Vg30i running issues after rebuild

[RCWD21]

I recently rebuilt my 87 pathfinder from top to bottom. New everything minus maf and TPS.

 

Now to the problem that's really driving me up the wall.. I really can't express my aggrivation in words on a forum.

 

It starts and runs has even compression across all 6 cylinders has new cap and rotor and 9mm silicon plug wires with new Bosch plugs that are correctly gapped and the proper heat range. I can run it up to temp and the whole time it's running and getting warm it misfires but it's more like it's loading up from fuel.

 

Once it's hotter than I can stand (only able to hold the upper radiator hose for about 2 seconds max and the gauge is right in the middle) will it run better. But it still had a stumble no matter what I do.

 

Here's a weird bit of info, sometimes it will run so rich that even with the pedal to the floor will it barely stay running while blowing thick black smoke out the exhaust. But I can shut it off wait a minute, fire it back up and it'll run fine. It's only done that twice.

 

Another thing is with the airbox off I can put my finger over one of the maf inlets and it will idle down and run better but only slightly.

 

I can unplug the maf completely and it'll run smooth like it's supposed to but it won't idle down either.

 

I can't get the idle under 1k rpm's no matter what I do to this thing.

 

Another thing on this long list of problems is that I can see fuel slightly puddle up on top of the butterfly and in the opening across by the mixture screw thing between the 2 solenoids.

 

It will idle with the idle screw backed out until the screw is no longer touching the throttle cam.

 

So to sum this up: it's been rebuilt, it won't idle down under 1200 to 1000 rpm. It will randomly run rich and runs better without the maf plugged in. If I plug it back in it will start to stumble again. I've tried everything the only noticeable difference I can see is if I take the fuel pressure regulator and hook it's vacuum line to one of the ports that actually has vacuum while it's running.

 

I'm at my wits end and I could really use my help on this.

[Slartibartfast]

Alright, one stupid idea first. Is your air cleaner on? I've read about TBIs getting upset when they're run without the full box.

I'm assuming your Replaced Everything list includes vac lines, temp sensor, and oxygen sensor, and that the wiring is all good, and I'm also assuming you've checked for ECU codes.

Given that the issue changes when you shut it off or screw with the electrics, the fuel puddling sounds like a symptom of the computer throwing too much fuel rather than a leaky injector. Given that the MAF is something you haven't replaced, and unplugging it seems to improve the idle issue, I'd try swapping in a known good MAF. I've actually got a TBI MAF on my shelf but because the donor was long dead, I have no idea if that MAF is any good.

 

I'll bet the idle is caused by the fuel issue, either directly or because the computer is trying to compensate for something. I'd focus on the fuel issue first and see if the fix for that clears up the idle too.

[RCWD21]

It actually idles the same with or without the airbox on. I got it to idle down low where I want it once today, but that was with the maf unplugged (going to be ordering a new one since I found one for cheap with a 10 year warranty) and the tps rotated counter-clockwise if you were in the drivers seat (going to be ordering one of those too since there seems to be a spot where it's worn out) but that low idle was the fact that it was running very rich to the point of black smoke coming out the exhaust. Most of the time with it idling it doesn't smell like it's running rich. It smells like a hot clean burning engine should.

 

I've replaced every vaccum line on there, but today I started to suspect the cylinder head temp sensor connection was a bit iffy so I'm going to find a good injector pigtail to test with and order a new one with a quick release clip on it so in the future the plastic won't shatter so easily from removing the clip. Plus it's sealed better than the factory plug.

 

Unfortunately I don't have access to a another maf yet, I'm going to be going to the junkyard at the end of the week to get my hands on a few different ones just so I have more than one to test with. Same with some throttle position sensors.

 

I'm basically dealing with a backwoods know-it-all's left overs. This is the first time this engines seen life since december.

 

Other than the fact that in my 2 mile drive home and all the testing I've done that's burnt a little less than a 1/4 tank it drives great minus the alignment and the flat spots in the tires..

 

All in all I'm just happy it runs and is somewhat drive able. I currently don't have the dash in so most of the wires are looped up with all the switches plugged in so I could at least get it home from my dad's shop.

[PathyAndTheJets]

I'd start by double checking the vacuum line routing. You said you swapped one onto the fuel pressure regulator, which from what I gathered from a quick glance at my spare fuel pump, is integral to the pump. Could be wrong but I didn't see it on the vacuum diagram in my FSM either.

 

But if I am incorrect in that, the fuel pressure reg should have full vacuum supply.

[RCWD21]

From all the pics I've found the way the FPR was hooked up prior to me experimenting today was the correct way, but with my finger over that port (basically the highest port on the throttle body) I can't feel any "pull" with my finger over it. But when I put a line from the regulator to a vacuum port below the butterfly the idle will lower just a bit but it will eventually climb back up slowly.

 

I'm struggling to get this to come down below 1k rpm idling. I'd like it to be around 750 to 800rpm.

 

As for routing the vacuum lines, I'm only sure of a few of the lines. All of the others are from memory (trips to the junkyard 2 hours away) and from looking at pics on the Internet in hopes of finding the correct info.

 

TBI is like my worst nightmare of a carburetor and fuel injection mixed into one lol. I need to find a very tiny mirror so I can see if possibly both injectors are firing instead of just one. It seems like the more fuel this gets the higher the idle will be up to a certain point and then it starts to chug and lope from loading up on fuel. I may even snag an ecu just to see. Would an ecu from a 4cyl truck run this engine? I have one and the connections look the same just not the mounting feet.

[RCWD21]

I found 2 things today that could be related but I'm not sure (I'm still searching for an 87 fsm) but:

 

1. I can crimp the fuel return line and the idle goes up and it smooths off pretty much completely.

 

2: the only code stored in the ecu is 12, according to the pinned thread that's the code for the maf.

 

So would the crimped return line be forcing the fuel through the injectors that it needs to actually run correctly because the maf isn't giving the proper signal to the ecu?

 

I've cleaned the corrosion from the terminals as best I could but I'm going to replace the terminals with new ones as I believe the corrosion went past the terminal and is now between the wire strands and the metal terminal (I've dealt with this on sunk jetskis and it's not easy to find sometimes)

 

Either way I'll be working on it more this weekend if it doesn't rain

[RCWD21]

I got it running much smoother now. I cleaned every terminal I could find. For some reason the harness to the CHTS didn't have continuity. So I replaced the terminals with some from a Chinese scooter of all things but will be ordering a new sealed terminal clip for it. It runs much better and part of my idle problems were due to the fast idle linkage being seized and keeping the throttle butterfly open more than it should.

[Cuong Nguyen]

That's good news

 

Sent from my SAMSUNG-SM-N920A using Tapatalk

[RCWD21]

I'm still thinking about buying a new maf since one of the hot wires is a little tweaked and the new one has a 10 year warranty with it

[RCWD21]

Just an update on this since I haven't been on in a long time and I haven't really touched the 87 since around this post time. I found most of my running issues to be a few stuck linkages on the throttle body, tapping on them to free them up after soaking in some pb blaster was all it took. Here soon I will be doing some major work to it to get it back on the road and deep in the woods where it belongs.