boba_buster57

Ok, well for the past about 3 weeks my car's performance has been steadily deteriorating and the check engine light has been on. It ran pretty ok for about the first week of the light being on, with occasional sputters and slight lurches when decelerating(and it seemed as though when I got these sputters and lurches, the check engine light would flicker in sync with the sputters and lurches). I tried to pull engine codes according to the online article that everyone uses, but for some reason after jumpering the connector and then grounding it to the batterie's neg terminal, and turning my key to the "on" position, my idiot panel lights-- including the check engine light-- would just stay on. No flashing whatsoever.

I decided to replace the vac lines and upper and mid intake gaskets-- not necessarily to get rid of the light or sputters, but just because I have been meaning to. I got every one of them except for the vac lines going to what I believe are the 5/6 port actuators that look like big dashpots in an awkward position underneath the lower manifold. They were being a total bitch to get off, and after trying to do so for a good 45 minutes and not making any headway at all, I thought that it's probably ok to not replace just those 2 lines. I put the manifolds and other things back on the car and started it up and my engine's pulse bobbed up and down in the 1100 to 1500 range. I was pissed and thought that I probably have an intake leak. I decided that it was probably because I did not brush any RTV sealer on the gaskets, and the mid intake manifold when I sat it on the lower manifold was very slightly off kilter, but since I haven't worked on cars much I didn't think it would be a bid deal if I put it on there tight enough.

It ran ok after that, but for about the past week to week and a half, when accellerating, especially when the car's cold, it runs really rough, almost as if the primaries are only spraying part of the time or something. Just within the last couple days, when I cold start and accellerate when it reaches the 3500-3800 rpm range, it sort of loses power like the 5/6 ports aren't opening, but as my car warms up, the problem gradually goes away.
This brings me to my theory:
I'm thinking when it's really cold in the mornings and I have bad compression, due to metals not being expanded yet, and also due to the intake leak, that maybe there is not enough of a vacuum for the port actuators to operate on, and as the car warms up and the compression gets better, there is more of a vacuum and the problem goes away.

What do you guys think? Other theories, suggestions, and/or comments?

flamin-roids

Check your sensors. Air flow sensor and what not. I had the exact same problem It turned out my thermosensos was unplugged. What work have you done on your car recently?

boba_buster57

Ok well since I'm not really that handy with cars.. Does anyone wanna let me know where the thermosensor is?

boosted1205

iTrader: (9)

Water thermo sesnor is below the alternator on the water pump housing.
It has a green colored injector type plug. You cannot miss it since it's the only one.
Look straight down and you'll see it. Even though it looks like it's connected, the clip could have come off the connector. Try push and tug on the wires.

Net Seven

iTrader: (5)

S5 ports run on the air pump, not vacuum.

To check for vacuum leaks you spray something like starter fluid or carb cleaner all around the areas where a possible leak could be, if the idle smooths out or changes then the leak is in that area. Then if something changes you probably dont got a leak.

boba_buster57

Thanks andrey.

WAYNE88N/A

Dude, if you can't figure out what the check engine light is trying to tell you, you need to go to the sensor inputs at the ECU and read them one by one during driving (if you just check them at idle per the FSM, you may not see anything wrong). Sooner or later you'll nail it if you leave the meter on each one for a while. Your list of suspects is also narrowed down because it will only be one of the sensors (or systems) that trigger a code. Most everything you need to know is in the "troubleshooting your car from the ECU" writeup. Do a search, I don't have the link on the 'puter I'm on right now...

WAYNE88N/A

Here ya go. Happy Thanksgiving

https://www.rx7club.com/showthread.p...leshooting+ECU