Topic: Gas in the intake manifold

[MYSTANGT]

Hey guys,

my 4 banger 97 TJ seems to have gas puddling in the intake manifold. I took off the filter/hose and opened the TB by hand and smoke started coming out. It smelled like gas and there was gas residue which i could feel with my fingers when I put them in the manifold. Inside the manifold and on the inner part of the TB.

The Jeep also doesnt idle perfect and makes some popping noise from the exhaust that sounds like unburnt gas in the exhaust - but no odd smell like its running too rich and lastly cranks a bit longer than normal before it actually turns over.

I also did replace injector #1 not too long ago as it was not spraying like the others. With the circuit tester I can see that all injectors are firing correctly but there's gas puddling in the intake....

ideas what this may be?     

[sharpxmen]

Hey guys,

my 4 banger 97 TJ seems to have gas puddling in the intake manifold. I took off the filter/hose and opened the TB by hand and smoke started coming out. It smelled like gas and there was gas residue which i could feel with my fingers when I put them in the manifold. Inside the manifold and on the inner part of the TB.

The Jeep also doesnt idle perfect and makes some popping noise from the exhaust that sounds like unburnt gas in the exhaust - but no odd smell like its running too rich and lastly cranks a bit longer than normal before it actually turns over.

I also did replace injector #1 not too long ago as it was not spraying like the others. With the circuit tester I can see that all injectors are firing correctly but there's gas puddling in the intake....

ideas what this may be?     

injector leaking, too much fuel pressure, O2 sensor reading off (can be a bad ground as well). Could be other things too but these are the most obvious. Make sure that your MAP vac line is not leaking, plugged or disconnected (but if it was disconnected would run pretty badly or not at all) - and since you have a TJ could be on the t/b so disregard the vac line comment if that's the case.

any codes?

[MYSTANGT]

No codes...nothing at all which is kinda odd.

My MAF sensor is on the TB itself and I dont think that i have vacuum leak. I feel like i'd hear it (meaning i supsected that before and did not find one - and i looked really hard)

Whats weird is that I di suspect that theres something odd about my fuel pressure too...but i always thought that it was weak because of my long cranking times but too high would make sense in the gas in intake issue....

I dont know what to think anymore....

Can i just swap a set of 19lbs injectors from a Ford and see if it helps in case it is a leaky injector?   ***without having tuning issues?   

[sharpxmen]

No codes...nothing at all which is kinda odd.

[...]
Can i just swap a set of 19lbs injectors from a Ford and see if it helps in case it is a leaky injector?   ***without having tuning issues?   

not on TJ, you have different pressure and flow rated injectors (read the injector FAQ)

i would suggest to check the pressure first to make sure you have it at the correct value. Also you could check the injectors to see if they leak when not running. If one of them squirts it can cause the same symptoms - you can try and unhook the injector connectors one by one at idle and see if one of them does not cause the rpm to drop (or very little compared to the other ones) - that can indicate which one squirts and not atomizing properly. You can also try the same test with the spark plug wires (carefully so you don't shock yourself). Also you can take the spark plugs out and see if any of them is wet as well - if they all look the same then it's a global issue and not isolated to one injector (like fuel pressure or some sensor), if they are different then it's related to one or more injectors but common sense would suggest that anything that controls all of them is not the cause (sensors, fuel pressure, etc). Try and eliminate possible causes so you can narrow down to the remaining ones.

[MYSTANGT]

hmm...

all the plugs are fine as I did check that since i originally thought that it was a spark issue...

I have a set of 19 lb injectors from a 96 4.6 mustang so ill pop them in and see what happens.

Can you tell me where i can get ahold of a fuel pressure gauge and what should i be seeing when i hook it up?

And do the 4 banger TJ's have a shredder valve and where is it located?  (im just asking because i dont recall seeing one when i was replacing injector #1 two weeks ago but ill double check tonight)

[FourbangerYJ]

hmm...

all the plugs are fine as I did check that since i originally thought that it was a spark issue...

I have a set of 19 lb injectors from a 96 4.6 mustang so ill pop them in and see what happens.

Can you tell me where i can get ahold of a fuel pressure gauge and what should i be seeing when i hook it up?

And do the 4 banger TJ's have a shredder valve and where is it located?  (im just asking because i dont recall seeing one when i was replacing injector #1 two weeks ago but ill double check tonight)

Those 19# injectors will be to lean for the TJ 2.5. You need 24#. The schrader valve in on the fuel rail.

[neale_rs]

Could this be a valve problem?

[MYSTANGT]

That did cross my mind but I figured its not as there is no noise and a stuck valve would really have no relation to the long crank times.

I am wondering, if the injectors dont spray in the umbrella pattern correctly, can i just clean them up with some alcohol and a little brush?

and when i have them out i'd like to replace the o-rings but cant find a kit....

what does a rebuild injector kit consist of for a 4 cyl 2.5L?

is it just 1 o-ring per injector or are there 2 per injector?

[FourbangerYJ]

There are 2 O rings. One at each end.
http://www.fiveomotorsport.com/Injector_Sets.asp

These guy's should have some O rings.

[sharpxmen]

That did cross my mind but I figured its not as there is no noise and a stuck valve would really have no relation to the long crank times.

I am wondering, if the injectors dont spray in the umbrella pattern correctly, can i just clean them up with some alcohol and a little brush?

and when i have them out i'd like to replace the o-rings but cant find a kit....

what does a rebuild injector kit consist of for a 4 cyl 2.5L?

is it just 1 o-ring per injector or are there 2 per injector?

o-rings and filter cups won't fix the atomizing or leaking issues on the injectors. you can't clean them with a brush - it's the pintle that goes bad or dirty (or the seat of the pintle) and that you can only clean under pressure with a special solution and an ultrasonic cleaner (and it's not guaranteed to work). If you have only one injector faulty would cost you as much to just replace that one as it would to "rebuild" all 4 (note the quotes, you can't really rebuild injectors unless they're old style diesel ones).

you need to find out why you have the issue though, the injectors could be good - you could be spending time on them and not solve the problem - find the cause first, will cost you less in time and money.

[neale_rs]

I read a bit in the FSM and it seems it could be a problem with the injector pulse timing.  Maybe it is spraying a bit late from when the intake valve is open. Otherwise it seems the gas would get sucked into the cylinder even if the spray pattern is a bit off.

Inputs That Effect Fuel Injector Pulse Width:
 Exhaust gas oxygen content
 Engine coolant temperature
 Manifold absolute pressure (MAP)
 Engine speed
 Throttle position
 Battery voltage
 Air conditioning selection
 Transmission gear selection (automatic transmissions
only)
 Speed control

The FSM says the synchroniztion is based on signals from the Crankshft position sensor and the Camshaft position sensor.  It may be a good idea to check these out.

[aw12345]

First of take a engine vacuum reading at idle, any engine diagnosis should start there
If the vacuum is good and steady then test the injectors on the Jeep it is not that hard. You need to find a little gadget from a good parts store or a tool truck that pulses the injectors and a pressure gauge. The basic idea is simple you pressurize the fuel rail pinch of the fuel line or lines so the pressure cannot bleed off. Then watch the gauge for a bit, in your case it most likely will bleed off slowly, which would mean a leaking injector or a pressure regulator that leaks internally. If that is good pulse each injector while restoring the fuel pressure after each injector test. The pressure drop for each injector should be close to equal for each injector If all is good then I would not worry about it

[MYSTANGT]

AH!!!

Could it be just a coolant temp sensor?

Mine seems always seemed a little flaky imo...it always reads low and sometimes ill turn the key on and the temp will be 200 but the moment I actually turn the Jeep on, the temp drops to 160 and goes up from there accordingly.

My Jeep will NEVER get up to 210. I have no AC and obviously no condenser so i made a little radiator block shield from cardboard but no difference. The Jeep still will NOT get over 190 whether its been at idle for 20 min or me driving full speed. On the highway its usually at 185 and about 180 at idle. BUT if im at idle and hold the gas pedal up to 1100 it will raise to 190 (the only way i have heat in the cab)  

Could the faulty sensor be reading too low and therefore causing more injector spray as the car is not at operating temp yet?

Any other reason that it might be staying at such low temps?

[aw12345]

The temp sensor for the gauge, would have no effect on running it uses a seperate one for the ECM. Check the temp at the thermostat housing with a infrared temp gun or just change the thermostat with a 185 one and be done with that part

[MYSTANGT]

I just replaced the thermostat with a 195 Stant thinking my old one was stuck open.

So the coolant temp sensor in the thermostat housing simply sends the reading to the gauge?

Doesn't it also tell the ecu what the temps are so that it can act accordingly?  (i may very well be wrong, i am just asking)