Stuttering/Hesitation/down on power & I kinda got electrocuted a little ;(

RacingTurtles

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Hi there folks,
So I am diagnosing some issues with my Burb and could use some help.
Prepare for the shitshow.

It is a 1990 GMC suburban with the 5.7L/350 backed by a 700r4.
Out of all my cars, that is the last running vehicle I have right now.
Everything else is down for some kind of maintenance/repairs, so I really need to get this running right.
I have always gotten the puff of smoke on startup, but no continous oil burning. So I'm thinking some valve oil seal is the culprit there.


PROBLEM(S)
Now that it's gotten colder it has taken longer to start up. Sometimes it just doesnt. But I am able to start it if I tap/floor the throttle while it cranks.
It has some kind of hesitation sometimes at idle and other times when I'm on the gas.
It has only started recently, like the past month or so.
I have noticed that it seems to come an go. I can start it and drive to work (8 miles) without issue. Other times it'll sputter around from the get go all the way to work.
Originally this started as an issue with idle. Per my sunpro tach, I usually idle at 1200 on startup and then it drops to around 850-900.
Lately it's been skipping a beat and drops to 700-750 then back up to 850-900.
Then it'll randomly miss and lose power as I'm full throttle on occasion.

Latest issue from the last time I drove it. I was coming home from my mountain house which is about 80 miles from my residence.
Around 5 miles away it got really bad. Sounded like marbles in a tin can shaking around the engine bay. It was not happening at partial throttle, only at 50% or more.
No backfiring as far as I can tell, just down on power. I have a Check engine light on the cluster and it never flashes during the stutters or anything.
On my other cars it usually flashes if it misfires, not even sure this thing has a "code" for it.


HISTORY
So I got this in 2018.
I see from my receipts that I did some tuneup type stuff to get it running as it was probably abandoned in a field somewhere and it probably didnt run for a few years.

June 2018
-I did a new fuel tank, pump, filter ( K7N), all new hoses.
-New Spark plug wires, AC Delco 9618V, I believe which was done correctly.
-New spark plugs Bosch 9659, factory gap at .054" (ROCKAUTO description says do not gap)
-Distributor cap, Airtex/wells 3D1046A
-I'm not sure about distributor rotor (wasn't present in the same receipt as above)

October 2018
-I do recall resealing the injectors with a gasket/rebuild kit for the tbi system. I used the entire kit.
I do have a video if needed on how the injectors were spraying before I did the new gaskets. I don't have anything after, but I can take off my air filter and record how it is spraying now.


I do see that the spark plug wire organizers are not there.
Some of the wires were touching my exhaust.
I was wearing my gloves and thought "huh thats kinda close", and moved the wire to see the white burnt deposit of the silicone insulation on the exhaust manifold.
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It's been an intermittent stutter so I thought "alright let's turn on the engine and see if it stutters when I jiggle the wire".
Luckily I had my rubber gloves on. I got zapped when I touched the wire and it made me tighten my grip for a second or two before I let go.
So the wires need to be replaced. I ordered some NGK wires and they showed up with different lengths.

REPAIR IDEAS
1. Definitely replacing the spark plug wires.
2. May do the spark plugs themselves, got some AC delco R44TS which come at the .044" gap that people seem to like here.
3. May need to do the actual distributor rotor, but since it is happening randomly, I don't think that's it. I'll still buy the rotor and keep it ready to go.
4. Could be the injectors themselves. Not a lot of choices for replacement parts.
 

gmbellew

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plug gaps should 0.035".

I'd start with plugs/wires.

easy enough to inspect cap and rotor. replace if needed.
 
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85K304SPD

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Cap and rotor will corrode, even if you don't use the truck. Do the cap and rotor with the wires and the plugs.
 

Originalthor

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There's also a little screen on the distributor that collects dirt and will cause condensation inside the cap and rotor. If it's all corroded inside there thats why when checking it out.
 

Snoots

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Plug gap for an HEI is .045".
Look at your plugs first. If they look okay, put 'em back in.
Change your plug wires one-at-a-time.
I'd bet your problem lies with the wires.
You can get high-temp sleeves for the wires where they are close to the exhaust.
 
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RacingTurtles

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Thanks for the replies folks.
Definitely going to get the new wires put on this weekend. If not then new plugs. If not then the new distributor rotor and cap.
Kind of strange to get so many different lengths from the wire kit.
One would assume there would be 4 lengths, with 2 of each.

2 - 39.5"
1 - 35.5"
2-31.25"
3-25.5"

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RacingTurtles

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Hey folks,
I wanted to provide an update on this.
On friday I changed the spark plugs and wires. No change.
Saturday I changed the distributor cap, rotor, and ignition module. At this point, the air filter assembly is removed so it ran perfectly fine.
I also noticed a hose was disconnected from my purge canister (from the gas tank), so I connected that back up.
After reassembly, it still seemed to be sucking for air.
Sunday morning, I changed the air filter out and it seems to run very good, although not as nice as without the filter.
My plugs didn't look too great either, I'll have to take a pic of them.

Idle needs to be adjusted. It used to have a 1200 rpm cold idle and then drop to 800 rpm.
Now it seems to hang around 800 no matter what.

I also seem to have significant rust buildup on the distributor shaft.
My distributor cap had a lot of corrosion internally.
The rotor was also pretty stuck on the shaft too.
That is definitely going to have to be changed out.


I'm also hearing a ticking noise coming from the rear of the engine.
It sounds consistent with the rpms but sometimes it goes away completely, so it makes me think it's something physically loose and rattling around.
Definitely coming from the rear of the block, can't determine if it's passenger or drivers side.


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Gardendelite

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Don't recall you saying what the mileage is? I have a 94 burb, had a stumble that a new distributor fixed. My first thought was timing chain needs replaced. A worn chain can affect timing.
 

Rusty Nail

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Looks like you need a new distributor.

"the air filter assembly is removed so it ran perfectly fine"

" a hose was disconnected from my purge canister "

This thread needs moar pix.

Pix of the connections at the air filter housing and connections at the purge canister.


They share a connection or no?

" I am able to start it if I tap/floor the throttle while it cranks."
 

RacingTurtles

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Engine Size
350 tbi
Don't recall you saying what the mileage is? I have a 94 burb, had a stumble that a new distributor fixed. My first thought was timing chain needs replaced. A worn chain can affect timing.

Mileage is 176,*** miles. It's got the 6 digit odometer so I know that for sure. No idea on if/when previous owners ever changed out the distributor. I definitely need to change that out. I'm really hoping the chain is ok, I've been very good about changing oil every few months, whether or not I even hit 3,000 miles. I use Mobil1 full synthetic 10w-30. I know it's no AMSOIL but it's way cheaper to keep changing it out this way.
Looks like you need a new distributor.

"the air filter assembly is removed so it ran perfectly fine"

" a hose was disconnected from my purge canister "

This thread needs moar pix.

Pix of the connections at the air filter housing and connections at the purge canister.


They share a connection or no?

" I am able to start it if I tap/floor the throttle while it cranks."

Yes sir, I'm genuinely surprised it even runs like that. When I changed the cap and rotor 3-4 years, I don't remember if it looked like it does now. Anyway, that's the next job.
I can get ya more pix if you really want them lol.

Just for clarification:

"the air filter assembly is removed so it ran perfectly fine" - during my maintenance over that weekend, I had to remove the air filter cover, accordion tube, and the air filter itself so I could access the distributor easily. I started the engine at that point ( hood open, parts removed as listed above) while it was in my driveway and it idled like I expected it to. Normally I have it all installed.
" a hose was disconnected from my purge canister " - After finishing up the work, I was double checking everything in the engine bay, specifically the TBI system. I noticed an empty vac line connection at the front of the TBI and I had a vac line that was on the drivers side of the engine bay just hanging out. There is a sticker that I happened to glance at and it showed the connection from that huge cylinder (purge canister?) located in the engine bay, front drivers side to the TBI. I connected it back up and even used some heatshrink to keep it in place.



" I am able to start it if I tap/floor the throttle while it cranks." - This mainly for cold weather starts. Also see below link

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