I recently had my engine rebuilt (professionally), and have about 500 miles on the rebuild. I haven't abused it at all, keeping out of boost, and i haven't gone passed 3k rpm. Now, my question is about the cold start. Is is normal for it to have a hard time starting when cold? When i start my car in the morning or when its been sitting for about 4-8hrs, it really struggles to start. takes a few seconds, and it slowly climbs the rpms, and i have to hit the gas or it dies. Anyone had a similar problem from the fresh rebuild? OH ya, its a full rebuild so all new seals and gaskets, and with a small street port.

 

anyone?

 

Did anyone reset the timing when the engine was reinstalled?

New apex seals? Did your housings have any flaking by the edges? Tried a compression check on the cold engine?

 

i have all new seals. all oem, its a full rebuild. the irons were lapped, the housings are in spec, i replaced one of the housings with when i had it rebuilt because it had a gash on it when the apex seal blew. i checked the timing, and its good. although i had not check the compression with a cold engine yet..... i figured that the compression won't be up there since its still fresh. only 400 miles now on the rebuilt engine.

 

Seals conform to the surfaces and seal like 99% within the first 20mins of running. You should have good compression. If you don't then something is wrong and you need to open the engine up and check the seals for free movement and recheck the tolerances.

Besides that I'd look hard at the injectors. A leaky injector will make cold starts hard. So will low fuel pressure. The FSM or Haynes manual outlines how to do a pressure check....

 

BAC removed? BAC helps cold starts (more air)

water temperature sensor on the back of the water pump housing could be bad (determines cold start fuel)

timing could be off

 

i'll have to check the injectors, but i'm pretty sure they are not leaking. I mite just take them down to rc engineering to have them cleaned and tested. I know my fuel pressure is good, I just did a rewire for the pump, and my fuel gauge shows it had 38-40 psi. I have the bac valve still, but not sure if its 100% working.

 

easiest way to test injectors is to use your fuel pump to spray them into an empty milk jug, watch the spray pattern for an even cone shape, and time how long each injector takes to fill the jug.

Test BAC first and the TPS and thermowax on the TB. Removing injectors sucks.

 

ya i know, i replaced my primary about 6 months ago, and my secondary like 1 month ago... so thats why i'm really douting that its my injectors. Tps is good, i already checked it with a tester. i think my bac mite be stuck..... how do you fix that???

 

You can take it off and clean it with brake parts cleaner/carb cleaner or any other similar solvent. You can usually test if it's working just by unplugging it when the cars running and seeing if anything happens.

 

When i unplug the bac the engine dies..... does that mean its kinda working?

 

Cold starts can be troblesome if the water thermo sensor isn't being seen by the ECU. If the circuit is open the ECU defaults to 176* and not enough fuel will be delivered during Start. And after the thing does start and the afm is being used, the engine will still be sluggish til the engine gets hot. After that whether or not the water thermo sensor is connected matters not as long as the engine is running.

IF you remove the BAC plug and the car dies, then it was working. If you unplugged the BAC with a fully warmed up engine and the engine died, then the BAC was working but take note that the idle speed has not been set right, because even with the BAC disconnected on a fully warm car, it should still idle if no loads are on the engine. Then again, this is a recent rebuild so that might account for it dieing.

Ah, pardon me, Argh already mentioned the water thermo sensor above in post #6.

IF it's a series four car, check the voltage on pin 2I with a fully hot engine. Should read a half volt give or take a small amount. LIke 0.4 to 0.5vdc.