I've been having an ongoing issue with a surging idle while the car is warm and cold. I have replaced the 02 sensor,coolent sensor,pcv valve,egr is blocked off, replaced the TPS and set to .54, removed cleaned and adjusted the IAC, new distributor,plugs and wires. Today i also removed and cleaned the MAF sensor(which iss definned and descreened, not sure if that causesed a problem) and that helps somewhat but still not 100%. A few months back i had to replace the lower intake gasket that had a vacuum leak. Car was always lean with the lower intake leak but the AF is on the money now and only shows a little lean idle in park or neutral,under a load its fine. If I watch the wide band 02 sensor the lean condition follows the surging. So I'm thinking it maybe a small vacuum leak i've missed or a bad MAF sensor? I'm not a real DIY Prom guy but I was told the GPS for the MAF should be between 4-8, I've attached a datalog with shows my maf grams at idle between 10-12? I've also attached my bin. Please take a look at my datalog and bin and let me know what you guys think might cause this lean/surging at idle?? thanks a lot! mods in sig.

 

anyone get a chance to look at the datalog at idle? Any insight would be great thanks.

 

From what i remember with my tuning/datalogs with my 383HSR before it was stolen was that around idle i was seeing prob around 10grams/sec on the MAF. The surging idle could be a few things. First thing that comes to mind is again a vacumm leak. Have you tried finding if there was a leak? using propane or something else around the intake etc to see if you can get the RPMS to raise up enough to find the leak.
How much is it surging?
1.) what are your IAC counts at idle when theres surging?
2.) what is your A/F ratio when surging?
3.) what are your injector pulse widths when surging?
4.) there are stall correctors in the tables for things like AC and other things that can raise the RPMS. I would check to make sure you have those tables turned off etc.
5.) what about timing that is in the surge area? if the timing is dead steady it will surge.

 

your IAC counts 35-70 dont seem that bad and are actually pretty fine... perhaps getting them down below 60 would help.

WHen u tried to find vacumm leaks how did u look for them? Ive tried the propane thing and it didnt work for me so ive always had issues trying to find vacume leaks.

Im wondering if it could be the MAF being the culprit... when you cut the fins u can sometimes disturb the flow across the meter. Also did you touch the idle RPM tables that i gave you in the bin at all? and at what idle are you idling at when its surging and how much is it surging?

 

I looked for the vacuum leak with carb cleaner. It didnt change my idle and wont be using it again because it wasnt good on my powder coating. I will give the propane a try and see if I have any luck finding leaks with that. I have been suspecting my MAF sensor. I removed the screens and fins years ago but who knows. I disconnected the MAF and the car wont run without it so it does work to some degree. I'm going to borrow a friends MAF sensor this week and see how the car idles with his. It surges a pretty lot on a cold start, like from 1500 to 800rpms. After a few mins it gets better once it ghets alittle warm..surges like 850 to 1200 when warm. When its in gear it only surges from 800-1000.

 

before messing with the tune, try resetting the min air

http://sethirdgen.org/minair.htm

then reset the tps

http://sethirdgen.org/tps.htm

 

yea the carb cleaner is a NONO! its too abrasive. perhaps starting fluid? just keep it away from hot exhaust lol. You know what would work actually? Sea foam! it has a straw now and everything and if you get it in a vacume leak/source you should get white smoke out the tailpipes! thats a sure sign of a vacume leak.

test the MAF and also test the vacumm leaks and let us know. thats ALOT of surging... i was thinking it was only like 50-200rpms.

 

he said he reset both, TPS to .54V which is fine and the IAC counts are low enough where it wouldnt be an issue.

Perhaps lowering the IAC counts alittle bit would be better? try to get them around 0-40counts.