Hesitation/missing on acceleration (under load) - long - Saabnet.com Bulletin Board

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Hesitation/missing on acceleration (under load) - long
Posted by Notnoel [Email] (#23) [Profile/Gallery] (more from Notnoel) on Sun, 9 May 2010 12:14:11
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I've been having some problems for the past few weeks with my 1990 900T vert. Car runs smoothly until I accelerate hard then starts hesitating (engine tugs like a missfire but never backfires). This only happens under boost, typically at the end of the yellow as the gauge crosses to red.

I've replaced a faulty TPS, put in a new fuel filter, changed plugs, wires, and cap, set timing to stock. Swapped out AMM, coil, FPR (3.0 bar), ECU, APC box, I've checked all of my Tubo hoses and vacuum connections. Idle is rock steady at 900 RPMs.

last week, after I put in all of the new stuff, I finally had it start throwing the CEL light on (its been giving me heartache for three weeks without the CEL coming on_ Now, It throws codes for trim too rich and trim to lean, some times back to back. I checked the voltage output on the O2 sensor: its seems pretty low. I am getting fluctuation but it is at 0.2 to 0.4 volts.

Seems like this O2 sensor ought to be the culprit, right? The O2 sensor in the car has only been in there about a year or so, and I'd assumed it was OK. However, I did have to replace my turbo last August (with all of the accompanying black smoke), so I guess it got coated with oil. I think this makes sense, but I'd have thought it would have crapped out shortly after the turbo went, not 9 months later.

WHATTAYATHINK? One other piece of information. I just checked the base boost and it is low 0.1-0.2 bar. I don't have the problem with the wiring to the BPV pulled, at all. I am guessing that that is only because I am not loading the engine up as much as before, and it is unrelated. Right?

posted by 96.255.16...

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