#4 Misfire

[ehsnils]

They are between the manifold and the TGV valves if I remember correctly.

 

It's rubber O-rings, and if they are original rings then they are a bit too small - which manifests itself at cold temperatures - and have to be replaced. Search other threads for this.

[aj_mariner]

Ah, then yes they were replaced. The originals were orange...but the new orange seals were a bit beefier. Everything was thoroughly cleaned and were installed dry.

[ehsnils]

Ah, then yes they were replaced. The originals were orange...but the new orange seals were a bit beefier. Everything was thoroughly cleaned and were installed dry.

OK good, always worth to check that issue considering the problems it leads to. Simple things first.

 

The #4 misfire is unfortunately a common issue also that may be caused by more expensive problems, including ringland failures.

 

Compression test (cold and hot) and valve clearance check are on the list.

[aj_mariner]

Understood. Trying to start with the intake system, since a small vacuum leak seems to be the most likely culprit due to colder temps. After the intake system is trusted, plan on moving to the fuel system and doing the fuel pressure reg mod.

[aj_mariner]

Installed new TMIC and bypass valve. Car seems to idle better but is still doing the wobble at same RPM range. Also, with temps now in the freezing range...the CEL will continuously blink when under good boost then go back to CEL on with CC blinking when backing off throttle. Vacuum evenly bounces slightly above and below 18.5” Hg vac when idle in park.

[aj_mariner]

I’m seeing two different specs for vacuum...both are for H4DOTC(ME)...one is -17.7inHg and the other is -19.7inHg. Which one is right?

[ehsnils]

If you have a flashing CEL - read the codes ASAP and check, flashing means that the EMS thinks something is really bad. Ignore the other flashing lights like Cruise Control, it always comes on with the CEL and confuses everyone. Get a code reader, it speeds up things a lot. And since it's under boost it's not a vacuum leak you are hunting primarily.

 

Don't mind the details of the vacuum specs at the moment, it's not critically important since it may vary due to many factors.

[aj_mariner]

Will the BtSSM app read codes on the go? Or can I just use the internal code reader (two white connectors in the fuse box) while driving? Been thinking this should be my next purchase since most of the things to mechanically check have been exhausted and I need to see more.

 

Forgot to mention that the internal code reader showed a #4 misfire (P0304) for the non-flashing CEL when I got back home after the test drive.

 

On a side note: sometimes the flashing CEL will just go away and not leave a continuous CEL with flashing CC.

[Max Capacity]

If you'd made sure the coil pack connector is tight and have swapped coil packs and injectors to see if the CEL follows one of them, and you have don't a boost leak test, the next step is a compression test of #4.

 

Sorry I didn't re-read the whole thread.

 

 

Most auto prats stores will read the CEL for free.

 

 

You do know these cars will burn #4 exhaust valve if left on the stock MAP.

[ehsnils]

Buying a good code reader and bringing it with you is a good idea since it is allowing you to catch even elusive codes and pending codes.

 

The problem with relying on auto part stores is that they are closed when you need them most!

[aj_mariner]

What is a good code reader than can grab codes while driving? Does the BtSSM app do this? I got a Bosch OBD 1150 but the manual says to not start the car for retrieving codes.

[ehsnils]

It shouldn't be a big deal to pull codes as soon as they appear, even if you have to stop first.

 

If codes are readable while driving or not is more depending on the car than the reader.

[aj_mariner]

Used the scanner and made the flashing CEL come on briefly, pulled over and found cyl 4 misfire pending. It’s crazy to know I can make it do it as well as avoid it. Also saw on the scanner while driving that my O2 bank 1 sensor 1 mA were jumping between 127.95mA to negative of the same value, 2.672V. Changed A/F O2 sensor and saw it does the same milliamp swing with a new sensor. Also tried to swap drivers side injectors but didn’t label them in my rush in the cold so need to do it proper next time so I know for sure. Sucks when your doing it outside without a garage in cold ass weather. At least it wasn’t raining. Will do this after work tomorrow in the warm shop. I used to love my car.

[Perscitus]

Its possible that the injector is clogged or starting to clog up, that would explain the misfires and the flashing CEL (transient misfire that's bad enough to potentially cause AF sensor and Cat failure if not fixed for x miles).

 

If you can live without the car for a few days to a week, pull all the injectors, send them out for ultra-sonic cleaning and flow calibration (typically 1/10th the cost of replacing all four with new OE injectors). Meanwhile, order up some new gaskets (typically 3 different ones per injector) and once they're back swap them back in... at least you'll eliminate one very likely source of the issue.

 

I'd also have a look at the in-pump fuel filter and pre-filter. Might be time to change those as well, especially if untouched since new.

 

BtSsm can read stored and transient codes, but not catch them real-time.

It will however give you Misfire counts per cylinder and all the typical SSM fields you'd expect (AVCS related: OCV, OSV, VVT, AF sensor info, O2 sensor info, Fuel Trims, AFRs, Final Fuel Base, Knock related info: IAM, FKC, FLKC, etc.)

[aj_mariner]

The injectors are new (10k miles on them), but am pulling the ol switch-a-roo to elimimate. I had the fuel strainer cleaned, and was told that it wasn’t a filter that needs to be changed...just an in-line strainer.

[Max Capacity]

In line strainer...I didn't realize these cars came with one.

 

Do you have an after market one installed ?

[aj_mariner]

No, I had the dealer do it a little while ago when the problem first reared it head. They told me that it didn’t have a fuel filter, more of an in-line strainer that can just be cleaned. So they supposedly cleaned it

[aj_mariner]

I remember it pretty well. Blew my mind that a car didn’t have a fuel filter.

[Max Capacity]

Well I guess you know the in tank filter is attached to the bottom of the fuel pump.

 

Some have installed a in line filter on the left front shock tower to help with the stumble starting about 2400rpm.

[aj_mariner]

Swapped #2 and #4 injectors today. Stumbled upon something interesting by dumb luck. When starting the car to let it warm up, it idled buttery smooth. Went to pull out of the shop and saw that the fuel pressure regulator sensing hose that connects to the intake manifold was still up by the windshield wipers. Put it on, and the engine started idling more rough. I think the car is jacking with me, or I’m starting to go crazy from being balls deep in this Mariah for too long. Either way, new fuel pressure regulator on order.

[ehsnils]

In that case you should reset the ECU and have it to re-learn and then do some test runs again since it's possible that the car has adapted to the wrong fuel pressure and that strikes back when you get under boost.

 

So there may be nothing wrong with the pressure regulator, just that the car has learned the wrong conditions.

[aj_mariner]

Awesome

[aj_mariner]

Tried the ECU reset and idle relearn and didn't notice much difference. Attached is a crude log of the parameters I can see on my code reader. Cold was early in the morning, before the ECU reset. Didn't try getting the readings with the hose off the FPR, mostly bc I got lazy and just wanted to get some coffee and a smoke on my sick day.

 

[Perscitus]

You should cross-ref the warmed up idle, post re-learn results against the SSM param sheet in the vacation pics. It will give you an idea of if you're 'within spec' or not.

 

Overall looks decent, except some params you're capturing have confusing naming conventions (must be the tool or the fact that its a mix of generic OBDII and a handful of or maybe no SSM params).

 

For example what the difference between EQ Ratio I vs EQ Ratio II

These must be referring to implied Lambda but in your car's case you should only have one (given H4, 1 bank of cylinders, 1 set of AF and Rear O2 sensors) So in theory you should only have 'EQ Ratio I' and it looks like its a bit rich @ warm idle.

What would be more telling is what the ECU is commanding (aka Final Fuel Base) vs what it's hitting (AFR, Lambda, Eq Ratio, etc).

 

Load as % is also not very useful, you want the proper g/rev SSM param.

Not the calculated load (off of MAF, RPM, etc.) represented as some arbitrary % value.

 

ST FTRM and LT FTRM are easy enough to understand (A/F Correct and A/F Learn) but not sure what the 1 vs 12 represent for ST FTRM?

 

Also here, what you'd want to see if your Rear O2 fueling contributions have not been turned off in the ECU mapping is:

 

ST FTRM 1 (aka A/F Correct #1)

LN FTRM 1 (aka A/F Learn #1)

ST FTRM 3 (aka A/F Correct #3)

LN FTRM 3 (aka A/F Learn #3)

 

First two come from the feedback loop with the front/pre-cat semi-wideband AF Sensor.

The latter two come from fueling contributions added by the rear/post-car narrowband O2 sensor.

[aj_mariner]

I have...but like you said, some of the parameters from the Bosch reader's real time data aren't exactly the same.

 

Looked into equivalence ratio's a bit and found a good link.

https://chemistry.stackexchange.com/questions/26656/equivalence-ratio-explained

 

For Fuel to Air equivalence ratios (phi): any number below 1 is lean, and above 1 is rich.

 

For Air to Fuel equivalence ratios (lambda): any number below 1 is rich, and above 1 is lean.

 

Maybe this is why there are two...going to test this theory out today and see which ratio our cars are using.

 

EDIT: Also forgot to mention that my MAF with the engine off is reading 0.15 lb/min...it is newer (10k miles on it). Scaling off? Does this need to be rescaled when replaced? Awhile back I got an oil change while in town and found that the jerks had disconnected the MAF to check the air filter, and didn't put the air filter back on correct leaving a gap. So I took the MAF out and cleaned with plastic safe electrical contact cleaner. But this was after my problems started.