93 J30 Hard Start

[DominickJ30]

I have a problem where when I start my car the rpm shoots up to about 1600 and then the car either sputters to 200 rpm and picks up again or simply dies. This only happens in the morning or when the car has not been run for more than 2 hours. Leaky Injectors, bad IAC? Anyone know what this might be?

[DAEDALUS]

Checked the MAF connection? Vacuum leaks?

[DominickJ30]

Checked the Maf and for vacuum leaks and there are none. I guess Im gonna have to pull the plenum and check the rain for leakage. Do you think a leaky injector could cause this?

BTW Ive already checked all the simple stuff.

[metaverse3]

Checked the Maf and for vacuum leaks and there are none. I guess Im gonna have to pull the plenum and check the rain for leakage. Do you think a leaky injector could cause this?

BTW Ive already checked all the simple stuff.

Yes..I experienced a leaky injector on my maxima causing a hard start..took me 3 months to figure out. slow dribble down cylinder walls causing vapor lock..flood like condition causing hard cranks.. Nissan is well aware of this problem given their numerous tsb's for nissan/infiniti products over the years.. If it is an injector issue, replace all 6. I can vouch for this personally..

[metaverse3]

I have posted some TSB's here.. Hope it helps: zerothread?id=113076

[DominickJ30]

Thanks for the info. I was able to hook the car to a snap on scanner and checked some data. It led me to believe that the IAC might be the problem. I am going to remove and clean it tommorow.

Do you think the injector problem would still happen with the car fully warmed up?

I am going to remove the pump fuse tonight and see if I have this problem tommorow morning.
Modified by DominickJ30 at 10:37 PM 4/21/2005

[DAEDALUS]

How long are the symptoms present? Do they clear up pretty quickly?

[DominickJ30]

How long are the symptoms present? Do they clear up pretty quickly?

Yes as soon as the engine temp is at about 180 the problem goes away. Another symptom is when the car is cold and I rev it the RPM drops then gets stable. IAC stays at 80%(open) through the whole process.

[DAEDALUS]

Is there a fast-idle cam on the car? On the Q there's a wax element that keeps the cam engaged when the engine's cold to flow more air. Tough one, but at least you have a scanner. Seems the engine would run when it's cold if there's a FIC...disconnect the IAC completely and start it up. If the problem persists, I'd suspect something other than the IAC. Hopefully it starts without the IAC.

[metaverse3]

Thanks for the info. I was able to hook the car to a snap on scanner and checked some data. It led me to believe that the IAC might be the problem. I am going to remove and clean it tommorow.

Do you think the injector problem would still happen with the car fully warmed up?

I am going to remove the pump fuse tonight and see if I have this problem tommorow morning.

Removing the fuel pump fuse will not do anything. There is already fuel in the rail, nothing short of depressurization of the system manually will not isolate this issue.. Don't waste time with that..

Try pinching the IACV valve regulator hose and see if the engine speed drops. Follow procedure on EF-EC 177 in the FSM. Follow the whole EF-EC Trouble diagnosis' that follow page 177.. Lots of things to check.O2 sensor..MAF, plugs etc.etc.. Lots of these issues are Throttle body, TPS and/or crank sensor related. Too many goddamn electrical gremlins in nissans..never fails to amaze me..

[DominickJ30]

By the pump fuse I meant remove the fuse while the car is running and depressurize it. Well it did not help. So I took apart the IAC and cleaned it with TB cleaner, this helped alot with start up(the car is not close to dying anymore) but the idle still hunts. Also if I rev it the idle hunts after dropping.

Now for the other stuff. I checked the TPS on a scope about a month ago, no dead spots and WOT is around 4.3V . I could not do a road test on the MAF, but I checked at WOT no load and the highest I could get was around 4V. Attached is my Ignition Scope Sheet.

These are exhaust readings in closed loop:IdleHC- 21ppmCo2 - 14.61%O2 - .97%Co - .038 %Nox - 15ppm15.5:1 A/FLong Term Fuel Trim was at 105.

I still did not try to unplug the 02s or check timing or fuel pressure. You guys think that low fuel pressure could cause any of the symptoms?

Related maintenance is cleaned throttle body and did intake decarbonization via BG. The car ran very good shortly after that but now I got problems again. I also cleaned the MAF(the film) with TB spray, could this have been a bad thing for it?

I really hate the FSM. It doesnt show any test procedure other that "test with a known good part" and unfortunately I do not have spare ECUs or crank sensors laying around.

I really need to get myself a Snap On Modis for this type of stuff. Thanks for all the help? What else you would suspect with the info given above?

[DAEDALUS]

I don't think the fuel pump could cause hunting, but it's easy enough to keep tabs on the pressure. Pressure gauge is a lot cheaper than a Modis! Would be a waste and a shame to get a Modis to work on a single OBD I vehicle, though I agree they are VERY cool. Hunting still sounds like a vacuum leak to me, but 21 HC isn't exactly running lean. Are those numbers an average, or just a snapshot at a single point in time? Have you tried spraying something around the plenum to check for leaks?

[DominickJ30]

The problem Im having is that there doesnt look like there is a test port on the fuel rail. I went to sears yesterday and the only pressure gauge they had was the screw in type without a 'T' .

I am a tech in training so a Modis is going to be a must have in the fututre. But I wouldnt mind having it right now.

The exhaust readings are a freezeframe at idle. The car is running lean. O2 level is higher than Co and the A/F ratio is on the lean side.

And yes Ive tried spraying some TB cleaner around the intake (im assuming the only gasket is at the end of the runners?) And the engine stayed at the same rate.
Modified by DominickJ30 at 11:05 AM 4/24/2005

[DAEDALUS]

To test pressure you'll need a cheap barbed 5/16 brass T-fitting. Use it with hose clamps, only takes 5 minutes to hook up just past the filter. I'm not familiar with the engine but I would think there has to be hose connections between the TB and the engine where air might leak in. Have you cleaned the TB?

[DominickJ30]

To test pressure you'll need a cheap barbed 5/16 brass T-fitting. Use it with hose clamps, only takes 5 minutes to hook up just past the filter. I'm not familiar with the engine but I would think there has to be hose connections between the TB and the engine where air might leak in. Have you cleaned the TB?

I have to buy the fitting tommorow.

I have to take off the throttle bodies and check the gaskets as well as clean them better. I only cleaned it from the outside with a tooth brush.

Like I said I have no found any major vac leaks, I will get a pump tommorow and see if it holds vacuum overnight.

[DominickJ30]

Im about to give up guys...

For the last 2 days (after I cleaned the IAC) the car starts and idles beautifully. So I was basically happy as a pig in sh1t. Drove better too(maybe thats just in my head).

But then tonight after school I go to start the car and BAM the idle drops.I guess the IAC motor might be messed up. I still have to check if it holds vac but Im pretty sure its the IAC now.

[metaverse3]

How did you clean the IAC ? Look here: http://www.twinturbo.net/ttnettech/iaa/iaa.html

This thing can be removed to loose parts and cleaned thoroughly. Try that first if you have not already.. You can also bench test the motor with plunger that is on there. It is the same one on a maxima. I can tell you that will indeed cause problems for it is a major culprit on maxima's, infinit is no different. If you were local to tri-state, I would have loved to take a stab at this issue..