My first TPI engine. Started it today, and it stayed at a very high RPM (3000). From there I proceded to retard the timing until the engine idled down a bit. I got it to idle but very poorly. Finally dug up my timing light and found the timing at about 13 degrees AFTER TDC From there I timed it to 6 BTDC and it seemed to run better but idled high. I removed the IAc motor and it appeared to be stuck, and while messing with it, I broke it. Well none around town so just to mess around I plugged the passage going to the engine side of the throttle body so no air could come through the idle air passage and then I started it. Now it idles at 4000 rpm and very roughly. I will get a new IAC valve, but am thinking I have a vacuum leak pretty bad. I have no obvious ones, are there any trouble spots for vacuum leaks on these engines???

Randy

Just Learning Fuel Injection Racing

 

Well, since you have the IAC out already and you say you have the passage blocked where the pintle seats...did you try lowering your idle at the throttle?
Is this a MAF or MAP engine? If it is a MAF engine then I'd tend to shy away from the vacuum leak idea. Any leak of the size it would take to raise the idle to 3-4k would be setting MAF codes in the ECM and the car would run like real dog crap.
If it is a MAP engine...dunno, don't own one of them.


~M~

 

its a MAP engine and I manually screwed the idle all the way down it would go.

 

Sounds like a pretty mean vacuum leak....

but 4,000 rpms.. wow.

Set your timing to 6_° BDC and fix it like that since thats the way its going to need to end up. Since its MAP you can run it with the TB exposed. I recommend doing that, then getting a spray bottle with water and spraying around the throttle blades, these can wear and leak enough air to make things get funky, but I SERIOUSLY doubt funky to the point of a 4k rpm idle. Anyways as you spray it with water the idle will stumble if there is air coming in at that point. If nothing happens your TB is sealing, then spray around the outside of the TB, IAC, EGR vacuum line, etc, try to make it stumble, if still nothing move back, spray around the plenum, there's a huge vacuum line at the back driverside corner for the brake booster. Then there is another big line for the PCV at the center driver side base. Keep spraying untill the engine stumbles, then search that area because thats where the leak is.

Hopefully you can find it.

 

well...I stuck a book in front of the throttle body for starters and with that sealed off it idled down to 2500 rpm. still a leak eh? well, i took it all back apart and found some major issues with gaskets and got it all back together and am confident that the runners and gaskets are all correct. I also got the new IAC motor and got it installed. All back together where i thought it would be perfect and it now idles at 2500, even with the spout connector disconnected which tells me its not timing. Like I said, I think I am confident in the no vacuum leak thing, the IAC is new, I tested the TPS and I replaced most engine sensors with the new engine.

WHAT GIVES????

 

I had this same problem after I built my tpi engine. I had a few small vacuum leaks here and there and overall it was like 1 big one. My first leak was the gasket in between the runner and intake. i fixed that and then got a new IAC motor and all new vaccum lines and it fixed the problem. if you put a book in front of the TB and the engine kept running then you have false air entering the engine somewhere. you cheacked all the trouble spots on the plenum right? Where did you buy your sensors from. Sometimes cheap sensors get you cheap results. is it the stock engine. did you mess with a new chip at all? are you setting any codes? how does it drive? your sure the dist is in right.

 

I'd say check for vacuum lines being backwards. Also, When installing the manifold, did you start from the middle and work your way out to the edges? Same thing with the runners bolting to the intake and plenum. Did you torque them down to specs?

 

make sure you block off you brake booster hose I have seen problems there and it will give you enough air to idle that high

 

No one has mentioned the obvious.... have you followed the IAC and TPS adjustment procedure, or are you just "turning the idle screw"?

The procedure is outlined below:

TPI Idle & IAC Valve Adjustment Procedure

· Key Off
· Attach TPS test harness
(allows multimeter to determine TPS voltage otherwise use a scanner)
· Insert Trouble code jumper
· Key On
· Wait 30 seconds for IAC pintle to fully retract.
· Unplug IAC harness
· Key Off
· Remove jumper
· Key On, Start Engine
· Adjust Idle screw to correct rpm
· Adjust TPS to .54 v using ohmmeter
· Key Off
· Replace idle air valve harness
· Remove TPS test harness

 

Won't the water pass thru the IAC passage when doing this and cause it to stumble?