ostie13

I have a problem that I am hoping I can get some advice on. I have a 71 Olds Toronado that has a 455 with a Fast Fuel injection system. The car has been running at 100% for several years now. I took the car out this week and drove close to 100 miles one day and put it back in the garage, all was well. The next day I started it up, let it Idle for a few minutes and started off to work. I noticed when I slowed down that the motor started to idle rough at the stop signs but when I gave it gas it took off like usual and ran good. Every time I came to a stop It started with the rough idle. I put it in the garage for thet day. The next day when I started it it ran very rough and would not idle almost like it was running on 3 cylinders. Dark smoke would come out of the exhaust and the smell was very abnoxious gas smell. I put new relays in to see if that help. It did not. Next I changed out the fuel filter and fuel pump. That did not help. Now I do not know what else I can do. I have a new fuel regulator I was going to replace but I wanted to see if I could get any advice from someone who knows more than me . That will probably will include 95% of the people that read this. Thank you for any comments.

Fun71

Leaky injector perhaps?

ostie13

The Fast Fuel injection is based on a 4150 style carb. I doesn't have fuel rails or multiple injectors. I wonder if the O2 sensor could be the problem.?

Fun71

Well it is a fuel injection system, so it must have at least one fuel injector, right?
And yes, the O2 sensor could very well be the problem.
Something else to consider: back in the early 90s I had a similar issue with a TBI vehicle that ended up being the throttle position sensor. Resistance measurements while moving the TPS through its range showed a couple of bad spots with high resistance, one being at the idle position. When the throttle was at those spots, the high resistance caused an incorrect injector signal.

70W-32

This could be any one of multiple trouble spots, do you have the instructions for the FAST unit. If not, go online to see if they have trouble shooting guide. Quit replacing parts until you have done more diagnosing. If idle clears up after warm up, could be temp sensor, or as mentioned, throttle position sensor, or computoer, or broken wire, or O2 sensor. See how this could get expensive if you just change out parts?

ostie13

Yes you are absolutely correct. It can get very expensive changing out parts.. I think I will pack up the FAST Fuel throttle body and the computer module and send it back to FAST FUEL and have them test it. If anything is wrong with it they can fix it. If it comes back and they don't find anything wrong I can start looking elsewhere. I did order a O2 sensor. Thought I would try replacing that before I disassemble everything. Thanks for your comment.

Vintage Chief

Pull the distributor cap and see if there is any arcing on the rotor button.

70W-32

Is the unit under warrenty? Have you talked with FAST about returning it? Did you install the injection? Does it interface with your distributor? Dont do anything until you diagnois? You could pack it all up, and find out you have bad plugs or wires on the distributor.

Vintage Chief

It has been my experience one of the first signs of a faulty rotor (in particular the rotor button) is a modest misfire and (in particular) a rough idle. Early in the degradation of a faulty rotor (the rotor itself or possibly the distributor cap) is the inability of the rotor button to make solid contact w/ the distributor coil wire contact located w/in the distributor cap - which can often be visualized by a slight arcing condition between the two contact points. At slow RPM these points of contact (or more appropriately the lack of contact between these two points) produce a worsening idle as it becomes difficult to overcome the insulation of air (between the contact points). As the RPM increases, the voltage increases & the gap (or possibly the corrosion) between these contacts becomes less severe as the higher voltage is able to 'arc' (bridge) to complete the gap. How long does it take to remove a distributor cap & evaluate its integrity?

70W-32

Exactly
And removing sparkplugs can reveal a few bad plugs, or maybe all 8 are fouled.

ostie13

Yes my friend that has helped me along the way also said for me to pull the distributor cap and check it before I do anything. . I will and let you know what I find.

Vintage Chief

Curious if the issue was resolved?

ostie13

[QUOTE=Vintage Chief;1385106]Curious if the issue was resolved?[/QUO
Yes! I should have finished the post. It was an O2 sensor that hooks into the FAST fuel injection. Run like new again, Glad it was that simple. Thanks for your help.

Vintage Chief

[QUOTE=ostie13;1385181]Very good. Glad you figured it out & it was a simple fix.

joe_padavano

I realize this particular post is old, but since the thread has come back to the top (and thanks for the update), I need to point out that the FAST system has EIGHT fuel injectors, which certainly qualifies as "multiple injectors". There are fuel rails built into the covers that are supposed to look like Holley fuel bowls. They still use the same o-rings as any other EFI injector, so they can have the same leakage issues.