could anyone help me with a few engine problems ?

[dorifuto.boi]

Hey guys,

I'm having a few engine problems and I was wondering if you guys could help me out a bit. I'm not sure if these are related but here goes:

1. When I suddenly let off the gas, the car VIOLENTLY starts to engine brake (even in 5th gear). Is this normal ?

2. Not pressing the throttle while in any gear causes the car to go lean and engine brake. However when the RPMs drop too low, injectors will resume pulsing and when this happens, my AFR is really rich: around 13:1. Is that normal or does that seem a little too rich ? (when my engine is warm)

3a. Once in a while (happening more and more often), the injectors will resume pulsing at an abnormally high RPM like around 2.5krpm instead of the normal 1krpm (when my engine is warm)

3b. Not sure if this is related to 3a but when I'm coasting downhill in 5th gear around 2.8krpm, my AFR goes lean, not lean, lean, not lean, lean, not lean and what I feel is engine braking, coasting, engine braking, coasting, engine braking, coasting. Normally, its supposed to be lean and engine braking the whole time when the rpm is that high.

4. Once in a while (happening more and more often), when I press in the clutch, my engine RPM will drop very quickly (much much quicker than before). Does anyone have any idea what might be causing this ?

5. When I'm idling, there seems to be popping sounds comming from the exhaust and everytime there is a pop, the RPM needle bounces down. Does anyone have any idea what might be causing this ?

6. When I start my car, the engine RPM goes up to 2k and then drops down to 700rpm (almost dying) before going back up to cold idle. Does anyone have any idea what might be causing this ?

In order to try to fix number 6, I sprayed TB cleaner in the IAC, measured the resistance of the IAC valve (normal), connected TE1 and E1 of the DLC1 (normal operation), and measured the resistance of the ECT sensor (normal range)


Any help is appreciated.
Thanks a lot,
d

[dorifuto.boi]

bump

[BamZipPow]

Check yer wiring harness and ECU connections. Have you hooked up a ODBII diagnostic computer to the system yet? Is yer check engine light on?

[Nark]

What's AFR and resume pulsing mean? When I had my cat-converter clogged up. It also produce a significant amount of engine brake at highway speed and also slight popping during idle.

[dorifuto.boi]

Originally Posted by BamZipPow

Check yer wiring harness and ECU connections. Have you hooked up a ODBII diagnostic computer to the system yet? Is yer check engine light on?

I'll check the ECU connections. Theres no check engine light on so if I plug in my scan tool, nothing really interesting shows up.

Originally Posted by Nark

What's AFR and resume pulsing mean? When I had my cat-converter clogged up. It also produce a significant amount of engine brake at highway speed and also slight popping during idle.

AFR is air fuel ratio. When I say injectors resume pulsing, I mean its adding fuel so that the AFR goes back to around 14.7. Usually when you engine brake, the injectors don't really pulse and AFR is lean (AFR > 14.7) and it will be "engine braking"

[fenixus]

can't really help, but can only say that AFR is supposed to go extremely lean for a few seconds when letting off the gas pedal and it should go extremely rich when flooring the gas pedal.

other than that it should be floating around perfect 14.7 ratio.

are you using your bluetooth OBD2 interface with an android phone for live feed off car computer while driving?
Torque Pro app has the AFR meter among other feeds, can't remember if it requires custom mode to ad it or it's just there by default on the list.

wondering if your Fuel Injection Computer (you still using it right?) is working correctly. maybe it requires some kind of calibration?

[dorifuto.boi]

Originally Posted by fenixus

can't really help, but can only say that AFR is supposed to go extremely lean for a few seconds when letting off the gas pedal and it should go extremely rich when flooring the gas pedal.

other than that it should be floating around perfect 14.7 ratio.

are you using your bluetooth OBD2 interface with an android phone for live feed off car computer while driving?
Torque Pro app has the AFR meter among other feeds, can't remember if it requires custom mode to ad it or it's just there by default on the list.

wondering if your Fuel Injection Computer (you still using it right?) is working correctly. maybe it requires some kind of calibration?

i get the AFR from my wideband O2 sensor that i have.

even when i had my fic installed a while back, these problems didnt exist. i was gonna unplug the fic and drive around for a bit to see if it helps but i doubt it.

i might just go ahead and change the ect sensor like you've been tellin me to just to see if it'll fix any of these problems... this is getting really annoying.

[Nark]

I think you've vacuum leak somewhere. Either intake gasket, injectors or hoses. Get a vacuum tester or liquid soap detergent and spray bottle.

If you fix #6 by either change, clean or adjust the IAC, you might be able to fix most of the problem...this can also be a combination of vacuum leak + IAC = 2k idle.

Just curious...What feeding AFR gauge. Is it vacuum line?

I'm just more familiar with "fuel economy gauge". It basically get an input from engine vacuum and this allow driver to know the optimum fuel economy.

[dorifuto.boi]

hey, i will check for vacuum leaks.

my afr gauge runs off of my wideband o2 sensor. my boost gauge runs off the vacuum/boost

[JohnGD]

I wonder if OP should clean the IAC by disassembling it. Otherwise it's hard to clean out the carbon at the bottom of the vane rotor so the thing still sticks.

[fenixus]

that's what I've been telling dorifuto.boi all along
I think spraying TB cleaner into IAC opening does not much if things are gummed up (or carbonized) bad already.
seeing my old IAC valve I think even a wire brush and sea foam wouldn't clean off the dirty layer easily ...

Originally Posted by JohnGD

I wonder if OP should clean the IAC by disassembling it. Otherwise it's hard to clean out the carbon at the bottom of the vane rotor so the thing still sticks.

[dorifuto.boi]

haha yeah. im gonna buy a new IAC valve and that should fix number 4 and 6 then. after i replace it, i'll post again to see if any of these problems remain.

thanks

[JohnGD]

Just clean the existing one, no need to buy a new one for now. The new valve will carbon up and do exactly the same thing if this is the reason.

[Nark]

I did some look up on M62 requirement last night and came down with one theory; defective IAC is leaning out your injectors duty cycle. When ever you let off TPS the computer decrease your injector and since your IAC is already wide open (due to defective), thus this already cause it to lean out, that would make it a double lean engine...and that would also explain no CEL...get it? Assuming you already have 450cc and up injectors and chip flash and all others goodies as required. This is what I would do...but you don't have to take my word for it.

Before cold morning cold start. Cut a small piece (3")of either duct tape or packing tape. Tape it across IAC inlet hole. Make sure leave about 1/4-3/8" for air to pass through. Make sure clean all grease so the tape will stick really well. This should give you about 1k rpm. If not, make a hole bigger. Once it warm up take it for test drive. Let us know how it perform....make sure get the rpm within 1k at cold start. You've about 5 minutes of window to do that. If not you'll need to jump 2.5k resistor across ECT terminal.

If it working out, I like you to do another thing. Get a vise grip and carefully (wrap with tape or something) pinch off an air tube that stick out from the IAC...not the coolant tube. Drive around and let us know how it perform. I bet you can gain few HP just by pinching off that line.

Make sure to remove the tape from IAC inlet when finish.

[Nark]

Originally Posted by JohnGD

Just clean the existing one, no need to buy a new one for now. The new valve will carbon up and do exactly the same thing if this is the reason.

Agreed, and also don't forget to adjust it. IMO, adjust it to within 1k at cold start is good enough for government works.