So, My check engine light has been on for a while (due to a deleted egr) but i figured i'd run by autozone to get an update or see if i have any extras...glad i did...

P0125 Insufficient Coolant Temperature to enter Closed Loop.
P0401 Insufficient EGR Flow.
P1400 Differential Pressure Feedback Electronic Sensor circuit Low Voltage.
P1405 Differential Pressure Feedback Electronic Sensor circuit Upstream Hose.
P1409 EGR Vacuum Regulator circuit malfunction.


I can see where the last 4 could be due to the egr removal. The first one is what's throwing me off...It's a 98 car with a 99 engine. currently the coolant sensors are both connected to the 99 intake using a t-fitting, and that may be the issue although it has been like that for 2 years.

My engine swap has been delayed a few weeks, and I dont want this thing blowing up on me or Tara in the meantime.

Thanks!

 

do you run a differnt thermostat ?
Maybe your thermostat got stuck open ?

 

it has the stock thermostat in it. and it's still good (i had it off on saturday to replace the o-ring).

 

If it is a stock thermostat you may try checking the ECT sender,does the fan stay on continuously.

 

well, basically, it should run fine if you dont rag on it......... the ECU just isnt going into closed loop operation........ so your not getting optimal performance at WOT....... most likely it is running too cool, but i would like to say it isn't because of the 4.6's tendency to run hot......


you said you had the intake T'd somehow............... are you bypassing the coolant sensors?

 

after reading your post again and letting it sink in, i would say definatly take a look at the connections to the coolant sensors.
how are they wired? i'm guessing you still have the old ECU and you just ran one sensor and wired both lines to it?

 

NPI intakes have 2 holes for sensors, the PI's only have 1. I used a nipple and brass T-fitting so both sensors could in effect go into the 1 hole. the problem is now they are suspended horizontally about 2" above the intake (where the "T" outputs), and coolant doesnt flow up there very well. IT hasnt really been a problem for 2 years, but i developed a leak at the t-stat housing-to-intake area, so this weekend I replaced the o-ring and added some RTV. I think this may have remedied it, as the car seems to run much better.

None of this will be an issue in 2-3 weeks, as the new motor should be going in

I just didnt want to tear up a good PI motor.

 

yeah, i knew the PI only had 1 sensor........ thats most likely the problem........

i would think you could just splice into the one coolant sensor and run the two in a series........ then you would only have one sensor, but two readings...... but what you did sounds like it works ok.......... i have also heard you can put the sensor in a port on the side of the block and it just screws right in with no problems...

anyway, yeah, with the new motor and ECU this wont be a problem anyhoo.........

PS. stick with the 98's fuel system, as i'm sure you know already !

 

When i first put the 99 motor in (at Need-4-Speed), we tied the 2 lines together, but the ECU wouldnt recognize either of them. With the new motor I also have an updated pi intake with aluminum crossover. I've already tapped it for the second sensor (see my other post about the powdercoating).

I would just go ahead and move the sensor to the plug on the side of the block, but it's hard to get to it on the ground, and my project vette jumped time and it's annoying to push that thing on and off the lift.

I will be using the fuel system and ecu from the 98, along with the coil packs. this will be the third motor in the car, and the 2nd PI , so I'm pretty familiar with the process.

Once the new engine is in, I'm taking the car for an SCT dyno-tune to turn of the EGR, so that should take care of the rest of the codes im getting.