Please, help. Not long ago, car was running beautifully, smooth and powerful with clean plugs. Then, I put in a Dawes Device boost controller and had clouds of thick black smoke coming out of the exhaust pipe in direct relation to acceleration. Plugs were covered with black velvet like powdery soot. All hoses and most ignition and injection components were new and all checked out for speficied voltage and resistance parameters. O2 sensor, FPR and coil were not new, but still checked out OK. I have now put in new O2 sensor and FPR. Still, I get overly rich fuel/air with Dawes Device boost controller.

(1) What is telling ECU to enrich fuel/air?
(2) Can the cure be raised boost to also raise air/fuel, perhaps checked with air/fuel meter, until plugs burn clean?
(3) Can engine mechanically stand 12 psi of boost, perhaps a bit more, with 150,000 miles in original bottom end, and 60,000 miles in over five years old head and turbo, as long as air/fuel is not too lean?

What a PITA Rafael. My boost controller became damaged last week. I'm back to the old hose, what a bummer. I left work and go onto the interstate. The car just sprang to life when I began merging. I backed off and noticed the boost guage was not working. I drove home carefully so I wouldn't blow my engine. I don't need that expense right now.

I took the device off and replaced it with the hose. Performance is down. I bought some fittings to repair it. I will post the results soon.
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Warren Bain - '86 744Ti M46 >285Kmi, '96 965 >99Kmi Wifemobile near Manassas Va.. I get e-mail replies to my postings.

Hello Warren:

As you know, my boost controller makes the car run rich. I am chasing a leak that should be there but I do not know where. I do not even know how to check for that leak beyond what I have done. Best regards.

Riv,

Check your Turbo hoses for any leaks. Some splits and breaks only open up under boost. Dumping intake boost from a bad hose can fool the ECU into thinking a lot of boosted intake air is coming in, but it's really escaping after being metered. The result can be a very rich mixture. Increasing you boost with the D-device may have caused an intake leak some where. I know your hoses are new but I'd check them and the intake connections carefully anyway.

Unless it is a leak that opens up only under high boost, I have checked, but I will check again. Yes, the hoses are new without any oil contamination, never mind soft spots. Short of riding under the hood while someone drives the car under full booost, I do not know where to look. Darren Dawes suggested I raise boost since I have too much fuel, but I worry whether mechanically the engine is up to 12-14 psi of boost. What do you think?

Raising boost is not the solution. You have a problem that needs to be fixed. Raising the boost to hide the problem will cause more problems in the long run. Chances are greatest that you have an air leak. High boost often creates or exacerbates them. The intercooler end tanks, the hoses, the compressor by pass valve, the idle air valve are all suspects. Another possibility is failed plug wires or cap/rotor that cause the spark to blow out. Another possibility is the fuel pressure regulator or injectors. The air leak is the usual suspect. You are far from the first to experience this, particularly on a 15 year old motor. On my car it was the idle air valve hoses. There was a crack inside the curve on one that could not be seen without removing the hose and that opened up only under higher boost.

Philip Bradley

Hello Philip:

Thank you for your reply. I have read many of your posts here at Brickboard, and I think even at Turbobricks, so I am aware you know what you are talking about. I will print your post and dilligently chase every suspect you denounce. If you have any suggestions about how to check for air leaks, please let me know. I have put in all new hoses, but of course there could be leaks in the intercooler, vacuum tank and other places. I will report back.