My last resort with this TPI.........

I've checked every wiring and its ok, Found out AIC was no working. Replaced it and adjusted and it ran fine until it was suppose to go into close loop, then it rattles and just dies. I cant seem to find the problem. Could it be the O2 sensor? Im gonna use a Snap On Scan Tool, but i cant get ahold of one till next week. If anyone has had this problem or any info please let me know. thanx

I'm sure you've already checked the fuel pressure in the rails.

Fuel pressure is at a steady 48 psi at idle and WOT and its got 5 gallons of it in the tank.

TTT:(

If it was the o2 sensors it would be running rough all the time (pretty sure of that). Possibly a vacuum leak somewhere or something?

I guess i can hook up a vacuum gauge and read it out. How much vacuum(PSI) should there be for idle?

Originally posted by jd13
If it was the o2 sensors it would be running rough all the time (pretty sure of that). Possibly a vacuum leak somewhere or something?

the computer doesnt read the o2 sensor until its in closed loop(warm)

Originally posted by BlowBye
I guess i can hook up a vacuum gauge and read it out. How much vacuum(PSI) should there be for idle?

I WANT to say 15PSI, but that might be inaccurate. Main thing you want to see is that the vacuum remains constant while this is happening. If not, then you have a problem for sure.

Originally posted by gun4hire
I WANT to say 15PSI, but that might be inaccurate.

:rolleyes: Time for a lesson. :rolleyes:

Vacuum is not measured in PSI.

Vaccum refers to any pressure that is lower than the earth's atmospheric pressure at any given altitude, and it is measured in relation to atmospheric pressure. The term used to measure vacuum is inches of mercury (in. Hg)

Vacuum is suction like the business end of a vacuum cleaner and is measured like 15 in/Hg.

PSI (pounds per square inch) relates to Pressure, such as the air you put in your tires.

So, gun4hire was partically correct. 15-22 in. Hg is normal vacuum readings for a healthy engine.

Your right dude, i meant in negative readings as in vacuum and was thinking psi. I have this vacuum gauge and it reads between 300mmHg to 400mmHG(On the gauge at 400mmGH it says "Late on Timing") The needle Fluxiates to 300mmGH - 400mmGH. Could this indicate a vacuum leak?

Possibly the wrong cam selection? or a worn out cam?

If vacuum is not somewhat steady, you've either got a huge cam (off-road) or wear problems. The last time I checked my '87 305 TPI, it was slightly fluxuating from 14-16 in. Hg. Not sure if it was the guage's fault (New Mac Tools guage) or if it was receiving vibrations from the engine causing the needle to vibrate. But my IROC has well over 156,000 miles on the original engine... so I could possibly have some cam wear. Runs fine though as you can tell from sig.

What would make you think its the cam? Im curious. I hate to think the cam went since its about 1k miles old and from Accel and broken in properly:(

Lobe seperation is a very crutial element of TPI engines. I am thinking it must be .114 degrees. But I am not positive on this figure. When fuel injected engines have different lobe seperation cams installed in them, it causes vacuum loss or gain. Fuel injected relys greatly on vacuum, especially Speed Density ('90+ SD) systems. Its not a fact that the new cam is wore out already, but you possibly could have been sent the wrong cam completly or you was misslead when ordering it.

I know you've heard these old carburated cars with a "loopy" idle where it seems like the engine is only hitting a lick or two every now and again. This is due to an oversized cam which is great for upper RPM's. Unless you did extensive tweaking to your PROM, one of these cams will only cause you problems.

Well i had this cam for about 1k miles. Its def. the right cam, i never had problems with it before. This problem that im having now all started when my ring and pinion locked up while going about 40mph and tore off the yoke and broke one crossmember bolt. :(

How did you guys get started with the cam? The cam works all the time, not just in closed loop.;) Give some more info on the car.

Id just like to let you guys know that the problem was repaird. I was thinking it could be the 02 sensor, but not as bad as a faulty 02 sensor should happen. Anyway i went through and ordered a ZR1 3 wire 02 sensor, spliced up a couple of wires and problem went away. At idle it at RICH,but after 2 min. I can see the pointer on the Air/fuel gauge move at a time towards lean,but idle is still fine...