veedubbed

I swear......


I was having a problem with a slight misfire every couple seconds at idle, and the car was only pulling 12-13 inHg at idle. Well, I decided that I probably had a vac leak, so I started tearing everything apart. The only thing south of the TB seal/gaket wise that hadn't been replaced in the last 500 miles are the injector grommets. Well, I replaced them, and did the TB mod while I was in there.... JB Welded the holes, got them sanded super smooth. Put it all back together, and guess what. Even worse misfire at idle and still pulling the same vacuum.

I still have the BAC, but no coolant running through it. This might be part of my problem, but when I jump the initial set, my idle goes to 500 and won't come up off that no matter how much I open up the BAC. Also, the variable resistor must be all the way lean in order for the car to idle somewhat smooth without sounding like a cammed V8.

My AFM screw has been tampered with before I had the car and I haven't the slightest clue as to where it is supposed to be set, or how to get it there.

I also probably need a new set of plugs. These plugs came in the engine that I bought off here when I put it in 2 months ago.

I'm sure the two things above are contributing to my problem, but shouldn't have to do with why I am pulling such low vacuum. Any ideas on that one? Low compression? I wouldn't think the car would even run if it had low enough compression to only pull 12 inches. My vacuum source for the gauge is coming off the UIM by the TB, sourcing after the plates, if that matters.

RExy4jay

your compression doesn't have anything to do with vac...
i can't remember what mine pulled (inHG) at idle

if you have a vac leak get some ether and spray(while running) LIGHTLY under and around your manifold. don't spray it on your exhaust..BOOM you know when you find a leak cause the motor will surge

i used that trick to find my leaky O-rings at the bottom of my LIM

hope it helps

as for the backfiring and other craziness blame the weather ...everyones cars are messing up all the sudden

turboIIrotary

iTrader: (9)

my rx7 sounds like a cammed v8 and there nothing wrong with my car

veedubbed

I will go ahead and add that I have almost no vacuum lines at all. ACV/EGR blcoked off. Injector bleed and boost gauge running off the UIM byt the TB, rest of those nipples are capped. MAP/BOV running off the nipple under the BAC. I cannot find any leaks for the life of me.

scrip7

iTrader: (6)

Do NOT use ether or carb sprays to look for vacuum leaks. I hate when people do that. It not only isn't safe, especially with the heat of a rotary, but it isn't as useful to pinpoint the leak as propane is. An unlit propane torch can be used at the air filter to determine if the mixture is lean or rich to start with. If it's too lean, take the torch and start narrowing down where a leak is. Turbo hose cracks are common, oil injector vacuum spiders are another, injector grommets etc. When you put the torch near a leak the engine will run noticeably different. I modified my torch with fittings to attach a long piece of vac hose to it. That way you can put the hose end under the UIM to check the vac spider, lower intake-to-block gasket, etc.

veedubbed

I just went out and soaked the whole intake tract down with ether. Nothing revved, nothing ran smoother, same misfire filled idle, and same low vacuum. I will try the propane thing tomorrow, but this car is really starting to get on my nerves.


I have no oil injectors.... only vacuum lines on my car are MAP/BOV, boost gauge, injector bleed, and FPR. All of those lines are new and verified leak-free, that's why I don't understand where the hell this leak could be coming from.

scrip7

iTrader: (6)

Do you have an egr valve?....it could be sticking open at idle which will lower vacuum as well as dilute the a/f mixture. It is not supposed to be open at idle. Also, with the engine idling, pinch off each vacuum hose one at a time with a pair of needlenose pliers and see if you get any changes in idle quality. And you said the coolant hoses aren't connected to the BAC. It doesn't have anything to do with low vacuum. It is only used to circulate hot coolant to prevent the pintle in the BAC from icing up in cold ambient temps.

veedubbed

No EGR and no ACV.

I have capped off every vacuum line running from the intake and no difference. Still a rough idle and only 12-13 inches. Brand new intake gaskets, injector grommets/orings and everything. I have no idea where this thing could be leaking at. I forgot to mention that on decel, the gauge will read 24-25 inHg.

Propane to the intake made no difference at idle.

I hate this car.

scrip7

iTrader: (6)

Sounds like it's time for a compression check. If just one apex seal breaks, not only do you lose compression on 2 faces, but the ability to pull in an intake charge (vacuum) is reduced.

veedubbed

I guess compression could be low, but it doesn't feel like it. This motor is a heck of a lot stronger than my last one.

I did the PVC cap on the turbo deal, but that was completely useless because the air just blows right through the motor. I sprayed everything possible down with soapy water while doing this, but never saw any bubbles.

Also, when i jump the initial set to set the idle, the idle immediately drops to <500, and the car barely keeps itself running. It never once did that before I replaced the injector grommets/did the TB mod the other day.

alexdimen

iTrader: (13)

Nope. Compression and vacuum are almost always directly related, since it is the sealing ability between the engine internals that determines both.

You should be in the high teens as far as vacuum and above 100 psi on a compression tester.

The first thing I would do if I read low vac is test the compression. I don't understand why nobody ever does during diagnosis. It's the easiest thing to rule out!