Okay, took it out last night about 20 minutes around the neighborhood. Didn't go over 25 or out of 2nd. I got it warmed up obviously. By the end of the drive, I had the car in the driveway idling without the heater/AC or lights on (just the dash lights/parking lights) and had it idling at 1000rpm and vacuum was between 16-18! Now, I adjusted the idle via the screw under the TB. However, after I got it to 1000, I would tap the gas to maybe 1600 and it would come back down, but to about 1200. Am I supposed to be jumping some terminals before I adjust that air screw so that I don't have any electronics trying to work against me like the ISC or TPS? Also, when driving...about 15-20 mph, staying constant on the throttle at about 1500rpm, and it would be bucking or stumbling...what are your thoughts? Weather the idle is 700, 800, 900, 1000 etc...it's always a smooth idle. I don't think I have low compression...oh...BTW, there was quite a bit of dark smoke from the exhaust initially before driving it...not white or blue...smelled like fuel/exhaust....i am sure that there is more smoke on account of no cats...Also, could some of the stumbling be because the fuel is a year old??

Trev

 

So what caused the low vac. initially?

 

When you adjust the idle you need to jumper the ten/gnd terminals in the diagnosis connector, its under the hood on the driver side with a plastic cap on it, it should have a label under the lid but they come off over time.

Now the bucking...I'd first start by getting some fresh gas in the car and see what that does. I've had this condition before and discovered I was running lean and fixed this via laptop on a PFC, is your car still on a stock ECU? I hope not if you are running around without cats. Don't worry about the smoke unless you notice it when you are driving or idling after a drive, smoke at startup is something most people on here have probably. It sounds like your motor is just fine, just get rid of that old gas before you really drive it.

I see you sold your MKIII.. owned two MA70's in that past myself. Fun cars in their own right, you won't miss it though.

 

I had an 87 that I swapped a 1jzgte in. I am going to put fresh 93 octane in. I was told to use some injector cleaner as well, even though my injectors have been freshly rebuilt. I have no idea what happened with the vacuum initially. Also, What you said about running around with a stock ECU and no cats...I have a ported WG...apparantly I need some better fuel control however...after all my searching o nthe FD, I somehow thought that with the ported WG, stock intake and full exhaust no cats, I was good on a stock ECU...may have to install a cat then...

Trev

 

My FD did that very badly until I adjusted the TPS.

Now it is very smooth. Adjusting the TPS did the trick.

BTW, this is easier to do with a PFC/Commander, as you can read the TPS voltage right off the commander rather than trying to get a voltmeter on the TPS leads.

 

i am realizing that I need a PFC BADLY!

 

Old gas doesn't like new sparks.

Get some new gas and go from there. Bad gas can cause problems.

 

as long as the engine is spinning whether is backfiring, misfiring or what, shouldnt it always pull a strong vac....it seems like you may definately have a vaccum leak thats causing the car to idle high and misread the fuel air mixture while throwing off the vaccuum signal

 

I believe my problem lies with 3 culprits:

1. Gas quality
2. vac leak of some sort
3. TPS is out of adjustment

 

sorry to bring up such an old thread.. but My fd seems to have the same problem.
It has been standing still for a long time before i bought it. now i've drove it for about 1000 KM's but the ideling is still high like your's around 1200 / 1300.. it also pop's at the exhaust at that rpm's.. sometimes it's at 800 and run's smooth and doesent pop.
did you fixed it in the end and what was the cause..

Im very interested as you might understand

jerome

 

id double check grounds to be sure as well. Very easy to do and solved my low speed/low rpm bucking

 

Hey man, haven't fixed it 100% yet. I am going to put in new fresh gas, check the TPS and check the grounds. I think I am missing a few...

Trev

 

So, tonight I checked the TPS...all in range, good to go. I had it idling smooth at 700,800,900 or 1000 and vac's ranging from 12 to 18 depending on the idle speed. When I would step on the throttle to rev it up, it would cut out and stumble badly and start to idle around 1200, and gradually stumble it's way back down. I took some starter/carb cleaner and sprayed it around the block offs for the acv and the two airpump ports I blocked on the back of the manifold by the firewall. I also sprayed it in various spots where the UIM meets the LIM. When I would spray it, the idle would dip and stumble a little....I thought if I were to have a vac leak and spray that, the idle would go up? So, i did an experiment, and pulled the BOV hose off its nipple on the uim...when I pulled it off (obviously creating a vac leak) the idle went up....so, isn't that the purpose of the carb cleaner..so make a temporary "patch" over the vac leak area and lower the idle...i am confused here...

Trev

 

The idle stumbling back down sounds like the Idle Control Valve. Pull it , clean it , test it. If you have a spare clean and test that one as well just to make sure both are testing the same. While you have the UIM off check the vac lines and make sure oll the nipples on the UIM are hooked up or capped off.

Before you put fresh gas in, pull the pump and look into the tank. Make sure there's no debris, etc. Then change the fuel filter if not done recently.

Get the Power FC as soon as you can. Its one of the best diagnostic tools you can have. Tells you what voltages are being sent and received by the ECU.

 

Thanks for the tip. I already put a new fuel filter in, and already put new gas in...didn't change anything. I am a little but at a loss...can I check voltages on the ISC with it still intact and plugged in?

Trev

 

Check the FSM. I'm pretty sure you'll need to pull it off.

 

Just pulled the ISC off and it is ohming out at 12.2...within spec....so....

TPS is good
ISC is good
airpump is on the motor, but unplugged and capped off
stock ecu
fresh reman with 500 miles
fresh gas
3"DP
gutted stock cat
HKS carbon/ti CB
stock intake
vac varies between 12 and 18 on idle

Also...when I crank the car...it cranks good for about 2 seconds, then stumbles, then cranks and fires....

Trev