Hi, just joined, I have a problem that I have to get fixed, so I can sell this car - the gas mileage was eating my son up, so he bought a Celica. Idle is very rich, will eventually die if I leave it idling. (Probably running rich at all speeds, I am getting 13.7 MPG with a light foot) This is strange: I pulled the IAC to clean it, ended up breaking the pintle and had had to install a new one. It idled rough for about a minute, I hit the throttle and right after I let off, it was rough for about 5 seconds, then I heard it smooth itself out, idling like brand new. I drove it around for about 30 minutes, ran great, no stalling at red lights, very smooth idle. Parked it overnight, and it's right back like it was. Only code it has ever thrown is O2 sensor, I have changed it 3 times in the year I've had the car, the rich running is burning them out. Got a new one on it yesterday, no change in idle - found a split vacuum line to the MAP sensor, fixed it - no change. I am going to change the CTS, cause it's pretty cheap, but I doubt that's the trouble. What has me stumped is the way it cleared up temporarily. Any ideas would be appreciated. Tookie

Can anyone point me to an F-body forum that may be able to help?

plenum gasket. i got a 92 3.1 and i got the same issues. mechanic said gasket i say gasket. 14.99 autozone

what's a plenum gasket? What's a plenum for that matter?

its short for=intake manifold gasket.if that helps dont have pics, but im sure you can look it up

I sprayed cleaner all around the plenum with no change in idle,
but I am going to pull the plenum to test the injectors this weekend,
so it will get new gaskets then.

let me know if that works, if that was the injectors. and if you change them search in the v6 forums, theres been tak of for 2.9 motor injctrs that work better than gm stock. and so far all good reviews. def worth checking out.

I am trying to sell the car, so if I find a bad injector(s), I am only
changing the bad one(s) $$ - if they are all bad, then I will possibly
look at swapping to the 2.9s.
I doubt it's the injectors, if they were bad, it wouldn't have cleared
up and ran correctly that one time - I am thinking sensor or wire/
connector issue. I don't know how long it's been running like this, I knew
about the bad fuel mileage, but I haven't driven it in a long time.
I just inherited it from my son, who says "well, it didn't die TOO many
times when I drove it."

I actually just got finished looking for the same problem. My problem was a brake booster line that had just barely slipped off the connecter. Check for vacuum lines (my best method so far has been to put my ear up in the engine while it was running). Other things I was told to look for were:
-EGR Valve
-MAP sensor
-O2 Sensors
-Idle Air Control Valve
-Throttle Position Sensor
-PCV valve
-Throttle body inside plate - the EGR puts exhaust right into the throttle body, can get dirty as hell inside
-Vacuum Leak
-Incorrect Timing
-ICM
-Spark Plugs/Wires

I would check Spark Plugs/Wires, Throttle body, Vacuum leaks (inspecting alll hoses and connections) first. Then start looking at the sensors. Hopefully it's not a EGR - you have an electronic one right? That mofo is like $230. Hope that helps.

I thought that price was bad, I scanned my sons Celica, and got a
code for a bad MAP sensor, so I told him to go buy one.
271.00 for a Toyota MAP sensor!!!

And thanks for the list, lots of good things to check there.
I actually may have a brake booster issue, I checked the other day to make
sure vacuum line was good, and if I pull the line from the booster and plug
it, the idle goes down a fair amount - I'll have to plug it and go drive it around
to see if it is an issue

Be careful - if you plug it, you won't have power brakes. Is the master cylinder full?

It gets stranger - O2 sensors have been averaging 3 months to burnout,
and when pulled, are full of black soot, plus I can see that the car
is running rich at idle, it will start putting out light black smoke if
it sits long enough (not to mention the fuel mileage)
So I changed the distributor cap and rotor, and pulled the plugs,
expecting them to be really sooted up, but they were spotless!!
I don't see how this car can run that rich and have clean plugs
Anyway, a couple of plug wires broke pulling them off the plugs, so
I guess it was time for new wires anyway - I'll be putting them on
tomorrow.

Put on the new wires, and changed the CTS - no change in idle, will
die most of the time coming to a stop, runs rich enough to water your eyes

Update: changed the TPS, no change in idle

Isn't light black smoke an indication of oil burning in the chambers? Could it be blowby? Could you have low compression on your cylinders because of worn piston rings or something? If your compression was low, that'd definitely cause the rough idle + running rich problem. Have you checked the compression on all the cylinders?

Oil would be whiter than this, plus no oil loss, low miles (under 80,000),
clean plugs... and I can smell it's running rich. Just pulled the plenum off,
gonna see what I can find

Get a fuel pressure tester and check for leak down. Put on the tester and check to see if it loose pressure after you shut it down.

If it loose pressure quickly you can have bad injectors or a ful pressure regulator.

HOw about a bad timing chain. jumped a tooth. Mine did that and ran like crap. Put a new one on.

Just checked the injectors - they all OHMed out to around 13.5,
hooked up a pressure gauge to the fuel rail, got 47 PSI, lost maybe
4 or 5 PSI over 20 minutes, I guess next thing is to block off the
EGR and see how it does - but I would think a bad EGR would
cause a lean condition, not rich? Also have to change that stupid
little fitting just under the thermostat cover, that has the hoses going
to the plenum - been leaking for a while, broke off in my hand when I
was taking the hoses off

I think I got it. I think the EGR is bad, and leaking a little thru to the intake. I made a block off plate, and put it into the line where the EGR meets the intake, like a gasket but no hole thru it. Car seems to be idling much better, no surges so far. Had to make new Plenum gaskets, because every parts store I went to pulled a plenum set with 2 different size gaskets in the box, neither of which fit my car, theirs looked like this.



But before I put it back together, I had to drill out and retap
the manifold, where the fitting for the heater/ coolant to throttle body was.
The fitting corroded and just crumbled when I took it apart, I just left off
the throttle body lines and went straight to heater with it.

For the (very few) people on this board who offered advice, thanks.
This car will be posted for sale very soon, 1990, auto, air, pwr locks/drs,
cruise, tilt, 77,000 miles, passenger door has some dings, rest of body
fairly straight, when I post in for sale, I'll include some pics

Got it all back together, went from 13.7 before, to 20.7 now

put ap26 autolights primin it i had a air/ful thing like that than go to the computer and egr

Huh?

^

If you have a junkyard nearby, you can get an EGR valve for about $5...MAP sensors, as well...that's what I did.

Yes, I think that's what I'll try, if I have a spare I can clean it
real good before installing.
I have a service engine light on now, scanned it and it says
"EGR malfunction" I didn't think it would throw a code, because
I blocked it off at the intake, but if I can't find a used one, I can live
with it until I sell it - I can't believe how much a new one costs

The resaon your o2 are going out because of the rich condition. It causes the o2 sensors to go bad. Mine did it when I ahd a bad timing chain.

would you still need th o2 if your cat is hollowed out?

Yes The o2 tells the computer to go into open loop. Better gas mileage

thought so thanks

Yes, I knew that was why they were burning out, the challenge was
finding the reason for the rich condition