Just got the L98 in and if you've seen my other post you know I've had some fuel pump problems. I got that straightened out and it used up all my patience so I'm turning to you guys again for some help from 'fresh' minds. I know I'm getting fuel and spark to the motor. When I turn it over, it will fire, run for 1-2 seconds and die. What would cause this? Bad sensor somewhere? TPS need to be adjusted? Please heeeeeelp!

 

did u set the iac?

if not then set the iac then set the tps

i cant think of anything other then that off the top of my head

good luck!!

 

Hey Nasty_Bird_'90,

If it ran for a few seconds then it should have been able to read the sensors(or not read them if something was wrong) so if you pull the codes it should point you in the right direction. Let me know what codes you get if any.

 

How many times have you started it and how long has the motor run? When I put mine in it started but ran like ****. More than once. It was so bad I was convinced I had the distributor 180 out (or something worse) and was ready to rewire it. One of the friends helping me "talked me down". I started it back up and had to keep it running, after a few minutes it smoothed out and ran fine. Just thought I would mention this, good luck.

 

It doesn't run rough, it just wont start. It will turn over and fire, and it will run for a second, then it dies. Is there something on the motor that detects that it is running and supplies spark, or fuel? Maybe the ECM isn't recognizing that the motor is running and thats why it shuts off?

 

Have you checked all the wiring?

The fuel pump safety cutoff, behind the engine with the oil pressure sensor... ( At least in my TPI car) ?

Are all the electrical connections underhood making good contact?

Did you try disconnecting the battery, to clear the ECM and starting from there?


Are the connections to the coil and distributor good?

You have to be getting fuel and spark. When your motor cuts off, it isn't getting one of the two....

I'd check out the ignition before anything else.



HTH

 

My bet ....

The distributor isn't close enough to the correct BTDC value in order to allow the motor to run. Been there, done that one too many times. Just takes some playing around in order to zero in on a distributor setting that will allow the motor to run while you set the timing. Make sure to unplug the brown/black EST wire on the passenger side. Cracking the throttle blades open more should help out some. Just don't forget to reset the idle and IAC once you are done.

How do you know that your distributor is installed correctly along with the correct rotor placement?

Tim

 

Well, I checked the timing with a light while cranking the motor over and it was dead on. I advanced it just a few degrees and that helped a little bit. What will unplugging the EST do for me? I'll check the distributor out once more. I suppose there is the possibility that it's flipped 180*

 

You have to unplug the EST to set the base timing. Correct me if I am wrong, but if you did not unplug it when you set your timing you would have it way retarded. This would probably explain the problems you are having. Try to reset the timing with the EST unplugged.

 

Another vote for timing....

 

The EST wire, would that be the single wire coming out of the harness right above the heater/AC box? It's the only brown/black wire I could find on that side. Thx.

 

I've detirmined that it isn't the timing. I pulled out the spark plug and was getting spart at #1 6* BTDC on the compression stroke. Any other ideas? VATS? I used a DMM to test the voltage at the injector and I have nothing. But the cold start injector is getting power. Could there be a problem somewhere with the injectors? They're LT1 injectors if it makes a difference. 24#@45 PSI

 

ok ill tel you about an experiance i had about a year ago...
i was an old airfield in new york doing another top speed run, i got up to about 130 and my car stuttered then died all within about 3 seconds it happend very fast...i slowed to about 60 and droped the clutch in 5th to get it to run (it wouldnt crank over)...
on the way home (10 miles), every time id try to go a littler faster it would stutter so id let up and it would run...it died for good aout 5 mins later..got it back to my house and went through everything....it had power to the fuel pump, it had spark, the igniton module was good, the vats was still good, i mean i went through all the basic crap
all my "gassing" caused the tps to burn out and the O2 to not funcion properly (i got the code on the freeway) and the fuel pump was working triple time so it burned itself out..
the driver rear injector was fried so it burnt up the computer...i didnt know this so i put a computer in it and it ran for about 7 mins, after digging for another week or so i replaced the inject that was bad.. And because of the past month i kept goin a little farther to make sure there wasnt anything eles..and i found that the solenoid int he air pump was bad, also causing the ecm to fry...
thats why i took the smog **** off lol

check the injectors....they should show 14-16ohms and there should be 11 volts or so goin to the injectors

check the air pump solenid....the ohms should be IIRC 5 or 6?

HTH,
Rob

 

I was on my way into this post to update you guys and then I saw f-crazy's post. Thx man. I narrowed it down to the injectors not firing. I'm getting no juice at the injector itself, or the ECM. The wires from the ECM that fire the injectors aren't putting out any juice at all. The ECM has power, and I keep getting a constand code 12 ( which IIRC means that everything is operational) so I'm now lost. Help!

 

The ECM grounds the injectors to fire them. One of the two wires on each injector has 12 volts run to it. The other wire (of the two) goes to the ECM which gets grounded to fire the injector.

So, key on (not cranking) one of the two injectors wires on each injector must have 12 volts (battery voltage). As there are two injector fuses make sure that all 8 injectors have power.

RBob.

 

Netither of the two wires has power and the ECM is grounded to the back of the head like it's supposed to be.

 

Well, now you know why they aren't firing, no power. The pink w/blk stripe wires to the injectors should have the +12 volts. They come from fuses INJ1 & INJ2 (in fuse block under dash on the left). The fuses get power from the ignition switch. If you don't have power there then check for a fuse on the pass fender under the hood and the fusable links off the starter.

RBob.

 

Actually, both wires should have 12 volts on them. If your fuses are good and your wiring is all hooked up properly then take a look at the dist. If the ECM doesn't see the reference pulses from the dist it will not turn on the injectors.

 

Well I got it running. I checked the fuseblock and bot inj 1 and inj 2 had 12 volts. I ran a 12v. wire to the lt. blue and lt. green wires on the ECM harness that are supposed to control the injectors and it fired up. Now I need to find the reason they don't have any power to them. What exactly should I be looking for on the distributor?

 

no problem glad i could help.....
have the control module tested..i beleive that when the rotor turns under the cap that w/e position its in it tells the injectors to fire.

the module is under the distributor cap and its the black thing with 2 connections in it...2 screws hold it on..

 

What do you guys think the chances are that I have the cam timing off by a tooth or two? Would the car behave like this if that is the case? Thx.

 

its possible, but it would still rev..

it doesnt rev AT ALL? like with the blades fully open...

ok ii want u to try something for me....when u have it idleing let it idle for about 5 mins then touch the ECM, it should be cool to the touch...if its really warm then theres probly an issue with the ecm

when i had my problems the ecm was hot..touching it longer then a few seconds was painfull...

it still sounds like your tps...or did u check that off?

 

TPS checks out. .55v at idle, and 1.4 or something like that at WOT.

I haven't been able to get it started lately so I can't check the ECM out. Thx though.

Any other ideas? I just need to get it started so I can diagnose it. It's alot harder to diagnose if it won't run at all.

 

Turn on ignition, but don't start the engine.

With a scanner: plug in the scanner and read the TPS voltage. It should be 0.54Volts +/- 0.075Volts


If out of spec, loosen the two screws holding the TPS to the throttle body, and slightly rotate the TPS up or down, reading the voltage until it comes into specification. Tighten screws. Using the throttle lever, rotate the throttle to WOT (wide open throttle). The TPS voltage should be over 4.0 volts. Close the throttle again, and then slowly open it to WOT, observing the voltage reading. It should increase progressively and in a linear fashion. If it sticks or jumps or falls off at all while doing this check, that could mean a bad TPS switch and could be a cause of stumbling and driveability problems.

After setting the correct voltage, turn off ignition switch. Remove jumpers/scanner and reconnect the TPS connector as required.


your idle vots are good but u should get 4.0 at wot

 

There is a blue 2 wire connector at the rear of the distributor that looks identical to a blue 2 wire connector that I believe plugs in to the IAT sensor at the bottom of the plenum. If you get them mixed up your car will not run. Maybe a wild guess but worth checking.

 

Are you referring to the MAT sensor? I will check that out. Thanx.