I guess I should have expected MORE problems getting the replacement engine running in the lemons racer...put here is the problem:

The car will start and idle REALLY LOW..like bottom of the tach or tach does not register and the warning lights come on...then it will surge briefly and the warning lights go away but still is idling really rough

The idle speed adjustment screw on the throttle body doesn't do anything....from the top to bottom of its range makes no difference

The "idle" switch on the TB does not work.....and jumping it to tell the brain the engine is idling doesn't help either?

The entire intake plenum-throttlebody-injectors are the same one we used in the last engine that worked fine....but we did NOT change the idle air valve...that could be bad

We also have LOTS of vacuum leaks...basically every single intake to head connection leaks.....the bolts are tight and we used brand new intake gaskets?? I guess its time for lots of make a gasket goop?

The last bizarre problem is when we tested the function of the idle and WOT switches at the L jet plug...we got nothing....do they need power to work? Since when we tested them on the TB the WOT worked but the idle was dead?

One last idea is the AFM got wet during the previous rain storms? Do you think that might be problem?

 

Until you fix this you are just pissing into a hurricane trying to diagnose all the problems.

Idle switch does not tell the engine to idle. I ran with mine disconnected for quite a while. It's a fuel cutoff switch for deceleration. Having it disconnected is a good way to have that "snap-cracle-pop" exhaust sound with a free flowing system.

 

Hacker
Thats what I thought and we DID have flames before.....

 

Excellent - don't "fix" that

Not having the idle switch connected will dump raw fuel into the combustion chamber on decel...not good for emissions or the CAT. Big fun on a track car with hot exhaust

 

dont worry about the idle switch as was said. You absolutely DO NOT want it connected on a race car. good to have fuel cooling stuff off in the heads on decel. PLUS, with a stick, it can be dangerous to have fuel cut off, as during racing, an abrupt lift of the gas and clutch in, can cause the engine to die, and then restart when you put it in gear, causing handling issues. Its strictly an emmisions gysmo.

as far as running low rpm, did you turn the idle screw up a little. remember, the Ljet is the best of the old school and new tech stuff. so, raising the idle is just as easy as turning the flat head screw at the base of the TB. intake leaks , usually kick up the idle, but if they are large, will make the car run rough. spray some brake cleaner or carb cleaner around the intake. (especially around the base of the U and the plennum connector areas) if there is a leak, the idle will spike upward noticebly.

WOT connection and operation is essential. you absolutely need it. easy to check on the Ljet box at the appropriate pin numbers you are just looking for switch closure at the Lject connector from the engine wiring harness. also make sure you hooked up Temp II correctly and didnt mix it up with the water temp connector. they are easy to mix up and if you do, you gurantee a blown temp II sensor. However, if it was bad, then it wouldnt really start at all, and would be real rich if it did. (the ole, 400ohm resistor trick can fix that for a temp fix to see it run)

Make sure the AFM, flappy voltage is between 4 and 4.5volts when idling. in fact, you can use a long screwdriver to open it up while it is running and richen the mixture up. this can prove a couple of things. If it runs better with the flappy opening up further at idle, then you have a vacuum leaak. If it runs worse, then its something else.

tell me more of the symptoms. can it ref up? is it missing, runn smooth at 3000rpm for example?


EDIT:
I just read it again. Sorry. Sounds like scots car when we didnt change the intake gaskets. we changed them to new and all was just fine. If the TB screw doesnt do anything, you have a real bad leak. you can confirm that by pressing down the AFM flap when running like this. any movement should increase the idle proving the issue. normally, moving the flap, only floods out the engine and it will die.

 

How did you test. you only can check it with an ohm meter and it should zero out when the idle swich is closed , like when you start the car up. the WOT swich will give you 0 ohms as well, but the throttle needs to be about 80%.

if you got the WOT switch to show 0 ohms on the harness connector, then you are good there. you just disconnect the idle switch connection anyway. one last thing on the idle switch, you especially do not want it on an automatic race car. going through a turn the engine can die and you cant restart by it being in gear, you have to actually turn the key. bad idea. cut that wire!


mk

 

MK
Interesting....the car DOES run better with the AFM slightly open....so it must be the extreme vac leaks causing a lean condition, causing the idle to drop...interesting...

I also was worried that the "wet" AFM might be messed up too...I will have to check the output voltage to see what it is.....where do you test it?

I tried the ohm test.... on the L jet connector....of course the idle didn't work...but neither did the WOT? when we tested the WOT switch on the TB it worked....odd....I'll have to check that again....

I wonder what will seal up the intake better.....maybe taking it totally apart (PITA) to get each one lined up then attach the top rubber boots....since we did it as an assembly this time, but last time did it 1 by 1, but it didn't leak?

the "brake cleaner" test does raise the idle anywhere near the base of the intakes...thats how we figured it out...

 

also if i pushed the afm door open a bit more, about 1/2 way, it would begin to surge up and down, the o2 sensor osscialting the fuel?


those leaks are totoally uncalled for! i said it in the begining, should haver gone with a carb setp

 

This just doesn't make sense. With new gaskets and still massive vacuum leaks, something is just not lined up properly. I think you'll need to reset each piece individually. Gasket goop shouldn't be necessary if you have new gaskets.

Like Eric says, there is no point in addressing the idle issues until you have the vacuum leaks resolved.

 

vacuum leaks. you are way lean at idle. usually ,a push on the afm door will kill the motor. o2 sensor doesnt do anything slow. if its working, the engine has to be hot, otherwise, it is in (EDIT) closed loop mode and not doing anything. you can check that by putting a voltage meter on the 02 sensor wires. when cold, it will be at a constant voltage, just as it is at WOT.

the runners dont have to be totally pulled off, but I would loosen all of them at once and loosen the rubber adapters and move them around and tighten . torque them pretty tight. I forgot the torque spec, but its normal for a 13mm bolt.

are you sure all the injetors are seated well? check for leaks around them as well. worst case, you take it all apart and put on some gasket goop and put them all together. thats going to take 1 hour, MAX.

mk

 

It doesnt have to be too extreme to do this. However how does it rev up when you push the throttle? so, the afm door push proves you have leaks. good, thats where you start. there are two leads off the afm electrical connector that you tap into to get the voltage. you can just test a few of them and find it. when you get around 5volts, thats the one. rev the engine and it should go up. push the flap and it should max out at 8volts. doesnt sound like that is the issue.

EDIT: regarding the Ljet test for the idle and WOT switch. make sure you have the right pin connectors. sometimes it is confusing what pin is what. remember, we are only talking a continuity check here. so, if the switch works, you should see 0 homes between the two connections at the Ljet connector. as was said, forget about the idle switch, just disonnect it at the throttle body switch..

 

Gotta get the sealing correct. Use new rubber. Look at the base of the TB where the hoses connect. And injectors like mark said.

You guys can slother the biatch with orange and black silicon caulk (for the judges) later, after you fix it.

 

you mean open loop, closed loop is when the sensor is hot and functioning

 

Yes, sorry. Open loop when it is cold or you are at WOT.