Rev drop when braking

[sibbers]

If you can identify which coil it is, you only need to replace the one. Maybe but two so you have a spare. Squealing belts happen on any car, and try are at least easy to get to and adjust on these but I understand the feeling of car despair chasing faults round!

Revs will drop naturally when you brake due to the brake servo, so if you are confident there is no vacuum leak then you can adjust the idle. It may be that it is set low which would exaggerate the issue you're having. Basically you get the car warm, remove a sensor plug then turn a screw until it sits at 950 revs or so. I'm hazy on the exact details but it's well documented and the same on all S chassis cars to my knowledge!

 

[RagamuffinRyan]

I'm going to try the paperclip trick so scan for codes tomorrow and get a volt meter on the coils, hopefully that will shed some light on the situation.

My car Idles at about 900-1000rpm, not sure what everyone else's Idles at, but on occasions mine drops to about 500rpm when braking, might get that looked into though.
Thanks for your help though!

I will update the thread once I've done some more investigating

 

[sibbers]

To be honest it sounds like you probably still have a vacuum leak somewhere, but it would be interesting to see what it idles at without the sensor plugged in at the AAC valve on the plenum as if it's low (with AC off) then you may have your fault. Very quick to check so worth a shot! Best of luck

 

[RagamuffinRyan]

UPDATE

Attempts so far:
No Fault Codes
Cleaned Maf
Cleaned IVAC (while on car)
Gap Sparks 0.7mm (0.28) NGK7 Iridiums
Smoke test (Leaks found and fixed)
Sprayed brake cleaner around engine (nothing found)

------------------------------------

At first I thought it has worked, I was pumping the brake and the idle only dropped a small amount as expected.
I took the car for a drive and on full throttle 0.5 bar boost at 5000rpm it began spluttering again.

I took the car back home nice and warm, put my foot on the brake and the car almost stalled again.
The fan seems to be cutting in and out as well while warm constantly making a clicking noise every minute or so which is affecting the idle, seems to make it hunt.

Thanks for your help so far guys, really starting to get me down now.

I'll update the thread as I go, maybe get some videos. Might help other people in the same situation.

 

[RagamuffinRyan]

Incase this helps anyone.

there is a small vacuum line that comes off the back off the BOV, if you follow it you'll see a T-piece, seems someone had bent the 3rd pipe coming from the T and pit a cable tie around it.

THIS DOES NOT WORK...very well. I took it off put a bolt in the end and cabled tied it as well for good measure and the brakes don't drop any further than 900rpm when braking.

1 problem solved! however the intermittent misfire and misfire under load still continues.

Re-gapping the plugs from 7mm to 8mm did help it run smoother and made the misfire less frequent at idle.

I've got Splitfire Coilpacks on the way from RHDJapan and hopefully that will be a fix!

They are taking their sweet time to dispatch them though!

 

[RagamuffinRyan]

Splitfire coils fitted! and problem still remains.

also the braking problem seems to still be the very rarely, usually when I'm braking going up hill.

anyone got a suggestion I've not tried?

 

[RagamuffinRyan]

SOLUTION:

Seems a boost leak was part of the cause, appears one of my spark plugs was also duff (despite it being new) also got a small crack in my manifold.

problem solved, hope this helps someone else

 

[phillll]

Thanks for posting, always handy!

 

[als_jordan]

Agreed excellent that you solved it.