The Renix throttle bodies have a strange and failure prone connector on the side where the MAP supply originates and then runs up to the MAP sensor located on the firewall. This hose/pipe assembly is no longer available for purchase.
The real kicker here is how critical this line is in supplying the correct vacuum signal to the MAP, the most relied upon sensor for the ECU to read regarding air/fuel ratio. Any cracks, melted spots, or loose rubber connectors can cause major starting and driveability issues.
There’s a simple fix though. All that’s required is a 1/8” NPT tap, a new throttle body gasket ( Napa FPG 60742 ), a vacuum fitting (Napa 05703-B102), two vacuum elbows (Napa CRB2670), and a length of new plastic piping (Napa CRB2672).
Remove the throttle body and take it to the workbench.
Using an oiled tap along with a driver, carefully thread the lower of the 2 holes of the throttle body where the old fitting was plugged in. Don’t go too deep. These are pipe threads.
Flush the hole with carb cleaner and inspect for any left over cuttings.
This is an excellent time to do a complete throttle body and IAC cleaning. See Tip 11.
Take the vacuum fitting (05703-B102 ) and apply a LITTLE bit of thread sealer on the threads only. I prefer Permatex #2 but almost anything is fine.
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Carefully screw the fitting in until snug.
Install one of the vacuum elbows on the MAP sensor so it points toward the throttle body, and the other vacuum elbow on your new throttle body fitting so it points up to the MAP sensor.
Cut a length of the new plastic tubing (approximately 13 inches) to fit between the vacuum elbows and install it making sure there is enough slack for some engine movement. Route it according to the photo. We don’t want any rubbing or chafing with engine movement. Not a bad idea to use some contact cement or Gasga-Cinch sparingly on the tubing to elbow connectors.
Revised 2-06-2016
What do you do with the top hole in the throttle body?
Nothing. It doesn’t go all the way through like the lower one does. Kind of a weird deal to hold the original vacuum tube in there.
Brilliant article, I recently purchased a rough running 90 XJ Wagoneer in the UK.
One of the issues was the missing fitting on the TB, I will be doing this upgrade.
Lots of good info on here, much appreciated that you are sharing.
Enjoy!!
Be sure to do Tips 1,3,4, and 5 first chance you get.
I used the factory rubber fittings and replaced it with 3/16 brake line. Would that allow too much air and throw off how sensor?
Not at all. You’re good to go.
Does the MAP sensor have to be connected to the lower hole in the throttle body? My MAP sensor is connected to a forward intake manifold vacuum fitting for some reason. Would the location of where mine is change the way things work?
Not an issue at all, Joe. As long as the hole in the throttle body where the hose originally connected is plugged.
I’ve done numerous ones that way.
Question on my 88 comanche I also have the two holes not being used by the throttle body and mine runs from the map to the forward intake manifold like Joe P mentioned and my two holes are plugged. My question is where does the tube now go that connects to the back of the valve cover? I have a little breather filter on there for now.
http://cruiser54.com/?p=121
I clicked the link but I have already read all that. I’m trying to figure out where the ccv hose connects too since the map sensor hose is in the hole that the ccv hose would go too. So I’m assuming I just dont use it and leave the breather filter on it?
You either have the vacuum source for the MAP at the throttle body or at the intake manifold. If using the intake manifold, the throttle body hole must be plugged.
Sounds great. The lower throttle body hole has a hard plastic hose going to the rear part of the intake manifold near the IAT sensor.
I need to see a photo of your vacuum routing.
How do I add pictures on here?
Email them to cruiser54private@gmail.com
I took pictures today, but not sure how to send them on here.
The lower throttle body hole shouldn’t go back to the intake manifold? I will take pictures tomorrow if I haven’t burnt the POS to the ground.
Can i use a NPT connector (1/8 thread) without factory rubber fittings? Only connected by a hose with the same size of the map terminal. Thanks. Excellent website.
I imagine you could, but using only flexible hose can lead to issues if the hose splits or collapses.
my 90 xj just recently started idling rough and sputtering when im on the throttle. I noticed that the line going in the throttle body is cracked at the tip but is still in the rubber boot. I tried going on napas website but cannot order the hose or 90* fittings online. what are the sizes and do you know any suitable substitutes? thank you so much for your time. I don’t want to give up on the battle wagon just yet.
Go to this link:
http://cruiser54.com/?p=280
Napa’s website is showing the Elbow and Tubing part numbers as Echlin Fuel System: CRB 2670 & CRB 2672. Are these still the same parts?
Thanks for putting this website together, it’s amazing.
Nevermind, I’m a tool. Just noticed they are the same, just without the dashes. Google wasn’t redirecting me to Napa’s website searching for “2-670” so it threw me off.
LOL. Glad you got it.
Finally getting around to this step. Continuing to work through the list. Running rough after shop replaced engine.
Good thing to do regardless.
Hey, Cruiser, not sure where to ask this question. I have an 87 Cherokee with a 4.0 and have swapped in a 96 engine and used all of your tips on how to re use the renix intake,etc. Where does the vacuum hose go from the barbed connector located a few inches behind the throttle body on the intake? When I removed the engine that was one hose that came up missing upon the reinstallation. In the pictures that I took before removal I can see it going from the connector ,over the valve cover and descending back near the firewall. Any help would be greatly appreciated. Thanks for all of your tips,this website is super informative!
That hose provides vacuum for the heater and vent controls on the passenger side rear of the engine bay/
Does this apply to a 2.5l TBI? I’ve got a crappy idle and a misfire, and the #2 (and only #2) plug is black as sin…been going crazy trying to find something that’d make only one cylinder go bannas
You need to do a compression test on #2.
Hey cruiser, I did this modification and now whenever the vacuum hose is plugged into the map sensor it idles at 3,500 rpms and when it’s unplugged it idles very rough at around 1,500 to 2,000. Any idea on what this could be?
Did you tap the correct hole?
I believe so, the hole above it doesn’t actually go into the throttle body, it’s creating vacuum I’m not sure if that vacuum line is actually the issue or if one of the sensors or something that was taken off in the process could be causing the high idle?
Hey cruiser. I got a question. What size tap and driver would I need to do this 1/8” npt tap? Can you break it down a little for me lol
A 1/8 NPT tap and driver.
Double check all connections at MAP.
This is a brilliant fix!
New owner of a 95’ XJ. I’ve been searching high and low, for this exact answer. Well almost. It appears that my intake manifold is from 99+ and has a second port, directly underneath and stands up and down. Should this be capped, or does it run to the MAP as well?
91 and later had the vacuum source for the MAP on the intake manifold. Is this answering your question?
When you remove the throttle body to do the threading portion of this mod, and go to reinstall the throttle body, do you have to adjust the TPS sensor or do you just plug it back up to the harness and leave it as it was?
No. That adjustment isn’t affected.
Hey cruiser I messed up and took off my original cable without checking if I had a driver and tap. Is it okay to drive without this connected just to the hardware store?
It will run pig rich if you do. I wouldn’t.
Hi Cruiser. first to all give you many thanks for your website, an invaluable source for keep ours renix’s on the road.
Ok, I have a 88 Laredo that runs well until a few months. Fuel pump die. Changed for a new one Bosch unit. Pressure its almost 30 psi when turn on key and 35 at idle. The problem is start its very very hard. Sometimes starts at first attempt sometimes cranks but doesnt starts until dry battery.
I follow all relevants tips, clean and measured every connector, terminals, sensors, throttle body, etc included infamous C101 with no luck.
I have another renix as a donor, change TPS, IAC, no change. Sometimes stars ok, sometimes can pass many days…
As a deseperate measure I move TPS to high position (about 0.9 V), engine dificulty starts then keep high revs. Adjust TPS as correct target but engine dies like running out of fuel. Repeat procedement but now I disconnect MAP hose and engine keeps running at 1200~1500 rpm.
Last to do: change MAP sensor from donor renix and now starts at first attemp, revs are steady at 650~700 rpm and all seems to be ok…
question: Can a failed MAP sensor create a no start condition? what another things to do?
sorry for extensive words and thanks in advance!
Cristóbal
A failed MAP sensor can indeed cause a bad start condition. If the MAP sensor sends a reading to the ECU that there is no vacuum, the engine will be very rich on start-up, even a no-start.