Hello all,
I am a new member and this is my first thread so, I will give it my best. I had a '90 firebird TPI that I recently had to junk due to an accident, before discarding it I pulled the engine and harness among other things. I decided to rebuild the engine and install it into my '86 MC. Now I know this is not an MC site but I am not allowed on the MCSS site being that it is not an SS vehicle. Also, it seems like many of you know what you are talking about on here so I figured I would give it a shot. So here it goes, I have a '90 roller 305 block with a TPI MAF set up and computer. I used the Painless harness with an '86 camaro MAF computer and bought the '86 TPS sensor, IAC, a used MAF that was in a working vehicle, (I witnessed the car on), knock sensor and put in the EGR with the heat sensor. The car would start, rev to 3000 rpm and shut down immediately, the computer seems to have a desired RPM of 3000 RPM for some reason, the TPS, IAC, O2 sensor and knock sensor seem to be fine according to the reading my buddy took using his computer and I cannot find any vacuum leaks. The fuel pump is a new MSD pump and I have 46 lbs of fuel. She will stay on if I feather the pedal but die as soon as I let off.
Would any of you have any suggestions? it would be greatly appreciated, I have been struggling with this for 2 months now. Thank you much.

Elco86
RIP '90 Firebird (MacPherson strut, TPI, 305)-Beautiful vehicle.
86 MC LS - Very slow, would the 'Bird live on in her shell?

 

sounds like a vacuum leak. check all your vacuum hoses to see none are disconnected or cracked and leaking. also could be an Idle air control valve, the only way to check that is to remove it and turn the car on and see if the pintle moves. sometimes its stuck, and sometimes its just broken and you have to replace it.

 

I have done that check on the vacuum hoses but, i will do it again. As for the IAC, i will make sure it does work, I know i can push it in and pull it out by hand so it should work, but, i will check that also. Thanks for the suggestions.

 

I have the exact same problem I find my self constantly adjusting my tps(new) just trying to make it idol and when I feather the throttle at all it the engine shoots to 3000 rpm sputters and then dies.

 

Zealand, did you happen to do anything to the car prior to the TPS sensor? I could not get the correct TPS sensor to the car but, a friend of mine had one that he used for about 30 minutes and let me have it. Maybe that is the majority of the problems.

 

lol I only swapped my stock carbed 305 to a 350 tpi (that I built my self). to me it seems my IACV is opening when I feather the gas. same with you?

 

I am not sure, I have not been able to play with it in the past week, the weather out here is crappy and I pushed out of my garage after the engine was installed, the thing is too heavy to get back in on my own. When the weather clears I will give her another shot when the weather clears.

 

dude, if you want to swap a tpi, you gotta have an intank pump with return and vapor valves, i say you just get another trans am and swap into that. i think retrofitting would cost more than the sweet bird on fire

 

I have the vapro return line with the fuel return line and an external fuel pump connected. I just welded another 3/8 line to my tank sending unit so that I can have all three lines. The fuel pressure is good at 46 psi with the return and all connected. All that should be good on my setup.

 

IS THE TPS ADJUSTABLE IF SO IS IT SET AT .54 VOLTS, WHEN YOU PUT YOUR IACV IN WAS IT SET TO 1 3/4" FROM THE BASE OF THE THREADS TO THE PINTLE. DID YOU CHECK YOUR EGR DIAG TEMP SWITCH?

 

try setting the idle by grounding the diagnostic link's A and B terminal turn the key to on position(not start), wait thirty seconds then unplug the connector to the IACV. remove the ground on the AB terminal from the diagnostic link. unplug the Timing wire (tan) start the car, set the gear in drive with an assitant holding the brake, set the throttle body idle screw to 450rpm. then turn off the car after in park. plug the connector IACV back in, then restart the car-this time check the timing of engine 6* btdc while in park. turn car off reconnect the timing wire (tan) and turn the key to on not start, probe the top two wire of the tps connector, it should read between .45 volts to .65v-(mines at .555volts ) turn key off, then on, let fuel pump prime (to prevent dry start) and then start. it should be smoother. do you need vacuum diagrams? the external fuel pump is over kill

 

did you change to computer? did you chip it to a 350

 

TRANSAMDUDE, I set the TPS to .54 volts, and it is still there after rechecking it. As for the IACV, I did not know to set it about 1 3/4" from the base, I will do that on monday. As for the idle adjustment trick, I will try that when I can get a second person to hold the brake for me. Thank you much.

 

Zealand, did you have any luck with yours yet? I haven't been able to play with my setup yet. Hopefully later today after work. I will keep you all updated. And many thanks for the suggestions.

 

TRANSAMDUDE, I did the whole IACV test and after jumper pins A and B and putting the car in the on position the IACV was making a tic sound, almost like a bad analog watch. After disconnecting it, I still could not get the car to stay on but, I think I did notice some improvement as far as the idle not shooting up as high. When the battery is done charging I can try it again and see what happens. As far as the IACV, like I said, it sounded weird and when you say it has to be 1 and 3/4 inches from the base do you mean the bottom base of the threads or the top bas of the threads? I also checked for more vacuum leaks and I think my throttle body was a little loose. That is all I have found so far. I can give you more when I play with it again tomorrow. Thank you again for the suggestions.

 

NOT 1 3/4 - ITS 1 1/8 MY BAD.

 

Oh, ok. I pretty much took it out as far as I could without knocking it out of place and then put it back in place. When I get home today I will see how it works out. Maybe someone I can use to hold the brake for me will be around. Thank you again.

 

I have a 350 program.

 

I took a look at my vacume lines found one that was pretty bad so i replaced it then i timed my engine. now it is running much better but i still have a jump in rpms with the most slight tutch of the throttle.

 

moving all of my suspention to the other car wouldnt be worth it plus i dont need an intake pump i modified my car to use the camaro's plastic intake.

 

there is a compiter?? haha jk yeah i have the 350 program.

 

Dude, that is awesome, congrats, I am jealous. Good luck with the rest of it. I guess I will go to checking all of my lines again and see what happens. Maybe I will have good news later today. If I can be of any assistance i wll surely give my best.

 

So I replaced a crappy looking vacuum line from the TB and kept the IACV unplugged and got her to idle for a while with little gas applied and the distrib plugged in, she also backfired lightly. I think if I up the idle and redo the timing I may be able to get her on long enough to tune. Thank you all for the info and advice, if you have more keep them coming, they are all appreciated.
Also, is the IACV suppose to sound like a ticking watch when the AB pins are jumped and the car is in the 'on' position?

 

I had this same problem with my TPI, the rev would rev up the engine, hold RPMs even with the throttle blades closed, and then let it drop back down. The issue was not TPS, or vacuum lines, but an intake runner. One of the intake runners were bent, causing the gaskets to blow out for a couple cylinders, making a major major vacuum leak. I would pull the TPI runners off, check the gaskets, then if they look fine, silicone the gaskets back on to make sure nothing is leaking

 

I had thought about doing just that. I guess if I cant make quick tuning of it because of the revving issue, I will do that next. Thanks.

 

Any luck yet Zealand? I have some idle but very rough and I have to hold the pedal a bit to keep her on.

 

I am waiting for better (cooler) weather. within the next week I will get my mid pipe welded back together. Wonder if that will help.

My car barely ran when I un-plugged the IACV

 

check your intake temp sensor. mine was shattered I am going to buy a new one tomorrow. and did you plug the vacuume port for cruse control?

 

My IAT is new, still in good shape last I saw, as for cruise I do not have cruise. Here is an important question tho. How important is the check valve off of the manifold to the FPR. I have my FPR connected directly to vacuum, does it need the check valve instead?

 

So, when you first turn these cars on, what is the RPM they jump to for initial flare up?

 

check you're runners when I tightened all the bolts a little more it completely got rid of the problem. hope it works for you too.

 

elco86, the fuel pressure regulator doesn't use a check valve, you have it right going straight to a vacuum source.
on cold startup mine will go up around 1000 or so and then drop to about 750 in a couple of seconds. im not sure about the MAF systems, but a guy at work who had one went a little higher and took a little longer to come down.

per your first post, sorry to hear about your fire bird.
also, just because you don't have a SS doesn't mean you wouldn't be welcomed over at MCSS.com
but there is more tech info here on thirdgen, especially for TPI.

 

Denn_shah: Thanks for the info, was actually thinking about that. I will definitely get on to MCSS.com also, good site for G-body tips I actually go on it alot just never signed up for it.

 

Zealand: Will do, congrats on your fix, enjoy. What did you torque them to if you dont mind me asking?

 

I retorqued the runners to stock spec and nothing, then added 1 extra lb of torque...nothing. how common is it to leak from the Throttle body. Zealand, you mentioned blocking the cruise, is there a port for cruise on the plenum I may be missing?

 

no port. there is a main vac port line that comes off the plenum far back passenger side. its right next to the fpr line. its routed to the cruise control and a few others acces.that line usually has a checkvalve on it. its always connected to a vacuum resivour. typically located in drivers bumper.

 

Really, I have my brake booster vacuum line connected to that directly, would you think that would be ok?