progress on my truck, but have some questions

[noom14921992]

1989 Chevy c1500 with 5.7 and 700r4 transmission.
Previous owner was evil to this truck. so many clipped wires and broken plastic. its just a shame.

*** the work done already ***

the main thing was a blown head gasket. my friend and i got that taken care of.
1.We did a full engine rebuild with all the gaskets and honing and all that.
2. we replaced the timing chain and water pump at the same time.
3. new distributor, wires, spark plugs and coil
4. new IAC
5. New fuel pump
6. new starter
7. new fly wheel
8. new rear main seal
9. replace a bunch of broken electrical connectors
10. new coolant hoses.

this is just part 1 of the truck. i plan to do all the other stuff also. but i want to getting it running well first.

*** where we are at ***

The truck start and runs great. we drove it around the block and it shifts wonderfully ( previous owner installed new ( rebuilt ) transmission ).
My friend even thinks it is way "stronger" than his 5.7 sierra. that does not matter.

basically, my friend said the truck is healthy.

*** the issue ***

The truck has a very slight surge at idle. I do not have a tach but it sounds like its just a few hundred RPM dip every 10 seconds or so. This is just based off of my ear. so take that how you will.
But it start right up, idles fine other than the slight surge and it never dies and you can rev it with no bogging down and you can blip the throttle and it again revs and does not bog down and goes back to there it should.

*** the question ***
With all the parts that have been replaces and the work that has been done, where should i look next?
would a slight idle down be electrical, mechanical, fuel related, spark related, computer/sensor related or what?

I am just trying to get some information from the hive mind.
I am not sure how to add a short video.



Thank you!

 

[Das Hatt]

Check for vacuum leaks. Along the intake manifold, egr, brake booster hose, etc.

 

[Hipster]

You said a rebuild but what is that? magnafluxing, full machine work, etc, some consider a rebuilt a can of spray paint. Let's start in the proper place. What is rebuilt to you? There are more questions then answers at this point.

 

[noom14921992]

friend did a smoke test on the intake and it had no leaks.
all the rubber tubes are new.

how do you check to see if egr is bad?

 

[noom14921992]

You said a rebuild but what is that? magnafluxing, full machine work, etc, some consider a rebuilt a can of spray paint. Let's start in the proper place. What is rebuilt to you? There are more questions then answers at this point.

All the gaskets and seals on the engine were replaced. We took it down to the block and replaced all the gaskets and seals.
the heads were machined.
put it all back together.
we reused all the internals like rockers, cam push rods.
we just replaced anything that was a gasket or was rubber.

we have proper compression on all cylinders. average was like 140/150psi. cant remember off hand.

 

[Schurkey]

No pistons? No rings? No bearings?

More of a re-seal + some accessories, than a rebuild.

In MY driveway, it'd get the usual scan-tool analysis, plus an ignition oscilloscope/cylinder balance test.

 

[noom14921992]

No pistons? No rings? No bearings?

More of a re-seal + some accessories, than a rebuild.

In MY driveway, it'd get the usual scan-tool analysis, plus an ignition oscilloscope/cylinder balance test.

that fair.
i got the truck for cheap cheap cheap.
i wanted to just get it running before i decided what i wanted to do with it.

the truck is an 89 so no scan tool. and the blink lights dont give me any codes.

 

[Komet]

There exists the ability to datalog an '89 ecm. At the very least, get some live data. And a tach. I would also do the IAC reset procedure as per the factory service manual.

 

[Schurkey]

the truck is an 89 so no scan tool. and the blink lights dont give me any codes.

Of course you can connect a scan tool to an '89.

Scan tools go back to the first years of computer control--that's how the dealership fixed 'em when they were new.

 

[noom14921992]

Of course you can connect a scan tool to an '89.

Scan tools go back to the first years of computer control--that's how the dealership fixed 'em when they were new.

I have only ever heard of the "scan tool" that you plug in and it just gives you blink codes.
I guess I am just a dummy. Haha
But some kind of data and live info would be nice.

Any preference on brand or model?