I looked up th resistances for the sensor for a 900 hard to start.

It decreases resistance as it warms up.

68 deg. =2,280 to 2,720 ohms

176 deg.= 290 to 364 ohms

Howdy,

I have been thinking about your problem and read your earlier posts on the subject.

I also think that I had a bad NEW fuel pressure regulator because gas shot out of it when I disconnected the vacuum hose at the end.

Have you replaced the "NEW" FPR?

From another post:

I inspected for vacum leaks and did not see any.

Use some liquid (WD-40 is a favorite around here) and spray along the intake where it joins the head. Spray the injectors too. Listen for a change in idle. Use a mirror to inspect under the intake for broken or loose vacuum connections.

I just thought of something else that I have experienced: coil breakdown with heat. If you have another coil, plug it in to eliminate that little beasty. I don't know how that jives with the pinched fuel return line making things better but it costs nothing to check if you have a spare coil.

--sd
--
Mr. Shannon DeWolfe -- I've taken to using mister because my name misleads folks on the WWW. I am a 52 year old fat man. ;-)

sorry for not mentioning that she is a 1989.

hello
it may help to give the year of your vehicle.
good luck
Mike

When the engine is warmed up it runs on less gas. It needs to run leaner.

Air IN = AMM's input voltage changes. Air out = O-2 sensor voltage changes.

Closed loop starts with coolant Tenperature sensor = pulse width changes rich or leaner.

Throttle Idle switch saying "idle" versa "Pulling". Ignition pulses/Crank Position sensor = for RPM.


ECU's have to have good information. This stuff travels as low voltage/resistances. Many times though a lousy fine filament wiring harness. These are subject to who knows what.

The coolant sensor for the ECU tells it what the temperature the engine is moving through. This is a separate sensor next to the instrument sensor. I think it has a covered rubber boot clip.

Rare that the resistance of the sensor is off. Back probe the connector at ECU. Connected or not. Check for all those above "inputs" and "grounds". The coolant sensor can be compared to charts in a manual or verify that it varies in resistance, cold to hot. Switch closures. It checks the harness as well.


I missed and don't know what year your car is!

May be a ECU. I always want to blame it the very last because there are so many other variables.

A good digital volt/ohm meter beats the R&R game with unknowns. Then add maybe good or maybe wrong specification on the parts?

Could be a expensive headache for you or a new boat that unsuspecting mechanic you are going to take it to tomorrow! If it's a Saturday a boat with TWO motors! GOOD LUCK!

PS! While I was posting, ODGRU has said the same thing. So two votes for you to keep looking or grab your shorts!

The only item that should change at idle when an engine comes up to temp is the fuel to air ratio should decrease (less fuel)to keep the warm engine running.

When you attempt to accelerate, more fuel should be injected to compensate for the massive amount of air that is available when the throttle body opens.

If that fuel is not available, the engine dies.

Since pinching off the fuel return line forces the fuel available to increase and keeps the engine running when warm, the problem is either in the sensor that tells the ECU the engine temp or the ECU is not rersponding properly to the temp signal.

Or there is a massive air leak that is leaning out the mixture to the point where it is not combustable.

Massive air leaks: Bad gaskets, damaged brake booster, open line to charcoal cannister and others.

Temp signal wrong is easy: Test the two pins from the sender at the ECU connector for a resistance according to ambiant temp graph.

A few idaes.

Duane

Howdy,

It sounds like the problems start when the system goes closed loop. Probably the O2 sensor. But, I wouldn't replace an expensive part on a "probable" internet diagnosis. ;-)

You are doing the right thing by sending it to a shop with diagnostic equipment.

--sd
--
Mr. Shannon DeWolfe -- I've taken to using mister because my name misleads folks on the WWW. I am a 52 year old fat man. ;-)