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.

no suggestions on this ??? map ? something to "TRY" ? would Low reading on Map cause this ??

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?

N/A

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

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.

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.

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.

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.

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.

As I live in Canada, I don't feel bad for you Florida people forvwhat you consider cold

yea, we do have good weather here, but in Canada you DON'T have to put up with Twump !. LOL

quote Originally posted by Lou6t4gto: yea, we do have good weather here, but in Canada you DON'T have to put up with Twump !. LOL

4 sure, Trump is not ideal. But remember, our choice was either Twump or Clinton 2.0....

going to try the New IAC today. really does sound like it could be a Vacuum leak( and it is "hunting" trying to correct it). if that doesn't do it, I'll use the "smoke can" on it.

new IAC, seems better, but still surges sometimes. no vacuum leaks found