TBI rebuild

[thinger2]

Tried setting my base idle today following the procedure. It was bouncing from 300-550 in gear with parking brake applied and IAC unplugged. Got it to 575 stablish and in park with the IAC unplugged, and up to ~650-700 in park with the IAC plugged in. I am no expert but i did not see a gap between the blades and the ports, meaning seems like fuel was just kinda pooling on top of the blades. Sounded much better idle but I dont think I resolved the issue with still a slight miss. I did notice my IAC plug was falling apart and may have been a bad connection (could hear erratic clicking while closing until I held connection in place then it was more consistent). I will redo my plug tomorrow, and order ESC pigtail and ICM to IC pigtail (anyone know rock auto part # for this?)

,tyler

Forgot to mention. The Dorman IAC plug that the online catalog claims does not fit your truck.
It does fit your IAC its a flaw in the online catalog.
Just notice it comes with 4 black wires so make sure you pay attention to which one goes where.
Ill see if if have the part number but Ive had it on my truck for over a year and it works just fine.

 

[thinger2]

I changed the firewall to frame with a 6 guage battery cable ( all autozone had) cause it was broke. I can get another and change the back of head to firewall also (still intact but in rough shape)

What's the symptoms if the firewall to head strap is bad?

https://www.autozone.com/batteries-starting-and-charging/battery-cable-and-lug/p/duralast-6-gauge-lawn-and-garden-switch-starter-cable/95947_0_0?cmpid=LIA:US:EN:AD:NL:1000000:BAC:71700000060662128&gclid=EAIaIQobChMI-4yv-v628gIVD21vBB3QvAfXEAQYASABEgKgufD_BwE&gclsrc=aw.ds

Plug fouling and misfires. The plugs ground into the head and the head grounds through the wire from the back of the head to a stud on the firewall then from that stud to the frame.
If that is bad, the plug finds ground through the head bolts to the block and through the block ground.
A much longer path and on a different "ground plane"
If that back of head ground is bad you may also see dash guage issues.
The basic idea for multiple grounds is to provide a short path to ground so ground doesnt find its way through the main bearings or the trans tailshaft or anything else that will get eaten up by that transient ground.
Steel plug to iron head to wire to steel frame is good.
Steel plug to head bolt to crank and cam bearings will disolve the bearings on its way to ground.
Look at it this way.
GM built them as cheap as they could.
If the accountants reluctantly agreed to put them in?
Those wires are the bare minimum they could get away with.
Dont ignore them, upgrade them.

 

[tsr2185]

Forgot to mention. The Dorman IAC plug that the online catalog claims does not fit your truck.
It does fit your IAC its a flaw in the online catalog.
Just notice it comes with 4 black wires so make sure you pay attention to which one goes where.
Ill see if if have the part number but Ive had it on my truck for over a year and it works just fine.

I got a acdelco plug, it had all black wires tho. Was pretty irritating to wire it in.

 

[tsr2185]

Plug fouling and misfires. The plugs ground into the head and the head grounds through the wire from the back of the head to a stud on the firewall then from that stud to the frame.
If that is bad, the plug finds ground through the head bolts to the block and through the block ground.
A much longer path and on a different "ground plane"
If that back of head ground is bad you may also see dash guage issues.
The basic idea for multiple grounds is to provide a short path to ground so ground doesnt find its way through the main bearings or the trans tailshaft or anything else that will get eaten up by that transient ground.
Steel plug to iron head to wire to steel frame is good.
Steel plug to head bolt to crank and cam bearings will disolve the bearings on its way to ground.
Look at it this way.
GM built them as cheap as they could.
If the accountants reluctantly agreed to put them in?
Those wires are the bare minimum they could get away with.
Dont ignore them, upgrade them.

I will definitely upgrade/change out that firewall to head strap. Is it ok to use the 6g battery wire at autozone? I was just gonna buy another to match the firewall to frame ground I put in.

 

[tsr2185]

Did you do the reset/ relearn procedure when you replace the IAC?
Did you do it with the engine hot and at 0 TDC?
Are you sure that number 1 piston is at TDC no matter what the timing mark reads.
They slip. They are known for it.
Pull the plugs, find TDC without referencing the timing mark.
Was the thermostat open when you did that?
Are you absolutely sure beyond a doubt that the distributor is not off one tooth and are you sure that is seated correctly and not moving on you.
Start from scratch.
Do it one step at a time and check it off the list.
All of the basic geometrys and rotations and timing need to be correct.
And wiring and vacuum etc..
Then all of the basic relearn and reset procedures need to be done in the proper order.
I think you are chasing a very basic problem somewhere in that process.

Did the relewen multiple times. Used tuner pro for rpm to set base idle and tps position too.

Honestly, when I installed the new distributer to get it running I just put it in as best orientation I can relating to original, and manually had to rotate it clockwise to even get it running. Assuming I skipped some teeth? Does that really screw it up even tho I used the timing gun at 0 mark? Do I need to pull it and get 1 at tdc and set the dizzy in to get it to point to #1?

I'm sorry of this is really stupid but I never thought about it or pulled dizzy to check since I installed it in dec

 

[thinger2]

Did the relewen multiple times. Used tuner pro for rpm to set base idle and tps position too.

Honestly, when I installed the new distributer to get it running I just put it in as best orientation I can relating to original, and manually had to rotate it clockwise to even get it running. Assuming I skipped some teeth? Does that really screw it up even tho I used the timing gun at 0 mark? Do I need to pull it and get 1 at tdc and set the dizzy in to get it to point to #1?

I'm sorry of this is really stupid but I never thought about it or pulled dizzy to check since I installed it in dec

Back to basics bud.
Pull the plugs,
Turn the crank untill you find TDC on number one either by sticking a plastic straw or a screwdriver or whatever into the plug hole.
TDC on the cpmpression ****** on number one.
Then look at the timing mark on the crank.
It should be at zero
The old school point the dist at number 1 doesnt really work on a TBI.
Look inside the dist.
You want the pointy parts to line up.
Ill get into that later if you need it
When you look at info on the web.
Make sure you are only looking at TBI info and not just generic chevy 350 info.
Same applies to any site.
Always look at TBI specific info and not ******** from somebody who sells scanners or doesnt even own a TBI.

 

[tsr2185]

Back to basics bud.
Pull the plugs,
Turn the crank untill you find TDC on number one either by sticking a plastic straw or a screwdriver or whatever into the plug hole.
TDC on the cpmpression ****** on number one.
Then look at the timing mark on the crank.
It should be at zero
The old school point the dist at number 1 doesnt really work on a TBI.
Look inside the dist.
You want the pointy parts to line up.
Ill get into that later if you need it
When you look at info on the web.
Make sure you are only looking at TBI info and not just generic chevy 350 info.
Same applies to any site.
Always look at TBI specific info and not ******** from somebody who sells scanners or doesnt even own a TBI.

Thanks man. So this whole ******* time could end up being cause the dizzy is a gear or so off, and I think I'm at 0deg...

I hope u are right, and I'm just another guy trying to do things I shouldnt be doing on a truck lol..

 

[CATman]

Thanks man. So this whole ******* time could end up being cause the dizzy is a gear or so off, and I think I'm at 0deg...

I hope u are right, and I'm just another guy trying to do things I shouldnt be doing on a truck lol..

I have been reading along this thread. Doing a rebuild of my tbi, exhaust manifold gaskets,and intake gasket. 95 7.4 L never been touched except for tune up parts. Thinger 2 is correct. Start with the basics, get the engine running as it should then do some modifications. I have been a Caterpillar diesel mechanic for 30 yrs, it is always best to go back to square one if you are chasing a problem. Just keep at it and you will find the issue. At least you are trying to do the work yourself instead of giving up and paying someone else to fix it. You don't learn anything by just sitting on the couch reading the internet. You got to get your hands dirty, scrap a few nuckles. Lol.
best of luck.

 

[Erik the Awful]

I've never heard of engine bearings getting eaten up by a lack of a grounding strap. I mean, it's feasible if you had everything on the engine insulated, the shift linkage was plastic, and the only ground path was through the driveshaft, but I've never seen it. I did just replace a choke cable on a Husqvarna because the engine was grounding through it. Still, you need the ground strap.

 

[tsr2185]

Back to basics bud.
Pull the plugs,
Turn the crank untill you find TDC on number one either by sticking a plastic straw or a screwdriver or whatever into the plug hole.
TDC on the cpmpression ****** on number one.
Then look at the timing mark on the crank.
It should be at zero
The old school point the dist at number 1 doesnt really work on a TBI.
Look inside the dist.
You want the pointy parts to line up.
Ill get into that later if you need it
When you look at info on the web.
Make sure you are only looking at TBI info and not just generic chevy 350 info.
Same applies to any site.
Always look at TBI specific info and not ******** from somebody who sells scanners or doesnt even own a TBI.

So I will do that hopefully next few days and get back with you...

So if I'm a gear or so off, even with the timing gun on cylinder 1 wire and esc unplugged and gun/HB says 0deg, it can actually be adv or ret substantially? Am I thinking right?

I'll get TDC on compression ****** cyl 1( confirm with comp guage and a straw)
Confirm my HB reads 0
Conform dizzy is pointed to 1
Confirm pointy things in dizzy line up.