2000 3800SC swap question (Page 1/2)
Lou6t4gto JAN 19, 03:24 PM
Here Tis: I swapped in a 2000 GP 3800SC and 4t65e-hd about 4 years ago. (other people's projects has gotten ahead of mine, so here I am 4 years later). car " starts", idles, but "SURGES" and wants to stall. I put in new fuel filter,(55psi Pressure) Cleaned all lines, removed all the injectors and internally "cleaned them" for proper spray pattern, checked all the wiring for hot to pink and pulse to other ( they are all fine). ordered a new IAC. (they're cheap). What could cause the "SURGING" ??? vacuum ?? Thanks for the help.
Lou6t4gto JAN 20, 12:26 PM
no suggestions on this ??? map ? something to "TRY" ? would Low reading on Map cause this ??
Lou6t4gto JAN 20, 12:33 PM
this engine is bone stock, still has the EGR present
OntarioKev JAN 20, 01:23 PM
Bad MAF could cause idle issues. Also do a smoke/boost leak test, its amazing what they turn up.

Did you replace the injector O-rings when you removed and re-installed them?
DimeMachine JAN 20, 06:08 PM
N/A

[This message has been edited by DimeMachine (edited 02-06-2020).]

Lou6t4gto JAN 20, 06:28 PM
new "O" rings installed. no 'Codes present. any way to TEST the MAF ?? (those are expensive little buggers, just to try to replace and not be it). already replaced MAP with a used good one I had.
OntarioKev JAN 20, 06:31 PM
Your not gonna like the answer Lou...

A very basic test you can unplug the MAF sensor and see if it runs better (this will throw a DTC, just clear it after re-attaching).

Best way to check the MAF is with a scanner live reading the airflow and seeing if it performs as expected... very low at idle with some constant changing a small bit, increases as RPM increase.
Lou6t4gto JAN 20, 07:30 PM
so, IF I "unplug it" and it IDLES better", and does Not Surge and stall, it should BE the MAF ? Correct ? If it Makes "NO difference" with it unplugged, it's not. just speaking of "IDLE Quality". it REVS fine.
OntarioKev JAN 20, 11:17 PM
If you unplug it and it idles much better it could be the MAF. It could also be a fairly large vacuum leak....

With the MAF unplugged it will switch to VE tables and run off of IAT/MAP readings. So if there is a large vacuum leak, it would run better as the map sensor would register that, where the MAF sensor cant read any air that enters after its placement.

Pressured smoke tester would be a good idea to use.
Lou6t4gto JAN 22, 04:47 PM
I do happen to have a Smoke Can "setup", I'll give that a try as soon as the weather warms up a little. (yes, this is Fla, but last 2 weeks we've had frost at night.