Car runs like it has a vac leak an no boost?

[dsmnthamakin]

Well i have done tons of searching an have found a couple helpful things but i am still at a loss. I have a 90 GSX mods are current on profile, and what is happening is when i start the car it reads like 15 in vac at idle till it warms up then it drops to about 10. will stay running but runs like crap. i found the taboo vacuum line elimination guide an routed everything as explained on guide, but still reading low vac. my question is when i unplugged my GM MAF the car almost seemed to run better. Could a bad MAF give a false vac leak? an another thing when i unhook the vac hose that goes from manifold to BOV my car used to shut off due to massive leak and since i did the work on the head it doesn't. could that be related to MAF too? Work that was done is as listed Cometic HG, ARP Headstuds, HKS 272 cams, V-Trim Turbo. All work done at the same time an still not running right..Also not producing any boost when i get on it it shoots to zero an makes no boost but i will post another thread for that. any help is appreciated.

 

[nlzn]

First you're gonna be at vacuum like that with big cams, welcome to my world .

If you've done the BLT and you have it hooked correctly is your MAFt set correctly? Unplugging it switches to your ecu to the default map.

 

[dsmnthamakin]

so im going to have vacuum loss due to bigger cams? I did not know that.

 

[dsm5062]

have you noticed if it is running very lean also? I just did the taboo vacuum delete on a running gsx and now it is acting exactly like you said your car is. Seems like giant leak that I can't find and driving it just shoots to zero not building any boost. I noticed on the wideband it is extremely lean. so if you find out a solution let me know.

 

[dsmnthamakin]

well im not running lean my wideband seems to read about 14.5 but i am still not getting any boost i had this problem when i tried putting on a super 20g an then i put my 14b back on an it boosted just fine now i put a v trim an have nothing even after i take off the hose from the wastegate.

 

[95fwdtsi18psi]

Blt Blt Blt

 

[92awddsm]

Fix the cam timing first. My fp4r cams make 12in/hg at 1100 idle. your 272's should make more than that at 850rpm idle.

As for boost issues, what style wg do you have? Same with the 20g? Do they have adjustable wg actuator arms(if internal)?

 

[dsmnthamakin]

yeah it has an adjustble wastgate actuator but shouldn't the boost spike way high if i undo the vac hose from actuator?

 

[92awddsm]

yeah it has an adjustble wastgate actuator but shouldn't the boost spike way high if i undo the vac hose from actuator?

If it is loose, it may cause really low boost. If your timing belt is off a couple or few teeth, and it has a loose wg actuator/flapper, it may cause no boost at all. First, double check all the timing marks and make sure it is correct

 

[dsmnthamakin]

i checked timing 3 times before i fired it up after headstud install an Hg but i will check again tommorow. if timing was off wouldn't valves hit? Also the actuator is not loose i have to pull it slightly to get it on the flapper arm.

 

[dsm5062]

UPDATE!!! Solved my problem,it was the mass air stopped reading correctly.Just put the new one on and it idled where it should,a/f is dead on Thank you God I missed my daily driver!! And if anyone needs one go to advance auto parts and ask for one from Rightchoice it's advance's own salvage yard, it only cost me $80. If anyone needs help getting one just PM me I am the commercial sales manager at the advance auto in berlin,md.

 

[dsmnthamakin]

see thats what i was wondering if my MAF could cause it? imma try and swap it out for another one. also did it take care of your boost not building?

 

[dsm5062]

Yeah the car is boosting like normal,I have been driving it for a few days and it is running better than it was before.

 

[dsmnthamakin]

alright so i got one of the 2 problems fixed. I cut out an egr block off plate an now i have BOOST.I need a tune but im boostin BABY. next does anybody kno about what my vacuum is supposed to be at. i installed HKS 272's an they told me it was going to drop vac. but when the car warms up it almost wants to stall. It reads just below 10 and i just did the taboo vac line removal so its pretty basic on where the lines run. it idles at about 1000 rpm im also running rich at idle do you guys think that would affect it that much?

 

[95fwdtsi18psi]

alright so i got one of the 2 problems fixed. I cut out an egr block off plate an now i have BOOST.I need a tune but im boostin BABY. next does anybody kno about what my vacuum is supposed to be at. i installed HKS 272's an they told me it was going to drop vac. but when the car warms up it almost wants to stall. It reads just below 10 and i just did the taboo vac line removal so its pretty basic on where the lines run. it idles at about 1000 rpm im also running rich at idle do you guys think that would affect it that much?

Below 10 is pretty steep, I don't have any experience with this cam in particular, but 12-14 would be decent I would say. You followed vac line removal per Taboo's diagram didn't you? Maybe something isn't plugged all the way or something.

 

[dsmnthamakin]

BOOM BABY... Vacuum is fixed at least i hope. i did a BLT and found some leaks. but it still did not fix it completely. So i went over to my CPS and i touched it an it moved causing the car to stall. The sensor was loose so i adjusted it, and boom my vac is up at about 14-17 in vac. Sounds good and idles just fine with that amazing lope that i have heard on so many other cars. Now i just need a tune.