Runs like crap in closed loop

[Strokermjcomanche]

Here's some info....,

 

90 XJ engine harness (no c101) , 4.7 stroker , std shift , nv3550 , new 746 injectors . 90 manual ECU

 

Here are the engine sensor readings brand etc to eliminate SOME questions :

 

Brand new mopar distributor, plugs , wires , champion plugs ...new mopar high altitude CPS and knock sensor .

 

Fuel pressure 31-39 ( Bosch 69302 pump )

746 Volvo injectors between 3.6 and 4.2 duty cycle at idle .

Engine vacuum 15-19hg

TPS (mopar) 17%

O2 sensor reads 6.3 ohms ( brand new NTK )

O2 relay voltage 12.9 with engine running

Rpm reads between 625-850 at idle

Battery voltage 13.8v

Exhaust reading rich

O2 reading .39 -1.52v

Fuel trim128 ( using base fuel curve )

 

If you need more info let me know ... I have the R.E.M. Monitor that nickintimefilms sells..

 

Starting the engine cold ,it fires right up and runs great in open loop for roughly 30 seconds and then switches to closed loop . After it switches to closed loop the engine idle drops to 3-400rpm and the engine barely runs and almost dies until the ECU switches back to open loop and then it will run fine for the next 30 seconds and go back to closed loop and repeat the previous symptoms . It will keep doing this until the engine gets warm never going to closed loop . Engine is running rich ...

 

I've cleaned the relays and connectors and swapped the relays as well . The ground that goes to the TPS and IAT

Has .07 ohms resistance, too much ? Where should I go from here ?

[DirtyComanche]

That vacuum reading is determined by the MAP sensor?

 

Coolant temp sensor is also producing reasonable readings?

 

IAT?

 

Got an O2 sensor you can swap in?

[Strokermjcomanche]

That vacuum reading is determined by the MAP sensor?

 

Coolant temp sensor is also producing reasonable readings?

 

IAT?

 

Got an O2 sensor you can swap in?

I'm not sure if the map sensor creates that reading , I can swap one from my other truck if need be ..

 

Coolant sensor seems to be reading right... nothing out of the ordinary. I can get the actual readings

 

IAT , can I test it ? Aren't they discontinued?

 

I have an extra 02 sensor , but it reads 10.4 ohms when I probe the red/black wires ...

[Jeep Driver]

Intuition says bad MAP.

[DirtyComanche]

The IAT is discontinued but there's a GM P/N that works, you'll just need to make an adapter pigtail, there's a thread on it somewhere that also has the resistance vs temperature values.  It can be tested like any other temperature sensor with a multimeter and a thermometer (and maybe a heat source).  It probably isn't the problem.  As long as the IAT and CTS are ballpark it won't cause massive issues.

 

I'm with Jeep Driver in that I want to say it's a MAP issue, or perhaps a vacuum leak causing such, as a hunch.

 

However you have an O2 sensor on hand, even if it is suspect, so I would try it and see.

[Strokermjcomanche]

Any link to the gm IAT testing ? I'm tired and it's dark , I'll swap a good MAP in tomorrow from my black truck , then the O2 if need be , thanks .

[cruiser54]

You can read the IAT with the REM.....

 

Also you can read the O2 sensor VOLTAGE. 

 

The 746s are probably not the correct injector on a stroker.

 

Check the MAP line from throttle body to MAP first. 

[DirtyComanche]

Any link to the gm IAT testing ? I'm tired and it's dark , I'll swap a good MAP in tomorrow from my black truck , then the O2 if need be , thanks .

 

http://comancheclub.com/topic/49753-found-replacement-air-charge-temperature-sensor-or-iat/page-2

 

Has the resistance tables and the GM P/N.

[HOrnbrod]

The 746s are probably not the correct injector on a stroker.

This. How long have you had them in? Do you have an A/F meter to see what happens to the ratio when it goes to closed loop?

 

If you had an HO I'd say invest in an adjustable FP regulator based on the A/F readings.

[DirtyComanche]

I guess the first question I should have asked was if it has ever run correctly?  I mean, is this a new thing that it's running poorly, or did you just build this stroker and it's doing this?  If you just built it I'm just going to step back because I don't know anything about strokers or what parts you should be running.

[Strokermjcomanche]

You can read the IAT with the REM.....

 

Also you can read the O2 sensor VOLTAGE.

 

The 746s are probably not the correct injector on a stroker.

 

Check the MAP line from throttle body to MAP first.

Will look at the IAT reading ..,

 

I listed the O2voltage above .39-1.52

 

746 injectors are too rich ? What should I run then?

 

MAP hose is fine , I have 5 spares as well ..

[Jeep Driver]

Reoccurring statement, particularly on the XJ forums-

 

I 'upgraded' to XXX injectors and now I have this problem..............

 

 

Just something I've seen numerous times.....but, IDK.

[Strokermjcomanche]

 

The 746s are probably not the correct injector on a stroker.

This. How long have you had them in? Do you have an A/F meter to see what happens when it goes to closed loop?

 

If you had an HO I'd say invest in an adjustable FP regulator based on the A/F readings.

Ive had the 746s since I started it for the first time , ran fine initially when I started it roughly a year an a half ago . It has probably 15 miles on the stroker I purchased .I'm going to take it to my buddy at the dealer that has an A/F meter .

[HOrnbrod]

I had to fool a lot with mine at first with fuel pressure and MAP voltage (vary the 5VDC reference) to get it just right. I know you are Renix, but you have to see the open/closed transition on an A/F meter. It'll probably be easy to spot the problem then.

 

With a stroker you should have an on board meter, unless the REM thing can do it.

[cruiser54]

 

You can read the IAT with the REM.....

 

Also you can read the O2 sensor VOLTAGE.

 

The 746s are probably not the correct injector on a stroker.

 

Check the MAP line from throttle body to MAP first.

Will look at the IAT reading ..,

 

I listed the O2voltage above .39-1.52

 

746 injectors are too rich ? What should I run then?

 

MAP hose is fine , I have 5 spares as well ..

 

O2 voltage should switch from .1 to 4.9 rather quickly. 

 

Do you have battery voltage to the O2 sensor's orange wire? 

Resistance reading at the black wire on the harness with it unplugged? 

 

746s are too small for a stroker. 

[HOrnbrod]

The 746's at the right fuel pressure might be just fine. Test first and see what you got.

[Strokermjcomanche]

O2 reading never got higher than the 1.52 reading

 

I will check on the voltage , thought it was a red black and grey wire on the sensor .

 

I'll get the resistance tomorrow on the black wire .

 

To clarify , I'm trying to get it running better so I can take it to my buddy so he can go over it at the dealer including the A/f ratio . When I hear the injectors are too small I think it would run lean ( not rich ) , trying to make the injectors be the last thing I need to address ...

[Ωhm]

Your REM readings show fuel trim @ 128. This value is either what it is, or its the default value used for open loop. Can you capture the REM fuel trim reading during the short time the vehicle is in closed loop operation? O2 value shows rich. Shot in the dark here, leaky injector. 

[cruiser54]

O2 reading never got higher than the 1.52 reading

 

I will check on the voltage , thought it was a red black and grey wire on the sensor .

 

I'll get the resistance tomorrow on the black wire .

 

To clarify , I'm trying to get it running better so I can take it to my buddy so he can go over it at the dealer including the A/f ratio . When I hear the injectors are too small I think it would run lean ( not rich ) , trying to make the injectors be the last thing I need to address ...

O2 sensor has 3 wires. Black ground, Orange heater voltage, gray is output to ECU.

If there is a poor ground to it or no power, it will stay in open loop.

 

Have you "indexed" your distributor per my Tip 13?

All the dipstick tube stud grounds on there and touching bare metal and not a ton of nice new paint? 

 

The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, failed emission tests, and wasted money replacing components unnecessarily.

All the components listed below ground at the dipstick tube stud:

Distributor Sync Sensor, TCU main ground, TCU “Shift Point Logic”, Ignition Control Module, Fuel Injectors, ECU main ground (which other engine sensors ground through, including the Oxygen sensor, Knock Sensor, Cruise Control and Transmission Sync signal. All extremely important stuff.

[Strokermjcomanche]

Well it's fixed , was a bad O2 sensor .

 

Started by checking the resistance on the black wire .05 ohms and the voltage to the red wire with the key on and not running .009. Then I cleaned all the grounds again and still no change .Then I figured I would start by swapping the old O2 sensor in , as soon as I swapped it in everything began to read normal . It's now running good in closed loop ( no stumbling ) , switching between rich and lean , the O2 readings are between .1 and 4.98 with them moving at a good rate/speed . Must have been a DOA NTK sensor , and I bought it so long ago I can't return it . I'm going to run this one for now and search for a NOS mopar one .

 

Thanks for all the help everyone .

 

The engine seems to have a little hiccup buts it's very minor , any suggestions on that?

[Jeep Driver]

O2 sensor reads 6.3 ohms ( brand new NTK )

 

:hmm:

[Strokermjcomanche]

.

[Strokermjcomanche]

 

O2 sensor reads 6.3 ohms ( brand new NTK )

 

:hmm:

Supposed to be between 5 and 7 , the one that worked had 10.4 . It's better then throwing random parts and money at it...

 

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

[cruiser54]

Well it's fixed , was a bad O2 sensor .

 

Started by checking the resistance on the black wire .05 ohms and the voltage to the red wire with the key on and not running .009. Then I cleaned all the grounds again and still no change .Then I figured I would start by swapping the old O2 sensor in , as soon as I swapped it in everything began to read normal . It's now running good in closed loop ( no stumbling ) , switching between rich and lean , the O2 readings are between .1 and 4.98 with them moving at a good rate/speed . Must have been a DOA NTK sensor , and I bought it so long ago I can't return it . I'm going to run this one for now and search for a NOS mopar one .

 

Thanks for all the help everyone .

 

The engine seems to have a little hiccup buts it's very minor , any suggestions on that?

Describe hiccups.