Replaced one thing after another, what next?!

[tkrolo]

Ok, I've got a 93 240sx se coupe with around 100k miles. Been messing with stumbling and backfiring for a couple of months and near my wits end. In its current state, it will start and run beautifully for 10-15 minutes, until it gets warmed up. After that, its like it isn't the same car. From a stop, you have to ride the clutch a give it extra fuel or it will stumble and die. After you get going you have to continue to baby it by easy onto the gas or it stumbles and backfires, at times, violently. It seems to idle fine and run fine once you get to operating speed as long as you don't have to touch the gas. I've replaced the fuel pump, filter, alternator, cts, tps, and adjusted the timing, but nothing helps. If you try to start it before it cools down completely, it takes several extended cranks to get it to fire. I just bought a set of injectors hoping that this is my problem, but any other suggestions would be GREATLY appreciated. Thanks in advance.

[Irukandji]

Distributor cap and rotor, new spark plugs, plug wires.

[tkrolo]

Those were replaced before also. Sorry for excluding that. My thought is that I'm not getting a good spray from the injectors causing fuel to pool instead of burn. Occasionally I get gas from the exhaust with fuel smell but exhaust seems to be normal coloration. The thing that has thrown me is that it is triggered by heat or when the car reaches normal operating temps. It runs fantastic when cold although idle is a little high, but that is normal at cold temps.

[OdessaS13]

maybe you shoudn't WAG. have you tried taking it to a shop and seeing what they think is the problem. Do you have any mechanically advanced friends that can take a look. If you are going to start replacing everything piece by piece just get a new engine that will solve all the problems for sure. try checking shorted wires? replace those too. tried pulling codes yet? try changing 02 sensor? Im not trying to be a asshole its just stupid to replace every single thing when you dont know that its the problem.
my 2cents
good luck

[tkrolo]

I would love to take it to a Nissan dealer but the closest is nearly 100 miles. I live in a fairly rural area and have about zero confidence in the local mechanics. Nearly everyone is strictly obdII and their diagnostic methods are nearly all computer based, and I don't feel like paying $50/hr for that. I have asked a friend who is a mechanic at the local ford dealership to come and take a look, but I'm not expecting much. Most of the parts were installed due to mileage and maintenance rather than necessity, but they were also replaced in order down a checklist from my chiltons manual. Silly to replace the entire engine for a "ghost," I don't have nearly that much invested. I am considering an sr swap, but don't have time or finances for that just yet. The only code I'm getting is for the oxygen sensor, but it was the very first thing I replaced after the trouble started. I suspect the unburnt fuel is fouling the signal. I have probably replaced a couple things that were functioning correctly, but some of them, probably most, were due for replacement. The alternator was replaced because it was no longer charging. Besides, if you look at the symptoms, any of the parts I replaced could have been the culprit. I will accept defeat if my friend and I cannot make an improvement, and make the haul to the dealership.

[Dousan_PG]

u change mafs too?

[tkrolo]

Haven't tried switching out the mafs yet, but don't expect improvement. Because the problem seems to have something to do with heat from operation, I don't think it is the problem.

[ledzeppelin240]

Well if the problem happens only when it is warm then it has to do with the closed loop operation. First thing I would do is check for codes, then O2 sensor, then check fuel pressures and flow. Then go from there...

[OdessaS13]

. Nearly everyone is strictly obdII and their diagnostic methods are nearly all computer based, and I don't feel like paying $50/hr for that.

The only code I'm getting is for the oxygen sensor, but it was the very first thing I replaced after the trouble started.

i dont understand if you already pulled codes or you cant due to the fact everyone is obd2. in the case that you havent pulled the codes
you can pull the codes your self..im too tired to search for you but the ecu is behind passnager side panel. you will need a flat head screwdriver to rotate the screw and watch the blinks ie # of long/ # of short then search for ecu code decoder. I think its fair to guess its a problem with fuel injectors or seals but dont take my word on it.

btw
replacing the egine was me being sarcastic.

I have a spare MAF if you need one. PM me if you would like and ill test it to make sure it works as i got it a while ago and its been sitting in a plactic bag in the garage as a spare

latez

[tkrolo]

If you would have read my last post completely, I did pull codes off the ecu.

I appreciate your humor, just wasn't sure how to take it. Thanks for the mafs offer. I'll let you know how successful I am this weekend, and I might take you up on it.

What I meant about the local service shops is that, if it isn't FoMoCo, Chrysler, or GM, they act like they don't know where to start. I've discussed the problem with several different local mechanics who, even though they may be "ASE" certified, act clueless as were to start diagnosis without the aid of their computers. In fact, they act as if they don't want the business. I'm not knocking mechanics in general, only those in my area. I'm sure they are more than adequate with their own products, but frankly, I'm not sure I want them digging around under my hood so they can learn Nissan.

Thanks for your continued assistance.

[aznpoopy]

Originally Posted by tkrolo

Those were replaced before also. Sorry for excluding that. My thought is that I'm not getting a good spray from the injectors causing fuel to pool instead of burn. Occasionally I get gas from the exhaust with fuel smell but exhaust seems to be normal coloration. The thing that has thrown me is that it is triggered by heat or when the car reaches normal operating temps. It runs fantastic when cold although idle is a little high, but that is normal at cold temps.

injector o-ring or injector is starting to go out, IMO.

[phrozen]

have u checked for spark on al cylinders? just because its been changed b4 dosent mean u got good stuff. get a cap and rotor from nissan dont be cheap that kragen shit dosent fit good. but some ngks. u try cleaning ur maf? changed the o2? o2 sensors are as cheap as 12 bucks if my mind serves me correctly.

try changing the thermostat and cleaning the iacv, and the egr stuff. just gotta narrow it down. its a 240 they run great as long as u take care of em. mine had 250k orignal and i sold it to my friend and its almost at 300k still runs like a champ besides burning oil

[g2ic02]

have you tested the circuit for the oxygen sensor. It could be something as too much resistence in the circuit. Or the coolant temp sensor. I know you replaced the sensor, but often times the problem doesn't lie in the sensor itself. I would do a voltage drop across all the wires leading to the o2 sensor and the coolant temp sensor. If you email me i will right up how to test the sensors, but you will need a wiring diagram. [email protected]