I have a '91 Protege that is having a very mysterious problem. In the morning time when the air is cool outside between 70 and 74 degrees, the car will run like a champ and seems nothing is wrong with it at all. But in the afternoon when the temp hits between 90 and 100 degrees, the car runs like crap. meaning that it will idle like normal, but, when the throttle is opened up it bogs down and sounds like it is getting no air to the engine at all. I can hold the throttle down to the floor and it will barely move when in gear or really sound like crap at an idle.

I have replaced the fuel pump, fuel lines, fuel filter, fuel rail, fuel pressure regulator, fuel pump relay, I also have done a complete tune up being sure to replace the air filter. Not to mention just about every sensor under the hood, whether the needed to be replaced or not. The engine has good compression and the injectors are firing like the should be. The car has a ton of miles on it. 240,000 to be exact.

I seem to think that it may be something in the timing or even in the distributer. I have put a timing light on the thing and it was advanced about as far as it will go. I then brought it back to where it is suppossed to be and the car runs very, very rough at idle or in gear. If i advance the timing it will start to run very smoothly, but idle rather high.

If any one here has any ideas at all? I am listening. Your help is greatly appreciated.

Thanks in advance,


addy

Addy

Have you checked for vacuum leaks?

You say that the engine performance depends on the air temp. When it's cooler out does the engine run well even though the engine warms up to operating temp?

It sounds like you've replaced a lot of parts.

Regards

Dan

Yep, when the air is cool/cooler out in the mornings, the car will run just. But, on some mornings the car will run just fine until it does get to normal operating temperature. Then it is like it is starving for air and the gas smell is overwhelming. I mean you can smell the gas fumes from 3 or 4 car lengths back.

I did find that the PRC valve (Pressure Regulator Control Solenoid Valve) was cracked and is in definate need of replacement. The part costs $129 and i have to wait until payday to replace it. When i do replace it? I will go ahead and check all the vacuum lines again and see what i get. Then i will post back and let y'all know what is going on.

I bought the car for $200, because it looked good and kind of ran ok. So i decided to go ahead and replace everything that the car needed, because it is worth it. The guy that i got it from messed up everything on the car. So i got to go back and undo what he has done.

Thanks for the reply... I will post back soon....

addy

A lot of electronics, especially ignition coils can be sensitive to temperature. A lot of times they'll run fine for 30 minutes, then stop working for a fair bit of time. Check your spark with a spark plug tester when it's not running properly and see if you're getting ignition.

One other thing to check. When it's hot, see if the throttle is opening properly and check the various mechanical stuff. Sometimes plastic swells. I forgot to mention above, relays can be very sensitive to temperature.

Also try to pressurize the radiator to see if the prssure drops, maybe the problem is the head gasket or try to make a leak down test this one is the most accurate than compression test, in the compression test you can have a difference of up to 28psi between pistons

What changes between the 2 conditions? Air temp, is your intake air temperature sensor reading properly? Car may be trying to adjust to temps it can not read. Also coolant temp, is the computer seeing actual temp? These cars are known for having idle air control and maf problems. Maf can be checked for resistance and idle air can be removed cleaned and checked fr operation.The car is trying to adjust to something it cannot, air leaks maybe, but a vacuum leak would present more at idle in this car.

in my professional opinion , you should burn the car for insurance money