Just started out of the blue the other day. When the engine is cool i don't notice it as much but as soon as it gets warm the engine starts vibrating bad. The rpm's go down to about 650 and it constantly feels like it is goin to stall when i come to a stop but it never stall just feels like it will. As i go the engine feels like it has no power and hesitates bad but once im up to speed [50 mph or so] i don't feel anything it runs great. Only when i'm at a stop and starting to go and only when the engine is warm...weird. Any suggestions on what to look at?

BTW no check engine light either.

 

Just checked the ecu for any codes and of course the famous 0304 KS code, i doubt that's what it is though.

 

is that the only code

 

Yea, that's the only code it spit out.

 

then its prolly that...if u had any other codes i would say fix the others first but if thats ur only one I woudl fix that

 

Well i replaced the pcv valve since it was really clogged up. That helped some but the problem still existed. I still had the code for the KS and replaced that yesterday. I really noticed a big difference in acceleration and power but the engine stumbling is still there. I checked for engine codes after changing the KS and got nothing 0505. I still have the engine stumble feel when i jump on the gas, if i go slow and steady on the gas i feel nothing. I haven't changed the plugs since i got the car with 136,000 and now i have 157,000 so i will change them and see what happens.

 

I noticed this also, dealers said it was my JWT Popcharger. I had been adding Gunk Octane Booster to 8 Gals of gas and this cured it during the summer. It doesn't seem to work with 1 can to a full tank tho, but the cold weather in NJ has helped.

 

Well before i change the plugs I thought about cleaning the IACV valve. It was really gummed up and cleaned her out good. Made a noticeable difference but the hesitation and floundering are still there, not as bad but still there. Onto the plugs I guess, then maybe the injectors if the plugs don't help. Weird that it only does it after the engine is warm. Keep you updated as I go.

 

Check the intake manifold gasket. A clogged PCV valve will cause the rubber gasket to be sucked into the manifold.

To check:
- listen for a loud sucking sound (like someone is inhaling through their front teeth) around the intake manifold.
- grab a can of WD-40. Spray around the rubber gasket on the front AND the back with the engine running. If it starts to race, you need a new intake gasket. It's only a 40 minute job to replace.

That's what happened to me. PCV valve got gummed up and caused the intake rubber gasket to be sucked in. I had horrible idle problems and it eventually threw a 0603 code (cylinder 6 misfire) but it would run just fine at 50mph.

 

Just checked that and no air sucking sound at all, sprayed wd-40 around the gasket just to make sure and noticed no difference, thanx for the input though.

 

Have you changed your knock sensor? If you haven't already put another in. Your knock sensor is 11 years old - might need a new one anyway.

I noticed you took apart the IAC valve and clean out the carbon. Don't forget to clean the MAF screen. Finally, get some Redline Fuel Injector cleaner, and put two servings into a full tank and take it for a run. If your injectors are clogged, it will cause poor idle. Have you cleaned out your throttle body recently?

If after doing all that, wait for the proper code to throw. Check it weekly - often the ECU will store a code until it worsens. Mine was like that - it held the code when my idle was rough.

I highly doubt its your plugs, especially if they are under 2 years old.

 

I think you mis-read my post, I have never replaced the plugs since i purchased the car. I have changed the KS with a new, cleaned ot the TB,MAF and IACV, i also ran 1 bottle of fuel injector cleaner and am waiting for this tank of gas to be gone to make sure it wasn't a bad tank of gas. As far as the plugs, what i was trying to say was that i bought the car with 136000 miles on it and it now has 157000 and i have never changed the plugs. Don't know how long they have been in there.

Thanx again for the suggestions. I am going to change the plugs tommorrow and will update after.

 

If the car is warmed up well and you shut it off, and then a couple minutes later start it back up does it start fine? I would take a look at the ECT sensor

 

No problem starting whatsoever. No hesitation or studdering at all when the engine is cold, everything starts to happen when the engine is warm.

 

Hear ya Dallas - I misread your post.

Pick yourself up a set of NGK Copper plugs (V-Groove). You could of course go with the platinums but I think they're a waste of money considering the premium they demand. Let us know what happens.

Question - have you changed the fuel filter yet? If not, pick up a 95/96 300ZX filter. Might pop out of the holder once in a while, but it's got twice the lifespan (40k vs 20k) and costs less.

 

Well the hesitation and engine stumbling is gone!!!!!! Listen to this, i go buy the NGK platinum plugs[$60] from advanced and the guy tells me whatever you do don't put champion or autolite in there cause they suck, i'm like ok [i already knew that] so i go home and take the plugs out and lo n behold, get this 2 champion plugs, 2 autolite and 2 ac/delco plugs in the car . I couldn't believe it. So i change the plugs and the oil and filter while i was at it and wound up changing the oil pressure switch because it was leaking pretty bad. Started the car let it warm up drove it around then decided to jump on it to see if the hessitation and stumble were still there. The tires lit up for about 50 feet and white smoke from the tires. I couldn't belive it the car has never had as much poweer as id does right now. I am thrilled with everything i have done. Thanx for all the input guys.

 

 

I had the same problem with my95 maxima and it turned out to be the mass flow air sensor. After i took out the entire intake and throttle body to have it cleaned and replaced old seals on intake ans valve covers. Also put new dampener and also changed fuel pump. nissan dealer could not figure it out the day i had it serviced they were embrassed. good luck

 

glad you found your problem. i'm experiencing hesitation too, i might have to check my plugs.