Burn Posted November 1, 2015 Share Posted November 1, 2015 Hi. I have a pathfinder I picked up cheap and I am trying to diagnose this problem. When it starts up cold it will start ok and idle fine but if you try to rev it up at all it just stumbles and losses rpm instead of gaining. So far I have cleaned the Maf, replaced the ECT sensor, threw in some other injectors and fuel pressure regulator and adjusted the TPS. It has around 43 psi fuel pressure hen idling and drops to 35 psi when shutoff. The fuel filter is new as well as the plugs. After it warms up it runs great. Trans shifts good and has decent power every now and then it will stumble at full throttle... but only sometimes usually it runs absolutely great after the initial cold stumble goes away. Seems like it is running rich from the look of the plugs I took out when I got it home. What else should I be looking at? I am at a bit of a loss as this only occurs when cold. No codes coming up Link to comment Share on other sites More sharing options...
ferrariowner123 Posted November 1, 2015 Share Posted November 1, 2015 Have you check the cold idle solenoid? Sound like it not doing its job very well and messing with the fuel mixture a little too much... Make sure all your connections are clear of corrosion and any other nonsense that shouldn't be there, grounds especially! Just clean them with some medium grit sandpaper, just enough to give a solid connection. And just checking here,but have you actually plugged a code reader in, to get the "no codes" claim or is the CEL just not on? Because a faulty, open loop O2 could cause some Fuel/Air issues. maybe the heater circuit failed in one causing the rough, cold running. Not sure if something like that would trigger a code, but maybe something to check. -Kyle Link to comment Share on other sites More sharing options...
Burn Posted November 1, 2015 Author Share Posted November 1, 2015 Thanks for the reply. Yes I put a code reader on it but it didn't pull any codes. I cleaned the idle control valve, throttle body and egr when I had the intake off but i didn't test that it was working. I will double check the connections. I read that the o2 sensors are not in use until the engine warmed up? It looks like one o2 was replaced not long ago I pulled them to give a look. Distrubutor also looks pretty shiny so I think it was replaced. Was going to have a look and see if there is some carbon tracking or something messing with the spark. Link to comment Share on other sites More sharing options...
jyeager Posted November 2, 2015 Share Posted November 2, 2015 (edited) You have been focusing on air/fuel delivery issues. Consider a spark issue. Read your resistance on the plug wires. An old plug wire will cause misfires. You might not be having a miss long enough to trigger the misfire code. But your symptoms sound consistent with a miss. ps. It wouldn't hurt to pull plugs and check their gap either. Edited November 2, 2015 by jyeager 1 Link to comment Share on other sites More sharing options...
Burn Posted November 3, 2015 Author Share Posted November 3, 2015 I will look at the ignition system next. I did.replace the spark plugs when I had the intake off for replacing injectors. Here is a video of the pathfinder when it is cold Link to comment Share on other sites More sharing options...
fixinto Posted November 7, 2015 Share Posted November 7, 2015 When you replaced the ECT sensor which one did you replace? the one for the gauge or the one mounted in the lower plenum. If it stuck in a condition that reads "warmed up" it would cause what you are talking about. Fuel psi sounds good, wouldn't sweat the O2 sensors as you stated they are not in play until high 140F. If plug wires are bad it will usually miss all of the time, not just when it is cold. If it were me i would plug in my 30$ obdII reader and turn on torque and see if it is in closed loop on start up. If so it would be the sensor in the lower intake. Also if you want to do a quick and dirty check of your IACV, bump the steering wheel one direction and then stop and the other direction. make sure the idle increases a little bit when u start turning, works best if you are sitting still and not rolling. turn on the AC "if it is functional" it should bump the idle up to compensate for the load. if it idles up under those conditions, it is probably OK. Link to comment Share on other sites More sharing options...
jyeager Posted November 11, 2015 Share Posted November 11, 2015 .. If plug wires are bad it will usually miss all of the time, not just when it is cold. ... I'm not saying it's got to be a plug wire. But what you said there isn't correct. When a plug wire is going bad, the resistance increases beyond spec. It results in the engine beginning to miss in the conditions that are hardest to ignite. These conditions are: 1) rich conditions...such as when cold. 2) high load conditions...such as when RPMs are low, in a higher gear and going up-hill or gradually accelerating. Personal experience there! Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now