87 tbi 350 popping at idle and running rich

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Ricko1966

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And your methodology will give zero results,unless he ponies up and buys an old snap on red brick. I was just pointing out he can test the sensors with a multimeter, a 2nd way to skin the cat.
 
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77Dmax

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Forward progress here has stopped.
 

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From personal experience with an '87 TBI...

You can run a few degrees of advance on the timing. I was somewhere around 8 degrees until I set it back to zero for the installation of the stage 1 chip.

There was originally an air pump that injected air into the exhaust manifolds to help the catalytic convertor work. The computer is set up for that to all be functional and it will never run 100 percent correctly with parts of that system disabled...UNLESS a custom chip is installed.

Are the original exhaust manifolds still on the engine?

Hear me out on this one...

Even with the air pump disabled air can and will still get into the manifolds unless it gets blocked off somewhere. With my manual transmission I had popping and backfiring between shifts no matter how smoothly I tried to drive it. I finally figured out I needed to block the air in the smog system even though the belt for the smog pump was not there to spin the pump.

The O2 sensor gives feedback to a computer that is programmed for a single, restrictive exhaust and a constant supply of fresh air from that smog pump. You can make great improvements replacing parts of the system, the MAP sensor, the knock sensor, the ignition module, the entire distributor... and yes you may think it is "running right" but it really isn't.


The OP still has a couple things to change and he may indeed have a serious vacuum leak somewhere or some internal engine issue.

My motor ran well enough to use and enjoy but it was not perfect with the original program. I drove mine for 3 years quite happily but I changed pretty much every electronic component before I finally installed a chip.

And please don't include me in the Pissing Contest. I want no part of it.
 

Ricko1966

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If you want to test the sensors and do not have access to a scanner with data logging. Find your coolant temperature sensor unplug it,check resistance with the engine stone cold, make a note of what your outside temperature is,disconnect the wire to the cts read the resistance. Write it down. Hook the wire back up, warm up the engine,turn it off,disconnect,check resistance again, leave the meter hooked up watch the resistance change as the engine cools noting any abnormal readings. If it went up and down with no glitch it is probably fine they usually stick and don't move. You can look up resistance at temperature cold and resistance at temperature hot and make an educated decision as to whether it's good . Intake air temperature sensor pull it out, note your outside temperature,check resistance,put it in the refridgerator,wait,check resistance,leave your meter attached let it come to room temperature ,watch for smooth resistance changes.Compare your three temperatures with a restance chart. The map sensor make sure you have a 5 volt reference wire and a ground,the other wire is your signal wire,key on engine off check voltage from the signal wire to a good ground,apply vacuum,watch for voltage change, if you have a vacuum pump it's better because you can use measured vacuum and check voltage at a given vacuum at 0 vacuum you should have 4.7 volts, at 20 inches 1.1 volts. With all these tests, tapping on the sensor gently with the back end of a wrench may give you a jumpy reading indicating a glitchy sensor. A lot like testing gauge senders.
 
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Vbb199

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Theres no IAT on tbi trucks

However heres a nice chart for resistance values and their relationship to engine temp.
You must be registered for see images attach
 

Vbb199

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For the guy insisting OP get a cable and computer -

You're part of the reason people just rip the TBI off and replace it for a carb.
Thats overcomplicating THE HELL out of a simple system.

You literally need a mighty vac handheld, a DMM, a basic manual and a brain to diagnose these systems , almost 9/10 times

Its a 100-400 baud rate system. Its slow as ****, and doesnt capture bugs or blips hardly AT ALL on data stream.
This isnt GM obd2 @ 1000+ baud rate or whatever that captures milliseconds
 

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I have typed this a few times on this forum so I apologize to those that are tired of reading it.

In 1987 there was no internet, there were magazines and there were rumors. GM had been installing TBI on the Camaro and Firebird for a few years, TPI was already on IROCs and Trans Ams but the trucks were still running carbureted 305s. I clearly remember driving my grandfather's beautiful '83 Silverado with its anemic 160 horsepower and 2.77 (I think) final drive. It was so slow...and it got about 13 mpg on the interstate. That truck "rode like a Cadillac", looked beautiful and was very reliable. But it was soooo slooooow.

Rumors of the '87 trucks getting fuel injection and a 350!!! had me wanting one so badly I could taste it. I was so excited, I cannot properly express it now. It simply makes no sense in today's Information NOW!!! world.

I finally got my '87 4wd with a TBI 350. I know these systems worked reliably back then, I know the parts still exist to keep them going. I have not ever considered going to a carburetor for this truck.

And to be clear, if I had found a decent '73 to '86 with a carburetor instead of this truck I would happily be running a carburetor.
 

Rustisbest

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How is plugging into the OBD port, entering some vehicle information and reading what's on the screen complicated?

I've got an older Autoxray scanner that I bought cheap years ago and has cords that work with everything. I considered it a good investment. Is there something I'm missing?
 

Redfish

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How is plugging into the OBD port, entering some vehicle information and reading what's on the screen complicated?

I've got an older Autoxray scanner that I bought cheap years ago and has cords that work with everything. I considered it a good investment. Is there something I'm missing?
I am not positive on this and I know someone will correct me...

The system on the '87 TBI is Very Primitive. If there is no check engine light (the OP did not say he was getting one) then there is no code to read and no information to be read by a scanner tool. If there was a check engine light the codes can be read by using a paper clip jumper wire and then deciphering the blinks of the check engine light.
 

Rustisbest

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I am not positive on this and I know someone will correct me...

The system on the '87 TBI is Very Primitive. If there is no check engine light (the OP did not say he was getting one) then there is no code to read and no information to be read by a scanner tool. If there was a check engine light the codes can be read by using a paper clip jumper wire and then deciphering the blinks of the check engine light.
I didn't know that about the 87's. It shows live data on dad's 92 Suburban. I just assumed they were the same. Good to know
 

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not knocking using a DMM, but if you can find a 1320 electronics or red river devil Bluetooth scanner and have a Droid phone with ALDLDroid, it gives you a lot more info than just the trouble codes and is very user friendly. here is my home screen on that app, but it shows even more data. and you can log data and export to an excel file.

I am sitting on the couch. so that's all just default app info displayed. before somebody tells me I have a lot of problems :)
 

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Vbb199

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To be clear, i as well have the equipment to diagnose and monitor an OBD1 system's live stream.

Im not saying its over the top for an individual to use-

Im saying the average truck owner with a tbi isnt going to have the patience or knowledge to get all involved in a technical level. Hell most people dont even know how to use a DMM. A laptop, cable or app is WAY over the top for most people
 

gmbellew

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To be clear, i as well have the equipment to diagnose and monitor an OBD1 system's live stream.

Im not saying its over the top for an individual to use-

Im saying the average truck owner with a tbi isnt going to have the patience or knowledge to get all involved in a technical level. Hell most people dont even know how to use a DMM. A laptop, cable or app is WAY over the top for most people

no doubt! no way I could use tuner pro or the more complicated software without a steep learning curve. I think ALDLDroid is about as user friendly as you can get for a non-mechanic like me. but even with ALDLDroid, you still need a vacuum gauge, timing light, DMM, and other tools in the toolbox.
 

Redfish

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I am just Happy to be Here. And even happier to have this forum with its vast resources to help me keep my Old Truck running. I appreciate all of you.

This is one subject where I can at least contribute some knowledge. I will leave the complicated stuff to those of you who are good at it.
 

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