That chip may be flooding you.....might consider trying the stock chip to see if it goes away.
A large backfire out of the exhaust may signify a very rich condition at the lower rpms.

From what I have seen and read, which is not a ton, the modifications on these chips seems to be adding fuel at the lower rpms to even out the low end performance.

The upper end of the AF map seems to be pretty good overall, so many just add fuel all the way across the board and that creates rich conditions at various rpms/load/elevation conditions.

might be worth swapping the stock chip back in...its a 15 minute test.

Rich

Well, the car runs very clean and the plugs look brand new with 0 color to them since I installed them 500 miles ago.

I am fairly confident this a lean condition.

But, I know never say never.

Ok, I spoke with Todd from Protomotive.

Here is some of the things he told me I could try:

1. On the Airflow Meter, turn enrichment screw under the aluminum plug.
2. There is an 8-position switch on the ECU that has different settings for different countries due to different climates, altitudes, and fuel quality. He said each turn was like 5% richer (don't quote me on the exact numbers/%'s!).
3. Last thing is the high-altitude switch that sometimes shorts out and leans the engine 15%!!! It is located by the main harness on the DME and has 2 brown wires? He said disconnect that and it will default back to normal AFR's.

I am definitely going to try #3 when I get home. I've never heard anyone address this one.

Where is the backfire coming from?
Intake or exhaust?

Rich

Exhaust

Typically a backfire in the exhaust is either a loose exhaust that is allowing air in, or a rich mixture.

Rich

Yikes, I would not touch those....they are not common issues with these cars and not symbolic with the problems you've described. Really, if you still have a stock chip, put it back in. It's simple and quick. If you don't have a stock chip, they are relatively easy and cheap to obtain.

Yeah, I don't have a stock chip laying around.....

This is starting to sound more like a seriously complicated and expensive CIS problem that could ultimately end up being a simple ignition problem as is often the case.

Could it be time to start barking up a different tree?




Cheers,

Joe

Brown wire is OK to disconnect under the driver seat.

There was a thread where an ingenious way to check for vacuum leaks, using a rubber glove over the AFM intake and 4-6 lbs of air pressure connected to a vaccum line i.e. cruise control.

+1 items 2 & 3, don't mess with those.

Check the AFR with a LM1 or LM2 or ghetto method, bring her up to 194+ degrees then put a DVM to the O2S and one of the black leads. adjust the AFR screw until your reach .6 volts. That would be close to proper AFR. LM1 or LM2 would be the best tool for this.

Then check and adjust BASE IDLE 880RPMs.

Sorry did not read previous post but regarding the back fires, do you have a Cat Bypass? If so this is a side effect. Mine burps during decel with the M&K Pre-Muff.

Jim

Yes sir. Valves are nearly quiet and it doesn't seem to smell rich at all. I don't have a Cat BTW.

The plugs look really brand new, no soot at all.

Joe, I'm woth you on this. It's one thing if you have a spare chip to throw in, and another if you actually have to start throwing money at a problem you don't really have a handle on.

I was totally confused to begin with....I always thought Turbos were CIS and not Motronic? And, is it really possible to have both at the same time? I know I'm a total rookie, but I've never even seen, read or heard of that before.

- There is no AFM boot, it is all cast aluminum piping for the turbo.
- I don't run an O2 sensor
- There is no catalytic converter, only a short amount of pipe from the turbine of the turbo and a 12", straight through muffler with a 3.5" inlet/outlet leading to a large tip.

Jim, are you referring to the brown "California" wire, or the two brown wires that lead to the High Altitude Switch? Either way, any could be pulled safely....I just thought that there was no way that the altitude switch had any bearing on his problems.

Hold up guys! :) This a factory Motronic, '87 Carrera with a turbo ADDED. Not a '87 911 turbo/930.

Todd at Protomotive said it would make the car 15% leaner. That is huge if so!

That is the first thing I am going to disconnect when I get home.

CR

Oh Damn, check if you can borrow a LM1 or LM2. this is the only way now to check your AFR.

What chip did you have before these symptoms?

Got to verify vacuum leaks. Check shops to see if they have a smoker. That is how I found my leak :eek:

Wait, you have a WUR, right? Like our Base Carrera's Fuel Pressure Regulator?

No WUR, for a Turbo Mod, right?

Yeah, I need and LMX!

The chip has been in there for about 4 years.

I used a whole can of starting fluid and if has vacuum running through it, I sprayed it with NO change to RPM.

I still wonder if the brake booster diaphram could be leaking......

No.

It only has a "rising-rate", fuel pressure regulator over stock.