Stumble/Bad Idle Problem

[Mugenlude]

General Info:1993 240sx SE, stock, 163k miles, current temperatures around 30­°

Background:I recently bought the car from a friend. It had what he believed to be a bad injector (#3 cylinder), he supplied me with 4 used injectors when I bought the car. Come to find out the injectors weren't even the correct ones (duh), so I went and purchased one new injector from Autozone to see if that would solve the problem.

Problem Timeline:2-11-05 :: Bad Idle (engine shakes), stumbling/hesitation (same type of engine shaking feeling) while trying to keep stready speed (ie near idle throttle position). Under accleration the car feels fine to me, at times if seems as if it is lacking, but for the most part it feels fine for a car with 160k on it.

2-13-05 :: Purchase and install new injector based on thread read on NICO. Intially, the car feels better. I can still sense some stumbling/hesitation while at steady speed, but idle is better to start.

2-15-05 :: Master Cylinder proceeds to go out... I don't believe this is related in any way, but you said to list recent repairs. Problem was present prior to clutch...

3-01-05 :: Get car back going... stupid damper block thing-a-ma-jig!!! @#$%!!!

3-02-05 :: Idle begins to feel rougher, steady speed stumble/hesitation still present. I begin read NICO to try to find info on the problem. I find the sticky at the top of this forum and begin wiggling harnesses... no effect. Begin sniffing...

3-09-05 :: Bad Idle is back to how it was when I bought the car. I smell fuel at times while the car is coming to a stop (this might have been present when I bought it but I wasn't really troubleshooting like I am now). Stumbling/hestitation problem is still present.

3-11-05 :: Above still applies (not getting better or worse), however, at times the car will not start now unless I provide a little gas to get it going, otherwise it will just crank over without starting.

---------------------------

That is where I stand today. I'm looking for some suggestion of where to go from here. The new injector seemed to solve part of the problem, but now it seems as if it didn't, I would hate to replace all of the injectors if they don't need to be replaced (that is expensive).

I have a multi-meter, and would be glad to check anything if I get some direction on how to do so (plug wires, signal to injectors comes to mind). My next planned step is to pull the spark plugs and see what they look like, I might just replace them. Any other thoughts would be appreciated.

It seems as this is a common problem, but no one seems to be posted results of what they used to fix it, if they fix it. Others seem to just live with it, that isn't an option for me.

Thanks.

EDIT to add progression:3-11-05 :: Changed plugs 1, 3, 4 (see post below). Car seems to run smoother on the short drive I took it on. The bad idle is still there, but the hesitation doesn't seem to be as bad. I'm going to try to get the last plug changed.

Modified by Mugenlude at 12:43 PM 3/12/2005
Modified by Mugenlude at 12:45 PM 3/12/2005

[navysnail]

good job on all the records, that makes it easier to get a general idea on what it could be.

it sounds like its putting in too much fuel, i would start by making sure that no injectors are stuck open or anything, also check your fuel pressure

try to start it, then pull your plugs after you cut it off, see if any of them are wet with fuel. you dont acually have to start it, just get the engine turning over is fine.

[NISTECH]

the way you have to start it[opening the throttle wider] suggests your getting to much fuel. on start up,and untill it reaches operating temp they use these sensors to control fuel mixture, in pretty much this order of importance. 1: airflow meter, check the ground on it with the car running if possible and hooked up, you voltage drop on the ground wire should be less then .02v. if too high add an additional ground to that terminal on the meter.2: coolant temp sensor. [the 2 wire one at the front of the intake manifold] unplug it and see if you got green crap building up in it. if so clean it ,tighten the female terminals in the connector so it will fit tighter on the sensor.3: crank angle sensor[ this does not so much control the mixture as it tells the injector when to fire via the ecm.] this is located in the distributor. make sure there is no moisture or other contaminites on the pick up wheel. do this after checking the other 2 more likely problems.

[Mugenlude]

i would start by making sure that no injectors are stuck open or anything, also check your fuel pressure

try to start it, then pull your plugs after you cut it off, see if any of them are wet with fuel. you dont acually have to start it, just get the engine turning over is fine.

Before I ask any more questions I have more info to add.

3-11-05 :: I got 3 of the plugs changed last night, see picture below (#4 on left, then #3, then #1 on right). I took this picutre this morning, so they have been sitting for about 12 hours (camera batteries were dead).

#1 plug had oil dripping off the tip#2 plug I couldn't get out, plug wire seperated on me (new task for today)#3 plug has oil on the thread

None of them really smelled like fuel... or seemed wet (except for oily one). How do the plugs look? I haven't really tried to diagnos anything w/ my plugs before.

Car seems to run smoother on the short drive 6-7 miles drive I took it on. The "bouncing idle" bad idle is still there (down to like 300-400 RPM's at times), but the hesitation doesn't seem to be as bad. I'm going to try to get the last plug changed.

OK, now some questions...How would I go about checking to see if the injectors are stuck open?
Modified by Mugenlude at 1:58 PM 3/12/2005

[PalmerWMD]

This probaby isnt the cause of your severe drivability problems,but Bosch Plat+4 and Bosch plugs in general , knownto have poor compatibility with Nissan motors,often causing drivability issues.

This is probably not the cause of your more significant problems but I am sure it isnt helping.Nissan Motors like Denso and especially NGK.

Fred..

[Mugenlude]

Yeah I read about the NGK plugs, as soon as I pulled the plugs out I was hoping the new plugs might help (as apposed to if there were NGK's in there already).

[NISTECH]

TAP TAP TAP

Is this thing on.........

Test test ...hello can anyone hear me???

[audtatious]

TAP TAP TAP

Is this thing on.........

Test test ...hello can anyone hear me???

Welcome back, man. You know we love ya!!!

[Mugenlude]

update... I got the last plugs changed that night. The car idled better, but not correctly

The problem has not gone away, and over the last week or so the problem has slowly moved itself back to how it was to begin with. So changing the plugs made it better (not fixed) for about 1 week.

So now I'm moving down the list of items in the drivability issues... thread. I did #1, no change. In #2 it smells like fuel, but the car starts and runs so it isn't flooded.

That brings me to #3, as noted above the car is "new" to me so I don't know the maintenance history.

I would like to check the plug wires and coil wire at this point. Does anyone have a link to a write-up for testing them? What kind of resistance should I be seeing thru them? What setting do I need to have my multi-meter on to get the reading?

Regarding #4 - aftermarket parts:I don't see anything that looks aftermarket with the distributor/cap/wires/etc. How do I check the injectors? They should be going TAP TAP TAP consistantly? Can I use the old screwdriver from my ear to the top of the injector method? If the injector is going TAP TAP TAP, at that point can I assume the signal from the ECU is working?

Regarding #5 - Grounding:Can someone provide me a picture/description to where the MAF sensor is located and what wire I should provide a new ground to?

Thanks in advance...-Jason