plug wires
tested voltage at regulator and ballast resistor.
Re-checked timing
Re-Checked valve lash
Did a propane bottle and carb cleaner vacuum leak test on the intake.

I am pretty sure I have eliminated this being a motor problem and now thinking converter or tranny. 8 months ago my 273 got a refreshed set of ported heads, cam, lifters, etc., increasing the compression HP etc. but nothing too racy, maybe an est. 250ish HP 273 that is driven daily and not hot-rodded. Until yesterday it has been running like a champ but I have noticed a slight harder "kick" when putting it into R or D over the last few weeks.

Any insight or advice is greatly appreciated.


Specs:
273, .473 lift cam 262 duration, eddy performer intake and 1406 carb, Mopar electronic Ignition and distributor, A904, 7 1/4 rear.
 
Sounds like you may possibly have low fuel pressure.
Is there any way to check it with a gauge?
Maybe the "sock" in the sending unit inside the tank has closed off.

Are you still running points, if so change the condensior in the distributor.

Not sure of the sudden loss in vacuum but the timing chain may have jumped.
 
A trans./converter issue won't usually cause the vacuum to drop that low. If it's not bad points like Sireland said it sounds like it's running lean. The "coughing" is clear evidence that it's misfiring whether it's due to ignition or fuel system related.

Related to rebuilding a carb, I realize you said you cleaned the carb but I've ran into them before that got crap in them that wouldn't come out easy. You should have blown it out with air. That will usually dislodge any foreign material in it and clear it out.
 
I'm thinking you have a carb problem at least. But I'm not familiar with yours to give any help there. Maybe something else is wrong too?
And vac probably is droping simply because the engine is put under a load.
What connection is there between the engine and trans that would cause a vac leak? No modulator circuit. Right?

http://www.forabodiesonly.com/mopar/showthread.php?t=194119
 
I vote fuel pressure, fuel delivery issue or possible bad gas. How old is the fuel? What is the coolant temp? Is the engine getting hot? The AVS carbs are known to boil fuel if things get too hot. What is the history of your trans?
 
Thanks for the replies, they are greatly appreciated.

The reason I keep thinking it is a trans problem is because the engine runs fine until put in gear, but now am leaning back towards the engine. No overheating, no missing while idling or revving. I got the gas that is in it now the day before the problem happened and drove about an 1/8th of that tank that day with no problems.

I'll check the fuel pressure today. I do know the tank is cruddy and regularly change out the fuel filter. The mechanical fuel pump has less than <1k on it.

The new timing chain and gears have <1K on them. If it were to skip a tooth wouldn't the timing at idle be off too?

I have a Mopar Electronic ignition (Orange Box) and distributor that have about 2k miles on them.

I don't have much for a trans/converter history. They came with the car 3.5 years ago and the fluid has always looked good over the 4k or so I have put on them . The filter and pan weren't too bad when I changed it yesterday.

Thanks again
 
Could be a problem with the ethanol in the new gas. If it separated in your tank, you'll have a big mess to clean up to fix it. I hope the problem is just the carb or fuel filter!

Good luck!
 
You say you have an MP Orange box. I don't know, just going off a whim, but maybe swap it out for the MP chrome box...

Do you have a fuel PSI gauge to monitor how much pressure you have?
 
seabee said:
I do know the tank is cruddy and regularly change out the fuel filter. The mechanical fuel pump has less than <1k on it.
Click to expand...

Just for grins, unhook your fuel line at the fuel pump and blow some air back through the line. If the sock is plugged this will help clean it out. See if it runs any better. If it does and the problem returns, it's time to clean the tank.

One of my Dad's old cars did this when I was a young pup and he carried a tire pump in the car. When it acted up he would blow the line out and it would run fine for quite a while then start acting up again. He did that for a week or two until he could get the car in and get the tank cleaned.
 
If the tank is passing crud it could have took out your fuel pump. It might pump enough to idle but not keep the bowlful at load. Plus edelbrocks are known to be more sensitive to dirt. Even though you cleaned it doesn't mean something still isn't clogged. Do you have a second carb to test to eliminate that issue? A filter befor the pump would protect it, I never understood why they never filtered before the pump.....
 
I'm going to be different then everybody else here only by a similar experience. I would do a tune up on it. My cuda did that after I bought it. She ran great in park or neutral. As soon as I put a load on it she would backfire and sputter really bad. It turned out to be the plug wires arcing to the block.
 
Fuel delivery or ignition box/coil/loose connections would be my guesses with seeing it.

Had a friend that had the +/- wires come loose at the coil. Car fired up and slowly lost power and would die.
 
Thanks for the replies guys. Just checked the Fuel Pressure and it was a steady 6.5 . I will put an extra fuel filter before the pump and recheck it again (great idea) I'm not ruling out something in the carb but when I disassembled it, ran everything through the ultrasonic cleaner, then blew 90psi through all the passages everything seemed and looked clear.

After lunch I'll recheck the coil and spark wires. Clean the connections to the ign box too.

Thanks again for insight. Hopefully it is something simple.
 
At night with the lights off, run it with the hood open to see if there's a spark show from any of the wires or coil. Then replace the affected wires as necessary.
 
If you are getting poor fuel volume from your tank from either clogged system or failing pump your carburetor bowl will typically be full at idle and when you go to moderately accelerate it will pull smooth for 5 - 10 seconds then the fuel supply issue will show up as the bowl full of fuel in the carb is gone and not being replenished quickly enough. Then once your running on diminished fuel volume, the car will bog, jump and jerk and possibly backfire up the carb.

Otherwise:

Be sure your ecu is grounded cleanly. Be sure your chassis, battery, engine grounds are great.

Check voltage at your ecu while under load by sticking a pin thru the + wire and running a extension to your voltage tester while you drive and a passenger monitors it.

Then check voltage at your coil while driving up a hill too.

I dont know what the voltages should be but I am estimating no less than 12 at the ECU and > 7 at the coil. Unless you have the original style ecu which has a 12 and a 5 volt supply.

If both voltages are good then replace the ecu and then the coil (hopefully with a spare you have lying around)

If it is missfiring and sputtering, it engine related. If it is simply loaded and bogged down but running smooth then I might suspect the drivetrain.

Is the e-brake on? J/K
 
Rice Nuker said:
Be sure your ecu is grounded cleanly.
Click to expand...

This. My car ran fine for years, one day, no start. Chased everything electrical and for some reason whatever space magic that ground it flew away. Re ground and off it went. Long story short, remove some of the Orange paint from the ECU. Its an easy one to eliminate and prevent future hair pulling.
 
Tonight I rechecked the volts and grounds to the coil,ecu,starter relay, and VR. Everything tested as it was before this happened. I swapped in another coil too. No chAnge yet.

Here is something i forgot to mention earlier and the main reason i pulled and rebuilt the carb. The passenger side air/fuel screw wasn't affecting the idle but it did in the past. Before pulling the carb i had shot air and choke cleaner through it many times to make sure it wasn't clogged but no change. When i took the carb apart and checked the A/f mixture passage it was clear and clean. After reinstalling the carb it still doesn't affect the idle. Driver side does.

Sorry for the long-winded thread. Maybe tomorrow I will take a video and post it here.
 
seabee said:
Tonight I rechecked the volts and grounds to the coil,ecu,starter relay, and VR. Everything tested as it was before this happened. I swapped in another coil too. No chAnge yet.

Here is something i forgot to mention earlier and the main reason i pulled and rebuilt the carb. The passenger side air/fuel screw wasn't affecting the idle but it did in the past. Before pulling the carb i had shot air and choke cleaner through it many times to make sure it wasn't clogged but no change. When i took the carb apart and checked the A/f mixture passage it was clear and clean. After reinstalling the carb it still doesn't affect the idle. Driver side does.

Sorry for the long-winded thread. Maybe tomorrow I will take a video and post it here.
Click to expand...

If there is no effect them something is wrong. Do you have a different carb to try out? How old is the carb and what is its history?

I bought a motor that came with a 600 edelbrock that the owner had set way to rich (black smoke at cruse). When I leaned it out it would bog and hesitate on shifts (manual trans in this case). I tuned and tuned on that thing and could not get the bog to go away. A new 600 Holley later and it was gone. Only other thing you could do is take it apart and soak it in carb cleaner for a few days. If it's used who knows what someone has done to it.
 
The idle mixture screw not working is a sure sign the problem is carburetor related. The idle mixture screws not only affect idle mixture but off idle cruise. When you rebuilt it did you take the boosters out and blow air through all the holes in them also? There are small orifices on the boosters (bleeds). Make sure their all open.
 
it has some thing to do with the fuel had a friends 64 Buick here last year and it ran like that replaced the fuel line blew air back in to the tank and retuned the carb, Eddlebrock
 
Well this should shed some light. Will report back later....

A8E5CCC7-1336-41EF-A497-72D72A34F42F-2064-000002D87030F00A_zps4c7d27b3.jpg
 
If the throttle plates are open too far at idle via the idle speed screw (to compensate for a big cam, or not enough initial timing) the engine will pull fuel through the main venturies and the idle mixture screws will become ineffective. It is possible that you are right on the edge of this and one barrel is pulling fuel through the main venturi. You can see this by looking down the primaries with a good light at the boosters while the engine is idling.
 
d55dave said:
If the throttle plates are open too far at idle via the idle speed screw (to compensate for a big cam, or not enough initial timing) the engine will pull fuel through the main venturies and the idle mixture screws will become ineffective. It is possible that you are right on the edge of this and one barrel is pulling fuel through the main venturi. You can see this by looking down the primaries with a good light at the boosters while the engine is idling.
Click to expand...


This is exactly what I first thought was happening. I've adjusted the idle screw while looking down the primaries and no fuel coming from the mains.

It's a real stumper. This carb is bare-metal clean in every little crevice too.
 
Was definitely the carb. Put the Holley on and now getting 20 Vac at idle. Took a short drive around the col de sac and no stumbling. Now I have to get a different kick down linkage and throttle cable.

Thanks so much for the input.
 
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