90 Beretta GT 3.1L rough idle

[1988GTU]

Pesky coils

[robertisaar]

and your choppy idle is explained.

you have a vacuum leak or the throttle is being forced so far open, the ECM has run less than 10* of advance to try and keep the engine from overrunning at idle. this is in addition to running the IAC nearly fully closed.

INT pegged its upper limit as soon as closed loop was allowed and never moved from there, so the ECM was adding a LOT of fuel, considering you mentioned it running better after about 2 minutes(closed loop happened at ~139 seconds) would make sense that there is a lot of unexpected air getting to the engine.

[DukenukemX]

See thing is I can't find the vacuum leak that maybe causing this problem. I took a can of carb cleaner and went all over the engine with it to see if there was a change in idle. I'll get a video of the stopper to show what's it doing.

[3400-95-Modified]

I think what he is telling you is the stopper issues is the vac leak because that meas the TB plate is getting pulled open at idle which it should not be.

[robertisaar]

either that(which is most certainly a problem) or there is a leak in a non-typical place, like the PCV valve being stuck open at idle, or the line to the MAP sensor being cracked(this happened on the wife's 90GP).

[DukenukemX]

Ok uploaded a video of me checking the engine with a can of carb cleaner. I think I found the leak and fixed it with gasket maker, but still seems to idle rough. Robertisaar I haven't checked the line going to the map sensor. Kinda forgot this car even has that. In the 15 years I've owned this car, I've never had this engine idle smooth. Maybe the very nature of the 60 degree v6? I'll get another data stream to see if it's truly fixed.

http://www.youtube.com/watch?v=7ekulmUSN1U&feature=youtu.be

[1988GTU]

You check the pcv HOSE? Check the FPR? Fuel is NOT supposed to be pouring out of the vacuum line off the fpr.

[robertisaar]

grab a log when possible.

see what happens when you remove the oil filler cap when idling as well. if there is a noticable change from doing that, you'll get to replace the PCV on the rear valve cover.

i didn't see fuel coming out of the vacuum line in the video, but it would be a good thing to check.

LH0s can most certainly idle smooth.

[DukenukemX]

Well the pcv was changed a few months ago, with a Delco part too. Removing the oil cap didn't change how the engine ran. I'll have to double check to see if the line pours out some fuel. About 7 years ago the fuel pressure regular was just dumping fuel into the throttle. Don't know how fast these regulators go bad.

Tomorrow I'll double check the vacuum line to see if there's any fuel. I have the log with the vacuum fixed, but engine still idle's rough when starting cold.

[robertisaar]

closed loop correction is still dumping in a ton of fuel, but not as much as before. INT settled at 156 before BLM started moving around.

up to ~5 IAC counts while idling, spark is still riding near 10*.

so, something is still letting in a lot of air, but there is marked improvement.

[1988GTU]

Well the pcv was changed a few months ago, with a Delco part too. Removing the oil cap didn't change how the engine ran. I'll have to double check to see if the line pours out some fuel. About 7 years ago the fuel pressure regular was just dumping fuel into the throttle. Don't know how fast these regulators go bad.

Tomorrow I'll double check the vacuum line to see if there's any fuel. I have the log with the vacuum fixed, but engine still idle's rough when starting cold.

pcv hose too?

[DukenukemX]

pcv hose too?

PCV was in great shape when I last looked at it. That's a 23 year old hose too. PCV hose going to plenum still has the clamp on there, as I make sure to reuse it. Still a pain in the ass to remove the hose and the pcv from it. So it's tight, but I'll double check it. Could the valve cover gaskets have anything to do with this? When I removed the oil cap it would make a sucking noise as I removed it. The engine didn't change in idle though.

I'll have to dig deep to find this air leak. Is it possibly that the exhaust may play a roll in this?

[3400-95-Modified]

Have you determined what the TB blade is doing when its running since you have questioned the throttle stop?

[DukenukemX]

Have you determined what the TB blade is doing when its running since you have questioned the throttle stop?

Yea it turns out it's the "thing" next to the battery. I'm guessing it controls the cruise control in the car. It's on a bracket, and it closes the gap on the stopper if I push against the bracket. I guess at some point the bracket was leaned on by someone and it would hold the throttle slightly open. I figured this out when I tried to find a vacuum leak today.

I started to wonder about the IAT sensor, the one sits on the intake. I've never changed this sensor and wonder if that's effecting the reading of high air flow. Cause I've been all over the engine and can't find a leak.

[robertisaar]

it gives off reasonable values in the log(starts at ~77*F) and changes predictably.. i wouldn't bother with it.