Renix issues for 89 Cherokee help...

Hey guys. Anybody have any issues with the old non h.o. engines not revving up??? My buddies with the newer cherokee's and TJ's with H.O. engines are able to bounce them off the rev limiters running up sand and mud hills and such. But with mine, it just doesn't seem to have the revving power uphill. It bogs down until it downshifts into first, but still won't rev like theirs. The engine is a stock healthy engine. Compression is fine, engine doesn't burn oil or smoke at all, just won't rev. Are there any mods that can really help this thing out? I'm running 5.13 gears and an automatic tranny. I have a freshly rebuilt 4 litre H.O engine on the stand for it if all else fails. Then I will have to deal with wiring issues.

May be either the CPS or SYNC sensor going out.

The CPS (Crankshaft Position Sensor, 11:00 on the bellhousing, facing forward) is the primarly sensor for generating timing signals as used by the fuel injection and ignition control system. The CPS reports when pairs of cylinders are at TDC (I believe the pairs are 1-6, 2-5, 3-4 - but I'd have to check.) If the CPS is gradually failing, it can cause problems (if it can't read the signal fast enough, it can cause an artificial "rev limit."

The SYNC sensor (Synchronisation sensor, found inside the distributor, and requiring removal and disassembly of the distributor for replacement) is what tells the ECM when #1 cylinder is coming up to fire. If this sensor goes out, the ECM can "guess" when it's going to hit on the cycle, but this will result in reduced performance.

The CPS can be checked with an ohmmeter, and you should get 200 (+/- 75) ohms between the two terminals. Operation can be verified by using an analogue AC voltmeter on low scale while cranking - there is no value given, but you should get something (I've got to find out what and record it one of these days...)

Here's the check for the SYNC sensor - it's a little more involved:

Using an analogue voltmeter, backprobe the Blue wire (terminal B) with the + lead and the GRY/tracer wire (terminal C) with the - lead. With the voltmeter on 20VDC, you should see +5VDC with the key in the ON position.

Hope this helps - if these check out, let us know and we'll see what else we can come up with.

5-90

An older engine that is starting to see performance drop offs and won't wrap as high or as quick is a candidate to have the CAT checked. They get plugged with age and cause the effects you describe.