I wrote earlier about not getting my tpi to run. I did not mention that it was also backfiring. I finally got the timing right, and no more back firing. But, the car still will not run. If I work the throttle with my foot, while turning the engine over, it will start, race to a high rpm, and when removing my foot, and throttle closes to its present placement, the engine dies. If I continue to work the throttle, it will continue to run, but, constantly reving up high rpms, and dropping like a rock. Someone suggested a vacuum leak. I do not have the egr valve connected to the computer, but is on the intake manifold. I used the old caasket when installing it. Whats the possiblity this is allowing a vacuum leak, significant enough to make the engine act this way? Any other ideas. Everything else is just as it should be... thanks much - kby

 

Sounds like a big vacuum leak. Can someone else keep it running while you look for a leak? Can you turn the base idle speed screw far enough to keep it running?

 

Are you sure the runners are on the right side? It is possible to put them on the wrong side resulting in a huge vacuum leak. I found out the hard way myself.

 

Which ECM are you using to control the TPI setup? Just wondering as with the Chevy ECM, starting the engine with your foot on the throttle signals a flooded condition, and the ECM signals the injectors to go lean since you're in open loop with a cold engine. Has the TPI system ever run before, or is this the initial installation?
Vacuum leaks are quite prevalent during TPI overhauls and/or refits. The first place to look into is the throttle body itself which has a take off on the passenger side for supplying filtered area back to the passenger side valve cover as part of the PCV system.

Another area to check are the throttle body to plenum gasket and the gasket covering the upper access area on the throttle body itself. Either gasket can deteriorate and cause significant vacuum leaks.

The idle air solenoid on the passenger side of the throttle body actually controls the TPI idle once the engine is running. If it's gummed up, it won't work properly and the engine will sputter and die.

If the throttle body and its components are new, none of the above should be problems. except for an uncovered fitting sucking air.

As for the EGR valve, remove it and make sure that it isn't stuck open allowing exhaust gases to flow back into the engine during start up. If you're not going to use it, block it off with an EGR block-off plate and gasket.

If your TPI is a Mass Air Flow (MAF) system, disconnect the MAF to see if you can start the car. A bad MAF sensor or relay causes havoc with the idle, but the car should run w/o it in a limp mode.

Have you checked to see if you have any codes stacked up in the system? Just checking would go along way towards pointing us in the right direction to attack the problem.

Good luck and keep us posted.

 

OK, I was wrong. It does still back fire. I had it running, long enough and slow enough, to hear the popping through the manifold. I checked the timing by, removing the valve cover and the number one plug and the distributor cap and bumped the engine over until, the compressed air pushed my finger out of the hole, the rocker arms are both closed and the harmonic balancer is on zero, and the rotor is pointing to the number one plug. And it still back fires. The cam is 224//224 over 450 / 460. I am not using the egr valve in the computer system, however, it is still on the car. I put sealer under it, a rubber vacuum hose cup on the vacuum end and a bolt in where the sensor would go - I am assuming this would keep in from functioning at all. I could not find a plate to cover the hole in local auto parts stores and did not feel like making one for it. It is an MAT. The caskets are new... I did not think it was possible to put the runners on the wrong sides... I assumed they only went on one way. I could be wrong, certainly. I think the backfiring issue is the main problem at this time. Any ideas on why it would back fire with the timing as described above? The engine is a 350, and it ran fine until the swap. A four barrel is starting to sound real good. thanks in advance... kip

 

Have you checked your spark plug wires to make sure you didn't accidentally route them incorrectly? Also look to make sure you're not getting any arcing because of bad or worn wires-- I assume you're using the HEI distributor, so you have a lot more spark energy than you used to.

Good luck!

 

the runners will fit on either side, but if you put them on wrong it causes a huge vacuum leak. It will still run with a lot of throttle, but not well. I found out the hard way. Very similar symptoms.

 

tpi will backfire if not getting fuel

check filter
check fuel pressure

when timming did you unplug wire at distributor ( this must be done to set timming)

 

So, what happened?