Engine Hesitation

[cmathews]

If this is in the archives, I am sorry, but I have never been able to search them succesfully.

My car has been acting really weird lately. When I press on the gas it feels like the timing is retarded, then after the revs get up, it kicks forward. I have new plugs (bosch platinum). New wires (although they need to be checked-- two were touching and got oil on them). I checked to see if any of the vacume lines were cracked but I couldn't find many lines next to the engine, and the ones I did find looked brand new.

I did see something, that looked like a cover for a metal tube that was cracked (might have been the tube itself but hard to tell as it was hard to get to), but I don't think that it was causing the problem-- and I have no clue what it was called. The metal tube was connected to a metal piece shaped kind of like a top (round, widest at the middle) but had pretty much a flat top and bottom. The pipe leading into it came off of the exhast.



The weirdest part is that it is inconsistent. Sometimes it does it, and other times it doesn't

I have:
1990 s13 240sx coupe 5spd (XE - no abs - no LSD yet - no HICAS - no power windows/locks/etc)
no known modifications
recently cleaned MAFS
87 octane mobil 1 gas
132,000 miles
all the repair records from the previous owner (in case I should look for something)
repaired the air tube (after the MAFS)
power steering pump inop. and removed
Custom Cat back exhast - flowmaster and 2.5in. mandrel bent pipe

I am stumped on this one. Maybe once I get it figured out my idle will improve too. If there is any more information needed to diagnose this problem, let me know.

{just had a brainstorm-- could it be fuel delivery related or not. Those problems aren't ussually intermittent are they?--- fuel pump or filter?}

[Powerzen2002]

Hey.  I got the same exact situation, same car and everything.  Every little detail you just put in, I have experienced.  I am still dealing with the problem myself.

HOWEVER, what I did notice improved the performance greatly
was upping to Sunoco 94 Octane for 1 full tank and blowing
it out on the highway!  (Now, I am TOTALLY against this, but
I went and added Gas Treatment. DO NOT buy Octane boosting additives. ONLY Gas Treatment.)

Then lowering down to 91 Octane regularly.

This helped greatly!  However the engine feels a little sluggish
BUT NO where near as bad.  And the idle on start does NOT
drop to 500rpms consitently like it was.  Does your do this?

Also, what wires are you using (spark plug wires?)

Hopefully this will help SOMEWHAT.

-Jay
NY SI

[cmathews]

I am using some lifetime wires from Autozone. I have no ignition or mods other than the exhast, so special wires are a waste of money at this point. As for the Idle dropping to 500 on a regular basis--- yes. In fact I have had it drop lower than that a few times.

I have a full tank of gas so I will have to wait to try upping the octane. Other than that I am still searching for answers.

Chuck

[cmathews]

I am using some lifetime wires from Autozone. I have no ignition or mods other than the exhast, so special wires are a waste of money at this point. As for the Idle dropping to 500 on a regular basis--- yes. In fact I have had it drop lower than that a few times.

I have a full tank of gas so I will have to wait to try upping the octane. Other than that I am still searching for answers.

I might try checking the fuel pressure.

Chuck

[Sick240]

When you guys say, it is kind of sluggish, then then just gets up and goes, are you saying it is like VVT (Variable Valve Timing) or VTEC? if so I have the same problem, but my timing is set, new plugs, wires, cap rotor, so I am also very conused lates

[TPnTX]

I have that problem as well. I do know exactly when it begain. I noticed that the plastic covers of the injector connections were cracked. So I took them off to clean the connections thinking that perhaps it would help on MPG. They were very corroded so I cleaned them with elec. cleaner, wire brush and a small file. Ever since I messed with them I've had this problem. I bought a new injector harness from Nissan. I was actually for a 300zx. I spliced all four in. No change.

I believe that it is the injector seals. Doing all this the injectors got turned some in the sockets. It doesn't leak gas but I do think it's the problem. One day soon I'll replace them and I'll let you guys know what happens.

[cmathews]

They say misery loves company-- and it sounds like I have plenty of it.

I am not sure how the injector seals would affect anything. As for the wires going to the injectors, my boot looks bad too. I really think the problem is coming from a sensor or something, though, because it feels so much like the computer is retarding the timing. I don't know if this means I need to replace the O2 sensor or what, but I hope someone out there has been able to fix this problem, instead of just be as lost as the rest of us who have been posting.

Chuck

[Powerzen2002]

cmathews, usually if your O2 is REALLY to the point of screwing with your performance you will get a check engine light.  "normally".

However, it wouldnt hurt to change it!  Have you ever changed it?

Although, it really doesnt sound like a O2 sensor.  
It does sound more like timing.  
Those "lifetime" wires from autozone, were before or after
you started having this problem did you put them in?

[cmathews]

This problem has been present since I bought the car. I thought, hey, just needs a tune-up. As for the O2 sensor, I will have to check through my archive of papers to see if the previous owner ever had it changed. I am planning on checking the static timing tomorrow. Problem with that is I need someone to tell me the car specific stuff cause I don't have a manual yet. Do I need to do a jumper, etc. to set static timing. On my civic I had to run a jumper, then it was just like an old muscle car. The wires and plugs, by the way, did seem to help.

Chuck

[TPnTX]

Before messing with the injectors connections I did replace the o2 sensor along with spark plugs & wires, rotor, rotor cap, all filters. I was trying to squeeze some gas milage out of it. I drive Highways mostly & I doesn't matter if I drive 55 or 85 I get around 22mpg. Anyway while doing all this I found the corrosion on the injector connections. Before or After I did the tune up I did not have this problem.

Here's how I've narrowed it down. I put the E-brake on, put the car in gear(auto) and from under the hood I press the throttle in some. As it starts to rev up with some torque because it's in gear, the problem appears. While doing this if I move one of the injectors, turning it clockwise or counter clockwise, it affects the problem. Now I thought it could be pulling on the connector wire or something causing it to short but I'm convinced thats not it because if I just move the connector itself it doesn't do anything.

So I can acutally turn the injector and make the proble worse. I fine a happy place where it seems to not be as bad but it's there none the less.

I don't know if I'm on to something or not but I think that these injector seals can be seated well for years and then you move them and all the build up thats keeping the seal no longer works.

Again my point is that I have the same problem that you guys are describing and I can make it worse by turning the injectors. If it aint broke don't fix it:)

[tnord]

i have the same issues and my EGR valve gets stuck closed or open or whatever sometimes. the car will even stall out every once in a while and not want to start. i don't think the higher octance gas has anything to do with it, it shouldn't make that big of a difference. just like somebody else mentioned, after you run the car hard, it seems to work fine. that's because the carbon buildup in the valve gets burned/blown out so it functiones better for a while. but it just builds back up and causes problems in the future. when i really have problems is after long drives at constant speed (driving to the track or to school; mn to ks). the only thing is, my check engine light came on when this happened, i don't know if yours did or not. although mine did go away by itself and it hasn't come back for months.

just trying to provide an alternative diagnosis.

[NutzDrifta]

My friend had the same problem, well kind of like that.  He would idle low and sometimes even die out.  Turns out when his dad checked it, he had to change something on the distributor.  Now he doesn't experience any of those problems anymore.  Sorry, I don't know all the details, but you might wanna check the distributor out.  Hope this helps.

[guy]

I had the same problem.  I turned the distributor a little clockwise and it seemed to solve the hesitation problem most of the time.  I put premium gas in just in case.  I don't have a timing light so I can't check the timing out, but it runs fine.  The idle dropping still occurs but not nearly as much.

[TPnTX]

Okay I had mine checked out and the diagnostics points at the TPS(Throttle Position Sensor). It's on the side of the Aluminum air intake thing. I know there has been a post or two about this thing but I can't get the search to work on this forum. I always errors out.

Anyway, I don't think you can just go buy a TPS and replace it. It requires some resistance settings and stuff.

[S13Grl]

Hey guys, you should just simply check the throttle valve. It could be something as simple as that. I don't know about 240s, but I had a bad idle and acceleration with my old car and that all disappeared when I replaced the PCV.

Injector seals do tend to get bad over time... especially with Nissan. Try and get a fuel pressure gauge and you can try and test that to help narrow down your diagnosis. I'm not sure at what psi it should be stock... anyone know?

[tkrolo]

If your problem is the tps, it will throw a code; and you can purchase the relay.  I think mine cost around $50-60.  It is a little difficult putting on since you have to remove the throttle body to get a good grip on the bolts.  

I am also having the drivablilty issues you all speak of.  Cleaning my mafs really helped, but it is still evident from time to time.  I have ordered a new cap and rotor, pcv, and plug wires.  Hopefully that will eliminate the problems.