Major idle issue...AARRRGGGHHH!!!

[TheNoachSHO]

Ok i'm playing with my 88 that has the 93 motor conversion. When the motor came out of my 93 it ran PERFECT. Now that it's in my 88 I can't get it to idle.

I've ran the codes. nothing comes up.

So far i've tried changing the following.

TPS
Mass-Air
IAC
Coil Packs
Ignition Modules.

It's only when it idles it goes high the comes down and wants to stall. Normally I would say TPS. I'm starting to wonder if it's the Crank position sensor.

Any thoughts? Other options?

 

[JamesBaumann]

Perhaps it could be a vacuum leak. That will cause an erratic ilde.

 

[TheNoachSHO]

I've thought of that but I don't hear anything. And it will idle completely smooth for a shirt time then start crapping out. I'm strating to believe it's a fuel system problem.

The kid that did the conversion hard wiried the fuel pump to be on at all times. I originally didn't think it would cause anything but maybe it is. I have a spare fuel rail/injectors i'm going to try next.

Any other ideas.

 

[wyominghotwheel]

i would have to say it's either an iac issue or a vacuum leak.............what is your tps set to? should be at .96 with a volt meter. What happens if you unplug your iac? The car should try to die, let us know what happens. Have you worked on getting the idle set? Try backing off the adjustment screw, then take it back in till it barely touches the throttle lever, with that done, check your tps volts again...keep trying that until the idle becomes smooth........if it still does it, go buy a can of starting fluid and start spraying little short bursts around the intake and vacuum lines, if the idle takes off, like vroooom, then that will show where the leak would be.........hotwheels

 

[351wcoupe]

The thing that would scare ME about it is that wiring. Is it an 8plug head? Mass-air? DIS? This guy wired all of that but couldn't wire the fuel pump circuit correctly??

 

[TheNoachSHO]

wyominghotwheel : I have the 93 motor in my 88. TPS voltage should be between 4 and 6 volts. It's at just over 5 so that's ok. No vacuum leaks.

351 : Yes it's an 8 plug head with DIS. I've gone over the wiring with a fine tooth comb. Plus the computer dosent register anything abnormal. The fuel pump thing did confuse me. He asked me about it and I suggested about wiring it that way. I've had cars do this so I fiugred it shouldent do too much damage.

I think I have it figured out though. After getting really bad gas milage i'm trying the FPR. I took the old one off and I got a little taste of fuel sucking on it. I'm replacing this and cleaing the injectors. Hope it works. Will let you all know.

 

[JamesBaumann]

TPS voltage should be between 4 and 6 volts. It's at just over 5 so that's ok. No vacuum leaks.

Your TPS votlage is a little over 5 volts? I'm assuming/hoping that you mean at WOT (wide open throttle). That has nothing to do with your idle problem though. Turn the key to the on position, hook the voltmeter up to the TPS (green wire) and it should be somewhere around 1 volt, maybe a little less. I have mine set at .98.

I think that the voltmeter should read somewhere around 5 volts at WOT, but that shouldn't have anything to do with your idle issues I don't think.

 

[TheNoachSHO]

James : .98 is what you want for the older non-dual plug motor. Here is my reference for my TPS info.

http://www1.autozone.com/servlet/Ui..._us/0900823d/80/19/4c/40/0900823d80194c40.jsp

 

[Stinger]

approx 1.0v is what your TPS voltage should be no matter what car or engine it is...it's ~5v at wide open throttle.

 

[JamesBaumann]

NoachSHO:

Just take Stingers and mine advice and set your TPS to around 1 volt when the throttle is closed. If that doesn't fix the idle problem, then you were right and we were wrong.

But I think it's worth a shot. Just try it and see how it goes.

 

[TheNoachSHO]

It's a fixed unit and, non adjustable unlike older motors. I tested both TPS units I have with the same results.

I'm waiting on my plenum gasket to come in to bolt her back together then I will know where my next step is if this dosent fix it.

 

[Stinger]

I will not believe anyone that says the stock TPS reads anywhere over 1.5 volts at idle...that's not how they work.

They are a simple potentiometer (variable voltage) and simply increase the voltage reading the farther the throttle blade is turned open. The range of the pot. is 0-5v...

The only way it can read 5v at idle is if you are reading the 5v reference wire and not the signal wire...or it's wired backwards.

 

[TheNoachSHO]

Stinger: Not to contradict you and please understand that I do respect you but are you saying the website I linked is incorrect? I followed their diagnosis procedures that's how I came up with the estimate I did.

 

[JamesBaumann]

Which colour wire is your voltmeter hooked up to when you are testing the TPS voltage? I believe that one of them doesn't ever change voltage, and the GREEN wire, is the variable voltage wire. When you say your voltmeter is reading a little over 5 volts at idle, which wire is the terminal connected to?

 

[Stinger]

Wire colors vary from year to year...odds are you are on the 5v reference wire as I noted above...simply try the other wires and you will find one is a ground, one is 5v all the time, and the other is variable 1-5v...

 

[TheNoachSHO]

Well in any case I figured out the problem. I feel at this time I should just take my head and shove it up my A**.

After putting the intake back together it still idled like crap. Then I tought I heard a faint sound of a vacuum leak.

Sure enough found it fixed it and now I have a 88 vert with a 93 motor. Runs great and couldent be happier. (until I get the v-8 in my other one.)

 

[JamesBaumann]

Good to know you figured stuff out. Usually it is simple stuff like that.