4.0 renix fails smog

[Davisrats]

My 1990 renix injected 4.0 is failing Kalifonia smog. The smog guy said it was a leaking/dripping injector, leaking on the inside causing it to fail the idle portion of the test, the high RPM test was fine.

Does this sound logical or a wild ass guess on the technicians part?

He also said it could be the fuel pressure regulator, it tested fine.
New plugs, wire, cap, rotor , air filter and oil change,

it idles about 850 cool and about 650 worm.

Any ideas? CAT maybe?

Thanks

[rick]

An injector can cause idle test failure. Unfortunately, the only way to tell for sure is to start swapping them out... I'd start looking for an ebay set of injectors. It sounds like you've covered all the other bases. The cat could also be part of the problem, but usually it is only part of the problem if you fail at idle. Basically, the cat can only make up for so much junk coming out, and then it can't keep up. If you know you need a cat, it might be cheaper to put a new one on than a set of injectors and it might pass when new (but it might not and then you're out $$). Once it starts to use up some catalyst however, you will still fail again if it is an injector. You could waste the cat fairly quickly if you have a bad injector...

[Davisrats]

Can you pull the fuel rail and charge the fuel system to look for leaks?
Leaving the system intact just pulling the injectors out of the manifold?
I agree on the CAT, the engine should pass with out one.

[cbremer]

Can you pull the fuel rail and charge the fuel system to look for leaks?
Leaving the system intact just pulling the injectors out of the manifold?
I agree on the CAT, the engine should pass with out one.

you might be able to, but it might be a bad idea- the injectors are under quite a bit of pressure and it would suck to have one pop out and fuel start spraying. one way to test is to borrow/rent a fuel pressure gauge, turn the key to run (not start), check the fuel pressure; turn the key to OFF, then come back in 10 minutes or so and check the pressure again. if it has gone down more than a few PSI (i.e.: back to 0), then you have a leak somewhere in the fuel system. The fuel system should should be able to hold most of the pressure for quite a long time.

one place to check for injectors for cheap is http://www.fiveomotorsport.com/ Since Jeeps use the Bosch type injector (just like a lot of Fords), you can find like-new sets for not much money since the Mustang guys swap their stockers out for higher flow injectors when they mod their engines.

HTH

[Davisrats]

Thanks

[Davisrats]

What is the difference in the renix computers between manual trans and Auto??

I have two renix 1990 4.0 XJs, the AW4 auto XJ is running rich at idle and failing california smog.

Can I used the manual renix computer to check the auto to see if a inject or driver has failed?

If the auto does not get data from the computer, what is the difference??

Ron
Joshua tree, CA
1990 XJ AW4
1990 XJ AX-15

[rick]

I'm not sure if there is a difference on the Renix. The later models the only problem that will happen if you run the auto computer in a manual is it will throw a code. There is a separate ECU for the tranny on the OBDI engines. You could try swapping the ECUs just for fun. Besides, I'm curious

[Davisrats]

The auto actually feeds a bit of data into the ECU -- the NSS (Neutral Safety Switch) has feedback to the ECU showing a signal whenever the tranny is "in gear" - when the signal is present, the ECU will be "more aggressive" in controlling the idle (as is want with an auto-tranny) ...

... Beyond that, the manual ECUs "pay more attention" to the TPS signal (the TPS output from the flat connector is for the ECU; the square connector is for the TCU)... but that shouldn't be too much of an issue

Really for "testing" things should be fine, but the engine may stall at lights and stuff when the tranny loads the engine at or near idle...

satan @ IloveJeeps DOT Com gave me this answer. Willl check it out this weekend. Again, this is RENIX stuff PRE OBD I.

[skates04]

I would agree on an injector popping out, I dont have a I-6 but, on the 2.5 and most fuel injection set ups, the injectors get sandwiched between the intake manifold and fuel rail, it would only take probably 10psi to pop an injector out since you can easily pull them out with your fingers.

[Dukes69]

I would agree on an injector popping out, I dont have a I-6 but, on the 2.5 and most fuel injection set ups, the injectors get sandwiched between the intake manifold and fuel rail, it would only take probably 10psi to pop an injector out since you can easily pull them out with your fingers.

The rail should be bolted to the intake manifold, and should not allow for any pop out.

[RangerRick]

Ron,
If you are still having troubles, take a look at the O2 sensor. Lazy sensors WILL cause a fail condition at the idle or low RPM portion of the test...
Rick OllllllO

[Davisrats]

Well I got my 1990 XJ to pass California smog today. The problem was not the
injectors, but a combination of oily plug wires, 02 sensor and a miss adjusted
TPS. I must have wacked the TPS when I installed the engine because it was WAY
off.
She passed, REAL clean. Cool for more that 200,000 miles.
Ron

P.S. Thanks Rick.