HELP! bogs really bad and tach drops to zero.

[peuglow]

Did you do anything with the CPS? You said it 'looked new'. I just replaced the CPS on my 1996, no frayed wires or anything. When I put the new one on, fired right up, all my intermittent bogging issues were gone.

I'd highly recommend swapping that out. It gave me some real trouble (over 2hrs) but that's mainly because I have thick arms and had a hard time getting the 2 bolts off and then back on. Theoretically it's a very easy job, but without a lift on my Jeep or a floor jack (and working in the pitch dark) it took some major time and patience. There are some good writeups on how to do it here.

 

[joe_peters]

cleaned the grounds and the throtlle body today. didnt help at all. and now its slow to start. turns over 6 or 8 times before it starts up.

Ok--RENIX--that stands for "SPIN IT UP BOYS!"

In the RENIX system the CPS WILL NOT GENERATE a signal strong enough for the ECU to trigger an ignition spark UNTIL THE ENGINE IS ROTATING AT 300 RPM OR HIGHER.

What this means is that our beloved RENIX XJs--1987 through 1990--must have GOOD STRONG BATTERIES, GREAT CABLES, AND WELL FUNCTIONING STARTERS.

In other words, the RENIX will never fire off as fast as other vehicles, that the battery must be the highest CCA you can cram in there, the main cables should be LARGE--1/0 gauge is good--connections KEPT clean and tight (maintenance), and our starters that end up getting regular oil baths should be checked, cleaned if necessary, and REBUILT when needed (I prefer rebuilt starters and alternators done local to REMAN from China/India/Mexico).

As this seems to be related to a driveability issue, maybe it is time for the BASICS--static batt voltage check; engine running batt voltage check; voltage drop test over your main cables, batt voltage while cranking engine check.

This isn't meant as a lecture, even experienced technicians will sometimes chase their own tales because they got too hung up on sensors and control modules.

 

[MaxxXJ]

Ok--RENIX--that stands for "SPIN IT UP BOYS!"

In the RENIX system the CPS WILL NOT GENERATE a signal strong enough for the ECU to trigger an ignition spark UNTIL THE ENGINE IS ROTATING AT 300 RPM OR HIGHER.

What this means is that our beloved RENIX XJs--1987 through 1990--must have GOOD STRONG BATTERIES, GREAT CABLES, AND WELL FUNCTIONING STARTERS.

In other words, the RENIX will never fire off as fast as other vehicles, that the battery must be the highest CCA you can cram in there, the main cables should be LARGE--1/0 gauge is good--connections KEPT clean and tight (maintenance), and our starters that end up getting regular oil baths should be checked, cleaned if necessary, and REBUILT when needed (I prefer rebuilt starters and alternators done local to REMAN from China/India/Mexico).

As this seems to be related to a driveability issue, maybe it is time for the BASICS--static batt voltage check; engine running batt voltage check; voltage drop test over your main cables, batt voltage while cranking engine check.

This isn't meant as a lecture, even experienced technicians will sometimes chase their own tales because they got too hung up on sensors and control modules.

That's why I suggested a new coil/plug/wire/dist setup. He cleaned the grounds, now he just needs good spark, mine really came to life after I changed my electrical.

With any engine, if it doesn't have spark/fuel/air it won't run.

Just crossed my mind, if your dumping to much fuel into the system you'll bog too, check the diaphram on the front of the fuel rail where the vac Line goes into it, if it has fuel in it it's faulty and cause it to run rich...
Also check your fuel pressure see if it has good pressure, if its not getting good enough pressure then it will bog from lack of fuel. (Until your engine is spinning to 3000 rpm's where your pushing enough pressure into the line)

 

[hotrodford88]

but should it spin over 7 or 8 times before it lights off? and it bogs over 3000rpm.

 

[Ecomike]

but should it spin over 7 or 8 times before it lights off? and it bogs over 3000rpm.

You may have two different problems. So don't assume they have the same cause. Jeep gremlins usually attack in pairs or packs like wolves.

The seven or 8 times is typical of Renix start ups. Bogging down at 3000 rpm could be fuel pressure or a bad TPS that is bad at that spot on the tps.

There is a way to get faster starts, but it requires modifying the CPS mounting to move it closer to the flex plate.

Can you give us a complete run down on the history, and problems? Small details can sometimes be huge clues for us.