dmoe69

Me: 1988 4.0 Automatic.

I started out with a blown motor at purchase. I replaced the blown motor with a long block. I have completed Cruisers tips 1, parts of 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 18, 27, 29, 31.

At the point I saw your video at your instrument cluster I had the same problem. I have taken a few more steps with less than stellar results.

Looking at the CPS with a mirror it appeared to be at the very forward edge of the timing windows (aftermarket flexplate). I spaced the CPS with one set of washers, which allowed the engine to rev a little higher, so I added a second set of washers. It then rev’d freely in park, but had the same symptoms on the road. Also, the tach would still top out at 2500 RPM even though the engine would rev freely above that.

You started out with a running vehicle. I installed all new parts before I ever tried to start the vehicle (starter, alternator, coil, ICM, battery, distributor, sync sensor, cap, rotor, FPR, all sensors except IAT (can’t source). Of the parts we’ve both switched at the point you started having problems (disregarding the heater core): Fuel injectors, vacuum lines, spark plugs, wires, fuel filter.

I also have low vacuum. I am going to say with some certainty that the low vacuum is not a leak, it is caused by the ECM pushing timing, either ignition and/or fuel. If I pull the vacuum line going to the canister and let it leak, the vacuum gage will actually read higher than with the leak sealed.

I removed all 6 spark plugs and gapped them to .34. Performance degraded. I then gapped all 6 plugs to .39. Performance degraded. I restored the gap to .35 and performance stabilized to the previous condition.

Following that, I indexed the distributor to 4 O’clock. The engine would run, but did not have enough power to move out of my garage. I then indexed the distributor to 6’ O’clock. The rev limited symptoms disappeared. I was able to drive the vehicle, but at significantly reduced power (1/4 mile to get up to 45 MPH), but something is very different in good way. I also rotated the distributer at all three indexed positions 4, 5, and 6 O’clock to see if the ECM was advancing/retarding spark past the reach of the blade on the rotor. That was probably inconclusive, but by observation I will say, no.

At this point I am waiting to receive a REM monitor from NickInTime and considering what affect the distributor being clocked at 6 O’clock would have on “something” that would cause this problem.

dmoe69

This was a response to the current thread "Renix Missfire over 2k... by aroundincircles. It was moved off by itself by the moderators.

aroundincircles

Thanks for the update, clocking my distributor is my next step. Just waiting for cooler weather.

aroundincircles

Did you have a high idle and did indexing the distributer fix your high idle?

dmoe69

That is a loaded question. I do not typically have a high idle. It settles down to 750 RPM as indicated on the dash tach. Upon initial starting it will increase to just under 2000 RPM for 5 - 7 seconds and then down to 1500 RPM for a few more seconds before settling out at 750. I have assumed this to be normal.

Rarely, but periodically I will get a high idle at around 2300 RPM. I learned a trick from another post to disconnect the connector to the TPS until the engine starts to slow down and plug the connector back together before the engine stalls. It has always regained the 750 RPM after that. Cause currently unknown

BlueRidgeMark

This is probably not your problem, but it can't hurt to double check. If you folllowed the spark plug wire diagram in a Chilton or Haynes, it's wrong. Alas, people have posted those wrong diagrams all over the 'Net. Here is the correct wiring:



Distributor to spark plug wiring.

aroundincircles

I have a high idle, between 900-1100 RPM, even when at operating temp. I'm sure that it is somehow related to my issue, but I've replaced the IAC, replaced all the gaskets, replaced and adjusted the TPS, but cannot for the life of me figure out why my idle is so high, no vacuum leaks that I can find.

and yes, I've taken the spark plug wires off and put them back on so many times, I know that isn't the issue.

dmoe69

I couldn't find it back in your original thread. Did it have a fast idle when you bought it? Or was that a second problem that developed with the Rev limit? Have you tried disconnecting the TPS while the engine is running?

aroundincircles

I did not notice a high idle when I bought it, but I posted a different thread here, and I think I figure out the issue after a TON of googling:

https://www.cherokeeforum.com/f2/ren...causes-262632/

In fixing the vacuum system I broke it, since I didn't account for the new valve cover. ~850 is a good idle? or at least acceptable idle? (in neutral/park).

aroundincircles

is there a good video showing how to do this? I'm not 100% sure I know what I'm doing and if I'm comfortable doing it, just reading the instructions. (clocking the distributer)

lawsoncl

You seem familiar with Cruiser54's tips, but I'll suggest a re-read of these.
Distributor indexing http://cruiser54.com/?p=68
Throttle Body butterfly adjustment http://cruiser54.com/?p=94

Have you traced the lines to the vacuum ball behind the passenger side front fender? Those lines sometime rot, and the vac ball is sometimes just plain missing.

dmoe69

The guy who made this video leaves out step one: Get the engine at top dead center of the #1 cylinder, Cruiser's tip #12, other than that this video explains it fairly well.

aroundincircles

Thanks, I watched a bunch of videos, but didn't come across this one... This is what I was looking for, and indexing your distributer fixed your non revving issues? I have a new distributer I was going to install. I might just install it first, see what happens, if that doesn't fix anything then index it.

dmoe69

When you swap in the new distributor you'll be pretty much committed to indexing it. If you haven't started that, make sure you are on top dead center of the number 1 cylinder before you start. You have a running engine so if the rotor is pointed towards the number 1 pole the engine is on the correct stroke already. Just needs to be lined up to 0 degrees. I intentionally took my distributor out of proper indexing (6 O'clock) and that did stop the rev limit. Unfortunately, and not unexpected, caused a significant loss of power. Unexpectedly though, after I re-indexed the distributor back to 5 O'clock the engine ran well for about a half mile before the problem suddenly returned.
I have purchased both a new NTK O2 sensor and AIT sensor. I don't want to swap them out until I have the REM monitor (coming today). I want to get some baseline data before I start swapping any more parts. I originally installed a Bosch O2 sensor and tightened in like a spark plug. Both the brand and my installation make it suspect. I am going to install the AIT sensor in the airbox.

dmoe69

I received the REM Friday afternoon. All data was good. After trying to drive the XJ it began to stumble. MAP at 28.6, vac at 1.6. rubber elbow at the throttle body (cruiser's tip # 31) had split and was the consistency of chewing gum). I replaced the elbows and hard tube with 9/32 vacuum hose. I also swapped in the NTK O2 sensor. All data was good again, very good even. Tried to drive it and it began to stumble (problems like layers of an onion) the O2 sensor was no longer cycling, it was stuck at 4.80v and 16.0 AFM. I let it cool down and tried again a few times. Each time the O2 would cycle correctly for a few minutes (I'm going to time this next time) and then stick at an AFM of 16.0. I am reading all I can on the function/operation of the O2 sensor. Interesting though, when the O2 sensor began to malfunction the engine developed a high idle 1850 to 2000 RPM.