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Discussion Starter #1
Engine is hard to start when it's hot after long highway drive since three weeks ago.

Once it get started, idling is rough and barely stays on the idle unless I push gas pedal constantly. If I try to drive, engine wouldn’t take the load and dies out unless I gas up over 3,000 rpm at least. Once it passes its hipcup intial stage, engine runs perfectly normal.

Two weeks ago, I experienced similar situtation while driving.

I was struck in the heavy bumper-to-bumper traffic during the unseasonably hot weather for an hour. My Saab began to jerk in the gasping breath. I thought I was out of the gas for a moment but the gas tank was full. As I pressed the gas pedal all the way on the floor, it wouldn’t supply fuel but kept jerking as if the engine dies off any second. I had to repress gas pedal constantly. Once the traffic easied out in normal speed, driving was no problem.



Cold start is no problem. When the engine is cold, it starts right away.



No OBD error code shown.

Engine temperature is normal.
Recently done :
-Thermostat, water pump and hoses replaced last weekend.


-spark plugs, spark plug wiring, distributor, distributor cap. O2 bank1 sensor replaced. (It -began to happen before I replaced these parts.)



-Fuel pump was replaced on 9/5 by a local mechanic.



Any thoughts?
 

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CPS

This is an educated guess; measure its resistance cold, and then hot.
I think that if its signal is too weak, due to the high engine heat, the fuel pump will not deliver full pressure, or it may stop and start completely..
Emissions will trigger the CEL; if all the fuel is combusted, then no CEL, even if the car is "running lousy".
 

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As the previous have said check your CPS resistance hot and cold as it can be signs of early failure.
suniku55 said:
Engine is hard to start when it's hot after long highway drive since three weeks ago.

Once it get started, idling is rough and barely stays on the idle unless I push gas pedal constantly. (If you push the pedal rapid and hard will it bog or try to die sounding like it's losing fuel when this issue is occuring?) If I try to drive, engine wouldn’t take the load and dies out unless I gas up over 3,000 rpm at least. (If you let off the gas will it drop to idle?) Once it passes its hipcup intial stage, engine runs perfectly normal (Do you get an occasional studder or drop out?).

Two weeks ago, I experienced similar situtation while driving.

I was struck in the heavy bumper-to-bumper traffic during the unseasonably hot weather for an hour. My Saab began to jerk in the gasping breath. I thought I was out of the gas for a moment but the gas tank was full. As I pressed the gas pedal all the way on the floor, it wouldn’t supply fuel but kept jerking as if the engine dies off any second. (Again, if pedal is released or car is put in neutral will it idle?) I had to repress gas pedal constantly. Once the traffic easied out in normal speed, driving was no problem.



Cold start is no problem. When the engine is cold, it starts right away.



No OBD error code shown.

Engine temperature is normal.
Recently done :
-Thermostat, water pump and hoses replaced last weekend.


-spark plugs, spark plug wiring, distributor, distributor cap. O2 bank1 sensor replaced. (It -began to happen before I replaced these parts.)



-Fuel pump was replaced on 9/5 by a local mechanic.



Any thoughts?
If you've answered yes to the above questions in blue it could be it's the MAF failing. I expierienced similar as you describe for over a year only when hot out or the car was hot (not moving with good airflow to cool engine compartment). No CEL, no exhaust emissions (passed smoke test), nothing showed on tech 2, and fuel economy was fine. A MAF swap however solved the issue. I do not advise a parts throwing ceremony. If this does turn out to be the issue. Contact me and I'll give you the name of a parts "recycler" that warrents his parts for 6 months. A recycled MAF delivered in the US is around ~$50 from him.
 

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Discussion Starter #7
Yes, I can say yes to those questions. Thanks! I will PM you to get part recycler.

green machine said:
As the previous have said check your CPS resistance hot and cold as it can be signs of early failure.

If you've answered yes to the above questions in blue it could be it's the MAF failing. I expierienced similar as you describe for over a year only when hot out or the car was hot (not moving with good airflow to cool engine compartment). No CEL, no exhaust emissions (passed smoke test), nothing showed on tech 2, and fuel economy was fine. A MAF swap however solved the issue. I do not advise a parts throwing ceremony. If this does turn out to be the issue. Contact me and I'll give you the name of a parts "recycler" that warrents his parts for 6 months. A recycled MAF delivered in the US is around ~$50 from him.
 

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Discussion Starter #8 (Edited)
I aslo noticed overall slight lose of power, not so dramatic. Non-saab driver wouldn't notice but acceleration is kind of 'dull' mode lately.

I will check CPS and MAF. Thanks for the insights.

Is CPS and MAF maintenance item needs to be replaced at the certain milages like a radiator hoses??
 

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CPS seems to last 150-170K miles or so. I've needed to replace two, one each in 97 NG900s, right about in that timeframe...
 
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