Rough erratic idle after installing Injen Short Ram Intake

[phatkorean]

I have a 91 S13 and just installed an Injen Short Ram Intake today. Before installing the intake the idle was ok. Now when I start the car the idle is fine, but when I drive for any length of time and then stop at say a stoplight the idle will be fine for about 15 seconds then start to go haywire. It will start to go +/-100 RPMs then 200 RPMs and then it will drop way off till it almost chokes and then shoot up to a range of 700-1000 and do this continually until I start to drive again. The engine never stops it just looks like it will stop. Driving the car is fine. There are no problems when driving, only when I stop.

This problem happened after the installation of the intake. I checked all the connections and they seem tight and properly fit. The ECU was reset by disconnecting the negative battery terminal for about 10-15 mins and then reconnected and idled for about 5 mins after that.

Anyone have any ideas?

[mbmbmb23]

The ECU might take a little more time to adjust to the new aftermarket peices. Thats my guess. Resetting an "ok" ECU back to "ok" is redundant, so give it a chance to straighten it's self out. You didnt touch the inside of the MAF did you?? If you get stuff (supposidly including oil from K&N and other oiled air filters) on that sensor it can mess up your readings...or so I've heard. Also relocating the sensor near a bend can mess up the reading as the air will speed up around a corner in the tubing.



-m

[phatkorean]

Yeah, maybe the car needs more time to adjust. I'll know more tomorrow after I drive to and from work.

I didn't touch the inside of the MAF.

[Muzzy]

or....do u have that fat hose commin off the plenum connected to the intake and if so is it tight and sealed???

idk wut the hell u guys are talkin about with the ecu gettin used to the intake. i have never experienced any weird stuff like that with any intake mod or any other type of mod:confused:

[phatkorean]

I've read that you need to reset the ECU after installing an intake. I don't know if you need to do this or if it is just some old wives tale. I do know that the instructions that came with the intake said to disconnect the negative terminal of the battery before installation.

I noticed something while driving to work today. While at a stoplight I took my foot off the break and the problem seemed to start to go away. There was still some fluctuation in the RPM's, but it was a lot less. I think the range was something like 600-800 RPM. I did it again at the next stoplight and then same thing happened. I tried it again but this time I applied the breaks when the RPM's started to return to normal and the idle became erratic again. The car is manual so obviously I was in neutral when I tried this.

One other thing. I don't know if this matters but the hose that comes off the engine to the intake, the one connected to the PCV, was giving me some trouble when I was installing the intake. I had to remove the PCV so I could get a better grip on the hose in order to remove it and replace it with the Injen hose. The PCV popped out of the engine very easily and I replaced it just as easily. It's not that is was loose it was just very easy to remove and replace. Again, I'm not sure that is the problem but I thought I would just mention it.

Thanks for any help.

[Dream240]

Well I have an s14, but in relation to your problem, did you remove any hoses from the PCV or nearby and forget to replace them? I had a similar problem after replace my intake manifold, I reversed to hoses on the back of the manifold and ended up with a Check Engine light and erratic idle. The Nissan Dealer fixed my blunder.

Check around the PCV for any hoses that might have come loose or hanging hoses. Also make sure you reconnected the PCV correctly. And finally check all the hoses you might have touched while doing the install for cracks that would cause a vaccum leak.

It's possble that you reconnected everything correctly but because you got in there and started tinkering you unintenionally grabbed an old hose that was on the verge of cracking and took it out of commission without even knowing it. I know it sounds like alot of troubleshooting but trust me its worth it to find that one 3 inch long piece of hose that is cracked and causing all your woes.
That's the best advice I can offer you.

Good Luck!

[phatkorean]

Yeah, I double checked to make sure all the hoses were connected properly. I'm going to take the whole thing apart this Saturday and see if I can find any problems. I will then take extra care in putting everything back on.

Thanks for the advice.

[phatkorean]

I noticed something when checking out the hoses tonight. There is a black box which sits by itself in front of the driver's side and just right of the exhaust manifold. It has a hose that connects between the air filter and the MAF. I started squeezing hose to see if I get a response and when I squeezed this particular hose the rough idle would almost disappear completely.

I also noticed that when I removed the stock intake this hose was positioned right about the stock air filter. Looking at the filter I saw that the hose spat some kind of oil onto the filter. The filter is only 2-3 weeks old and there isn't a whole lot of oil. It looks like a bird took a really big dump on the filter. What is the black box and the hose? This could be the problem as the hose is now connected to a spot right in front of the MAF. It could be that the "oily air" is messing up the MAF at low RPM's.

[driftmaster04]

ill bet that box is causing hte problem because my 240 was havin weird idle problems like yours. but when i made my own intake i bought a breather filter and put it on where that hose comes out of the box and my car ran fine afterwards. because that box lets air from your ehaust back into the intake or somethin like that but when they start to get all gunked up the reeds in it will get messy and theres a faq on 240sx.org that tells how to clean it. if i remember right its called an aiv valve servicing on the site. hope this helps.

[pitbullpwer]

the ruff idle is from either a loose vaccum hose or like everyone else said the ecu. ive had the same problem. try taking the negative battery cable loose and letting the ecu reset.

[phatkorean]

I've already checked all the hoses and reset the ECU.

[phatkorean]

driftmaster04, the problem was the AIV. Apparently I have the same problem you had. I disconnect the hose from the intake and had no idle irregularities. I drove to work this morning and there were no problems. I now have a smooth idle at 700 RPM. I guess I'll need to look into cleaning or replacing the AIV. That or some kind of breather filter.

I'm not saying that this should go into the FAQs section, but I do think it should be know that replacing a stock intake with an aftermarket intake can reveal a problem with the AIV.

Thanks driftmaster04 and everyone else for taking the time to help me out!