E30drift

After spending all spring break fixing 4 leaking lines on the hydraulic system, I took it for a long drive to make sure all was good and just to have some fun. The previous owner told me about a bad missfire when in boost but it had never happened to me yet until now.

-When lightly accelerating there is a huge lack of power right before peak boost pressure but it does start spooling. It will not rev through it though, you have to shift or let off.

-When under hard accel, it will start spooling and as full pressure is reached, it will missfire and act like it has launch control.

-Engine will free rev just fine and only misses under load.

-It runs great and reaches full boost for 10 mins after it is started, the problem only starts when it is completely warmed up.

I also ran the codes and came up with 2223 which is the altitude sensor. Could this really make full boost pressure not attainable? I thought it was more of a fine tuning sensor that only effected the pressure minutely. If this sensor could cause this problem, then I guess it makes sense that it only happens in closed loop mode? Maybe? Unless the ecu uses the altitude sensor in open loop as well, then im stumped.

Kneale Brownson

Try to replicate with the radio and A/C on and listen for clicking sounds. Could be the wiring to the A/C clutch. See this: http://www.sjmautotechnik.com/troubl...lec.html#click Also go through: http://www.sjmautotechnik.com/troubl.../20vboost.html

E30drift

The AC was removed by the previous owner and the radio doesnt work nor is there even any speakers to listen with it needs some work...

yodasfro

I would check to make sure your altitude sensor didn't get wet or something and that the connector isn't corroded. It's possible it just went bad.
Need to pressure test the intake to check for boost leaks good chance that is your problem.
On the ignition side of things make sure you have the correct narrow tip dizzy rotor bosch 1234332414 and correct factory spark plugs or equivalent.
More info on boost leak testing
https://www.audiworld.com/forums/aud...tions-2843297/
Testor

E30drift

Alright, got some time to work on it today. I did plug wires as the old ones were on the edge of spec. I checked the plugs and they look really good, previous owner changed them trying to fix the problem but used the 2 prong bosch ones not the stock ones but I dont think that is the problem, they are almost brand new. As fas as I can tell they just dont last as long. I went through the entire vacuum system and replaced a couple bits and tested it and it seems to be fine. I will do a proper intake pressure test next week and see what happens.

yodasfro

2 prong plugs are totally wrong. I'm sure they are not helping the situation. I would get a set of stock plugs.

E30drift

Ok I have some more info. I got the original 13$ a piece plugs and put them in and also got a cheap boost gauge to see what was going on. I did another visual check for boost leaks and couldn't find any rips or anything. Took the car for a drive and it misfires in boost all the time now, doesn't seem to be temperature dependent. It seems to be fine at partial throttle 20-50% and up to about 8psi but any addition of throttle makes it misfire bad. When I pulled the old plugs they were very dark and its obvious the misfire is a rich or weak spark condition. I reset the codes again and the only one that is coming up anymore is 2121 which is the idle valve reaching its max adjustment I think which means potentially extra air introduced after the maf i.e. boost leak. I still need to do a proper leak test... which I'm hoping reviles a leak. Other than that I have no other thoughts on what the problem would be. Thanks for all the help!

E30drift

I did a 5th gear pull at around 40mph and it runs smooth and feels good till it starts building boost, then you can hear the diverter valve release randomly and quite often, even at continuous full throttle. Not sure if this also points to a boost leak. This was on full throttle, diverter valve should not have been going off I don't think. It is new and I replaced the vacuum lines associated with it as well. Any thoughts would be helpful. Thanks

Kneale Brownson

<img src="http://www.pbase.com/kneale_brownson/image/115984380/medium.jpg">

Or

<img src="http://www.pbase.com/kneale_brownson/image/146292396.jpg">

See Testor

E30drift

Finally got around to doing a boost leak test and found a leak at the diverter valve and fixed it. Went for a drive and the problem persists... I keep getting the code 2121 Idle Switch Problem. Does this code refer to the idle valve? Could it be sticking open on acceleration and therefore throw off the ecu because more air is getting around the throttle blade? Im completely stumped. The problem still only happens after a couple mins of driving and it gets warm, runs decent in boost when cold, but I dont want to push it too hard before its warm.