I recently swapped a '91 engine/transmission into a '90 pioneer. The '91 engine had 140k miles vs 460k, and the transmission was shot on the '90. Other than a shot transmission and an older/more used engine the 1990 was in really good condition. Really I just wanted to give an engine swap a shot. There are a few concerns I have now that the '91 engine is in the '90.
1. The position of the coolant temperature sensor on the '90 was near the driver side engine mount, on the '91 it's on the thermostat housing. The connector is also slightly different but still just two leads. Can I just grab the wiring side of the connector off the '91 and splice into the line of the '90? Do the sensors function as 1 to 1?
2. There is no mounting hole for the knock sensor on the '91 engine. The knock sensor was also located near the driver side engine mount on the '90. There is a threaded hole on the passenger side near the engine mount on the '91. I would prefer to drill out an existing hole and tap that, than to drill a new hole in the engine block. Is there an issue with changing the knock sensor mounting position on the engine?
Thanks.

 

CRUISER'S MOSTLY RENIX TIPS

HO INTO RENIX SWAP

OCTOBER 31, 2015 SALAD 61 COMMENTS

This swap is easier than some will lead you to believe. And generally Pooh-poohed by those who have never done it. Those of us who have done it, like myself, will share with you the things that need to be done for a successful swap. Just think of it as swapping in a long block.

• XJ Cherokee and ZJ Grand Cherokee 4.0L engine blocks interchange.
• 2000+ TJ Wrangler and WJ Grand Cherokee 4.0L engine blocks interchange.
• YJ and 1997-1999 4.0L TJ blocks will interchange in XJ/ZJ
• XJ/ZJ blocks, and the 2000+ TJ/WJ blocks do not interchange without significant modifications.

TJ/WJ 4.0L Engine blocks underwent clean sheet design changes effective in the 1999 WJ Grand and 2000 TJ Wrangler. These blocks are not interchangeable with XJ/ZJ engine blocks. The reason is motor mount bolt holes and belt driven accessory mounting bolt holes are in different locations, or not present at all, TJ/WJ vs. XJ/ZJ.

Now that we know which engines we can use, let’s get down to business.

The HO and Renix have some differences but none that can’t be overcome very easily.

One running change was that the rear of the head was no longer drilled and tapped for the temperature gauge sender beginning in the 96 model year. The sender can be relocated to the threaded hole in the thermostat housing taken from an HO engine. You’ll have to extend the wire to that location. Some brave souls even drill and tap the HO head at the rear for the sender.

You will be using the intake and exhaust manifolds from your Renix, along with all your sensors and wiring. Since the intake ports of the HO are slightly different, you use a new Renix gasket. Exhaust ports are identical.

An alternative on exhaust manifolds:

As far as exhaust, you can use the Renix exhaust manifold and be fine.
If you want to use the HO exhaust manifold, you must go with an HO headpipe and screw your O2 sensor into that headpipe. Standard Renix harness is plenty long to do so.
A bung can be welded into the HO manifold to accept the EGR tube.

You will need to use your Renix distributor as it is different than the HO design. See Tips #12 – Setting Your 4.0 to #1 TDC and #13 – Distributor Indexing to be sure you get the distributor installed correctly.

The flywheel or flexplate from the Renix must be used so your CPS gets the correct signals. The valve cover from the Renix allows you to keep your CCV system intact and requires no modifications.

The HO block will have a plug in the coolant galley on the driver’s side of the block, closest to the front, which needs to be removed so your Coolant Temp Sensor can be installed in it’s place just as it is on the Renix. It requires a 5/16” square drive or a modified 3/8” drive that has been ground down to fit. Do this before installing the engine.

As for the knock sensor, which is located just above the oil pan on the driver’s side of the engine about mid way, all the blocks I’ve seen are threaded for it. If not, I’ve heard they may be drilled but not tapped. Tap the hole if that’s the case.



XJ: “Regular” (not Grand) Cherokees ’84-’01
ZJ: Grand Cherokee ’93-’98 (Gen1)
WJ: Grand Cherokee ’99-’04 (Gen2)
YJ: Wrangler ’87-’95 (Gen1)
TJ: Wrangler ’97-’06 (Gen2)

 

Hey, thanks for the info. I got another question. When I was doing this engine/transmission swap. I never separated the 91 transmission from the 91 engine when I put it in, so the flywheel from the 91 is now in the 90. I clearly didn't read close enough cause now I have crank no spark, and I'm pretty certain the flywheel is the issue. The CPS isn't reading out high enough, and I can just see there's a pretty big difference in the flywheel tooth pattern. Can I take the flywheel from the 90 and put it into the 91 transmission?

 

Absolutely.