Please help! Misfire and fuel related issues

A

AndrewC08MS3

Greenie N00B Member
Greenie Member
171k and 20k on sp63 engine. The car has been my daily driver for the past 5 years. Last week OMW home from work the car started stuttering under a load and the idle is a little off. There’s a slight popping you can hear coming out of the exhaust when idling. No abnormal KR while driving. When this started, I checked HPFP pressure right away while driving but it goes right up to 17-1800psi like normal but at idle it was about 100psi low (low to mid 300’s). Also the AFR’s are wacky too, anywhere from 13.96-16 at idle and part throttle cruising, and between low load shifts, it sometimes takes a couple seconds to return from 29.25 down to the 14’s which isn’t the norm either. MAF G/S seems a bit on the low side to me as well while driving. I’m getting random CYL3 misfire codes and I did get a lean idle condition code also. Also this engine has absolutely no oil consumption and never much of anything to drain from the OCC’s.
I went over all intake/boost tubes, catch can hoses, and wiring in the engine bay to confirm no leaks or damage to anything and found nothing. Also pulled and replaced all plugs. They all looked a bit lean so it’s not 1 individual CYL that’s off which tells me the injectors and ignition wiring likely are not the culprits. I ran fuel inj cleaner through the system and oddly, my idle FP returned to the 400’s but nothing else has changed. Also ordered new MAF and downstream O2 sensors and waiting for those to come but I’m afraid this will turn into a (buying and throwing parts at it) kind of thing and the rest of the options are quite expensive and time consuming. Any insight would be much appreciated! Thank you!
 

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What is your fuel pressure keoeo? Do the prv test
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The ITFP is putting out 57psi

I’ll do the pressure relief valve test now

As soon as I turn the key off the pressure immediately goes down to 57/58psi and stays there. Never climbs

@Awafrican does that sound like the fuel pressure relief valve being stuck open? I certainly hope so because although expensive for a damn check valve, it’s much cheaper and easier to do than some of the other fuel system parts.
 
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That could have been done in 1-2 posts...posts merged itfp pressure should be about 60psi so that's good.

So cars HOT, you turn the engine off, flip back to koeo and it never goes past itfp? That's bad prv, to me. If you're not doing it with the engine hot you won't get the pressure to build.

@Sho prv is more up your alley than mine thoughts
 
Sorry I was doing house duties and car diagnostics at the same time yesterday. And yes the engine was hot. I had just finished test driving it prior to the tests. First I tried a couple KOEO just shutting it off at idle (HPFP act. Pressure 350-420’s). 57-58 psi immediately after shutting down. Waited 45 seconds or so and pressure never climbs like it’s supposed to. So I decided to try shutting it down with fuel pressure higher (1000-1200) to see if that gave a different result and it did not.
I ordered the PRV so we’ll see what happens when it shows up in a few days. Can’t tell you how much I appreciate your help with this!
 
The one thing that has me wondering if there isn’t something else going on in addition to the PRV is it doesn’t idle well even when HPFP Is maintaining 400+psi. Is that common in this scenario?
 
Could be struggling to maintain sure, could be spill valve not playing nice perhaps the ground near the hpfp isn't doing so hot either check it and make sure it's clean and tight.

Sometimes the simple solution is the easiest solution
 
Ok,
So I spent Friday night and yesterday working on the car at work. Replaced the PRV and no change, so then I installed the MAF and downstream o2 with no luck, then I pulled the spill valve and it was fairly dirty. So I removed the HPFP and completely disassembled and cleaned it and the spill valve but again it still didn’t change the way the car runs.

Keep in mind I’m not driving the car at all because the misfiring and lean readings make me not want to chance anything. The fuel pressure is rock solid and reading normal but AFR’s are still lean and fluctuating all over btw 14.4 and 15.8 at idle. And when I bring the RPM’s up to 3k or so, you can clearly hear a constant misfire like it’s only running on 3 Cyl. At this point I’m pretty convinced that one of the injectors is down, either clogged or not firing but would like some input from you guys on whether I’m going in the right direction or not. Replacing an injector is the last thing I want to have to do because I have CS seals and as far as I know, you can’t buy one of those from any of the vendors so I’ll be looking at another $600 or so just to replace 1 injector.
The Snapon guy comes to my work tomorrow so I’m going to see if I can borrow a scanner capable of turning injectors on and off independently to try to isolate the problem. Thoughts?
 
You can re use the CS injector seals, just increase the TQ by 3-5ft lbs I think it is, I know some people have used them up to 3 or 4 times.

Sorry to hear prv and spill valve didn't help, certainly could be the injectors, may be worth pulling them and sending for cleaning and flow testing, the new seals for injector to fuel rail can be had off rock auto look for the gb remanufacturing kit, heck some people have even used the injector to block seal on that kit (OEM style) with success for stock ish power.

Compression test and leak down test may also be in order
 
Ok that’s great news that I can reuse the CS injector to block seals, and I got the GB’s from rockauto for top of the injectors last august when I installed the engine so I’m confident that those will be fine. If I have time tomorrow after work, I’ll warm her up and do the comp. and leakdown tests because I wanted to check the new plugs anyway to see if that tells me anything.

As far as sending out the injectors, is it a bad idea to find someone local to me rather than actually sending them off to someone that specializes in MZR injectors? I only ask because time is of the essence as I’m borrowing a car right now for transportation but I dont necessarily wanted to cut corners either
 
Ok so,
Snapon guy comes to my work every Monday so I borrowed his triton scanner in the hopes of being able to control injectors independently and identify the one that isn’t working if indeed that’s my issue. No luck on being able to do that yet but I happen to do the PRV test again now that I have the new valve in and instead of going straight down to 57psi, it just slowly goes down from 430 to to 57 (over about 2 minutes) it never climbs above the idle pressure of 430 up to the 1875 like it supposed to to crack the PRV.
 
How hot was the car on this last test? It needs to be fully up to temperature
 
I was idling it in the shop for almost 45 minutes doing diagnostics with the scanner so the coolant had already cycled back-and-forth from 190 to the 217° radiator fan kick on. I believe it was at 192 when I did the PRV test several times. I am still having the same problems as I did from the start with the exception of fuel pressure at idle is now normal. I’m not driving the car at all but I still plan on pulling and checking the new spark plugs, and doing a compression/leakdown test. I will post my results as soon as I get off work early enough to do it this week.

EDIT: 7/17/22
Late day at work today so I didn’t accomplish more on the car but before I left, (which is where I’m storing the car) I did the PRV test again and it miraculously functions as it’s supposed to. Nothing else has changed though. Still pops slightly at idle, hesitates and shutters slightly under loads that are above .8ish. AFR’s fluctuate at idle BTW 14.4 - 16, and also any time I let off and get back on the throttle it goes lean to the tune of 17’s-18’s and then slowly over the course of 3 to 4 seconds or so, AFR’s make their way back to the 14’s as long as I stay slightly on the throttle. Fuel pressures all the way around are completely back to normal now though. This is driving me crazy. One thing I will add that could be relevant is when I disassembled the HPFP for cleaning, every single part was removed and cleaned individually except I was not able to pull the collar off of the piston shaft. It wasn’t loose and easy to slide off like a video I watched showed. I didn’t want to scratch or scuff anything so I didn’t disassemble the Autotechs completely.
 

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So another thing I might add is when I removed the spill valve from the high-pressure fuel pump housing there was noticeable metal flakes at the bottom of the bowl mixed in with the fuel. I’d like some input from you guys on this but one hypothesis I have is that the autotech piston is seizing with the collar, scuffing against each other and creating the metal flake I found in the spill valve cavity. Those small flakes of metal have made their way down to the fuel rail and clogged one of the injectors. I really didn’t want to have to do anything with the injectors without confirming 1 of them is causing my issue but I am out of options at this point I think and I can only work on the car on the weekends. Have any of you guys ever heard of HPFP internals failing? See picture above showing the collar I’m talking about that I couldn’t separate from the piston shaft
 
Compression left to right 178 180 178 178
Cylinder 3’s new spark plug with about 1hr of idle time doesn’t look like it’s burning anything. The other three look rich as if the fuel system is compensating for an injector that’s not firing. I’ve confirmed cyl3 does have spark just as strong as the others. Does anybody have any insight to my previous post?
 
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