Ibanezz

Hi guys, have been having a very weird problem, and now that its been getting colder out, its been getting worse.. And since this is my winter vehicle, I am getting worried, and would really like to get this issue fixed before the snow flies..
This is a 95 Cherokee 4.0 automatic.. OBD 1

So... the car has always taken a while to start, takes a couple seconds for it to finally kick over, although when its hot it starts quicker.. but when its cold out, on cold starts, the car will want to stall right out.. in order to avoid it stalling you must keep it at at least 1500 RPM for about 30 seconds, then it will be okay, but if you give it just a little gas, it will make it stall even faster.. The really strange part, is that if it does stall, it will immediately start right back up and run absolutely fine, without any issues....

Since I have gotten this car in June, it has a completely new ignition system (new wires, spark plugs, cap, rotor, and distributor). While trying to fix this issue i changed the TPS sensor, IAC Valve, and cleaned the Throttle body. And a new fuel filter.Nothing affected it.. and as far as I know, i don't have any vacuum leaks

on a side note, but could possibly be part of it, is when it does start without stalling, if I dont let it sit and idle for a good minute before slapping it into drive and going... if you just touch the pedal a little bit, the RPM's drop and feels like it wants to stall, you have to give more than just a little throttle.. But thats only for the first minute.. strangest thing..

Do our jeeps have MAF or MAP sensors that could be part of the problem? Or does it sound fuel related? (FPR, injectors, fuel pump). Or could it be a bad PCM??

Any and all input is greatly appreciated.. Thank you for your time.

syncview

check your ground connections and battery terminals - make sure they are good else renew them

check for vacuum leaks and make sure there are none - the best method IMO is the propane - search online how to use propane to find vacuum leaks - 1st check with a dead cold engine then check with engine at operating temperature

check fuel pressure - everything you mentioned sounds like the fuel pump is being lazy and its check valve is bad

it can also be a leaky injector - separate the injector rail from the manifold, place a shop rag under the injectors. . Power up the fuel pump and check closely if any injector leaks. Any injector that leaks more that 2 drops a minute needs to be replaced. .

does your engine have a FPR on the fuel rail? if it does, pull its vacuum like from the manifold end and run the engine for about 5 mins, check if it leaks fuel from the vacuum line. if it does, its kaaaput...

is the TPS adjustable on this one? have you checked if the TPS you have fitted works fine?

Ibanezz

Thank you for the reply. Those all seem like relative parts that could be plaguing me... As long as it isn't the fuel pump, then I'll be content.... I have been wanting to check the fuel pressure. Haven't been able to find a thread that shows my year, with the pressure it should have when the car is off with ignition on, and then the car running...

Is that the procedure to check if the FPR is bad on the 4.0? My other car, you just pull the vacuum line and if you smell gas its bad...

I have no idea if the TPS is adjustable. But as far as I know, it isn't, only had a plug connector, and the 2 holes for bolting it to the tb.

Will definitely inspect my grounds. Any insight into the locations of all the major grounds are?

Roler

Have a look on the Great Info Threads sticky. CCKen has a few good pics of the grounds. Battery to fenderwall, dipstick tube to the block, grounds near the coil, grounds near the PCM side fenderwall and groundstrap back of the block to firewall.

frado2jr

The Map sensor is on the driver side firewall. It has a 3 port wire comming from it. Yours sounds like something my truck was doing

Ibanezz

Was about to buy a map sensor when I was under the hood. Found that the vacuum elbow on the FPR is completely shot. Parts store don't carry them. Does anyone have a part number and know where to get it? Would like to change that out before I drop another 40+ on a MAP sensor and 50+ on a FPR

Ibanezz

Well, figure I should post an update. New FPR and MAP didn't have any affects. But during last week I noticed it was taking even more crank time to get the engine to start, until ultimately I was left stranded at the grocery store and had to get a tow home.. Figured the fuel pump finally died. Swapped that out with my brother, and was still having issues starting.

On the few occasions it finally did start, idle was sparatic, ranging from 400-500 (amazed it was even running) to surges at 1200.. and other times it would idle perfectly at 750-800... When it did die or we turned it off, we couldnt start it back up. rented a fuel pressure gauge before the whole ordeal to make sure it was the pump and not wiring issues, and after it died, fuel pressure was instantly dropping, and was only at 18psi to start with... so was losing pressure at the fuel rail.. could almost hear a faint hiss..

Turned out, probably due to my own error, that the o ring on the new FPR i put in was torn. Realistically was probably the cause of my jeep being dead in the water at Wegmans... but it was almost a good thing as I knew the fuel pump was dying and I was hesitant to undertake that..

Car definitely runs better, and takes less time to crank over than before. But I am still plagued with two issues that are probably related, and hope you guys can help me with.

On very cold start up, the engine stalls out a few seconds later. And as of this morning, about 25-30* out. It died twice upon start ups, and then is fine...

Secondly, also on cold start ups, but after the stalling and its running fine. For the first couple minutes before its up to normal operating temps, if you just touch the throttle a little bit, instead of the RPMs increasing, they actually drop. Feels like a stutter, until you get to a certain point and then it Revs like it should..

At this point, things that are new include
Plugs, wires, cap and rotor
TPS and IAC valve, and cleaned the TB completely
New fuel pump, filter, fuel pressure regulator and vacuum fitting going to the FPR
MAP sensor.


What else could cause the issues? At this point I feel like it has to be electrical, or a sensor.. Crank position sensor? ECM? are there any air intake temp sensors? Thought I saw some sensor on the top of the intake manifold near the firewall, but was unsure what it was. Could an o2 sensor be to blame?

car is a 95 with OBD1 so I am not as familar with how the computers work and cope than OBD2

Ibanezz

Oh, and what exactly is the Auto Shutdown? I read a lot about people just telling others to check the relay and make sure you're getting power to the relay box and all that. But what exactly does it do and how does it work?

Ibanezz

So just wanted to leave an update. Maybe this will help someone in the future.

So made it through winter. Had no improvements even with everything I replaced. During summer I believe my thermostat became stuck open. So I replaced that, the coolant temperature sensor, and did a coolant flush. Wouldn't ya freaking know it, the car now starts up with ease. Starts quickly, much less hesitation... I cannot comment on the stalling issue, as it only occurs in cold weather, but I am very hopeful that it is fixed, but will let ya know. Flabbergasted is an understatement to how I feel. Never would have guessed the ECT sensor can cause an issue like that.

Is this sensor the type with two outputs? One goes to the dash for us to see and a different reading goes to the computer for calculating temps and what not? Because the dash gauge seemed very accurate. Have to assume the computer was getting a bad reading and assumed it was either hot or cold on start up. Regardless. Glad it wasn't my computer. And hope anyone else with a similar issue can get it worked out.

ElMartillo

I'm beginning to experience a hesitation right off idle when the engine is cold. Otherwise always starts up and runs fine cold or hot. I'm going to replace the coolant temp sender for the ECU to see if it helps.

Ibanezz

Let me know how that goes for you! Would love to see my troubles help someone out. Such a strange solution lol

R3vpanda

@Ibanezz Did you ever solve the stalling issue? I am starting to see this with my 98 V8 GC limited and it's bugging me to all hell.

SilverfoxXJ

Hi panda-did you ever solve this or by a Toyota?

R3vpanda

Kinda It's a bit of a crapshoot but here's what's worked for me
high quality Idle air control valve.
Replaced the pcv grommet and valve.

Hope this helps really this issue can be a bit difficult to get to the bottom of. I would also suggest taking a look at your serpentine belt.
Mine was due for replacement and made a world of difference.​​​​​

SilverfoxXJ

I reconditioned a throttle body last year, with all new TPS,IAC (German made) and map unit, but with one thing and another never got round to fitting it??
Hence my question? I assume you mean the valve on the rear of rocker cover? I already checked the front hose to filter box and ther are traces of oil?
so rear one may be clogged? I have owned this old girl since 1997 (ex fleet ) and it has served me well now like me it is enjoying retirement at 400,00 kilometres
Replaced CPS , Cam sensor, plugs and coil in the last few weeks- but putting old coil back as it showed 13000 and new aftermarket showed only 6000 !
All I ever changed over the years is full exhaust headers and cats ,in 2004 You could get a complete system made up for the price of a US exhaust manifold on its own??
Oh yeah have run on 15w40 DIESEL oil last 23 years changed once a year with filter? Cherokees love the extra ZINC in the oil !
Thanks for giving me confirmation panda