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350 TBI engine stumble????--Update FIXED!!!!

T

tch777

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Colorado Springs, CO
Okay so the Suburban was due for plugs and some PM. It was running okay but felt flat on the highway no real git up and go if you punch it. And at times while idling I would get a minor stumble.

So I bought and changed the following:
new AC Delco plugs they were gapped at .038 which I figure okay with the new Accel coil.
Accel coil
Accel cap and rotor
Accel distributor module
Spark control module, the Factory stock replacement.
Fuel filter.
New radiator.
New HD fan Clutch.
New B&M stacked plate tranny cooler
New vaccum lines to the cruise, vaccum resivour, air cleaner and pcv.
new pcv.

Now after all this she starts up and purrs like a kitten. I top of the Anti freeze and tranny fluid.
Test drive that night runs really nice.
It sits for 1 day and the wife takes it for a spin.
Now every other time you punch it at like 35 MPH to get around some one it acts like it is out of gas, just about dies!!!!! And now this morning it starts up and sputters and chuggs like it is missing. Then it warms up and idles fine!?!? Then wify comes to see me at work and it is running really well takes a corner and it almost dies.
Guage says 1/2 a tank, but is acting like it is almost empty. Where should I look? Fuel pump? Sock filter in the fuel tank? I had a motor vac performed 3 years ago and they said fuel pressure was low. Told them to fix it and the next morning they called and said they double checked and fuel pressure was okay so they didn't work on it. Oh yeah when I changed cap and rotor I had to yank a couple wires that I could not swap over to the new cap so I used firing order and wire diagram to put back together. If I messed up order whouldn't it run crappy or miss all the time not just stumble erratically?

Help!?!?
Thanks sorry for the book but I wanted to give the details.

Oh PS plug wires were new 2 years ago 8.5mm Taylors.

Tim
 
Re: 350 TBI engine stumble????

Still may be wires... And if you messed up the order, it would run horrible all the time.

How long since you changed the TPS?

Also could be a worn timing chain.
 
Re: 350 TBI engine stumble????

My sub was doing what your decribing. It was because the gauge is jacked up'd. my gauge shows 1/4 and actually it's on empty. I would check your fuel system and your fuel guage.
 
Re: 350 TBI engine stumble????

I changed TPS, IAT, Knock sensor, temp sensor, and MAP 3 years or 30K miles ago. EGR valve and sensor were done last year. If I do swap plug wires who carries a set of straight plug boot wires verses those retarded 90 degree boots that you have to kill yourself getting off around the dip stick tube?

Thanks

Tim
 
Re: 350 TBI engine stumble????

Sounds like you are getting ready to need a fuel pump. My sub did the same thing and it turned out that the pump was starting to go bad. If the wires were in the wrong order it would have a constant miss or you may have water condensation in the cap.

bigred81
 
Re: 350 TBI engine stumble????

Well I dumped in 10 gallons of gas and it is still stumbling. So it is not empty. And the gauge on mine is messed up too if it reads 1/4 tank then I am on Empty. So I guess the next step is to get a fuel pressure gauge. The thing that gets me is the stumble was never occuring when I punched it before only at idle once and awhile then I did all the work to it. /forums/images/graemlins/doah.gif
Suppose I can check the cap and rotor to make sure there is no moisture in there too.

Thanks

Tim

Any other ideas???? /forums/images/graemlins/ears.gif /forums/images/graemlins/1zhelp.gif
 
Re: 350 TBI engine stumble????

I'd check the fuel pressure,sounds like the pump could be weak.But check your fuel first--you may have water in it,that will make an engine run lousy,especially when its cold--throw some isopropanol dry-gas in it and see if it improves.I know all you guys reading my posts probably think I blame water in the gas a lot--but I've found water in 90% of the vehicles we pull the tanks out to change the fuel pump or sending units--and I'm talking gallons,not just a pint or two--makes me wonder if the arabs that own all the gas stations around here are watering it down to"stretch" it--. /forums/images/graemlins/thinking.gifits happenned a lot recently in this area--maybe its the weather making it condense?? /forums/images/graemlins/dunno.gif.
We had one customer at a friends shop complain his truck ran lousy,especially on rainy days--he hadn't tuned it up for years,so he figured it needed plug wires,and a complete tune up--we did the tune up,and it still ran like squat!.We checked EVERYTHING and found no defects--until I smelled gas near the filler neck--it had about a six inch "slot" rusted away,right where the rear tire throws salt and sand at it!--we pulled the tank and tried to drain it--it was about half full of silt and mud,even some leaves got in it!--the owner bought a new tank since cleaning it would have been difficult,and it was rusty anyways---it left purring like a kitten.We tried lighting a sample of the gas with a match--it wouldnt even light--it put the match out!.I still dont know how it ran as good as it did!. /forums/images/graemlins/eek.gif /forums/images/graemlins/screwy.gif /forums/images/graemlins/screwy.gif
You could have a lot of other issues too--you'll have to try and narrow it down to fuel or ignition--I'm unfamiliar with TBI,havent owned one yet--I only know what I've seen my friend fix on later vehicles at his shop,you could have a bad sensor,or coil,and other things wrong--have you checked to see if it has any "codes" in the computer(had it scanned??). /forums/images/graemlins/thinking.gif
 
Re: 350 TBI engine stumble????

[ QUOTE ]
... takes a corner and it almost dies.

[/ QUOTE ]
When most people have a stumble problem when taking turns it's usually related to broken baffles in the tank.
 
Re: 350 TBI engine stumble????

Thanks for the suggestions guys. I will pick up some HEET and dump it in the SUB. It sat for a week without running when I did all that work. I am leaning towards just doing the fuel pump thou and fixing the sending unit while I am in there. I bet the baffles make a difference too when you punch it, because it will jump when you nail it then bog and stumble. I can see the spray pattern of the injectors on the TBI and see droplets form on the throttle butterflies I am betting the fuel pressure is low.

I will keep you posted on what works.

Tim
 
Re: 350 TBI engine stumble????

Update:

The tank is 1/2 full I dropped it today.
The baffles are fine.
Can't see any real debris in the tank, except for a little bit of grunge that dropped in when I took the pump out.
Added 2 bottles of Isopropal water remover.
Changed pump and strainer screen.

Result is a very smooth idle.
Same stumble and missing crap when you get on it from a stop or agressively ease into it at speed.
If I nail it while moving I get a stumble and hesitation but then hauls but. Basically the engine is running good at idle and WOT!
Tomorrow I will start replacing the parts I added with the stock parts, ESC, distributor module, coil.
Then if I am still having issues I will get another fuel filter and a new set of plug wires.
Then I will rebuild the TBI to make sure all the seals are good and what not.

Oh yeah and now it does not start good when the engine is warmed up, like when you go into the beer store then come back out. It cranks for a long time before it fires.

Any other ideas I am all /forums/images/graemlins/ears.gif.

Thanks

Tim
 
Re: 350 TBI engine stumble????

Well this morning my wife says change the coil out first, I have a feeling!

Changed it out and all is better.
Smooth idle, no more stumble or anything while driving.
Man I love that woman!!!! /forums/images/graemlins/waytogo.gif

So the Accel coil is messed up, must have some internal damage.
Guess I didn't need to do the fuel pump really. But I am glad I did I know I would have to sooner or later.
Hope this helps some one else out!!!

Thanks for all the ideas

Tim
 
Re: 350 TBI engine stumble????

A friend had lots of trouble with the Accel module he put in the HEI in his 62 Nova he built--the module looked like a peice of a transistor radio rather than the familiar "boomerang" GM stock style.It said on the package it would replace all 4 prong GM HEI modules,but the guy at the speed shop parts counter said it was meant only for an Accel distributor /forums/images/graemlins/confused.gif--we put an old used GM module from my parts pile in it and all the hard starts,pinging and poor performance woes went away.I dont have much love for Accel's parts,other than their caps and rotors.I've seen their wires fail in short order,and the spark plugs with their name on them seem to foul really easy--for the price they charge,you'd think it would be better quality stuff--. /forums/images/graemlins/thinking.gif
 
Re: 350 TBI engine stumble????

[ QUOTE ]
I dont have much love for any Accel's parts

[/ QUOTE ]
/forums/images/graemlins/whistling.giffixed it

The problem I was just having was caused by Accel cap and rotor failing in less than a year. The sparkwire contact fell off inside the rotor causing a missfire on one cylinder. Pain to find till I decided to change the distributor and found the problem /forums/images/graemlins/doah.gif should have looked there first.
 
Re: 350 TBI engine stumble????

Well it looks like the Accel distributor module I have is okay it is an exact replacement for the factory 8 pin in my SUB. I will keep the factory one in the tool box just in case. The Coil I can only exchange so I will see if the next one is better. This is a first for me Accel has always been quality parts before this. Maybe they have done some cost cutting over the years too. The last Acell cap and rotor lasted 3 years no issues. When I took it off it was just worn out at the contacts.

Tim
 
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