Ok, So i've talked with NA SVT about this on FB, but i hate to bother the poor guy constantly. I did a 4V swap into my '98 GT (yes, hate me, i do not actually own an SVT product :bash: ) the engine came out of my buddies totalled '96 Mystic. swap went well, car has run great since October, then i had this great idea to remove the IMRC butterflys and have my tuner change some things up, to see if i could pull a little more HP out of it in the upper RPM range. did a little online searching, found the removal and install info, so i got to work. gaskets were reusable, GREAT! got it apart, pulled the IMRC's, removed the butterflies, put it all back together with a little RTV, car started and ran like shit. only pulling 2-5" of vacuum off the intake. found i had some vacuums mixed up, fixed them, and nothing. took it all back apart again, bought new IMRC to head gaskets thinking that was the issue, went ahead and removed the shaft and epoxied the holes shut(the shaft holes have been checked for leaks and are solid) put some RTV on the gaskets let them sit for 4 hours slapped it back together and BAM, same issue, 2"vacuum. tore it down the third time, bought all new gaskets from the intake runners up. put it together, same deal, 5"vacuum. i have ordered another set of IMRC gaskets, thinking (praying) maybe the RTV wasn't set and i screwed it up. so i will be removing it for the 4th time today and i'm curious if anybody can offer help. i am throwing a P0171/0174, which leads me to believe theres still a leak causing me to suck in unmetered air and the car beliwve i'm running lean. i'm just curious if you guys can think of anything else that could possibly be my issue. EGR gasket is new, PCV works properly, Idle stays constant at 900/1000, so i don't believe it to be the IAC. (I also put in all new plugs while i was at it) i guess i'm just looking for somebody to throw out some possibilities. yes, i did also torque the intake down to 22ftlbs in what i thought was the order. i later found out that was removal order, however, i don't believe that, that is the cause of such low Vacuum, though i will use the new torque sequence this time around. :cuss:
IMRC delete/Vacuum leak questions
- Thread starter schiffy
- Start date
You sure you purchased the right plugs? Did you gap them correctly?
It was doing this before the plug swap. I bought them pregapped to see if it would help and it didnt. Could a bad wire possibly cause an issue resulting in low vacuum?
You say you bought them pregapped but did you actually check them?
No,
If your IMRC butterfly bores are sealed, then its something dumb. I don't think a tiny leak in the IMRC gaskets would kill vacuum that much. The intake isn't sitting right or you have some plumbing messed up on the intake.
Try the cigar trick to see where it is leaking: https://www.youtube.com/watch?v=zMok2y05jNE
Bad plugs would give you a misfire DTC, not a lean DTC.
do not rtv the gaskets.
Low vacuum is being caused by a leak somewhere, either the gaskets (IMRC, manifold-upper or lower), vacuum lines, IAC or TB.
An air leak prior to the TB but after the MAF will cause idle problems but the vacuum will not be affected as much.
tq sequence isn't critical with these gaskets; I rarely pay attention to it.
can you post a pic of the inside of your intake?
Low vacuum is being caused by a leak somewhere, either the gaskets (IMRC, manifold-upper or lower), vacuum lines, IAC or TB.
An air leak prior to the TB but after the MAF will cause idle problems but the vacuum will not be affected as much.
tq sequence isn't critical with these gaskets; I rarely pay attention to it.
can you post a pic of the inside of your intake?
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Inside, as in, where the runners are, or to see what year intake we're talking about as far as the 2 bolts inside under the lid? i'll look and see if i have any on my phone, otherwise i'll have to take some when i take it back apart again.
just went through my phone, i have a few pictures of the intake, but from the front angle, not top down shots. Is it possible for the IAC to be leaking somehow unnoticeable to the eye, yet the idle stay steady at about 900?
I may give that a shot this afternoon, but holy hell that dude is something else! LOL
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