OK, I just finished replacing all of the fuel injectors with a good set of 2nd generation bosch 19lb/hr injectors. All new intake / TB gaskets, car runs smooth, drives good. Last night we drove it around town, and once up to operating temp, the idle slowed down, and was ~ 700 rpm in park or neutral. This morning I drove 25 miles (70mph hwy driving) to work and now it does not want to idle lower than ~1250-1300 rpm?

The car had apparently been running rough with a couple of bad injectors for a while before I bought it, so I'm wondering if it just needs to go through several more drive cycles to re-learn everything now that it has 8 good injectors? Any ideas? Is there a way to lower the idle speed on this thing? TPS voltage, maybe? Or should I drive it a few more days first?

This Is the first TPI GM car I have owned, so I am not familiar with working on it other than what I have learned since i bought it last year... This site, and the people here have been very helpful to me. Thanks for that BTW.
John C.

 

TTT

 

While it's idling high, check for a sticking throttle blade not returning all the way closed, and/or a vacuum leak.

 

Idle relearn is pretty quick. And while it's learning, it won't be up at 1300 RPM.

Since your car recently went through minor surgurey, my bet is on a vacuum leak.

 

OK, Just got home and made a few stops along the way that required shutting off the engine for a few min each time. It will idle slower now, but sometimes it's @ 650-700 and other times it's a little higher, like 1000 or so. Seems like every time I start it the idle is at a different rpm. :-\
I know the throttle plates are not sticking because I cleaned the TB while I had it apart, and i checked to make sure that it moved freely after mounting it and connecting all the cables.

I made sure that all gaskets were replaced with new fel-pro ones (TB, Upper plenum to runners, lower runners to the lower intake) and the bolts are all there and tight. When I first started the car after re-assembly I found the brake booster vac hose was not connected at the rear of the upper plenum. But I imediately connected that and checked over all the hose connections, and as best I can tell everything is connected correctly at this point.

I looked at all the vac lines closely when the motor was apart and they all appear to be very pliable and in good shape, so I don't think that there are any cracks or breaks. Is it possible/probable that the temp sensor for the engine computer is in need of replacement or has a bad (intermittent) connection which is causing the computer to get goofy voltage readings from it? Idle Air Control motor dirty or acting up maybe?

Oh, yeah, the SES light came on for literally 2 seconds when i was driving home, then went off and has not come back on again.?.?.

 

You want your idle to be at or near 700 to 800 rpm. My car idles between 700 and 1,000 rpm's but it won't hurt anything. I have no vacuum leaks or anything but you may.

 

It's common for a TB to start sticking right after being cleaned. How did you clean it? and did you lube the shaft afterward?

The SES light could indicate a vacuum leak or misfire.
Check for leak between the MAF and the TB. I would also check all of your plugs and look for evidence of misfire.

 

Cleaned 1/4 inch of black crap out of it which was mostly on and around the throttle blades (inside and out) while I had it off with a can of gumout carb cleaner and a rag. It was sticking closed when I got the car, 'cause it had 129k miles of crap in it. I did not spray any lube on the shaft, but it would be easy to do. The idle of the engine is not erratic, and the engine is running smooth. It just acts like a carbed engine that needs the idle screw backed out a little....As soon as I have better weather, I will be able to look at it some more.

 

OK, a few questions.
1. Is the softball sized black vacuum "canister" or "accumulator" or whatever it is down inside the front driver's side fender (in front of the wheel, below the washer reservoir) supposed to have a small hole in the bottom of it (~2-3mm) where air can enter it? Mine does.
2. I noticed my pcv valve tends to rattle/buzz sometimes, and if I pull it out of the valve cover, or pull the hose that runs from the pass side cover to the tb loose (with the pcv valve installed) engine speed will decrease a couple hundred rpm. Is this normal?

3. Where is screw that is turned to adjust the air/idle when performing the adjustment procedure for the IAC valve? I have not been able to locate one, nor the cap that would be covering it if it hasn't been serviced before. And, is that the iac valve at the bottom on the pass side of the tb? (appears to be round)

 

I pulled up a picture of my old vacuum canister from last year and nowhere on mine were there any small holes at the bottom of it. At the top were a few small places for a connector and PCV system but nothing else.

 

Thanks. Is that the sphere shaped one on the driver's side, located under the car in front of the front tire?

 

There should not be a hole in your vacuum reservoir, aside form the hose connection(it's the softball shaped peice under the front left corner). It's a reservoir and should hold vacuum for the HVAC controls. Fix or replace it. The buzzing in your PCV valve may be nothing but I've also seen this in connection with leaky intake valves. Try cleaning or replacing the PCV. The base idle screw is on the driver's side. The plug that you need to remove to adjust it is on the back side of the TB at the top corner. Trouble with IAC is fairly common on these cars. Remove it carefully and clean the passages in the TB. You'll want to remove the TB for this and that will give you easier access to the base idle plug. If problem persists, replace the IAC and repeat idle learn. The CTS can cause a multitude of problems. if you think you might want to replace it for any reason. Go ahead. Be sure to use a quality part like AC Delco.

 

What ASE Doc said. ^^^^^^

 

Thanks for the help guys. I had wondered about the possibility that the temp sensor could cause some idle issues if it were not in good shape... How many different temp sensors are there? Doesn't it have one for the guage, and another for the ecu/ecm? (Not sure what the correct term is for the engine computer on these cars) If so, what is the location of the sensor for the computer? If it's relatively cheap, I'll replace it because it's probably the original one w / 129000 miles on it. I'm guessing it would not turn on the SES light even if the coolant temp sensor is out of range?
Thanks,
John C.

 

There is a coolant temp sensor for the ECM. It's located at the front of the intake manifold, below the thermostat. it has a yellow and a black wire in a two wire connector. There is a temp gauge sending unit in the driver's side cyl head. The CTS can cause a SES code if it is too high or too low.