Help!! Fuel/Vacuum issue?

[ryan]

Hey everyone. My name is Ryan and I live in santa barbara, Ca. I am new here and have spent a good deal of time searching the threads, but reached a point where i need a little more specific expertise. Thanks in advance. The car in question is a '90 festiva L. 4cyl 5spd. Here is the issue...

I drive to the store and shut the car off to go inside. car is running fine. i come out of the store hop in, start the car, and it starts right away, but immediately runs rough as if misfiring or has a dead cylinder or something. the car then cuts out and dies. i pop the hood and check for immediate signs of a problem. vacuum line issues, loose spark plug wires, etc. nothing found. i get back in and start the car. again it starts immediately but runs rough. i give it a little gas and it seems to smooth out. then returns to idle and starts running rough again.

i decide to see what it will do under load, since the store is two blocks from my house. i am able to nurse it home without much of an issue but as soon as i get home and pull in the car begins to run rough at idle again, then cuts out. the car seems to run decently while i am giving it gas, but as soon as it returns to idle it runs terribly. if i dont move the car i can start it and it will stay running at idle, but it sounds terrible. i can get it to drive but if i don't keep giving it gas it cuts out as soon as i slow down or let off the gas pedal.

the car has new cap, rotor, plugs, and wires. so far i have checked the compression and all cylinders are between 190-200psi. i have completely taken out and cleaned thoroughly the throttle body. i have also pulled the clips on the fuel injectors individually while the car was running, and every one made the car immediately stumble and run worse, so i believe the injectors are good. two things i have noticed: the oil now smells like gas, and the new plugs are black after only a short test drive. i am not the best with electrical diagnosis so i dont know where to begin with checking sensors, etc.. my only idea right now is a bad fuel pressure regulator. any help is greatly appreciated as i am walking 16 blocks to and from work at odd hours, and would love to have my car back..

[iceracerdude]

Look at the fuel pressure regulator as a potential suspect. It's the thing that the return fuel line is attachrd to. If you pull the vacuum line off of it (the fpr not the manifold side) plug the line with something and then run the car, you should see no fuel coming from the fpr. If you see fuel, the diaphram within the fpr is ruptured and the fpr will need to be replaced. You should also do the same thing with the spark plug leads you did with the fuel injector plugs, you may have a spark plug that's not firing the fuel, and you do seem to have plenty of fuel right, pulling the plugs from the injectors wasn't what we want here. I don't mean to seem condesending in my explaination, it's just that I don't know what you know is all, so for that I'm sorry. Let us know what you find.

[FestYboy]

also look for cracks in your intake tube right after the VAF. a small crack can cause a false air issue and therefore a stumble/rough idle. actually, ANY opening between the VAF and intake anywhere along that tube can cause those symptoms.

[ryan]

I will check these ASAP and let you know what I find. Thanks guys

[Movin]

Check that your VAF door inside the air cleaner did not stick wide open.
That is exactly how they run.

[ryan]

Ice and festy- thanks for your help and suggestions. I appreciate it. Movin- that's exactly what it was! Thanks for saving me hours of troubleshooting! Problem solved..

[iceracerdude]

Which thing...A cracked tube or a fractured FPR or both?

[ryan]

It was movin's suggestion. The damn door on the vaf was stuck open..

[rmp2711]

I'm having the same issue with my 90. Back in June my VAF went bad and had it replaced.After it was replced sometimes it would idle around 500 to 600 rpms,but if I hit the gas and rev it up it would go back to 750 rpms and run fine. Today its idling rough at 500 rpms and won't smooth out. Where is this door on the VAF, how do you get to it, and how do you unstick it? The VAF was a remanufactured one. Could it be defective? Things that I recently did to the car. Tune up in May. Today I changed the oil, added fuel injection cleaner to the gas tank and filled the tank with gas. Shorty after is when I started having problems. I don't think I have any vacuum leaks,but I will check tommorow. Any input from you guys would be great. Need to drive 200 mile round trip tomorrow and I don't want to be stuck on the side of the road.

Tanks, Rich

[RhodeStiva]

i would check the spark plugs, wires