Ruff idle, low vac.

[bigburban]

Sooooo as some of you might know, I got into another gtp a few weeks ago witha few mods already done, one of which is a comp vs cam.

To make a long story short it's always had an idle on the ruff side, but I was thinking it was due to the cam. But after listening to some idle on YouTube I started thinking that isn't the case and I have an issue. My symptoms are a ruff idle and a rich smelling exhaust.

This weekend I changed the plugs and wires in hopes to help, which it didn't do lol. Today, after I was installing my new matching radio and amp, I decided to unplug the maf like bill suggests to see if it smooths out, which it did. So now I know I have an issue somewhere. I pulled out my new to me scan tool and see what I can figure out. First I am getting the p0300 code for random misfires. I checked the parameters and noticed a few things, first of which is at idle, in park, I am seeing -15inhg (increases to 17-18 with maf unplugged). I also noticed I get a lot of misfires at idle, all of which go away as soon as I take off, most of them seem to occcur on cylinders 2 and 4. Anyways, sprayed carb cleaner on the lim and got the idle to jump a little when I sprayed around cylinder number 4, but it wasn't very noticeable.

Should I replace both the lim and maf? The fact that it smoothed out with the maf unplugged makes me think it's bad, but maybe it's just the lim. Also what inhg should I see at Idle?

[WolvesSoulZ]

15in/hg is too low.

Spaying around the cyl 4 part of the lim could be the vacuum hose going to the MAP sensor, hose might be due to change, check around there and see.

[bigburban]

Good suggestion. I just checked and it looks like its fine. I found no noticeable cracks or dryrot

[WolvesSoulZ]

It only takes a pinhole sometimes. Considering your car is a 1999, if they weren't ever changed... The hard part that connects to the map, or the hose or whatever, could be leaking.

Billboost will surely come around at some point to guide you more than me.

[Seachicken]

bigger cam = less vacum, can somone runnin a vs cam chime in on how much vacume they have,

im sure you still have a vac leak if you got the idle to jump a bit

how long ago was the cam installed?

[sseilmnop]

bigger cam = less vacum, can somone runnin a vs cam chime in on how much vacume they have,

im sure you still have a vac leak if you got the idle to jump a bit

how long ago was the cam installed?

VS cam for 5 years
17 for vacuum
No misfires
Smooth idle not rough.

[sseilmnop]

I've had misfires in past and it was vacuum lines. Found with hand vacuum pump.

[bigburban]

Took a vid this morning and uploaded it to photobucket.. Still trying to figure out how to post it here lol

[bigburban]

http://i1120.photobucket.com/albums/...ps18c0f7ef.mp4


lmk if that works

[BillBoost37]

1. Get the pcm programmed. Remove P0300
2. When the PCM see's misfires it works to fix things
3. Did I miss which cam this is?
4. Was the pcm programmed with lots of fuel at idle in order to get rid of the surging that some have an issue with at cold idle?

[bigburban]

1. Get the pcm programmed. Remove P0300
2. When the PCM see's misfires it works to fix things
3. Did I miss which cam this is?
4. Was the pcm programmed with lots of fuel at idle in order to get rid of the surging that some have an issue with at cold idle?

afaik, it has never been tuned, its the factory tuning... I do have a slight manifold tick that for the most part goes away when its hot. I was planning on replacing that when I do headers, but if thats causing my issues maybe Ill just do it now.. also its a vs cam

[bigburban]

fwiw, the p0300 didnt come back last night after I cleared the codes. Ill check and see if its pending now

[bigburban]

Its back.. Just in pending for now

[Ryan99639]

mines doing the same thing since I bought it like two months ago I replaced plugs and wires, didn't fix it, found a vacuum line disconnected so I plugged it back in thinking that the problem would be gone but nope still there , it surges hard at idle and sometimes the flashlights dim down from Roma slowing down so much . I'm getting a p0300 and p1380 code that come right back when cleared with my scan gauge, so I'm stuck I'm getting so sick of buying new parts and not fixing the problem

[Ryan99639]

dash lights ***** lol autocorrect ... not flashlights

[bigburban]

What is your scan gauge showing as far as in/hg at idle?

[bigburban]

I'm gonna replace the lim gasket next weekend

[Ryan99639]

what's in/hg sorry lol I should know this

[bigburban]

Vac at idle

[Ryan99639]

o ok it's usually somewhere between -14 to -18 at idle on my mechanical boost gauge I'll have to check the aeroforce to be exact