Exterme Hesitation/misfire when at temp

[Jesse122333]

Hi Guys

I am having a bit of a major with my 97 PFL Legnum and only when the engine is at temperature.
The engine is hesitating and misfiring (to the extreme) as soon as it gets up to normal operating temperature but runs fine when cold and warming up.
It is worse under load than at idle or at "cruising" and especially between 2 - 3k RPM.
I have changed the spark plugs (using NKG BKR7EIX gapped at 0.8), cleaned the MAF, checked for vacuum (replaced brake booster hose with the inbuilt check valve) and boost leaks.
The issue seems to have gotten worse when i fixed the vacuum leak.

I have an upgraded FMIC and piping, MBC, Walbro fuel pump (hotwired to run at constant voltage) and after market FPR. I have turned the boost down to 7psi while I have the issue which has had no effect.
I do not have any CEL's on.....I have checked codes and I am getting 12 & 25 both pointing at the MAF, but don't actually think this is the issue (I will test a replacement as soon as I can get my hands on one) as when i disconnect the MAF the issue is the same except the idle is even worse.

When idling I can feel the engine "jumping" like it is trying to figure out the correct AFR.
I have ordered a VAG COM cable which I will DIY so that I can use Evoscan (if I can figure out how to) so hopefully that will tell me what's going on.....I am trying to avoid changing (IFS, TPS, O2 sensor, leads, coils etc. etc.) chasing this issue.

I have searched the forum and the coil packs seem to be a common point to check...is there a way to test them other than replace them?

I guess I am mainly after some advise on what systems are changing when the engine is cold vs at temp that might point me in the right direction while i wait for my data-logging cable.

I do have an innovate MTX-L AFR wideband gauge/sensor that I will also install, as soon as I can figure out which of the wires (brown I think) to use so that it will emulate narrow band, in place of the factory o2 sensor and where I connect it to the ECU.

Sorry for the long post.

Thanks
Jesse

 

[benny__S]

Possibly crank sensor could explain the hunting ?

 

[jungle]

Why did you change the FPR? These on stock cars are generally very very good. Why did you change it out?
What FPR are you using and what did you set the bass pressure to? what sort of rising rate is it, one to one or something different.

In the absence of anything else,what you have done Sounds fine. If you still have the stock FPR, stop and put it back on I would suggest this is your problem.

My car is running bit over 250 kW on stock FPR.

 

[VR45UM]

My thoughts would be the O2 sensor, only because your saying during warm up its fine. On warm up the ecu uses a closed loop setting so the values for the AFR are fixed, once its warmed up it goes to open loop which uses the O2 sensor to determine the correct AFR. If the sensor is buggered it could be giving the ecu the wrong reading.

I dont know how the check is on our o2 sensors but im pretty sure they are meant to have a set resistance, which you could check before swapping it out.

Just a guess

 

[Jesse122333]

Why did you change the FPR? These on stock cars are generally very very good. Why did you change it out?
What FPR are you using and what did you set the bass pressure to? what sort of rising rate is it, one to one or something different.

In the absence of anything else,what you have done Sounds fine. If you still have the stock FPR, stop and put it back on I would suggest this is your problem.

My car is running bit over 250 kW on stock FPR.

The FPR is a SARD Adjustable Fuel Pressure Regulator, it has been on the car working fine for a for years....It was installed by the previous owner so I am not sure why it was installed over the factory FPR.

 

[Jesse122333]

My thoughts would be the O2 sensor, only because your saying during warm up its fine. On warm up the ecu uses a closed loop setting so the values for the AFR are fixed, once its warmed up it goes to open loop which uses the O2 sensor to determine the correct AFR. If the sensor is buggered it could be giving the ecu the wrong reading.

I dont know how the check is on our o2 sensors but im pretty sure they are meant to have a set resistance, which you could check before swapping it out.

Just a guess

I was thinking the O2 sensor was the likely culprit and was about to start pulling the passengers panels off, so that I could at least disconnect the sensor to see what happened........Got my hands on a spare MAF and coils so thought I would rules these out first.

 

[Jesse122333]

Update - symptom fixed
First off, thanks for the reply's.
Secondly, I wanted to make sure that I updated this post in the hopes it may help someone in the future.
Third, should have listened to all of the previous posts/wisdom on here pointing at COILS!

I managed to get my hands on a spare MAF and three working coils. While i was waiting for the MAF cleaner to do it's job, figured I would get to work on replacing the coils in case my current ones were fried.
Pulled the first coil (passengers side) out and it was covered in oil.....The rubber seal on the spark plug hole looks shot (likely from being put on to tight the last time they were changed). I pulled the plug and there was oil in the bottom of the chamber and the plug is already covered in soot, even though they were changed only approx 5K KM ago. I cleaned up the chamber as best I could, replaced the plug and coil and then put it back together. The second chambers only had a small amount of oil (compared to the first at least) so I left the plug but replaced the coil. The third looked ok so I left the plug and coil alone. After connecting everything back up and letting the engine get to temp, the sound of the engine already seemed promising....went for a quick spin and I have a new car!

As per above, I have fixed the symptom only at this stage, the root cause of the seals will be dealt with shortly.

 

[naughtika]

also, quick test on the coils

If they have white powdery residue where the black coated,. whilst idling, spray soapy water on the coils, you'll see the spark come out of the plastic housing.

just my 2c

 

[slickd1]

Update - symptom fixed
First off, thanks for the reply's.
Secondly, I wanted to make sure that I updated this post in the hopes it may help someone in the future.
Third, should have listened to all of the previous posts/wisdom on here pointing at COILS!

I managed to get my hands on a spare MAF and three working coils. While i was waiting for the MAF cleaner to do it's job, figured I would get to work on replacing the coils in case my current ones were fried.
Pulled the first coil (passengers side) out and it was covered in oil.....The rubber seal on the spark plug hole looks shot (likely from being put on to tight the last time they were changed). I pulled the plug and there was oil in the bottom of the chamber and the plug is already covered in soot, even though they were changed only approx 5K KM ago. I cleaned up the chamber as best I could, replaced the plug and coil and then put it back together. The second chambers only had a small amount of oil (compared to the first at least) so I left the plug but replaced the coil. The third looked ok so I left the plug and coil alone. After connecting everything back up and letting the engine get to temp, the sound of the engine already seemed promising....went for a quick spin and I have a new car!

As per above, I have fixed the symptom only at this stage, the root cause of the seals will be dealt with shortly.

Did you ever try the VAGcom cable? I've got an openport, but the bro has a cable from his Audi that would be awesome to setup for him.

 

[Jesse122333]

Did you ever try the VAGcom cable? I've got an openport, but the bro has a cable from his Audi that would be awesome to setup for him.

Sorry for the slow response!
The VAGcom cable arrived but I fixed the issue before needing to test it with EVOscan.
I was going to say you can have it if you want, but it will probably cost more than it's worth by sending it to Oz.

 

[Nitephyre]

How amusing this thread popped up today... I think one of my coils has finally shit itself. I was having symptoms as described today, just suddenly started running like complete arse under load, firing like a machine gun :/

Yay.

 

[Jesse122333]

How amusing this thread popped up today... I think one of my coils has finally shit itself. I was having symptoms as described today, just suddenly started running like complete arse under load, firing like a machine gun :/

Yay.

Hopefully it will be a quick fix for you!
Drove me nuts looking for gremlins. My coils were actually fine, it was just oil getting inside the spark plug holes from the seals being shot.

 

[naughtika]

How amusing this thread popped up today... I think one of my coils has finally shit itself. I was having symptoms as described today, just suddenly started running like complete arse under load, firing like a machine gun :/

Yay.

sounds like my car when the spark plugs were goners... this was with the NGK BKR7EIX (regapped at .8mm) and factory coils from memory that was at 35k kms

 

[Nitephyre]

Yeah, mine are a taaaaad older than that

You don't happen to have any spare factory coils at all?

 

[Nitephyre]

Changed plugs today, didn't fix the issue... looks like I'm going coil pack hunting.

Audio

 

[Nitephyre]

Turned out to be the 9yo (almost to the day, they got installed 12/09/2010) ICE leads. Put stockers back on (with coils from @Just a Magna wagon as a 2nd attempt to fix) and it stopped hesitating first start, with all the borts back were they should be

 

[Baba Galant]

Anyone looking for aftermarket coil packs can use the following alternatives
You will need to seperate your old boot from the coil as the new ones are too long.
I picked up 3 new ones for about $150 delivered.
Only the right hand side bolt lines up but I haven't had an issue as the boot also helps and it's unlikely to come loose.

099700-048; MD361710; MD362903; C980-07