aack

Hi everyone,

I know there is tons of topics already online about this, but I have gone through all of them and I still have this problem, so i'm looking for some new ideas.

Ever sense I bought my car, I have noticed this this very small but annoying intermittent engine stumble at idle. It's very minor and most people probably wouldn't notice it until driving the car for awhile. Combined with the strange shake at idle, it also seems to stutter/sputter just a little when accelerating from 2 to 3k. After that, it revs nice and the car feels good. When it comes to the shake, it comes and goes. 80% of the time it's always there but sometimes I will notice there is no shake.

Here is what I have done(all new): fuel pump, fuel filter, injectors(thought it fixed at first but didn't), distributor, spark wires, & brake booster valve. I have also checked plugs(they looked new but didn't check gap), cleaned maf, checked timing, checked engine grounds, adjusted TPS, cleaned throttle body and IACV. When I bought the car it had a check engine light for knock sensor and EGR. Thought that was for sure my problem but changed knock sensor and found the vacuum line that connected the two EGR valves had a hole so changed it. Codes went away but the shake did not.

I have done a lot of work and the problem still persists. I've narrowed it down to a few options so let me know if you think any of them could be it.

Maybe a bad connection somewhere? I've checked all the connectors in my engine bay to make sure they were clean, but I have not gone though with a multi-meter and check all the voltages.

Dirty EGR or AIV? Like I said, the vacuum line that connected the two EGR valves had a big hole. The engine bay was very dirty before I cleaned it so maybe a dirty EGR? I haven't touched the AIV, I just don't feel these equipments could make any difference.

Vacuum leak in the intake manifold gasket or around there? There is no sign of vacuum leaks, or at least none that I can hear. I've fished my hand through as many of those rat nest lines in the back of the engine as I could and haven't felt any holes. I have not tried to spray carb cleaner to find any leaks because i'm scared it will damage the vacuum hoses.

Engine mounts? I've inspected all my mounts and they all look pretty new and not torn. I will say my tranny mount shakes super SUPER bad which is something I will fix soon. But because my problem is intermittent and comes and goes, I don't think that would be my mounts.

I honestly don't know what it could be. My gut from the start says it's a vacuum leak, but I really don't feel like pulling my intake manifold off and doing all the gaskets. It just seems like an annoying job especially with all that vacuum stuff in the back and the EGR. I can maybe try new plugs but not confident that's it. Anyway, let me know what you think or if you have any other ideas. Any info is greatly appreciated!

jedi03

to help us help you...engine, mods, tune, chassis...but common things if its under power spark, fuel and air and calculations to correct...you could also perform compression check, run engine cleaner such as seafoam, use better fuel, many ideas, you got some good ones covered tho and if you think vacuum leak spray carb cleaner or similar around the engine and see if theres a change in idle.

aack

Sorry, completely forgot about specifying a car. It's a 1993 240sx, KA24DE completely stock.

Done a compression check, had perfect 185 across the board. I run the best fuel I can get at the pump in California which is 91. I have not tired seafoam so will probably try and do that.