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I hope someone on this 700 board could help me. I posted my question in the 900 section a couple weeks ago and nobody could help.
Car is '93 940 Turbo, 188K. B230FT engine, same as in 740 Turbo.
This car has been acting up in the last 8 weeks, since outside temperatures are warmer. Conditions are worse and car pings with greater frequency when ambient temperatures are above 80 degrees.
When accelerating with anything more than 1/3 throttle (merging on highway, or going up a hill, apprx. 3200 RPMs), engine will bog down and lose power. If I'm not careful and back off of the throttle, I will hear the engine ping. Above 85 degrees outside, engine will hesitate and ping more readily at lower RPMs and even 1/4 throttle. I must take off from stop lights pretty gently to avoid the ping. Increasing the load on the engine by running the A/C and carrying more weight causes more frequent losses of power and pinging.
Occasionally, the car does not want to idle after it is restarted when hot. I can be out running errands, have the car off for anywhere between 10 to 45 mins., crank it and it will die right away. I have to hold the gas pedal at 2000 RPMs for 30 seconds and then the car will idle on its own. After this happens, the idle typically surges (between 800-1200 RPMs) for as long as 5 mins. (car sometimes dies). When holding the throttle, the engine is clearly missing as the tach needle jumps and the turbo/vacuum gauge fluctuates.
Last week, I let the engine idle with the A/C on for 10 minutes (90 degrees outside). When I got in to drive away, it instantly pinged under hardly any throttle.
It is as if some component (sensor?) is heating up and causing the engine to run lean. When engine is cold or temperatures are cooler, it runs pretty normal.
My Volvo-only shop cannot find anything wrong with the car. They tested the fuel pressure for main and in-tank pumps (perfect), ignition timing (correct), vacuum leaks, etc. They are suspecting a bad Air Mass Meter and ordered a new one to try out. This does not make sense to me since I have swapped in 2 spare AMMs I have and the car runs the same regardless of part.
New parts in last 5,000 miles:
- main fuel pump and fuel filter
- cap, rotor, plugs (NGK standard copper)
- idle air control valve
- oxygen sensor
- vacuum lines
- cleaned flametrap
- cleaned AMM
- cleaned throttle body
- 93 octane Shell gas
- compression test: 150-145-145-145
Does anyone have any ideas? What is the shop failing to see?
When engine is cold or it is below 72 degrees outside, there is no hesitation or knock and it runs normal.
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