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89 idles great wont run above 1500rpm ?

D

drj89xj

NAXJA Forum User
Location
Mesa, Arizona
I just did a re-ring and bearings on my 89 got the motor back in the truck and cant seem to get it dialed in .. starts and idles great .. I try to give it some gas and it stumbles spits sputters and pops ... wont go above 1500 no matter what I do ... Ive got fuel to the rail ... Ive checked tdc and made sure the distrib is on #1 ... not sure what to look for now .. sensors maybe ?? anyone have any Ideas ??
 
I would bet money it's your Crank Position Sensor. Either not seated fully, or it chipped the magneto (or whatever it is) off the end of it.
 
not sure what it's called on an 89 but sounds like you need to adjust your air temp sensor on your engine intake.

doug
 
First thing I'd do is clean the CPS connector with a good contact spray. Scrub it out with a pipe cleaner and spray it again. Then do an ohm test on the CPS, 200 ohms plus or minus 75. Sounds an awful lot like a CPS I had that had 290 ohms of resistance. Just a little out of the envelope, but enough to cause some serious grief on occasion.
It acted a lot like when I disconnected the vacuum line on the MAP, that's what I though it was at first. It would barely run, I had to feather the gas pedal to get any sort of RPM's out of the motor.
The next thing I'd look at is fuel pressure and then maybe the TPS. That is if your absolutely sure the "1" plug is on the "1" pole at the cap. And the rotor is slightly before the "1" pole on the cap, when the timing marks are aligned, at TDC "1".
 
Step1 open hood
Step2 replace Crank Sensor
Step3 ????????????
Step4 PROFIT!

I had the EXACT same problem about 3 weeks ago..... Do yourself a favor and buy 2 of them (especially if you wheel in far off places)
 
big black xj said:
Step1 open hood
Step2 replace Crank Sensor
Step3 ????????????
Step4 PROFIT!

I had the EXACT same problem about 3 weeks ago..... Do yourself a favor and buy 2 of them (especially if you wheel in far off places)
Click to expand...

Aw crap, we're getting slashdotted.
 
Quote:
Originally Posted by H8PVMT
not sure what it's called on an 89 but sounds like you need to adjust your air temp sensor on your engine intake.

doug



HANKHILLVOICE-WHUT THE HELL-?????\HANKHILLVOICE
Click to expand...

I couldn't think of the part.....it's called the MAF sensor :repair: but that is on an import sedan, it's called something else in a Jeep =)

yep
 
I checked the ohms on the speed sensor it reads 223 I took it out and cleaned it .. situation didnt change so I will check the distributor again .. If I have the harmonic balancer timing mark at 0 should my rotor fall directly on #1 ?? seems Ive been able to get it to fall just on either side of #1 but not exactly on ... thanks for your help, Jason
 
drj89xj said:
I checked the ohms on the speed sensor it reads 223 I took it out and cleaned it .. situation didnt change so I will check the distributor again .. If I have the harmonic balancer timing mark at 0 should my rotor fall directly on #1 ?? seems Ive been able to get it to fall just on either side of #1 but not exactly on ... thanks for your help, Jason
Click to expand...
It can be hard to figure out where it should fall. I'd mark exactly where it is now, and then try for one tooth forward from that. If there's no change, or it gets worse, you'll know where to set it back to.
 
Mathew is right on with his diagnostic. I have seen a bad coil do this but the distributor is most likely.
 
Fuel to the rail and correct pressure are two different things- The check is free, rent the tester from Autobone, when you bring it back you get your money back. No parts to remove, you have a schrader valve to thread onto, so you probably won't even get dirty.
Low fuel pressure will do exactly what you say. A plugged fuel filter is a serious candidate, as well as a weak fuel pump. Watch the fuel pressure when it starts stumbling, I bet it drops to under 15psi.
 
If you've had the TPS off recently, double check that the stud is on the right side of the TPS sweep arm.
Stock position for the rotor is slightly before 1. If memory serves me right. Though some after market cams and worn distributor gears work better with the rotor a measured distance past "1" (Indexing). But this will usually mess you up later in the RPM band, it will buck and snort. Unless your 2 teeth off, it often doesn't affect much at all.
 
Bad TPS or low voltage at the TPS might do that. Check pin B to pin C on the three pin flat cable, ECU side of the TPS, engine off, power on, at WOT. Should be reading over 4 volts, if it reads something less than 2 volts it is limiting the throttle rpm at the ECU.


Pin A to pin B should be near 5 volts.

Both are simple ohm meter tests.

Also sounds like no vacuum (or leak) to the MAP sensor, check for a loose vacuum line at the throttle body that feeds the MAP sensor.
 
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