This is somewhat of a duplicate post. I've greatly enhanced my detail and changed the thread title to be more accurate.
Here’s what’s happening:
I performed a PI intake swap with non-PI heads on my 98 Mustang GT with 58,000 miles. There is a faded sticker in the front of the engine bay that indicates a Ford dealer has modified something previously. The original intake was badly cracked at the tstat housing and there was coolant everywhere.
Since the swap, the car runs great when cold. It screams! 10-15 minutes after I start it up the idle will drop 300-400 rpms (from 1000). Once warm, it’s like a carbed car with the choke shut. Backfires under throttle, won’t rev smoothly, sounds like its loading up, etc. This happens whether it sitting idling or being driven. There is no CEL (check engine light) ever. It starts right up when cold, and is very difficult (sometimes impossible) to start when warm / hot.
I’ve replaced the ECT and the front O2 sensors already with no change.
All sensors are hooked up and all vacuum lines are visually solid and not cracked.
Because it’s a 98 I did not have to remove the water pump because the nipple on the back matches the 2001 return line I installed. I did not disconnect the fuel rails during the swap, but I did replace the injector o-rings. The pintle caps looked good with no cracked injectors. I used OEM PI intake gaskets and gray permatexed the two coolant passages to avoid leaking. In fact I used all Ford parts ( Tstat gasket, return line, o-rings). I torqued everything to Haynes specs. I did not remove or replace the spark plugs which I wanted to do after the swap was complete and correct. I try not to introduce too many events when doing something significant like this. Needless to say, there was substantial coolant in the plug holes after removal of the original intake which I wet-vacuumed out and then dried with a rag. There was probably slight moisture still present but if that’s the problem, why would it run perfectly when cold? Anyway, I vacuumed all debris while the intake was off. It has a 192 degree thermostat. I noticed a previous repair to the DPFE… seems a hose was replaced with a fuel/emissions hose of a possibly slightly larger inner diameter and the plastic hose barb on the DPFE had been glued or epoxied back together. I also noticed rusty brown emissions from the pipes after start up. There is no white smoke and otherwise the exhaust is normal. I plan on power flushing the system once everything is running well (one event at a time!).
Please… all suggestions and questions are welcome!
Dave
Here’s what’s happening:
I performed a PI intake swap with non-PI heads on my 98 Mustang GT with 58,000 miles. There is a faded sticker in the front of the engine bay that indicates a Ford dealer has modified something previously. The original intake was badly cracked at the tstat housing and there was coolant everywhere.
Since the swap, the car runs great when cold. It screams! 10-15 minutes after I start it up the idle will drop 300-400 rpms (from 1000). Once warm, it’s like a carbed car with the choke shut. Backfires under throttle, won’t rev smoothly, sounds like its loading up, etc. This happens whether it sitting idling or being driven. There is no CEL (check engine light) ever. It starts right up when cold, and is very difficult (sometimes impossible) to start when warm / hot.
I’ve replaced the ECT and the front O2 sensors already with no change.
All sensors are hooked up and all vacuum lines are visually solid and not cracked.
Because it’s a 98 I did not have to remove the water pump because the nipple on the back matches the 2001 return line I installed. I did not disconnect the fuel rails during the swap, but I did replace the injector o-rings. The pintle caps looked good with no cracked injectors. I used OEM PI intake gaskets and gray permatexed the two coolant passages to avoid leaking. In fact I used all Ford parts ( Tstat gasket, return line, o-rings). I torqued everything to Haynes specs. I did not remove or replace the spark plugs which I wanted to do after the swap was complete and correct. I try not to introduce too many events when doing something significant like this. Needless to say, there was substantial coolant in the plug holes after removal of the original intake which I wet-vacuumed out and then dried with a rag. There was probably slight moisture still present but if that’s the problem, why would it run perfectly when cold? Anyway, I vacuumed all debris while the intake was off. It has a 192 degree thermostat. I noticed a previous repair to the DPFE… seems a hose was replaced with a fuel/emissions hose of a possibly slightly larger inner diameter and the plastic hose barb on the DPFE had been glued or epoxied back together. I also noticed rusty brown emissions from the pipes after start up. There is no white smoke and otherwise the exhaust is normal. I plan on power flushing the system once everything is running well (one event at a time!).
Please… all suggestions and questions are welcome!
Dave
