Topic: Car hiccups when driving at pace

[sharpxmen]

Would worn out spark plugs or spark plugs with a too big gap be responsible for this kind of behaviour?

it can cause misfires so yes, but that depends on how much worn we are talking about - if in doubt replace the plugs with new ones, they are $10/set so really you should have them replaced.

[Jeffy]

What's your gap at?  .035" is stock.  I wouldn't really recommend going less then that.  You might consider checking each plug & wire to see if you get a arc.  If the engine is shaking then you're down a cylinder for sure.  The engine will really feel gutless too.  Idling it would sound almost OK though.  Check your rotor and cap while you're at it.  Although it could possible be a fuel issue as well.  Maybe one of the injectors is going bad?  But then again, it should throw a Code 27 and light up the CEL.

[Eucalypta]

No codes and although it feels a bit gutless I do not feel the engine is shaking. Idling is ok.
There seems a small lag between opening the throttle and picking up refs but thats only a 1/2 second or so.
At WOT on the highway it seems to be dragging and slowing down, while when I release the throttle it feels like the car accellerates a bit.
Injectorcleaner didn't help.
Fuel pressure is ok though (31psi-39psi), fuelfilter has been replaced with the fuelpump a half year ago.

So:
-check/replace spark plugs/wires/rotary cap
-swap injectors with other stock injectors (I can use a set from a friend, which are ok)
-I can hook up the OTC monitor when I get it here and see if it tells me something

What's your gap at?  .035" is stock.  I wouldn't really recommend going less then that.  You might consider checking each plug & wire to see if you get a arc.  If the engine is shaking then you're down a cylinder for sure.  The engine will really feel gutless too.  Idling it would sound almost OK though.  Check your rotor and cap while you're at it.  Although it could possible be a fuel issue as well.  Maybe one of the injectors is going bad?  But then again, it should throw a Code 27 and light up the CEL.

[Jeffy]

At WOT it's probably running lean which is why you lose some power.

If you were dropping a cylinder, you'd know it.  Running on 3 is like running on 1.  It barely has enough power to move the Jeep.

Is this an intermittent issue?

[Eucalypta]

At WOT it's probably running lean which is why you lose some power.

If you were dropping a cylinder, you'd know it.  Running on 3 is like running on 1.  It barely has enough power to move the Jeep.

Is this an intermittent issue?

It is always there: the slugisness at WOT, the 1/2 second lag when opening the throttle valve and the hickupping due tot he sensitve throttle.
It has enough power to run the car and the engine seems to runs smooth.
You see how I am puzzled?

[Eucalypta]

  I hit it...at least part of it....I think...

The transfer case mount has a stabilizer. I did replace it together with the transfer case mount. I must have made a mistake because the stabilizer bolt was not securely tightened.
I tightened the 2 bolts (top and bottom) and it looks like the car doesnt really hickup that bad anymore. Seems it picks up the throttle bit better to make the car move forward. Also, the stickshift isn't moving sideways as much as before.
Still the stabilizer doesn't seem to be mounted properly:

It looks like I am missing some parts on it.
I can tighten it to the skidplate but I cannot tighten the rubbers on top of it to the transfer case bracket.

Parts I have on the stabilizer from top down:

Nut
Washer
Rubber (with narrow part down)
[transfercase bracket]
Rubber (with narrow part up)
Washer
[Nut of the stabilizer]
Washer
[Skid Plate]
Washer
Nut

Can anyone tell me if there should be something else on the stabilizer? Maybe an extra nut so I can tighten the stabilizer with the rubbers tightly to the bracket or something to push the rubber upwards to the bracket?

The sluginess at WOT still is there; that problem I still have to tackle...

[Jeffy]

Sounds about right.  The rubber bushings pass through the transfer case bracket and don't clamp tight against it.

If you want to firm it up then get some poly motor mounts.  That will really firm it up.  You'll end up with vibrations throughout the Jeep though.  You'll feel it mostly when idle, everything will shake.  Some things might not like the vibrations though, like the exhaust.

As for your WOT problem, did you ever say at what speed and at what RPM you're at right before?  Also, what gearing you have?

[Eucalypta]

Nah, don't like the polyurethane mounts; too stiff.
I tightened the rubber TC mounts on the stabilizer by adding some rings under it and the stick shift is not moving so much anymore, also the ride seems better.
Don't know if my stabilizer or skid plate likes it though....

I haven't really noted at what speed/rpm's it occurs.
I have 4.11 gears and 33" tires; I think get about 2500 rpm and would go 115 km/h (72 mph) on satnav in 5th gear.
Most of the times I do not go over 100 km/h (62 mph) but I notice it when I overtake a truck driving in front of me; when pushing the throttle, the car seems to slow dawn, when releasing the throttle a bit,the car seems to speed up.

[aw12345]

That last bit means it does not get enough fuel, not enough fuel volume under full load.

[sharpxmen]

That last bit means it does not get enough fuel, not enough fuel volume under full load.

x2

[lqdtrance]

I had a similar problem with my Jeep. Turned out to be the MAP sensor. I had to bend the bracket down so there wasn't as much tension on the wires and replaced my MAP sensor. Never had the problem again. I changed my distributor, cap, wires, fuel pump, cleaned out fuel tank, checked exhaust.... everything. Friggin MAP sensor was all it was.

[alext1399]

i had a similar problem in my yj, and it took me forever to figure out what it was. it turned out to be my distributor. the upper support bearing in the distributor was shot so there was a wiggle in the shaft and when there was a hard load on the motor it would get sluggish, hesitate, and buck back and forth. so the air gap on the cam sensor in the ditributor was loosing signal, easiest way to check it is to pull the distributor cab and rotor off and grab the shaft and see if it has a side-to-side wiggle, if it moves at all replace it and you should be good

[Eucalypta]

That last bit means it does not get enough fuel, not enough fuel volume under full load.

Presure is checked: OK
How much should the pump deliver? And should this be before injectorrail and presure regulator (no presure on pumpcurve) or after the injectorrail and presure regulator? The volume could collapse when the pump has to deliver under pressure.
If the injectors have passed some water/fuel mixture; would that damage them in a way they would deliver less fuel/pulse ??

MAP should be ok...the OTC doesnt throw a code. Anyone know what voltage should be comming out of the MAP under what condition (pressure)?
In the danger of sounding stupid...what does the MAP do? Does it advance the ignition (like the vacuum timing advance of a carburetor)?

Will check on the distributer tomorrow; it's dark and cold outside now...

[aw12345]

You would want to see what the fuel pressure is when it acts up, to test the pumps volume test pressure at top speed in top gear preferably going up hill which is a bit hard for you in flat waterland, you could ride the brakes a bit to lug the engine some more. Map voltage is roughly 1 volt at idle and around 4-4.5 at wide open throttle. You can drive it at top speed and see what the fuel trim does with the scanner have somebody ride with you to check the readings, if it adds a lot of fuel well then you know what to do

[Eucalypta]

Been wheeling it a lot since my last reply.

I did check the fuel pressure, also the 2 second pinching of returnline and it all seems to be working within specs, the MAP sensor also seems to be fine according to my OTCscanner. (Thnx Torch_Ind)

Maybe I finally learned to drive or the problem has miraclely gone.

It is frustrating not to know what the problem was or if it could re-occur but for now I am happy with how the car handles.
Thanks for all your help!

On to the next projects:
-overhauling the clutch and AX5 gearbox
-mounting a tirecarrier
-buying and mounting a winch (not a Witch)