OBD1 S52 Dr Jekyll Mr Hyde

[M3PO]

That boot on #1 may be causing your issue.

[hammslice]

That boot on #1 may be causing your issue.

I noticed that too. Any idea why some are flared in vs out on the bottoms?

[hammslice]

An update: 6 new Bremi coil packs with 6 new Bremi boot connectors.

Felt a little refreshed (smoothness and torque-wise) but the problem of the hesitation between 2-3.5k still exists...

Still getting 1271 and 1274 codes.

When a VANOS unit needs a rebuild, could it act like this or is the symptom more erratic and/or thoughout the entire RPM range?

[berlow94]

IMO when vanos isn't working, it just doesn't do anything. (Your engine remains at normal timing). Never heard of it having a negative effect on the engine.

Unless it stays stuck on... If that's the case the car would hardly idle...

[hammslice]

IMO when vanos isn't working, it just doesn't do anything.

I agree. That make sense to me. I'm grasping at straws!

[M3PO]

I agree. That make sense to me. I'm grasping at straws!

Your original rationale for it not being VANOS still holds if you ask me. Have you ohm'ed out the crank and cam sensors?

[mda185]

hammslice, I responded to your PM asking about my experience and mentioned that I had a bad fuel injector in #2. I thought about your symptoms some more and realized you could be having problems with a vacuum leak.

With M54 engine in my 03 530i, I was getting hesitation and bogging at 2500 rpm under hard acceleration. The OBD II system was yielding ignition misfire codes. As I learned more about this, I realized that the DME can't tell the difference between misfire caused by coils, injectors, or vacuum leaks. It only knows that there was a misfire condition. With the M54, it turned out to be vacuum leaks from the crankcase ventilation system. When I replaced all those parts, the engine ran perfectly. The OBD I system is even less capable in terms of telling you why you have misfire. You have done all of the standard troubleshooting so I think it very likely you have a vacuum leak. Where I would guess the leak is depends on which intake manifold and CCV system you are using.

[mda185]

With my M54 engine, it would pull strong above 3500 rpm even with the vacuum leak. I forgot to mention that. I suspect the vacuum leak was worse when the airflow was near its designed resonance point that helps with cylinder filling. With M54 engine, the intake manifold is actually a dual plane design with a valve to switch between long and shorter paths right in the rpm range I was having problems. I know the M50 and S52 manifolds are simpler designs but would still suspect that you have a vacuum leak since you have ruled out ignition coils.

[hammslice]

I had a bad fuel injector in #2. I thought about your symptoms some more and realized you could be having problems with a vacuum leak.

Thanks for the reply. I have a couple extra injectors. Running 24# and since they are common on mustangs, they came as a set of 8. Hoping to have time swap out this weekend. Will definitely pour over the vacuum lines while I have it all torn up!

Also, I have an M50 manifold on the motor.

[hammslice]

Replaced 2 injectors. Put a clamp on the vacuum line to the fuel pressure regulator because it seemed loose. No change. Same codes.

Didn't see any noticeable vacuum leaks but I need to look closer to be sure.

[mda185]

How did you plumb your crankcase ventilation? Are you using the air/oil separator that is part of the S52 system or are you using the simpler M50 design? The S52 design has more potential to cause vacuum leaks that are hard to detect. For example, the air/oil separator has a drain line that is connected to the S52 dipstick tube. That can cause a serious vacuum leak if the rubber is deteriorated. Likewise, the O ring on the base of the dipstick tube can be a problem if it is old and hardened.

You told me you are using the M50 intake manifold but either crankcase ventilation method can be made to work with this manifold.

Another source of vacuum leaks that gets overlooked is the line going from the intake to the power brake booster.

[hammslice]

Crank position sensor must have been damaged when I was having cooking issues.

Cleaned cam posi sensor, verified knock sensors weren't swapped, disconnected DME for reset, and replaced crank posi sensor.

Issue resolved! Thanks for all the replies!

[mda185]

Glad to hear you got it sorted.

[dunebuggyjay]

Crank position sensor must have been damaged when I was having cooking issues.

Cleaned cam posi sensor, verified knock sensors weren't swapped, disconnected DME for reset, and replaced crank posi sensor.

Issue resolved! Thanks for all the replies!

Can you explain the knock sensors being swapped? I also have an obd1 s52..and both knock sensors are exactly the same.

Im having issues with my swap...so maybe this is something that I can look into in my car.


Thanks
Jay

[M3PO]

Can you explain the knock sensors being swapped? I also have an obd1 s52..and both knock sensors are exactly the same.

Im having issues with my swap...so maybe this is something that I can look into in my car.


Thanks
Jay

He means swapping the cam/crank sensor with the knock sensor I believe since they have the same plugs