Idling at >2k, hesitation, bucking

[huguetguy]

I've noticed the above symptoms since getting my car back from the shop, and will be taking it back to them, but this is my 3rd time taking it back and I'm starting to lose confidence in their ability to diagnose and correct the problem...

my sig shows all the mods done to the car, and the new engine was just swapped in a couple weeks ago. since getting it back, the car died and had to have some more head work done, and I just got it back a week ago, and it's getting worse.

upon cold start, the engine stumbles around 1.1-1.2k rpm and I have to give it some gas to stabilize it...

If I'm driving in 4th gear around 40mph and tap the throttle a little, the engine bogs down and stumbles...

last night I drove home and it was doing all this stuff, and I thought I'd check how it started while warm - so i parked it, shut if off, and tried starting it. It just turned and turned, but wouldn't fire up. I tried a few times with that and I got worried - thought I'd have to get it towed again... but this morning I came out and it started up, with the same stumbling and problems as before...

does this indicate something common - would a vacuum leak cause this sort of behavior?

keep in mind, I don't have an EGR or an AIV - they're blocked off using a kit...

Dave

[QuinGarcia]

yeah, a vacuum leak could cause a high idle like you have, and a lean condition resulting in stumbling. Check all over the place for those vacuum leaks including in the intake tract after the mass airflow sensor. Maybe when you blocked off the egr and aiv you either misrouted, disconnected, or broke some vacuum lines.

[nismofan14]

Have you checked the MAFS. Mine went out a while back and it started out like what you are describing then it eventually got worse and quit all together.

[datkwikracer1]

i have the same problem kinda, i did a lil search so i wouldnt have to start a new post, since i know u all love that. anyways my 92 240sx w/ injen cai and a 2.5 in. custom exhaust and 147k miles will start to hesitate at 2300 rpm i think the vacuum lines are ok is there a way to check to make sure? it all started last thursday i usually warm up my car before i drive it but this particular time i got a booty call round 3 am so she wanted me there quick so i didnt warm it up and took off. it was cool i got there came back. the next day when i was going to work was when it started doing this it never happened before i dont know what it could be.

i am at best a novice mechanic but want to learn to do my own work. so any suggestions will be cool.

[datkwikracer1]

Quote »yeah, a vacuum leak could cause a high idle like you have, and a lean condition resulting in stumbling. Check all over the place for those vacuum leaks including in the intake tract after the mass airflow sensor. Maybe when you blocked off the egr and aiv you either misrouted, disconnected, or broke some vacuum lines.[/quote]

so what, do i check for sounds while the engine is on the rpms bounce between 700 and 450-500 could it be the feul pump, i replaced the feul filter round 2k mi. ago do i need any specialty tools to check this out?

thanx in advance

[QuinGarcia]

a bad vacuum leak can be heard with a hissing. But you should just look all over your engines rubber vacuum hoses and check for cracks. Also check the intake bellows (rubber accordion). CHECK everything for breaks or cracks. If you dont find anything try spraying some carb cleaner around the throttle body while the engine is running to see if the engine speed changes when you spray. Do the same thing where the intake meets the cyl head.

[s13EastTN]

If you spray WD40 around your vacuum hoses, if there is a leak the engine will rev up a little bit. If you feel bad about spraying WD-40, carb cleaner will do the same thing, but it will cause your engine to sputter instead of rev, either way it should tell ya.

[EDIT] WOW just noticed how old this thread was [/EDIT]