Misfire, stalling on Braking 3.5L gen 2.5 Montero

[rahee006]

I just replaced the Valve covers and sparkplugs, wires on my 3.5L Pajero NL. (6G74) Now it has a Rough Idle, Bogs when stopping and then stalls. Feels like misfire. it has to do something with fuel, i was driving the gauge showed 1/3rd of a tank, then i was idling 2mins ago, and it showed its empty. and i am on a flat surface. Firing order is correct. 524163. Any ideas? It was running fairly ok this morning with a slight misfire, But never stalled or struggled.

 

[rahee006]

i used PK16TT Sparkplugs from Denso and NGK 7005 plug wires.

 

[Salonika]

You have a few threads going at the same time here so I'm a little confused as to what all you are up to. Weren't you also reporting O2 sensor issues on another thread? Did you ever resolve that? If you are trying to troubleshoot without your O2 sensors, you might have issues.

 

[normal_dave]

If you are working on a 6G74, 3.5L, then let's try this:

The firing order you listed is not correct for this engine. (you didn't post the specific year) This picture shows the coil locations on the newer models, but the firing order is the same.

If I recall correctly, If you have a distributor ignition, then at TDC, the rotor should point roughly to the firewall and actually be under the #2 plug wire tower.

Edit: just looked closely at your picture, of course you don't have a distributor! (duh) When I pull the upper intake, I always leave the coils in place. Many folks simply number the plug wire with white out or similar marker. The coil numbers are stamped on the intake, and the coil leads typically are the correct length to fit the coil. Since you've replaced everything, simply trace each lead from the cylinder in the picture manually all the way back to the correct coil number and you should be good to go.

Other issues could be vacuum leak at intake gasket, but I re-use them if they are good, vacuum lines, missed an emission plug somewhere on the harness?

 

[rahee006]

If the firing order is correct, i had 2 in the wrong place, i fixed it according to the diagram.
I made a video of the car idling. I will change the Fuel filter in a little bit, see if that helps it. I dont think i missed any connector. I replaced the Throttle body coolant lines with Silicone hoses. New gaskets on the upper and lower intake. I used Felpro, but was not very happy how it fit the gasket. was probably 1mm longer then it needed to be. but i dont see any oil leak or anything.

 

[rahee006]

Car is idling okay now, My firing order is marked on the plenum, so i went according to that, Car stalled in the middle of the street, checked fuel pump, spark, used starting fluid, car wudnt start, then i noticed theres a 4 Pin conncetor on the middle of the engine that had the inner rubber seal blocking it from getting or sitting properly. so I have fixed that and car runs fairly ok, just a slight hesitation, but i feel lots of power. Will replace the fuel filter and see what happens.

 

[nwoods]

Wow that idle video sounds terrible! sounds like it's missing 3 cylinders, not 1, and what is that periodic growling noise? Sounds like a loose motor mount or something is vibrating the whole car. I have no idea what is causing those things, I am far, far from being a mechanic, but i agree that your video sounds bad!

 

[rahee006]

the video was taken with the plug wires in the wrong places. the sound is coming from one of the drive belts, I have motor mounts on the way so i will be changing that soon as well. There is no vacuum leak to my knowledge as isprayed starting fluid on the upper intake and lower intake areas, no rise in idle or change in idle. Might do a smoke test when possible.

 

[normal_dave]

Maybe a little late since you've already done the valve covers, but from the video, I'm wondering if the valve lifters are contributing to the noise? Did you happen to pull a rocker arm and take a look at the lifters?

Here's how to inspect, clean, and bleed them, replacing damaged ones with OEM only.
http://www.club3g.com/forum/maintenance/165458-how-bleeding-lifters-v6.html

In the meantime, if you don't have an automotive stethoscope, do the old timer trick, cut a piece of wood dowel rod a little over 2' long, and CAREFULLY, rest the rod on top of each valve cover in several places, with the other end touching your ear and listen for ticking under the valve cover, engine running. See if one area is worse than the other. There will be some noise of course, but yours does sound pretty loud. If your lifters are pumping up properly, you will have drivability issues.

This ticking noise should change with engine RPMs and may fall away at higher RPMs, but NWoods is right, even with fixed plug wires, pretty noisy.

 

[rahee006]

with the valve covers off, i only have these 2 photos. I was not the happiest with the Felpro Gasket, If i take off the plenum again, i will replace it with OEM valve cover gaskets. but it seems like i have no leak anywhere. I do have an automotive stethoscope. I will inspect the lifters as soon as i go home.





also these are the old spark plugs

 

[normal_dave]

You know, none of those old spark plugs look really bad, that's good news.

This may be one of those "blinding flashes of the obvious", but you mentioned rough idle and stalling while braking. I think your '98 would still have the vacuum operated brake booster. The inner diaphragm can develop a leak and of course loose braking power assist and at the same time create a nice vacuum leak. Sometimes the leak doesn't appear unless you are pressing the brake pedal, and I imagine it would be worse when idling in gear. A simple test is to have someone apply the brake pedal, engine running, and listen for a change in engine sound, or here hissing from the booster body. Also you could take a pair of vice grips or clamp and close off the vac line running to the brake booster and see if there is a difference, or just disconnect the line at the booster end, plug it and see how it runs.