Xj help

[GRADESCHOOL]

So i got the brakes working properly thanks to Tim noticing my dumb mistake...

So Now it is still running rich and smoking. It also is not idling to well. I replaced the crankshaft position sensor and the throttle position sensor. It also tries to cut out once in a while. Also when i get on the throttle it sometimes tries to cut out but it makes popping noises then i get power after a couple seconds. Tim told me to check the coolant temp sensor so i pulled it and it was pretty dirty so i just cleaned it up and am going to put it in and give it a shot but i am out of ideas. If rev it up to around 3500-4000rmp it sputters but will hold that rmp. If anyone has any ideas i would appreciate the help. It is also backfiring every now and then

[tobyw]

Check fuel pressure across the RPM range and get back to us...

[sams88]

Mass air??

[GRADESCHOOL]

Its a 90' so i dont think it has a mass air sensor.

[Grumpy]

Almost all FI systems have a MAFS on 'em.

[Grumpy]

Okay, Scotty, here's two I came up with. Jose says that monster is a Renix, so here ya go:

BillaVista Tech on Pitate 4x4 - PDF manual for the Renix is there.

Talk to 5-90 on NAXJA - Rumor is he knows his stuff.

Let us know what you find.

[OldGreen]

Almost all FI systems have a MAFS on 'em.

not really. . .his doesn't. . .MAP, TPS, CPS, CTS, O2, and IAC are about it. All GM TBI motors are the same deal too.

Coolant temp if it runs rich at startup and 02 or Coolant temp if it is rich after it gets warm. MAP could cause full rich all the time too. . .could be as simple as a cracked vacuum line in the MAP circuit. Troubleshooting it shouldn't be too bad. It just sounds like it is in limp mode.

Don't just throw parts at it. You can check the CTS with an ohmeter and a cup of hot water (google it). spray carb cleaner around to look for vacuum leaks. Read everything on the internet about this problem with YOUR motor. Pull the O2 sensor and clean it with a wire brush...remembering that the O2 sensor is nothing more than a dead stick until the CTS tells the computer that the motor is warm.

Number one cause of limp mode or full rich on a FI motor is a vac leak. . .CPS, TPS, CTS after that since it doesn't have a MAF.

Learch. . .am I close?

[foursix]

Check the vacuum line going to your fuel pressure regulator. It is on the front end of the fuel rail - not sure of that is a renix I thought they got rid of that in 89? If there is gas in the vac line you have a bad regulator, they can/do cause a variety of symptoms. You could also have a bad line they have rubber boots on both ends prone to dry rot. Also dont overlook the possibility of scuzzy injectors that are hanging and or opening improperly.
Hope this helps eliminate a few things...
Kevin

[GRADESCHOOL]

I went through the injectors and made sure all the o-rings were good and checked the connections of that vacum line

[Grumpy]

Almost all FI systems have a MAFS on 'em.

not really. . .his doesn't. . .MAP, TPS, CPS, CTS, O2, and IAC are about it. All GM TBI motors are the same deal too.

Coolant temp if it runs rich at startup and 02 or Coolant temp if it is rich after it gets warm. MAP could cause full rich all the time too. . .could be as simple as a cracked vacuum line in the MAP circuit. Troubleshooting it shouldn't be too bad. It just sounds like it is in limp mode.

Don't just throw parts at it. You can check the CTS with an ohmeter and a cup of hot water (google it). spray carb cleaner around to look for vacuum leaks. Read everything on the internet about this problem with YOUR motor. Pull the O2 sensor and clean it with a wire brush...remembering that the O2 sensor is nothing more than a dead stick until the CTS tells the computer that the motor is warm.

Number one cause of limp mode or full rich on a FI motor is a vac leak. . .CPS, TPS, CTS after that since it doesn't have a MAF.

Learch. . .am I close?

Hey, I said Almost

[commando14]

I think the O2 sensor would be a good thing to check like OG said.. and the MAP and associated vacuum lines.

Another thing to check would be the stator in the distributor. Look here: http://www.lunghd.com/Tech_Articles/Engine/Cam_Position_Sensor_and_Sync_Pulse_Stator.htm

Does it idle any better if you start it up with the TPS unplugged?

[Lurch]

Jims right on. I doubt that it has a fuel pressure problem because it's running rich and runs poorly at an idle. It could be seval different things you best bet is to look around online and see if there are any common problems with your particular engine that could cause the problem your having. Let me know if you need some help. I have a buddy that works at a jeep dealer. I'll give him a call and see if he knows anything.

[commando14]

It may be worth plugging in a different ECU as well... just to eliminate that. I have one here that I pulled out of a manual 4.0L Renix cherokee.

[Lurch]

Pull the engine, throw it away and put in a small block.

[Grumpy]

Small block Ford, that is

[GRADESCHOOL]

I unplugged the O2 sensor and now she runs good....

[OldGreen]

Try cleainging it up first and if that doesn't work, get a new one.

You definately want it in the loop!!!

[tobyw]

Still running good this morning?

[GRADESCHOOL]

Running like a top. thanks for the help Toby

[Roman]

2 out of the 18 replies are from the Milk Man and you say "thanks for the help Toby" Wow . . .

[BullRider]

Scotty, if I recall correctly I mentioned I replaced my O2 sensor on my old xj with the same symptoms during the naches trip! Anyway, glad its running great. Lets ride soon.