Car: 1988 vert s4 t2 motor... after the swap the car ran not good but ran, i replaced the exhaust manifold, lower intake manifold, radiator , removed emissions and replaced the wiring harness and now.
Symptom: Car starts then dies, if the gas pedal is pressed it will run very rough and then die once off the gas.

I am almost sure this is a fuel problem, i think it is running lean when i spray starter fluid into a vacuum line the engine runs rough and jumps to about 2500 rpm. I think there is a huge vacuum leak the only way it could get enoguh air to raise that high i have plugged every line that not being used. Has anyone had a similar problem, ive searched and havnt found much. im running out of ideas
I have checked fuel pressure it is 40psi and drops to 35psi when the motor is running i have check volume output from the fuel pump and it is low but fine. Does anyone know what the vacuum should be on the motor. it only pulls like 11in i think. I have also checked the throttle plates and they seem to be closed completely. any help would be great guys thanks.

 

If you have a large vacuum leak the car will not idle. I've had success using carb cleaner to find the source of vacuum leaks. On my rebuild, vacuum at idle was approx 16in

 

the long bolt on the intake upper intake manifold is missing. I torqued all the bolts to spec and am going to replace the long bolt tomorrow in hopes that that is the cause of the vacuum leak. i adjusted the lean rich screw by the map sensor all the way to rich and The car runs for about 20-30 seconds now and then dies. I believe this is the 20-30 seconds is the period that the ecu is running off of its start map. then it switches off and the car dies. it is an instant death fuel pressure doesnt drop engine just dies. I watched the vacuum gauge it stays around 10in with little/ none flucuations. If the engine is suppose to be around 16in this would indicate a big vacuum leak. i also ran the codes which indicated a problem with the water thermo sensor. says it runs 80c as default

 

where is it coming from??? check the egr for corroded vacuum hoses?? it also can be that its plugged...just for reference....

 

i would belive its a huge vaccume leak aswell. i had a huge leak for a month till i found the BACV tube was unhooked

 

well i unplugged the water thermo and sure enough now it will idle a little high a little rough but hey it doesnt die after 30 seconds. the vacuum is still around 10- 11 in steady, im still thinking there is a vacuum leak im going to remove the turbo intake because when i spray carb cleaner by this area the idle changes pitch and raises slightly.

 

i removed the egr and egr solenoid. i do believe there is a leak the size i dont know. If 16in of vacuum at idle is the norm im def low. all vacuum lines have been plugged except the ones in use and those are new lines. ill be pissed at autozone if they have a hole. only vac lines are the fpr straight from lower intake. oil injector air bleed, oil injectors, doulbe throttle(which is soon to go), and thermo whatever on the throttle. the pcv has been blocked except one house to prevent pressurization. anyone know if that line going to the carcoal canister is from the pcv? i have blocked it off at the block. it is on the drivers side by the oil filter fairy large sized. or is this a vacuum?? doesnt look like one but how does this evap cansiter purge. the setup is very odd to me.

 

dies after 30 seconds? is it like clock work? .... cold start switching over. warm start switching over.
um...
hmm
arnt there things in the throtle body that keep open durring cold start or warm start that closes after the ecu gets out of those modes? vice versa?

just a thought.

 

yea thats what im thinking but ive cured that from taking off the connector to the water thermo sensor. so probably the 30 seconds then dies issue was the first 30 seconds was a start up map then it switched to using the sensors and the thermo switch was reading wrong so it just killed the engine. either flooded or leaned i have no idea.

 

The START MAP ends when the rpms get over 500 rpm.

Then the airflow meter takes over. Got the afm plug on good?

 

the airflow meter is good from what i see i dont have a scope or anything so i can really get a good check. The engine is running now pulling about 12in of vacuum and when i spray carb cleaner by the secondary injectors the car idles smoother. I believe the sub zero assist has a vacuum hole that was never blocked. Does anyone know of a good way to block off this hole? silicon? im afraid of the silicon being sucked into the engine

 

So another weekend and not much progress maybe next time... seems like you fix one problem just to get another. I was wondering why the vacuum levels are so low still. Maybe where im pulling vacuum from is bad(the top port behing the throttle on the side of the intake further away from the firewall). next time ill try a t off of the map sensor port. Put i fixed ever vacuum leak and double checked the others only pulling 12in of vacuum, thought maybe the cat was clogged hard to think with a new 3in high flow cat. replaced the cat with the straight through test pipe and no difference still 12 in of vacuum. When the car hits about 2000 rpm theres a vibration throughtout the car and doesnt really go away. Next weekend i go out theres im going to check compression which ive been trying to avoid. But does anyone have any other ideas about the low vacuum and hesitation. When searching i found something about the tps i adjusted that but ill have to check it for dead spots.. Thanks guys