I will apologize for the length now. Sorry.

I just swapped my VE into the third Sentra. Hopefully third time is the charm. First one hit a rock , swapped all my stuff over to an SE shell. Couldn't get it started, sent to shop .... same result. Towed from shop to a place where myself and another forum member could do another swap. Bought an SE-R . Swapped , took a couple hours more than expected but the VE was running. After about 2 years down and out, yup 2 years ! She started without problems... yet.

The VE had a little bit of a rough idle. Not too bad. bounce around a little bit ( about 900-1100 rpm. ) Then seemed to even itself out. I drove home about 25 miles. No problems. Took it easy not reving past 4500 . Just to make sure everything works fine. Next day wired up my MSS. Cam activation works. :biggthump . Man that was what I missed !!!. Still had a little bit of an idle problem. It would sometimes stall when coming to a complete stop. Start it up, and just have to give a little gas to keep from stalling.

Then comes sat night. The first time I got to pull it pretty hard , Not shifting it hard just reving it up to 7500. WOW:D I love the cams switching. It is LOUD without a muffler;)

That was about a 10-15 min ride on the highway. A couple good pulls in 2nd and 3rd. Then getting off the exit ramp at the stop light it stalled. Tried starting it up, and it would just turn over. After about 2 minutes of trying and swearing. She stumbled to life. Fluctuating Idle from 1400 rpm to just about stalling ~500 rpm. At first it wouldnt respond to throttle input. Then it responded and I got to my destination less than a mile off the exit ramp. My schedule didn't permit me to check it out right away. So I jumped on my train and hoped it would start for me on Sun night when I got back .

When I got back sunday night. I tried starting it with the same result before. I also pulled the fuse on the MSS to see if that was the problem. Nope. No change. Just turning over not starting. Same thing about 2 min later she started, then stumbled. goes from 1300 - 500 RPM ( Almost stalls then kicks high , almost stalls kicks high, repeat) It seems to run fine above 2500 rpm. Although the throttle must keep fluctuating. If I try to keep the throttle steady below 3000 rpm, it drops to the rough idle area. After a couple minutes of making it warm up I could keep it running. I drove it home with a little heel toe action at stop signs and stop lights. It was about midnight so no traffic.

I just towed my shell to another shop to swap over the rest of my suspension. And this ish happens. :squint:
Has anyone seen or heard of anything like this? The car drives fine, runs good while driving. but at idle sucks ass.

Don't know what to do, checked for vacuum leaks. Everything looks fine. Any suggestions would be appreciated.

Scott

What fuel system are you running? like ecu? what injectors ?

Oh Sorry. My engine mods are:

JWT ECU with 8K rev limit
W/ DE Maf
Stock DE Fuel Pump
VE injectors
Unorthodox Pulleys
K&N cone
SSAC Header

I pulled each Spark plug wire, to see if there is a misfire. All are getting spark, and the engine will remain on, with any one unpluged. The RPMs go from 500-900. Drops fast then revs 900 within a second, and drops fast back to 500. If I leave it , it will not stall . But it sound like a sick dog.

If I warm up the engine. ( keeping revs between 2-3.5K for about 1 minute) the engine will idle between 1500 - 2000 for about 5 seconds. Then drop down to the rough idle mode again.

And adjusting the AAC valve doesn't do anything

jwt ecu programmed for what? like what does it say on the ecu?

i have expierenced something like this, but not as severe as yours, when driving easy it is ok... but when driven hard and then coming to a stop the idle falls to 450-500 almost like it is going to stall, but then it goes up to 900 i haven t figured it out... but your case is extrme

Damn, I know I have a pic of it I just can't find it. It is programed for what I have on my car. VE injectors and DE Maf.

This same setup ( minus the Pulleys ) was in another vehicle running fine.

make sure the plug on the harness is all the way down on both sides.. connecting to the ecu...

Injector O-rings perhaps?

Does sound ECU/Electronic ohterwise.

Double checked the Batt connections and the ECU connections. Both good. I checked the Voltage of the battery 12.6 off and going between 13.5-13.7 if I have the engine running with the rough idle. Correct me if I am wrong. I thought the voltage while engine is running should be 14.4 volts?

Also checked the wires going to the MAF. Ground good. Power good. The other wire was about 1.0- 2.14 going with RPM. Didnt' rev that high though.

Stick a vacum guage on the IM and see what that sucker is doing when u leave it to idle.

If u can't find a vacum leak in any of the hoses or between the throttle and MAF then inspect the throttle body for any unusual problems like loose throttle plate, dirty should not really be an issue here but if u get the idling sorted come back and clean it. Another possible source of vacum leak is the brake booster.

If u are using the VE IACV valve setup unbolt it and clean it with a foaming Carb spray, let it soak with that stuff and then spray out with the fast evaporating stuff or with just water, repeat if necessary and u can use a soft bristle brush to assist. It doesn't have to shine like St Pauls dome, just get the gunk out if there is any. Unscrew the plastic air control screw and clean it up as well, replace with silicone grease or rubber compatible grease. If it is coming out hard use some spray to lubricate it and work back and forth so that u dont strip the plastic threads.

Once u get the car idling stable at whatever RPM u will need to set up the TPS timing and idle speed based on the ecu u are using.

If u are using the VE IACV valve setup unbolt it and clean it with a foaming Carb spray, let it soak with that stuff and then spray out with the fast evaporating stuff or with just water, repeat if necessary and u can use a soft bristle brush to assist. It doesn't have to shine like St Pauls dome, just get the gunk out if there is any. Unscrew the plastic air control screw and clean it up as well, replace with silicone grease or rubber compatible grease. If it is coming out hard use some spray to lubricate it and work back and forth so that u dont strip the plastic threads.


That sounds like a good idea. Thanks.

EDIT : Problem still there. That was pretty dirty though , glad I cleaned it.

You might have a short somewhere. I had a cheap dome light bulb short out on me and I could only tell when the door was ajar. Took me forever to figure it out!

Unplug TPS and see if idle stabilises, if car stalls try to restart with TPS unplugged

else

Clean or replace the MAF.

TPS unpluged - Problem doesn't change.

I might have another MAF around , I'll try that.

Edit : Found my other MAF - Problem Doesnt change.

This is frustrating. Especially when I warm it up a little. idle stays high ( ~1500 RPM) but stable for about 5 seconds - just enough to tease me , then drops back down in that stupid rough idle mode.

Stick a vacum guage on the IM and see what that sucker is doing when u leave it to idle.

Just did that, It reads 10 Hg of Vac @ 500rpm 15 @900 . If i rev it up it will show briefly 0 , due to the air being sucked in. Then go up to 20 and remain stable until the idle drops. I probably reved to 2500 max.

So this kind of rules out the vacuum leak idea. Any other suggestions. I will try to bring it to a place that can hook up to my OBD I, although there is no Check engine light on . I'll Search , but if someone knows what the readings should be, and what I should focus on It would be appreciated.

one more test... from my end..


put in your DE ecu. see what happens...

^ Good idea would eliminate any problems with the ecu.

Idling at about 800 rpm, I read a little less than 25 inHg with an autometer vacum guage. VE throttle body. Vacum tap point immediately after the throttle body on a port directed towards the firewall. I think you don't have enough vacum but wether it is being controlled via the ecu or a leak is the question.

Is your throttle plate fully closed when the engine is warmed up?

If u can check the resistance of the coolant temp sensor as well, this may be a bit off base but I have had a hunting idle similar to that when the car was out of tune i.e. TPS and timing and air screw. I had the mechanical cold fast idle disabled so the throttle plate was always closed. Anyway the ecu would fast idle the car starting at about 1200 and gradually come down until the car was wamed up but at some inbetween temperature the idle would hunt and go high and low like u described for maybe 30 seconds or more and then settle out. With the engine set up properly it doesn't occur anymore.

You should check the resistance of the coolant sensor at the ecu and if there is a problem at the sensor to eliminate any wiring issue.

Have u tried a good old ECU reset?

I too have a JWT computer for the VET. The car runs like total crap with this program. Stalls when I let off the gas every now and then. The car runs pig rich and fouls plugs out too. I am hoping when I get everything finished I can get it running perfect but the computer pulls timing back really far I think and the injectors are flowing way too much. I have nismo 740cc injectors. I think it may be the computer but when I was NA the JWT program worked ok. Still backed timing off too far though.

^ Good idea would eliminate any problems with the ecu.

Idling at about 800 rpm, I read a little less than 25 inHg with an autometer vacum guage. VE throttle body. Vacum tap point immediately after the throttle body on a port directed towards the firewall. I think you don't have enough vacum but wether it is being controlled via the ecu or a leak is the question.

Is your throttle plate fully closed when the engine is warmed up?

If u can check the resistance of the coolant temp sensor as well, this may be a bit off base but I have had a hunting idle similar to that when the car was out of tune i.e. TPS and timing and air screw. I had the mechanical cold fast idle disabled so the throttle plate was always closed. Anyway the ecu would fast idle the car starting at about 1200 and gradually come down until the car was wamed up but at some inbetween temperature the idle would hunt and go high and low like u described for maybe 30 seconds or more and then settle out. With the engine set up properly it doesn't occur anymore.

You should check the resistance of the coolant sensor at the ecu and if there is a problem at the sensor to eliminate any wiring issue.

Have u tried a good old ECU reset?


Good. Got a couple Ideas to try. ECU swap good idea. I'll check that throttle plate.
Now if that doesnt work. Then I will check the resistence on the Temp sensor.

How do you reset the ECU, or even should I with the JWT tuning?

Thank you. I appreciate the suggestions. An update will be soon.

Scott