Topic: Hesitation at 45mph

[bluebomber]

OK, here's the latest update.  I disconnected the lockup solenoid to take it to a tranny shop and had them check out the driveline.  It ran like crap.  They said the driveline looked fine but it felt like I had a miss somewhere.  My brother and I checked the timing over the weekend and it was running around 12 degrees.  I know that timing can't be set because it's computer controlled and the reading I got probably wasn't 100% accurate.  We also checked the compression on #3 cylinder just to make sure that I was getting compression and it came out to about 135 pds. engine cold.  We didn't check the rest because it was a PITA to get the gauge into the plug hole.  I found a plug wire that wasn't crimped correctly, fixed it and the Jeep had more power, duh.  I'm still occasionally getting a miss which is causing the lockup converter to not operate efficiently. Plugged the lockup solenoid back in and I ran the Jeep around the block yesterday, about 8 miles, and everything seemed fine.  I dumped two bottles of gumout injector cleaner in the tank with a 3/4 tank of gas.  I also checked the oil to see if there was any coolant leak and the oil looked fine.  When I brought it into work this morning I let it run for about 5 minutes and then started on my journey, about 25 miles.  I was OK initially but about half way here it started to miss and buck when the converter locked in.  I also noticed a slight miss/hesitation in 1st and 2nd.  It didn't happen all the time.  My brothers friend said that it could be the fuel pump but fuel pressure has been checked by the garage that installed the motor and they said I was getting about 45 pds of pressure.  It kind of leads me to believe that I may have an injector problem.  I'm going to take the Jeep home tonight and check the plugs out for color.  My brother has a fuel pressure gauge so I'm going to do that sometime this week.  To recap:

New rebuilt engine, map sensor, plug wires, plugs, cap, rotor, TPS, IAC, Magnaflow catalytic converter, Borla cat back exhaust, Air Hog high flow air filter, two bottles of gumout in the fuel tank.
About 200 miles on the rebuilt motor.
No codes found after about 8 attempts with a scanner.

Problem:  Slight sporatic miss/hesitation between 1st and Drive,  rough idle when in Park and at stop.

1.)  Could I have a weak fuel injector?  The # 4 cylinder and head gasket went in the original engine, that's why I replaced the motor.

2.)  Is there a way to check the injecters using an Ohm meter?  If so, does anyone know what the resistance should be?

3.)  Should I drive the jeep for a while to see if the condition changes?  I only have 200 mles on it and it seems to happen only under load.

4)  Is there maybe something else I should be looking at?  I have no codes to go by so I'm at a loss right now.

       

[sharpxmen]

OK, here's the latest update.  I disconnected the lockup solenoid to take it to a tranny shop and had them check out the driveline.  It ran like crap.  They said the driveline looked fine but it felt like I had a miss somewhere.  My brother and I checked the timing over the weekend and it was running around 12 degrees.  I know that timing can't be set because it's computer controlled and the reading I got probably wasn't 100% accurate.  We also checked the compression on #3 cylinder just to make sure that I was getting compression and it came out to about 135 pds. engine cold.  We didn't check the rest because it was a PITA to get the gauge into the plug hole.  I found a plug wire that wasn't crimped correctly, fixed it and the Jeep had more power, duh.  I'm still occasionally getting a miss which is causing the lockup converter to not operate efficiently. Plugged the lockup solenoid back in and I ran the Jeep around the block yesterday, about 8 miles, and everything seemed fine.  I dumped two bottles of gumout injector cleaner in the tank with a 3/4 tank of gas.  I also checked the oil to see if there was any coolant leak and the oil looked fine.  When I brought it into work this morning I let it run for about 5 minutes and then started on my journey, about 25 miles.  I was OK initially but about half way here it started to miss and buck when the converter locked in.  I also noticed a slight miss/hesitation in 1st and 2nd.  It didn't happen all the time.  My brothers friend said that it could be the fuel pump but fuel pressure has been checked by the garage that installed the motor and they said I was getting about 45 pds of pressure.  It kind of leads me to believe that I may have an injector problem.  I'm going to take the Jeep home tonight and check the plugs out for color.  My brother has a fuel pressure gauge so I'm going to do that sometime this week.  To recap:

New rebuilt engine, map sensor, plug wires, plugs, cap, rotor, TPS, IAC, Magnaflow catalytic converter, Borla cat back exhaust, Air Hog high flow air filter, two bottles of gumout in the fuel tank.
About 200 miles on the rebuilt motor.
No codes found after about 8 attempts with a scanner.

Problem:  Slight sporatic miss/hesitation between 1st and Drive,  rough idle when in Park and at stop.

1.)  Could I have a weak fuel injector?  The # 4 cylinder and head gasket went in the original engine, that's why I replaced the motor.

2.)  Is there a way to check the injecters using an Ohm meter?  If so, does anyone know what the resistance should be?

3.)  Should I drive the jeep for a while to see if the condition changes?  I only have 200 mles on it and it seems to happen only under load.

4)  Is there maybe something else I should be looking at?  I have no codes to go by so I'm at a loss right now.

       

your Jeep should have 49psi fuel pressure, so if it's 45 that is insufficient - the shop should've known that. If that's at idle then for sure under load would go even lower.

also, you're saying one of the wires was not crimped and then you re-crimped it - i would just bite the bullet and buy a new set - should be around $20 for a generic one.

1. you might but since the fuel pressure is below required value i would check that first.
2. yes, but that would not account for a plugged or leaking injector - the Jeep injectors are high - impedance, that means they should be between 12 to 16 ohm (dunno the exact value in your case) and you should not have a difference higher than 1 ohm between them (measure all 4 if you do it). A faulty injector solenoid would trigger a CEL i believe, so i don't think that's your problem but doesn't hurt to verify. Again, if the injector is plugged or leaking or squirting it will not come out on the impedance value.
3. If you're running lean i would suggest to fix the problem first, that can affect the life of the engine so imo you shouldn't drive it like that if your pressure is below required value (but again, since you have an '01 the low fuel pressure should trigger a code, something like "unusual lean/rich afr correction factor was triggered by a rich/lean condition" or something like that)
4. I would say to make yourself a fuel pressure gauge and drive around monitoring that (just because the shop said it was at 45psi) - seems the best lead so far


have to mention that if this is auto-tranny related i have no experience with that so by no means i am excluding that possibility, all the above is just my guess on the matter.

[bluebomber]

Thanks for the reply sharp.  I agree and that's why I'm going to check the fuel pressure again when I get the gauge from my brother.  He's a fork lift mechanic and knows the troubleshooting tips, I finally broke down and called him this weekend.  He also keeps me from banging my head against a wall or running out and just buying parts.  The garage said that the pressure was "even" throughout throttling the motor.

The wires I used were a generic brand and I was thinking about buying some Bosch pre-fit ones.  I hate to waste the money on some Accel since it's such a short run.  When I fixed the wire I made sure that I ran the electrode on the solid side of the terminal and clamped it down.  After that the Jeep ran great.  No more generics for me.  I was surprised at how well it ran actually.  Shifted nicely without any hesitation or miss.  It had nice power throughout all shifting ranges.

I'm also going to check the resistance on the injectors tonight and report back what I found.  I thought maybe an injector could be partially clogged and incorrectly supplying fuel. 

I've read that some injection systems will try to make up the difference in pressure between injectors.  does the injection system on the '01 2.5 have this type of setup?

Do you think that what I'm assuming is a miss is being caused by the fuel pump/filter in the gas tank?

[MYSTANGT]

I had some issues with fuel recently that i couldnt figure out for the life of me.   

I had a misfire at idle and the car was weak to say the least. It drove fine and no codes but it just wasnt right. I didnt ahve the stuttering like you but maybe because i have a 5 speed. I did however have issues going up the slightest hills and I felt the car bucking while trying to make it up...maybe you are experiencing the same thing but your computer is locking in gear to help you haul up... i wouldnt have that happen as i was the one downshifting and staying in gear revving it out to make it up.

Finally I replaced the injectors and the car feels really strong (for a 4banger at least) and the idle is now steady.

When i had these issues I had no codes, no CEL and a few mechanics weren't able to tell me what the issue was. No one pointed me in the right direction.    thats why i decided to bite the bullet and start throwing parts at it. I was EXTREMELY lucky to have guessed the issue off the bat but thats usually not how it happens.

I hope this was of some help....

PS - check if you have any gas residue in your manifold. Mine used to be really moist and you can smell the gas a lot if i opened my TB after just shutting the car off.

[bluebomber]

yeah, this a real head twister MYSTANGT because I'm not getting any codes.  If I had some codes to go by it would be a lot easier.  The only reason I'm thinking it's an injector is because #4 cylinder broke apart in the old engine.  Maybe I'm just getting an ongoing problem from the injectors.  If the fuel pressure checks out I'll probably change the injectors next.  I don't know.

[sharpxmen]

if the pressure was constant at 45psi while driving it (so that means under load and wot) then it's one of 2 things:

1 - their fuel gauge is off by 4psi
2 - your fuel pressure regulator is off by 4psi (but in this case would not explain the miss and rough idle unless you go wot - o2 feedback should be able to compensate in closed loop and it could be that a CEL would not be triggered, not sure).

[bluebomber]

I can't say that they drove it with the pressure gauge on.  I'm not sure if I'll be able to either.  I'll know more when I get the pressure gauge from my bro.

I checked resistance on the fuel injectors and they were 13 across the board.  Am I to assume that they are good then?

I also pulled the #3 and #4 spark plug.  the garage put Bosch platinums in.  I wonder if that could be the problem since I checked them side by side with some Autolites specified for my vehicle and since the electrodes are of a different type they didn't reach down into the cylinder as far.  the Autolites had an "L" shaped electode like the old standard and the Bosch had two short electrodes on the sides. ?? 

I think I'll stop by the Jeep dealer and get the equipment for a stock tun-up so I'm starting from square 1.

[sharpxmen]

...
I think I'll stop by the Jeep dealer and get the equipment for a stock tun-up so I'm starting from square 1.

you can do that no prob, but why not try to buy a set of recommended NGK spark plugs for $12 (or even cheaper i think) and take it from there - you'll find the correct ones in any catalog at any parts store (dealer costs will take you about $8/plug at least). up to you.

can't remember if if mentioned this in here or somewhere else: when was the last time you changed your fuel filter? if you never did and you dunno when it was changed i would just go ahead and do it prior to your fuel pressure check - that way you don't have to wonder if it's the filter or the pump if you find something (add the FPR in there as well).

[bluebomber]

I've read that some aftermarket plugs cause misfires in different vehicles.  I didn't want to use a plug that wasn't suggested by the manufacturer, I have two sets of those already. 

Since the fuel pump, regulator, and filter were all in one place on these models, the tank, I was trying to avoid dropping the tank unless I knew for sure it was one of the three.  If the pressure test comes up bad then I'll probably just go ahead and replace all three to get it done.  I hate the idea of dropping the tank more than once.  I wish they would have left it like the olden golden days and made everything accesible outside of the tank.  That way you could check/change each part without the headaches of removing the tank.

[sharpxmen]

I've read that some aftermarket plugs cause misfires in different vehicles.  I didn't want to use a plug that wasn't suggested by the manufacturer, I have two sets of those already. 

Since the fuel pump, regulator, and filter were all in one place on these models, the tank, I was trying to avoid dropping the tank unless I knew for sure it was one of the three.  If the pressure test comes up bad then I'll probably just go ahead and replace all three to get it done.  I hate the idea of dropping the tank more than once.  I wish they would have left it like the olden golden days and made everything accesible outside of the tank.  That way you could check/change each part without the headaches of removing the tank.

i'm pretty sure you have a filter outside the tank on the driver's side ahead of the rear axle, the one in the tank is the pre-filter (also called the sock  for some reason). the filter outside the tank is meant to be replaced just like the air filter and the oil filter, on a regular basis. It has more filtering capabilities than the one in the tank (the one outside is finer) and is meant to protect the fuel injectors.

I was not suggesting to use spark plugs that are not recommended by manufacturer, ngk and denso are very good plugs for the money and i have ran them in my Jeep for quite a while to be able to tell that they work 100% - chosing one from the catalog means it will be made specifically for the engine based on manufacturer specs of head length, heat range, resistivity and whatever else - but that doesn't mean there's any harm in buying from the dealer.

[MYSTANGT]

Please do share if there actually is an external filter. Ive been putting away changing mine so that i can change the pump and regulator at the same time as well.

I will be extremely happy to hear that this is true!  =) 

[sharpxmen]

Please do share if there actually is an external filter. Ive been putting away changing mine so that i can change the pump and regulator at the same time as well.

I will be extremely happy to hear that this is true!  =) 

i did a quick search on google and I got mixed results - one said that is on the frame covered by piece of metal, and quite a few said that on the TJ the only filter is in the gastank (Chrysler had me on this one, what a bummer) - anyway, with about 10 to 1 in the favour of no external filter seems that I have been wrong assuming there is an external one like in tons of other efi engines - this is imo a design flaw, why in the world would you need to drop the tank to replace the filter beats me

[Jeffy]

i did a quick search on google and I got mixed results - one said that is on the frame covered by piece of metal, and quite a few said that on the TJ the only filter is in the gastank (Chrysler had me on this one, what a bummer) - anyway, with about 10 to 1 in the favour of no external filter seems that I have been wrong assuming there is an external one like in tons of other efi engines - this is imo a design flaw, why in the world would you need to drop the tank to replace the filter beats me

TJ's have a combination fuel filter/fuel pressure regulator that sits on top of the tank.

[dwtaylorpdx]

YJ's have the frame mounted filter below the driver area.

Just to complete the data set! :)

Dave

[sharpxmen]

TJ's have a combination fuel filter/fuel pressure regulator that sits on top of the tank.

so you need to drop the tank for that then? unless there's another way to do it that's a pretty stupid setup, i like the YJ fuel system better - not to mention the no schraeder valve on the fuel rail either. I wonder why they didn't put a access cover in the tub i that case.