New & in need of advice

Thanks Everyone for all the great suggestions I installed a new single wire 02 sensor and it ran great for about two minutes and then it started backfiring again so I’m now in the middle of installing a three wire heated o2 sensor fingers crossed this is the issue. I had a muffler shop install all the piping for the exhaust after I installed the headers, I’ll look into the idea of a blockage tomorrow morning, thanks for the heads up C10MixMaster, that never crossed my mind. My TBI didn’t have a smog pump on it from the start. I did install a new set of Accel shorty header spark plugs, i to thought I might have cracked a plug along the way some how, still backfire but idles much smooth now at least. Tomorrow morning i’ll finish installing the heated O2 sensor, check the rest of my vacuum lines, fuel lines and I’ll change the fuel filter just for the heck of it after all that hopefully I’ll have some good news to pass along. Thank you again everybody for your input I really appreciate your help.

If you have been messin with an old Chevy long enough to end up HERE? There is no question you belong homeboy, you are ALREADY DOWN.


I had a couple of thoughts.

One was that song..it seems that you're having some trouble in dealing with these changes.

1-8-4-3-6-5-7-2

That was another...

I read you verified the plug wire routing but maybe you could check it again?

Jeepndan said:

Seem to run sporadically better after letting it warm up for 15 or more minutes tried that out this morning, just kept a medium to high idle going, seems to take off better but backfire and stutter now at 30-40mph.

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This.
This is the HARD STOP. Your trouble lies HERE and we need only to decipher what your LO5 is trying to say with it's new for '91 powered metal timing components and 30 spline axles. Wait..


SPORADICALLY better. Like how, exactly?

https://www.dictionary.com/browse/sporadically

You must first check the coolant level and report your findings here.

15 minutes to maintain a medium to high idle is 100% unacceptable and WRONG. Is a thermostat installed?


30-40 miles per hour. Torque convertor lockup is at 42....do you run in "D" or "O-D" ?

READER: What happens in an LO5 at 30-40mph ?
Depends.
Is the THERMOSTAT opened OR closed?
Is a proper fuel return available? because fuel , returns or is certainly intended to.
Operating temp?
Verified gauge accuracy?

Look, if the computer runs it cold and it's choking out because it CANNOT return that gas then yeah, it's gonna pop and stutter.

Hook a scanner to it and see what temperature the computer THINKS the coolant is.

You want to fix it or does your plan include throwing more parts at it? I vote we stop spending money until we have an target. The TBI was updated to provide improved fuel metering in 1991..

Lookin at you ignition module and thermostat mounted coolant switch (that ground) - BUT I AM WAAAAY more interested in the gauge's sender that WAS DISTURBED while installing headers.
Disturbed?

That could cause ALL of these symptoms and you REALLY SHOULD check it out and POST A GAWDDANGED PICTURE. GRR!

If you've been lurking around then YOU KNEW THAT WAS COMIN!

Your camshaft did NOT develop a flat lobe...You will NOT find solution in an 02 sensor regardless of how many wires it has..

The Heep, the small block, whatever! Pictures or GTFO.

Let's shoot for a pix of the sending unit on the driver side cylinder head between numbers 3 and 5! Pix.
Little green wire attached like a speaker terminal?
Pix.

Spade connector. Female.

Hope this helps!

He said "Disturbed"!
You ******. Get up!

Thank you Rusty Nail For the new insight on other areas to check out today. Yes it does have a thermostat in it, water level is good where it should be right at the top. Operating temperature is 197 to 200 wee bit warm but it is a brand new motor with only 300 miles on it. I will look at the gauge center unit the moment I get back to the garage, I didn’t realize that would affect the symptoms I am incurring. I comment for sporadically better, When the engine is cold or first started it idols beautiful and the moment you apply the throttle it backfires and will not move forward without great difficulty sputtering and backfiring, revving the RPMs up in park for 10 to 15 minutes then trying to drive off it will but only sporadically better.

All these issues develop the moment the headers were installed, I will first check that sending unit between number three and five cylinder head that was a great suggestion thank you.

I’ll repost my findings this evening hopefully I have good news and yes I’ll try to pot a few pictures on here, thanks again everyone.

Is your TPS sensor the adjustable type? I'm also wondering what you have your ignition timing set at? And was the distributor clamp bolt tightened down enough? An electronically controlled engine will do some real funky stuff if the timing is way off.

The plot thickens..installed new 3 wire o2 sensor, checked all vacuum lines, sensors hands on. Now it starts, runs and drives with-out backfiring but has a miss fire when I go to accelerate. I decided to check for codes, though the engine check light has not come on but I must have be blind because it has 15,22,24,42,43 and 44. 6 codes. I’m thinking 42 is the product of 15 or 22. The really strange thing is, I had No codes before the install of the headers. So I ether I burnt all those connections (visually they look fine) or ?

I’m completely stumped!!

Bucket, the timing is set to 0 degrees, and no the TPS is none adjustable. Distributor is tight, ran perfect before header install.

I <3 auto repair over the internet.

Hey @bucket - clock me out when you wrap up, will ya?

Jeepndan said:

The plot thickens..installed new 3 wire o2 sensor, checked all vacuum lines, sensors hands on. Now it starts, runs and drives with-out backfiring but has a miss fire when I go to accelerate. I decided to check for codes, though the engine check light has not come on but I must have be blind because it has 15,22,24,42,43 and 44. 6 codes. I’m thinking 42 is the product of 15 or 22. The really strange thing is, I had No codes before the install of the headers. So I ether I burnt all those connections (visually they look fine) or ?

I’m completely stumped!!

Bucket, the timing is set to 0 degrees, and no the TPS is none adjustable. Distributor is tight, ran perfect before header install.

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With the older GM stuff, you always try to diagnose the lower numerical code first. I don't remember what code 15 is though, lol.

When you do get this issue figured out, go ahead and set the base timing to 8-12 degrees advanced, the engine will be much happier. With your fresh engine, 12 degrees should be no problem on 87 octane.

Thank you Bucket....When I can get it back to normal operations, I’ll give that a try, though I do know anything past 8 degrees advanced will not pass smog in California. But that is only ever 2 years I need to run that smog gauntlet.

Dang. 8°...

Oh yeah, code 15 is coolant temp sensor. That's most certainly the issue to look into first. If the harness checks out ok, put another sensor in it. I've seen new replacements fail in short order before. It's sad, but it happens.

Well I installed the 3 wire O2 sensor finally, (funny how life get in the way of working on your project) made a little difference, no more backfiring but now it stalls out when Idling and it has no power. I’m going to have a shop take a peek at it, I feel like I’m running around in circles at the moment, fix one thing and something else goes out. I checked all the code, and there is no way I have 6 codes going out all at once, I did find a 20amp fuse blown and my amp are only reading 10amp now. I think I have a short or a ground wire off somewhere.
I’ll post what the shop finds wrong with it.
Thanks for all the support this far. Nice to know their are so many helpful people out n about who will take time out of their schedule to lend a hand/idea to help a total stranger.
Thanks everyone!!

Jeepndan said:

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Well I installed the 3 wire O2 sensor finally, (funny how life get in the way of working on your project) made a little difference, no more backfiring but now it stalls out when Idling and it has no power. I’m going to have a shop take a peek at it, I feel like I’m running around in circles at the moment, fix one thing and something else goes out. I checked all the code, and there is no way I have 6 codes going out all at once, I did find a 20amp fuse blown and my amp are only reading 10amp now. I think I have a short or a ground wire off somewhere.
I’ll post what the shop finds wrong with it.
Thanks for all the support this far. Nice to know their are so many helpful people out n about who will take time out of their schedule to lend a hand/idea to help a total stranger.
Thanks everyone!!

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Sorry it has to go to a shop. But your persistence is awesome.

Hello gentlemen, drum roll please!!!
The Ignition module was causing all the issues I had experienced. You would figure a brand new distributor maybe 2 months old would have held up better, it was an AC Delco I purchased on RockAuto as an original stock replacement.

Thank you everyone for all your great suggestions, I’ll keep an eye on this form and visit often to lend any advice I may be able to offer. Wish everyone a fantastic weekend.

Hello everyone I’m not sure if this will reach those who help me in the beginning with my TBI 350/O2 sensor check engine light issues and pour running. I’ve been working on this diligently since July of this year and finally figured it out, it appeared that two ground wires were not reattached after the motor & transmission were rebuilt and re-installed, so this was the cause to all the issues and false readings from the O2 sensor and the engine running poorly. Thank you again everybody for your assistance and help and ideas most of all. wish you all well