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TC running rough


Guest hike2812
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Guest hike2812

My '89 turbo 4 is running rough. It bucks when stepping on accelerator. Will get to speed and run fine when accelerator is carefully eased but merging, passing, starting out from a stop, etc. is an experience. Check engine code says MAP sensor (13). Have changed MAP sensor, Hall effect sensor, throttle position sensor, and all vacuum lines. Situation is unchanged. Any suggestions out there??

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Guest Jim_McNally

Sure sounds like a vacuum line issue to me. Can you put a vacuum/pressure gauge on the manifold to make sure that there is good vacuum at idle, and boost on acceleration, then move the same gauge to the MAP sensor line (before the MAP solenoid) to make sure the same readings are there? Then check after the solenoid to make sure it's not blocked. It could also be an electrical problem with the MAP sensor wires (since that's all the SMEC sees...) I would check to see if the proper voltages are coming out of the MAP (should be about 2-2.5V with engine not running, then lower/higher at idle or boost). Might also try disconnecting the big SMEC connector to see if there's any corrosion in there.

Good luck,

Jim

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Like Jim, I suspect a vacuum leak somewhere closely realted to the MAP sensor line. Those stiff factory 1/8" vac lines can crack and yet look fine until they need to carry boost pressure, then they 'open' and all sorts of weird symptoms can happen. CAREFULLY trace the route from intake manifold to the 4 way split, then each line out of the split (they can even be loose in the split). Be especially critical of the MAP line itself. Also look at that big 3/8" line that runs to the charcoal cannister, also Ive seen the lid on the cannister pop loose a few times...

Alan

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