Jump to content

Intermittent issue - sounds like a vacuum leak?


willaay
 Share

Recommended Posts

Hey everyone, I'm new to the forum but have lurked for answers for a while. This issue has happened to me twice so far that it left me stalled in the road and I'm not sure exactly how to pinpoint it. I bought a 95 Pathfinder with auto transmission in November and in January for seemingly no reason the RPMs seemed to drop really low after I had been running errands and left the car parked for a couple of minutes. This happened after the engine had been warm and driving for a while. When I was coming to a stop at a light, the car stalled. I was able to start it no problem but the car would keep stalling unless I kept the revs up. Luckily I was close to home and when I got there I checked the codes and none showed up.

 

After I checked the codes the car seemed fine and drove fine for a week and I brought it in for an unrelated timing belt replacement. It's been a couple weeks since then and the car has been fine until yesterday which was the first day I had used the AC (maybe since the initial stall). The car sounded like having the AC on was using a lot of power: some RPM changes, at a stop it would kind of 'lurch' a little until finally the revs got pretty irregular and the car stalled again. Again, I could start it fine and I turned off the AC and drove home and by the time I got there it seemed to be totally fine. 

 

Today I tried to replicate the issue by just running the car in drive (but at a stop) for a while with the AC on. The car eventually started running odd and eventually the RPM irregularities returned. Not only that but the car took 2-3 times to start only when warm and I've been noticing a weird no-crank start on some trips lately but haven't been able to pinpoint a cause. A video of the irregular idle is here: https://streamable.com/sh1lh3

 

Anyway sorry for the wall of text but I want to take a long trip soon and don't want to worry about this weirdness. It sounds like a vacuum leak but could that be so intermittent? I've sprayed some carb cleaner on the lines earlier today and noticed some rev changes but can't be certain if they were accurate - when the engine warmed up I couldn't get the spray to change revs. 

Link to comment
Share on other sites

The stalling sounds like what my '93 did when the idle air control was acting up. Cold idle was fine, but now and then, on warm idle, it would try to idle very low, low enough that it would stall when I put it in gear or came to a stop in gear. It drove fine otherwise, it just forgot that idling was a thing that it was supposed to do. The issue was intermittent and drove me bats as I'd mess with something, think that fixed it, and have it crop up again later. What finally worked (so far!) was to disconnect the hose going to the idle control (there's the big corrugated hose between the MAF and the throttle body, and there's a smaller hose with some elbows coming off of that and going under the intake back to the idle control--I disconnected that one right at the corrugated hose where it's easy to get to), shot some carb cleaner down it, and started the engine to suck it through. I did this a few times in a row in hopes of flushing out whatever gunk was making the idle control stick. It was hard to start immediately afterwards but cleared up quickly afterwards, and it the idle hasn't been an issue since.

My '95 did the surging thing, though I don't remember the aircon being involved. I don't remember finding a smoking gun, either, IIRC I just messed around under the hood checking stuff for a while and then it sort of went away. The aircon system tells the computer to bump the idle up, so it could be a different symptom of the same fault with the idle control valve, or maybe I had a bad connection in one of the plugs I checked for corrosion. I think I checked the plugs for the MAF and the TPS, and probably the EGR control solenoid as well. I remember it stalling out once when the EGR solenoid plug fell out. That was fun to plug back in on a hot engine.


It's probably not a vac line issue, but if they're original, go ahead and change them. They're cheap and easier to replace than to try and diagnose around if they're old and suspect.

Not sure what you mean by a no-crank start. Click/no start is pretty common on these.
 

Link to comment
Share on other sites

I've been hearing the idle air control valve come up a couple times while I've been troubleshooting - I will definitely give it a look tonight and see if I can get some carb cleaner in there. The MAF seems to be good, I checked that yesterday. Thanks for your input!

Link to comment
Share on other sites

Hahaha. That surging is all too familiar with me. I deal with it on a weekly basis. The later models (94/95) came out with a TSB where they added a pigtail with an external ground to the MAF harness plug to the sensor.  Poor ground or corrosion/connectivity will cause that idle surge and stalling when rolling to a stop. 

Link to comment
Share on other sites

I had a stumbling just off idle issue that ended up being that MAF plug. I tightened up the terminals with a pick (probably not the right way to do it) and it's been fine since.

Link to comment
Share on other sites

Posted (edited)

The MAF seems to be in good shape, I had the throttle body and IAC cleaned out and the issue hasn't resurfaced yet. I'm going to take a little round trip drive between Chicago - Milwaukee this weekend just to see how it does. 

Edited by willaay
Link to comment
Share on other sites

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 account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...