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argg. spit, sputtering, backfiring thru intake, & high idle

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Thats what my truck does.... And I think its the TPS, because it runs ok with the pedal pressed about an eighth of inch (1/8" or say about 2 ounces of pressure on pedal) and when the RPM's hit around 2500 it feels like it regains power..

 

It first did it after a fuel fill up about a week ago.

 

Filled tank to the top, pulled on the highway going up an incline and felt like a brief loss of power, then ran fine for about +/-20 miles on the ride home.

 

The last 5 miles it started to run really bad.. Spitting, sputtering, no power, bucking, muffled backfiring through intake, acting silly....

 

At first, my initial thought was bad gas, but I've dismissed that because of the backfiring through the intake.

 

I haven't been able to dig in it to much because of removing my Zuzu Rodeo's cyl heads [(another long story)(and a huge PITA)]

 

I think its the TPS, or CKS... If the CKS is going it would just stop though right??

 

Could someone give me a quick run down on test procedures on the TPS??? I've did the test once when I bought the truck...

 

I have noticed a high idle sometimes, sometimes its a real low idle, sometimes its just right,,, I'll just say erratic idle...

 

I am getting alot of upper cylinder noise, noticed oil coming into airbox with no CCV blockage, and low oil pressure (2 or 3 psi) when hot at idle with a light knock (bearings I know, I know)

 

Grounds are good, dash has been shaken from halfway removed project replacing the heater core (Thinking ECU a possibility? :dunno: )

 

So tomorrow I will pull the plugs, inspect them, test TPS, and if the first two are fine I'm going to do a compression test and leak down..

 

Isn't there a cam sensor on the dizzy?? Anyone know a test for that??? Thanks :thumbsup:

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Yea.......I'm thinking timing too with the backfiring :hmm:

 

There is a "Cam Positioning Sensor" too -

 

You can find the info Here

 

Unless........

 

Your MJ is jealous at you for buying that XJ :rotf:

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update... TPS within specs. +lead to A= 4.86V +lead to C= .83V

 

Did fuel pressure test..

17/18 PSI switch on

15/16 psi engine running

clamped off return guage went up maybe 2 psi if that

Pressure IS NOT holding when key is switched, a relay beside batt clicks pressure goes to ~19psi then relay clicks and pressure drops.

I have some sort of fuel problem... Pump runs when switched... filter is flowing good,, refurbished rear ground on tail light, banged on tank, still running low..

Going to pull plugs and see if injectors are stuck... be back in a bit.

 

 

Whats the way to test pressure regulator???

 

 

Eagle,, how can I tell if i have water in gas????? Tank level at 3/4

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Right... I thought it should be around 39psi...

 

Pulled all plugs... they look kinda ashy white, telling me running lean... Guess I can rule out leaking injector..

I thought when your pump builds up pressure it stays there.. Like the pump has a check valve on it right??

 

I guess my next step will be dropping a 3/4 full tank..... jamminz.gif

 

 

 

 

:ack:

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The Renix FSM I have posted in the DIY forum has all the testing procedures in it if you haven't looked at that too. Make sure you have done all the proper tests...the right way, on the fuel system before dropping the tank. You likely know this, but...if it's a pump problem you don't have to drop the tank to get at it.

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The Renix FSM I have posted in the DIY forum has all the testing procedures in it if you haven't looked at that too. Make sure you have done all the proper tests...the right way, on the fuel system before dropping the tank. You likely know this, but...if it's a pump problem you don't have to drop the tank to get at it.

I can't open that file for some reason Brent.. I'm at my buddies house and for some reason his pc won't load it or the copy I brought with me on my thumb drive,,,, :dunno:

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It's a ZIP file so you have to be able to extract it first. I don't know what kind of computer you are using, but I thought all versions of windows came with a basic ZIP extractor.

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It's a ZIP file so you have to be able to extract it first. I don't know what kind of computer you are using, but I thought all versions of windows came with a basic ZIP extractor.

 

I tried to extract the file and it pops up saying I need to insert the last disc.. I'm thinking its the windows set-up utility disc thats not installed. :dunno:

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4.0L MPFI

1) Remove cap from pressure test port in fuel rail. Connect

Fuel Pressure Gauge (J-37730-1) to pressure fitting. Start vehicle.

Pressure should be approximately 31 psi (2.7 kg/cm ) with vacuum

hose connected to pressure regulator.

2) Pressure should be 39 psi (2.74 kg/cm ) with vacuum

hose removed from regulator. If fuel pressure is not to

specifications, check for kinks or restricting bends in fuel supply

and return lines. Check fuel pump flow rate. Pump should deliver

minimum of 1.06 quarts (one liter) of fuel per minute with fuel

return line pinched off.

3) If flow is inadequate, check system for plugged fuel

filter or filter sock. Fuel pump flow rate can be checked by

connecting a hose to fuel test port on fuel rail and inserting other

end in clean container.

4) To operate fuel pump, install a jumper wire into

diagnostic connector terminals D1-5 and D1-6. Pinch off fuel return

line to ensure that no fuel returns to fuel tank. If fuel pressure is

still not to specifications and fuel flow is normal, replace

regulator.

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4) To operate fuel pump, install a jumper wire into

diagnostic connector terminals D1-5 and D1-6. Pinch off fuel return

line to ensure that no fuel returns to fuel tank. If fuel pressure is

still not to specifications and fuel flow is normal, replace

regulator.

Where is this diagnostic connector?? Is that those yellow caps things over the relays beside the batt??

Nevermind... Found it... Thought so...

 

untitled-1.jpg

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A lil update...

 

Pulled fuel rail and found gas sitting in # 3 and 4 injector connectors.. Not sure what that means but its what it had..

Didnt see any drips and the o-rings looked pretty good. They were changed before I got the truck.

The pressure regulator seems to be in good shape, going to put a controlled air pressure on fuel rail side and check for any leak down.. Pull a vac on where the vac line goes and see if holds vac.. That should rule out regulator being the culprit..

I still am kinda dumb founded at the injectors having gas in the connector though.. :hmm: :dunno: :hmm: :rant:

Maybe the plastic body has cracks,, maybe the o-ring was leaking.. Either way going with precision ones from Ford.

>>These ones<< that Brent hooked us up with.

Wonder if the gas in the injector was shorting out the injector from opening.. :hmm:

 

The injector ports look like black crusty holes.. I'm going to clean them up by removing the spark plug and pushing air through the the cyl with the valve set on the intake stroke for that cyl.. I guess... Thats the only way I can think to do it without getting the crap in the cylinder.

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Gasoline does not conduct and cannot short out wires. If it did your fuel pump and fuel level sending unit would not work because all the bare connectors, not to mention the electronics themselves are completely immersed in gasoline.

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Gasoline does not conduct and cannot short out wires. If it did your fuel pump and fuel level sending unit would not work because all the bare connectors, not to mention the electronics themselves are completely immersed in gasoline.

 

Well that makes sense... Is there anyway a 4.0l can jump timing??

 

Recap on what its doing...

 

Idle erratic.. Runs better going downhill, no load, like crap with any kind of load..

 

Sometimes I find I have to pump the pedal to get her running at all..

Low fuel pressure, good pump flow, 2 leaking injectors, and regulator seems like it has a strong seal..

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I had an old escort that did something similar and it was the wires.anytime i let off the gas and tried to reapply pressure to the pedal it had no acceleration (like it wasnt getting gas). i would have to put very little pressure on the pedal to get it to "catch" and then it woul take forever to get up any speed.

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Before you do any more diagnosing, get the fuel pressure back to where it should be. Gas in the connectors is an indication that you have a fuel leak at the rail and your pressure not holding when the key is switched on is a confirmation of that. Getting the fuel injectors to seat into the rail can sometimes be a real PITA. Make sure your o-rings are all in good condition with no cuts or you'll most likely get a leak.

 

Once you get 39psi of fuel pressure at idle and with the vacuum line removed from the regulator, report back here and we can go from there, but I have a feeling once you obtain that, your problem will be solved.

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Just thought i would give my opinion. My MJ (2.5l) had the same type of problems (backfiring thru intake etc). I replaced the timing chain and CPS, no good. Then i removed the lifters an noticed that the exhaust lifter on number two cylinder was shot. Next step was to remove the cam and found no lope left on the 2 exhaust. This was causing my issues.

I'm not sure if it possible to remove the lifters in a 4.0 without removing the head but it is on a 2.5.

Hopefully its something with fuel and not mechanical.

Just my limited info.

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Well.. I never did do a compression test... Thing is it only backfired when rpm's were low. above 3000 rpm (if it ever gets there) seems to regain power... Got my new injectors ordered today.. I'll get an compression test done tomorrow afternoon..

 

Two vehicles are down,, now... Getting around is kinda a bi+

 

 

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can't pull the lifters on a 4.0 without removing the head, unlike the 2.5 (just for future search purposes)

 

In my beer-fessional opinion :D loss of power under load coupled with backfiring out of the intake points strongly toward bad ignition. Didja pop the dizzy cap and check underneath?

 

I do agree with the others on the fuel pressure issue, though.....get that straight to eliminate any problems that might be causing, then you can baseline it and troubleshoot from there (but I'm still going for an ignition problem of some sort)

 

Jeff

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can't pull the lifters on a 4.0 without removing the head, unlike the 2.5 (just for future search purposes)

 

In my beer-fessional opinion :D loss of power under load coupled with backfiring out of the intake points strongly toward bad ignition. Didja pop the dizzy cap and check underneath?

 

I do agree with the others on the fuel pressure issue, though.....get that straight to eliminate any problems that might be causing, then you can baseline it and troubleshoot from there (but I'm still going for an ignition problem of some sort)

 

Jeff

 

I did pull the dizzy cap and everything "looked" ok.. Not sure what it'd look like if it was bad,, meaning the pulse mod ring thingy.. I have the fsm page saved to check all those lil sensors, just havent had time to do it..

Dint have time to check the compression but will this weekend,, I hope...

 

I think I'm going to post the fsm on those too so I can find them easier...

As soon as my injectors get here I'll be installing them and checking fuel pressure again..

 

One thing is for sure,, I'd like to do one thing at a time, just so I know exactly what was wrong with it.. Not that it really matters; cause it'd be fixed, but just cause...

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