Most stubborn cylinder 1 Misfire/rough idle ever?

[Smith]

Ok the title may be a bit dramatic, but I definitely need help. I've been around here for years since I got my first R50, but I honestly don't remember if I have ever posted. I have mostly just read and absorbed until I've come across an issue that I can't seem to figure out. Thought I might see if anyone has an ideas for me that I haven't tried already.

I'm on my second R50 now, which is a 2003 with the VQ35 and about 135k miles. A while back I started feeling a little roughness in the idle but only once the engine was fully up to temp and at its lowest idle (in gear). At the time there were no codes aside from one regarding the key chip not being recognized some of the time (I forget the acronym) because I'm using some cheap aftermarket key. Regardless, I figured that shouldn't have any effect on anything once the engine is running. Time goes on, the roughness in the idle gets a bit worse and I finally pull a Cylinder 1 Misfire code (probably P0301 but I'll have to confirm later). Started with replacing plugs then swapping coils around to see if it followed, it didn't. Compression test showed within a few percent of the other 5 cylinders' PSI. Injectors were all pulled, tested, and cleaned on a little homemade rig I made out of a 12v battery, some spare hose, and a can of carb clean. Fresh o-rings and those went back in. Aside from maybe running slightly better overall, the same idle issue and Cyl 1 Misfire code remains. No apparent vacuum leaks, and the one leak I did find with the "spray carb cleaner around the engine bay while running" test was a huge crack in the underside of the intake hose/pipe which has since been replaced and apparently wasn't the problem, despite my excitement in thinking I had found the issue.

One other likely important detail that I forgot about until this point in the post is that sometimes I'll have to crank the starter for 3-5 seconds to get it to start, and when that happens it seems to dump quite a bit of fuel out the exhaust immediately after start. I'm assuming this is fuel that is being passed through Cyl 1 without being ignited while cranking. This hard start also seems to only happen if the engine is warm but has been shut off for greater than a couple minutes. If it's cold or was just shut off, it usually starts just fine.

Any tips or help would be massively appreciated, as this has been keeping me up at night quite a bit. I'm usually fairly decent at diagnosing things like this but apparently I'm missing something. I know there is a ton of experience rolling around in these forums, so I'm hoping one of you knows exactly what's going on so I can feel dumb and have a smooth idle again.

[CamperDan]

2 hours ago, Smith said:

Ok the title may be a bit dramatic, but I definitely need help. I've been around here for years since I got my first R50, but I honestly don't remember if I have ever posted. I have mostly just read and absorbed until I've come across an issue that I can't seem to figure out. Thought I might see if anyone has an ideas for me that I haven't tried already.

I'm on my second R50 now, which is a 2003 with the VQ35 and about 135k miles. A while back I started feeling a little roughness in the idle but only once the engine was fully up to temp and at its lowest idle (in gear). At the time there were no codes aside from one regarding the key chip not being recognized some of the time (I forget the acronym) because I'm using some cheap aftermarket key. Regardless, I figured that shouldn't have any effect on anything once the engine is running. Time goes on, the roughness in the idle gets a bit worse and I finally pull a Cylinder 1 Misfire code (probably P0301 but I'll have to confirm later). Started with replacing plugs then swapping coils around to see if it followed, it didn't. Compression test showed within a few percent of the other 5 cylinders' PSI. Injectors were all pulled, tested, and cleaned on a little homemade rig I made out of a 12v battery, some spare hose, and a can of carb clean. Fresh o-rings and those went back in. Aside from maybe running slightly better overall, the same idle issue and Cyl 1 Misfire code remains. No apparent vacuum leaks, and the one leak I did find with the "spray carb cleaner around the engine bay while running" test was a huge crack in the underside of the intake hose/pipe which has since been replaced and apparently wasn't the problem, despite my excitement in thinking I had found the issue.

One other likely important detail that I forgot about until this point in the post is that sometimes I'll have to crank the starter for 3-5 seconds to get it to start, and when that happens it seems to dump quite a bit of fuel out the exhaust immediately after start. I'm assuming this is fuel that is being passed through Cyl 1 without being ignited while cranking. This hard start also seems to only happen if the engine is warm but has been shut off for greater than a couple minutes. If it's cold or was just shut off, it usually starts just fine.

Any tips or help would be massively appreciated, as this has been keeping me up at night quite a bit. I'm usually fairly decent at diagnosing things like this but apparently I'm missing something. I know there is a ton of experience rolling around in these forums, so I'm hoping one of you knows exactly what's going on so I can feel dumb and have a smooth idle again.

If your scan tool reads live data take a look at your Mas airflow sensor and make sure it's reading at least 3.5gs as I had a very similar issue and just like your self once the engine was warmed up when ever I came to a stop at a red light I would experience a bit of a stumbling idle. Turned out to be a bad Mas airflow sensor that was under reporting data 2.97gs to be exact. Oh and I have a video you can checkout on said issue as well. Here's a link.

 

Chris.

 

 

[Slartibartfast]

The MAF is a good thought, and an easy one to check if you've got a half-decent scanner. Could explain the hard starting, too. That said, I wouldn't expect it to only cause problems on one cylinder.

 

The service manual offers a little troubleshooting for misfire codes. Might be worth a read. Looks like you've tried most of what they suggest, though.

 

I would follow the compression test with a leakdown test. When the head gasket let go on my neighbor's Toyota, the compression still tested fine, but when I applied shop air to #4, it bubbled out of the radiator. (I didn't have a leakdown tester at the time, so I stripped the compression tester down to just the hose, and stuck the air nozzle in the end.) It's probably not the head gasket--I don't remember anyone else on here having a head gasket let go on a VQ, and I imagine you would've mentioned if it was losing coolant--but it's still worth ruling out.

 

When you replaced the plugs, did #1 stand out from the others? Color, deposits? Might give a clue if it's a mixture issue.

 

When you installed the injectors, did they all go back in the same holes they came from? And did you flow-test them after cleaning them? If #1 has its original injector, untested, I would not rule it completely out yet.

 

Are you sure what you're seeing in the exhaust is fuel? My dad's '03 burned an alarming amount of oil, especially on warm starts, though I don't remember it throwing misfire codes.

 

Have you checked your your power valve screws? Long shot, but if one of the butterfly plates fell in, I can imagine it getting stuck in front of an intake valve or something.

[Smith]

19 hours ago, CamperDan said:

If your scan tool reads live data take a look at your Mas airflow sensor and make sure it's reading at least 3.5gs as I had a very similar issue and just like your self once the engine was warmed up when ever I came to a stop at a red light I would experience a bit of a stumbling idle. Turned out to be a bad Mas airflow sensor that was under reporting data 2.97gs to be exact. Oh and I have a video you can checkout on said issue as well. Here's a link.

 

Chris.

Thanks for the response! I also somehow completely forgot that I tested out swapping the MAF a while back and that didn't fix the issue either. For good measure, I checked on my scan tool and am getting reads of around 3.6gs so should be good there. Haven't had a chance to give the video a watch but will do so after work, so thank you for linking that.

[Smith]

10 hours ago, Slartibartfast said:

The MAF is a good thought, and an easy one to check if you've got a half-decent scanner. Could explain the hard starting, too. That said, I wouldn't expect it to only cause problems on one cylinder.

 

The service manual offers a little troubleshooting for misfire codes. Might be worth a read. Looks like you've tried most of what they suggest, though.

 

I would follow the compression test with a leakdown test. When the head gasket let go on my neighbor's Toyota, the compression still tested fine, but when I applied shop air to #4, it bubbled out of the radiator. (I didn't have a leakdown tester at the time, so I stripped the compression tester down to just the hose, and stuck the air nozzle in the end.) It's probably not the head gasket--I don't remember anyone else on here having a head gasket let go on a VQ, and I imagine you would've mentioned if it was losing coolant--but it's still worth ruling out.

 

When you replaced the plugs, did #1 stand out from the others? Color, deposits? Might give a clue if it's a mixture issue.

 

When you installed the injectors, did they all go back in the same holes they came from? And did you flow-test them after cleaning them? If #1 has its original injector, untested, I would not rule it completely out yet.

 

Are you sure what you're seeing in the exhaust is fuel? My dad's '03 burned an alarming amount of oil, especially on warm starts, though I don't remember it throwing misfire codes.

 

Have you checked your your power valve screws? Long shot, but if one of the butterfly plates fell in, I can imagine it getting stuck in front of an intake valve or something.

I'm with you in that I've never really come across head gasket issues on a VQ, and I've had a few myself with higher mileage. Definitely not losing coolant, but I agree that it might be worth doing a leakdown at some point.

I don't remember specifics on when I pulled that plug but I do remember thinking that it was an unburnt fuel situation. I'm finding very strong spark every time I test, which is frustrating. Figured that could also indicate that the injector was dumping too much fuel into that hole, which led to the pulling and cleaning of those. I did not swap that injector to a different location when putting them back in, and now I'm rather regretting that decision. Also no flow test, but from what I saw the flow shouldn't have been TOO far off from the rest. If I go back in that deep, I'm probably just going to end up replacing all 6 injectors this time around. Speaking of which, how much trust should I put into aftermarket injectors? It's hard to stomach spending OEM money on something that may not even be needed, ya know?

What I'm seeing come out of the exhaust is definitely fuel and not oil. I'm all too familiar with the sights and smells of both. As far as the power valves go, I'd like to believe I would have spotted an issue there when I had the intake apart but I didn't check those specifically and I'm far from perfect. I'm thinking at this point my next steps might need to be leakdown, then pull the intake back off to check those and swap out injectors just to eliminate some of the more pain-in-the-ass possibilities.

Thanks for the help!

[Slartibartfast]

Yeah, I hear you on not wanting to throw expensive parts at it on a hunch. I don't know how good aftermarket VQ injectors are/aren't, but I remember Cuong Nguyen had a hell of a runaround with cheap injectors causing problems on his VG. I think he ended up getting a set of OE ones from the wreckers. Being a cheapskate myself, I'd probably try and swap the injectors from hole to hole before buying new ones, but I also understand not wanting to have to take it apart a third time if it turns out the injector is the problem.

 

I would be tempted to also check under the valve cover while it's torn down, but that's mostly because I just opened up a misfiring Dodge where the roller decided it was done and ate the cam lobe. I haven't heard of a VQ doing that either, and I imagine the noise would've tipped you off if yours somehow had.

 

Hopefully it ends up being something simple. Good luck!

[CamperDan]

17 hours ago, Smith said:

Thanks for the response! I also somehow completely forgot that I tested out swapping the MAF a while back and that didn't fix the issue either. For good measure, I checked on my scan tool and am getting reads of around 3.6gs so should be good there. Haven't had a chance to give the video a watch but will do so after work, so thank you for linking that.

Ok so that rules out the MAF then.

 

Chris.

[CamperDan]

5 hours ago, Slartibartfast said:

Yeah, I hear you on not wanting to throw expensive parts at it on a hunch. I don't know how good aftermarket VQ injectors are/aren't, but I remember Cuong Nguyen had a hell of a runaround with cheap injectors causing problems on his VG. I think he ended up getting a set of OE ones from the wreckers. Being a cheapskate myself, I'd probably try and swap the injectors from hole to hole before buying new ones, but I also understand not wanting to have to take it apart a third time if it turns out the injector is the problem.

 

I would be tempted to also check under the valve cover while it's torn down, but that's mostly because I just opened up a misfiring Dodge where the roller decided it was done and ate the cam lobe. I haven't heard of a VQ doing that either, and I imagine the noise would've tipped you off if yours somehow had.

 

Hopefully it ends up being something simple. Good luck!

Yeah used O.E.M junkyard parts are better than crappy new aftermarket parts any day. My ALTERNATOR recently gave up the ghost and I replaced it with a used O.E.M one from the junkyard and all is well again. Now at least when he swaps the fuel injectors around and the misfire moves he will know what to do from there. The con is having to tear things down again.

 

Chris.