Topic: Time to build it! Got a few questions

[bigal389]

That's good info to have! I may try the egr delete. I'm also working on getting the throttle body bored to match the spacer that I got from Chardrc.
Al

[chardrc]

I would definitely get the manifold bored to match the larger tb especially since you will have the manifold off the jeep anyways so you can make sure no chips get into the engine.

[bigal389]

Just finished gasket matching the intake and exhaust manifold and believe it or not the head had already been done. I got the intake bored to match the spacer also. While I was at it I tapered the sharp edges toward the runners on the intake. The engine had a couple thousand miles on since it was rebuilt but since  the head was already ported I'm unsure what else was done. The guy I bought it from had paperwork with the mileage shows the engine was bored, rebuilt and a performance cam was installed but that's really all it says. I plan on degrading the cam to try to figure out what it is.
Al

[bigal389]

That should have been degreeing the cam.
Al

[bigal389]

I haven't had a chance to work on the engine any this week, I have been working a lot this week with the cold. Lots of power outages and when your a power lineman that comes first. I did find that both the manifold air temp. And the manifold coolant sensor are both bad. The coolant sensor has a broken wire at the sensor itself and the air sensor was completely non functional. The problem is I can't find replacements any where. Does anyone have any suggestions for a replacement or an upgrade for these sensors.
Thanks, Al

[sharpxmen]

i have no idea what works on the TBI, likely that the IAT is the same as the newer models and possibly so is the coolant sensor but you'll have to doublecheck that to make sure.

[bigal389]

I picked both sensors today for a 98 4.0, the only ones that I could find. From what I've read when the sensors are warm they should read 1k ohms for both the air and coolant temp sensors on the tbi. I have not found the specs for the mpi sensors but after heating the mpi air sensor with a hair dryer it reads 1.2k so I should be able to wire a 200 ohm resistor in line to bring it within spec. Heating the coolant sensor in water to 200* it read .950k ohms so it should work, I don't think 50 ohms will be enough to make a real difference. Correct me if I'm wrong here but I believe this should work. 
Al

[sharpxmen]

i wouldn't add the 200 ohm resistor for 2 reasons: 1. i think the thermistor values were unchanged since forever on those, 2. adding 200ohm in series to 1.2kohm would result in 1.4kohm, in parallel would be a little under 200 ohm. Thing is that with thermistors you can't correct the curve since they are not linear so even if you make it a value identical to the specs at a certain temp they would be out of spec at a diffenrent value (and possibly by a lot and make it worse).

just run them like they are and see how it goes, you'll be able to tell shortly after warmup by the way it runs.

[dwtaylorpdx]

Thermistors also wont read correctly on a standard Ohm meter. I used to work at a place where we tuned thermistors by trimming the resistor media with a laser. The ohm meter was a very special voltage modulated signal and was a 4 probe unit that could cancel out the lead resistance and contact resistance to the part. If you run power through a thermistor very long it changes value, not always predictably.. If you use a normal digital VM you need to take short measurements several seconds apart and dont keep contact longer than it takes the meter to get a immediate reading.

Dave

[bigal389]

Oh ok. I'll just give it a try with just the sensor then. I will post more info when I get farther along.
Thanks, Al

[chardrc]

Here are the TBI coolant and air temperature sensor curves from the FSM.



Oreilly had the coolant temperature sensor in stock at the store 2 years ago.

coolant sensor (used by ECU)
MaterPro Part # 2-9384
Murray Part # 36400
BWD Part # WT5011

These only cross reference to Renix fuel injected engines (AMC 2.5l with TBI or 4.0l with Renix MPFI (pre 91). Could just be a different thread to go into the manifold rather than the thermostat housing but I don't know for sure.

Coolant temp sensor for the gauge is BWD Part # WT412 and is the same for all jeeps with the 2.5l before 97


I couldn't find the air temperature sensor on the Oreilly or auto-zone website. The jeep part number is "3300 2382"....

[dwtaylorpdx]

Has anybody tried going to a aftermarket GM/TBI controller rather than wrastle the Jeep version?

Youd think something would be out there for the iron duke that would run a jeep.

[chardrc]

Has anybody tried going to a aftermarket GM/TBI controller rather than wrastle the Jeep version?

Youd think something would be out there for the iron duke that would run a jeep.

Not that I have heard of. Would be interesting since the TB components are so similar. would have to do some work on the distributor as the GM TBI systems use a Cam sensor which the TBI 2.5l jeep engine does not. But between gm parts and the mpfi 2.5l distributor (which has a cam sensor) someone could figure something out.

[sharpxmen]

i can't see why you'd spend the time on a TBI migration/swap that is not plug and play and not go with an MPFI to be honest. I can't think of any benefits to make you stay with TBI.

[dwtaylorpdx]

Well,, I was just thinking keep it near to the same as possible so the smag nazis around my home base couldn't tell.

Plus the TBI doesn't have the flywheel sensor as I recall? Doesnt it use the dual sensor distributor? Or is that he GM verson?