Got a new issue(for me at least)..I'm looking to the collective wisdom of the forum to point me in the right direction. Lost my water pump last week. Car got hot, and as I was pulling in my driveway, I blew the bottom radiator hose. I've just put in the new water pump, thermostat, and hoses. While I had the intake off, I switched my throttlebody back to stock. I had been trying to run a 52MM throttlebody, but everything I had read said I didn't need it. With the 52MM, I had an idle of about 1200, and could not get it any lower. Now that I've got the intake all back together, I crank it up, and try and set the min. air. I can get it to idle at 650, but only in a very narrow range on the idle screw. If I try and open the blades up any more to raise the idle, it instantly dies! I can get it to idle at 650, for as long as I want ( even let it idle for over 45 minutes), but as soon as I touch the throttle, it instantly dies! Cranks right back up as soon as I turn the key, and will idle forever, but as soon as you crack the throttle blades it dies. Any thoughts are most appreciated

Cheers,
Michael

Well, went back to the basics...checked for vacuum leaks with propane...none, checked fuel pressure...OK at 38#, checked spark...OK..replaced fuel filter...no change, unplugged MAF...BINGO!! idled ok, revved ok, no more instant shut-off....replaced MAF, all seems to be ok...idle steady at 750, revs as high as I want to go....just need to take it out for a ride, and see how she does....stay tuned!!

Cheers,
Michael

 

It should tick over like a fine Swiss watch. Is the IAC fully seated? You are getting extra air (vacuum leak) from somewhere.

RACE ON!!!

 

Went thru the Min. Air procedure, with the jumper between A&B. I could hear the IAC clicking, so I have to assume that it moved to the closed position. My first thoughts were a vacuum leak, and I tried the propane and the carb-cleaner trick, and could find nothing..put a vacuum guage on the motor at idle, and it showed 20"...did not bobble, remained rock steady. Of course, as soon as I tried to crack the throttle blades, the engine died, and the vacuum went to zero, so I could not tell if I had something else going on. I'll keep looking for a vacuum leak!!

Thanx,
Michael

 

like CFI-EFI said, it sure sounds like you are gulping air somewhere that you shouldn't be. The next thing I would check would be the fuel pressure at idle, and slowly open up throttle and see if the FP rapidly drops.

it sounds like either excess air or fuel starvation.

 

Fuel is steady at 38#, of course, it dies as soon as I try and crack the throttle blades, but it doesn't show any indication of starvation, but it's hard to tell since it dies so quickly....

 

Then what? Did you leave the A-B jumper in place, with the ignition on for 30 seconds or more? Was the A-B jumper in place with the ignition still on when you unplugged the IAC? You DID unplug the IAC, right? What do you have your TPS set at? You have false air from somewhere.

RACE ON!!!

 

OK, I would still stick to the internal combustion basics, and I would check for spark next. Open up your throttle blade enough so that the car will not start(either by adjusting your TB set screw or putting a screwdriver under the TB butterfly to open it up part way). Then pull a plug and ground it against the engine block. Turn engine over and check for spark. This would be checking the integrity of your ICM and Coil.

When the engine is running, is your idle smooth or choppy?

So, at Idle, you seem to have the right combo of:
<air>**<fuel>**<spark>

so I am summising that anything above Idle, one of the above elements is out of whack...???? You just need to figure out which one it is.....(easier said than done, ehhhh!!!)

 

HUH??? Are you suggesting that a no spark condition could be the cause of too fast an idle? If he had no spark it wouldn't start, in order to idle too fast.

RACE ON!!!

 

I think he's suggesting that somehow spark is lost when the throttle blades are opened. It fits the symptoms, but I give it a 0% chance of being the answer.

 

Yes, this is what I was trying to convey. I am assuming if the TB butterfly is opened somewhat while trying to turn over the engine, that the car will not start. At this point, check that he still has spark.... Process of elimination of the simple things first...and I agree that this is a stretch, but it is an easy thing to check and rule out.....

 

Are we mellowing in our old age?

And I concur that air is getting in somehow and if I had to guess I would say around the throttle body It may not be seated or have some obstruction between it and the intake like some old gasket or something
Doesnt take much of a leak to cause this
Also not tightening the throttle body nuts could do it

Good luck

 

Yes, left the jumper in place for a minute..jumper was in place when the IAC was unplugged, and yes, the IAC was unplugged. Reset the TPS to .54...I know you're right, I just can't find a vacuum leak. I would think a leak that effects it like this would be rather large, but I have'nt found one yet....I'll keep looking.

Cheers,
Michael

 

Checked the spark, all plugs are sparking...engine idles very smooth

Cheers,
Michael

 

Check your intake manifold bolts. If any are loose, you have a gasket leak that may not be visible to you.

 

Checked these items you suggested...everything seems to be ok here...sprayed carb cleaner around the throttlebody, but noticed no change in the idle....I was hoping a vacuum leak would show up when I sprayed it with the Carb Cleaner....I'll keep looking, but it's beginning to get a little frustrating..probably something simple I'm over-looking...

Cheers,
Michael

 

Yep, checked those first...all tight, and when I sprayed them with carb cleaner, showed no sign of a leak...

Thanx for reminding me to check these!!

 

Where does it say that the car won't start with the throttle blades open? Starting under any conditions was never stated as a problem.

The engine dies when the throttle is advanced because the ECM isn't enriching the mixture as it needs to be. It goes dead lean and dies like a cold engine with no choke. That is why I mentioned the TPS setting. It was said that the minimum air setting couldn't be set, so my first thought went to whether the IAC was truly closed. I thought maybe the ECT sensor might not be hooked up, but it should run pig rich if it weren't and that wouldn't have affected the minimum air adjustment.

RACE ON!!!

 

That is why I said "I am assuming the car wouldn't start with the blades propped open somewhat". His symtoms would suggest that this would be true.

mk842766 - will the engine start with partially open TB butterfly ?

Also, the cutting out could be caused by both an extrememly lean OR extremely rich condition upon increasing RPM's. But a lean condition sounds more plausable due to the rapid shutdown of the engine above idle.

Not trying to be combative here, just trying to figure out what this fella's problem is.

 

another thought would be to slap that 52mm TB back in there and see if problem still exists.

 

Are you 100% sure of your spark plug wiring ??