Hello all I am new to the boards. I have found that they are very helpful after reading many questions and answers.

Well here is my prob.
My car is idling low in Drive. I don't know what the problem is
I just put some new 9mm Taylor wires and new plugs. I have not messed with the timing yet. I also just replaced the TPS (throttle position sensor) (is that sensor adjustable?).

Engine: 5.0L V8 TBI OHV 16V


I just bought the car and car fax report checked out fine.
I also just bought a rearend off of a 87 z28 with rear-disc brakes posi and just installed 3.42 gears.

 

My truck was doin the same thing and its got TBI too. My friend (Jprevost, moderator here) said it was the computer kinda stumbling and messing up; not being able to adjust right. Try posting at the electrical section too. Sorry man, thats all the help i can give.

 

Thanks,

My uncle has a 86 with a 350 TBI and his was doing the same. He replaced some sensors and tuned it up. Someone at his shop told him it was the computer.

I figured that may be my problem too, I was just hoping that wasn't it.

 

Hey man, have you tried the Idle Air Control valve. It controls idle speed or is the car idling low in just drive?

 

just to clarify, what exactly do you mean by "low"

 

I would have to say there are too many definitions of low...

take my car.. hot idle in gear is 500, cold idle in gear 750...

only difference temperature, ie closed loop vs open loop

Take another member's low idle... 500 avg idle, gear or not.. turns out he was at least 4 degrees retarded on timing... we fixed that and he went to the same idling scheme as me.

IAC is what controls idle, if its out of range or braking, stumbling/high or erratic idling occurs. Some case low idling, but doubtful since it always ends in a stall event.

You're gonna have to talk more about what is a low idle to you, and what it was doing before, and what you've done to it recently, or what has happened to it in its lifetime. Too little information given at the moment to make any kind determination of the problem, let alone fix it.

 

Hey all sorry I haven't been around.
Thanks for the replies.

I haven't tried the IAC yet. Yes the Car is idling low in just Drive.
In Nutruel or Park its between 800-1000 depending on temp.
In Drive after car is warmed up it's between 500-600.

I recently I put new Taylor wires, new plugs, and replaced the TPS sensor. When I bought the car I don't remember it being this noticable, but then again I was probably just too excited back then to notice. The average temp. on the car used to be 180 a/c or no a/c, because I installed another fan in front of the Radiator. I think my radiator is going bad because with the a/c on its at 210 sometimes over with the extra fan running. With a/c off it runs 180 no prob. So a new radiator is going in very soon. I replaced the thermostat to 160 to see if that would help but same temps.

So my problem is still it idles low in drive or (gear).

A friend told me to replace the IAC and the map sensor.?

 

my car idles at around 500 RPM when in drive and is very smooth, i thought that was normal correct me if i am wrong

 

Well when cars are new they idle 1000 in drive.
I know when cars get older and more mileage they tend to idle lower. When mine is all warmed up it idles 500-600. It feels rough, not too smooth. It may be normal to idle in 500 smooth but not normal to feel rough and unstable. But it just doesn't feel right, I know there is something wrong.

 

good luck idling around 1k in gear with the stock tc, it stalls at 1200 rpms. youll have to give it gas to have it do that. The tc pretty much forces the engine to idle at around 500 or so rpms when its in gear. My engine likes to truck along at around 1000 rpm when its warm and idling in N. When its in drive, it drops to around 650 rpm. Hehe... funny idle... im running around 20+(its way off the tab so i can only guess) some odd degrees of base time with my engine so the idle is a little flaky. If i rub it the wrong way by turning on all the acc., itll die ocasionally from the alternator drag.

 

heh

 

I'm sorry, but not all new cars idle at 1000 RPM. It has to do with alot of factors. For example, 4 bangers typically idle higher because they have a greater potential to stall out. A V8, however, idles as low as possible to save gas. My new Z28 idles at 550 in drive and 600 in neutral (when warm). An idle of 500 may be slightly low, but I'd shoot for about 600.

The main things that will effect the idle quality are sensors and timing (as was mentioned). Retarded timing will cause a rough, kindof loping idle that is quite low. If this is the case, advancing the timing will cause an increase in RPM when you get it close to acceptible timing. Also, an older engine with low compression will have a rough idle. I hope something here helps.

 

Thanks...

Now since I'm such a newbie can someone tell me the best way to set the timing? I know you can turn the dristributor also there is this electronic gun they sell that help set the timing.

Any help is appreciated.
Thanks guys,

 

It's quite easy.
Thinks you'll need: White out, timing gun, distributor wrench
First, find your timing mark on the harmonic balancer and highlight it with the whiteout (you may need to crank the motor around to find it). Next, clean off the timing indicator tab( I forget what this is actually called) so you can see the marks. They should be something like 6, 0, -6, -12. I think our TBI's are factory set to 0, although an advance of 2-6 degrees is nice with premium gas.
Start the car and let it warm up. Turn off car.
Connect the timing light to the battery and to the number one plug wire. Disconnect the EST wire (located on passanger side wheel well, one wire, I think it's brown). Restart the car and point the gun at the timing mark. The white line you highlighted should be near the 0 mark. Left of the zero is advanced timing, and right of it is retarded.
To adjust timing, loosten the bolt at the base of the distributor so that the cap can be moved with slight resistance (so it can be adjusted with the car running). Turn the distributor clockwise to retard timing, and counterclockwise to advance it. When your done, tighten the distributor bolt and reconnect the EST wire.
Your done

 

cool! Thanks for the info.

What do people usually set their timing to?
How do I know what is good and not good? Listening to sound? Idle?


edit: well I guess that is what the gun is for. correct?

 

The EST wire should be tan with a black stripe - NOT the tan wire!

On my 305 5.0L TBI LO3 this wire is on pass side, comes out of harness close to strut top with a connector in it (so as to easily disconnect/reconnect).

The tan wire without the black stripe is something else.

 

Look at the tag under your hood, it will tell you the recomended timing for your car. Unfortunatly, timing by ear just doesn't work for our cars because the computer automaticly retards the timing under a pinging condition. So, using the gun is the only way to go. I set mine to 6* advanced, which I am going to back down to 4 I think.

 

My Lo3 idled at 500 in gear smooth, I can do that with the motor I have now but it requires the disabling of the IAC and slightly less timing then I have now. I'm at 650 in gear right now and 750 in park/neutral. When you have too much timing the car will idle but sometimes it'll miss so bad that you'll either stall or ender stall saver and the idle will bug out. I've had this happen a few times and retarding the timing has solved the issue. The only reason I have as much timing in as possible is because without it the car will sometimes backfire through the intake (lag issue with timing is my guess).
If it's rough and moving up and down then double check that all your spark plugs are gapped correctly. The last 2 guys I've had to fix idle issues with had a plug that was zero gap from being dropped . You might want to clean out the IAC passage but I doubt that's an issue, it sounds more spark related. You've replaced the cap, rotor, plug wires, now double check the spark plugs and gap them accordingly.

 

Well I just put the plugs in a month ago gapped to factory request, and none of them were dropped.

Also it's getting a little worse. After I replaced that TPS sensor it seem to work better. But I'm still noticing a little hesitation and funny movements in the RPM tach. It's not the tranny because it was just rebuilt 2 months ago. I'll try the timing and the IAC.

Leave plugs for last cause I'm sure they are fine.

 

Hey guys just looking for some more opinions.

I never replaced the IAC and was going to mess with the timing.
But for people in Houston you know it's been raining and the weather has gotten cooler. High's between 65-70 lately.

So all of a sudden my car is running right/great.
Picks up and goes when I put my foot on it. No hesitation at all.
I remember when the problem got bad it was just not moving when I put my foot on it. It would barely turn the tires for a scratch.
But since it's gotten cooler, it's been acting great, burn outs are gravy.
Alot of people said it was the IAC.... not saying they are wrong, but will the IAC act different at hotter or cooler temps?
Someone told me it may have been bad gas, but I don't think so...?