My car runs rich especially on start up and it idles rough when the idle starts dropping down below 1500 or so. Doesn't matter if it is warmed up or not. It does this in drive or park. Seems to get worse the lower the idle. I have an adjustable fuel pressure regulator but my pressure is sitting still at 13 psi. I have an air/fuel gauge and it seems to be reading fine most of the time. (Loosing faith with that thing anyhow.) The TBI, and injectors are fairly new. I just put in new spark plugs, cap, and rotor. The IAT sensor looks fine. The timing is dead on and doesn't move a bit. Could this be a vacuum problem? Any suggestions as to what could be causing this idle problem? Thanks.

 

QUOTE:
idles rough when the idle starts dropping down below 1500 or so

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Eh? 1500RPM idle is high... mine idles around 500-600ish
(EDIT) BTW, have you changed your O2 sensor? Engine Coolant Temperature Sensor (not to be confused with the one that sends the temperature to your gauges) can send the ECM messages saying it's too cold ( 0 degrees if it is not hooked up or just plain not working at all) and tells the engine to pour in gas so that it will heat it up faster.

I'm going to guess that you still have the stock Q-Jet Carb, so I'd say that you cant really adjust it very well manually, the computer does that pretty well for you.

So if your computer is not getting the correct information (from several different sources, such as oxygen sensor, and ECTS) then it will act accordingly.

 

Well, the O2 sensor isn't too old. The coolant sensor sounds like a good candidate to check. I don't have a stock TBI I have one from TurboCity. It has been bored out some and polished.It has matched 61lb. injectors. Not a carb though. It is a 90RS but there isn't much left of the old 305 stuff.

I'll give that coolant sensor a try and see what happens. Thanks

 

where's the ECTS located?

 

I guess I should clear that up. What I meant by 1500 rpm was when you first start the car it goes up that high and then drops down to a lower idle. Well, my car seems sluggish even at that high of an rpm. When the car gets above 1500 rpm the sluggishness seems to go away but that is probably just because of the higher rpm and I can't feel it anymore. I can definately smell it when I shut the car off and get out. I haven't had time to check that sensor yet.

 

Is that tbi larger than stock if so I would think you may need some reprogramming but if that is what comes stock on there you may have a map sensor problem.

 

I'm not sure on TPI cars, but on TBI cars it's right where the thermostat housing is. you can do a search for "engine coolant temperature sensor" or just go to the tech articles

 

It is a bit larger than stock but I also have a custom chip made. I have been running with no problems for a while now. That is what lead me to think it might be a vacuum problem or some sensor going bad or something. I did make a change to my AFPR a while back but it wasn't much of a change. I am planning on adjusting it back to where it was and see if that helps any.

 

Tune up anyone?

 

No doesn't need a tune up!

 

Did you check the map sensor make sure it has vaccum going to it because if it doesnot it will make the computer think that you are accelerating and call for more fuel.

 

wow, I think I just found out why it seems that my choke is always on... thanks guys.

when I installed the Nordskog instrument cluster and used the temperature sender that came with it, I must've disconnected the one that goes to the computer (I thought it went to the old instrument cluster... ) alright, that might solve all my problems... but I'm still gonna get a new carb anyways cause even when my computer is telling the engine to use up the right amount of gas it's still burning up more than I can afford.

before nordskog: 16mpg consistently
after: 12-14mpg

who knows, when my investments close I should have enough to replace the carb with the edelbrock 1403 500cfm carb.. if it runs too lean I'll just install water injection.


heh, I have a sticker on my car that says :built with my children'$ inheritance.... I'm truely living up to that... though I'm only pulling out my failing investments.

 

Does TBI have a map sensor? Where is that located?

 

The map sensor should be on the firewall I have seen them on the air breather on some cars.

 

Well, it took me a while but I finally found the problem. Vacuum! I found it by accident too. I was trying to install a new stainless fuel line when I seen a vacuum check valve broken in half. Replaced it for about $3 and now the car idles right, mixture is back and is no longer sluggish. What a day!

Anyhow here is a pic of the part sorry but it is a bit blurry:

 

Where is that valve located?

 

It comes off the intake manifold on the passenger side just behind the TBI.