average mileage in the city for a 4.2L

has anyone checked their city mileage for a 4.2L?

As I listed earlier I changed the carb and header on my 89YJ, 31" tires I dont know the gearing (stock im sure), and the thing is running sweet. BUT I just checked the mileage.....10.50 MPG!!! I have another issue that is not helping, maybe you guys have some ideas. The choke is sticking on the last stage. The linkage is loose and everything seems fine, just a lot of metal grabbing. so in stop and go traffic idling at 1000-1200 instead of 800 would make a fair bit of difference wouldn't it?

any suggestions are appreciated.

Reply to
Pi-eyed Piper
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That is crappie mileage. First I would check the odometer to see how far off it is with the 31's on there. Even if they are off 10% though you still would be getting crappie mileage.

The only 2 reasons the fast idle is staying on is dirt or the choke is bad. Some carb cleaner spray on the linkage parts can do it wonders.

Then figure idle at 500-700 vs 1200. 1200 isn't a good thing.....

Will the idle come down to 500 or 600? It should come really close to that, mine is running around 600 right now. If it won't maybe the mix is off or the idle tubes are plugged which is an easy fix.

Does the choke have a good electrical connection?

Is the computer having a brain fart clamping it into 'limp home' mode or did you wire the ignition module direct to the distributor to bypass it or put some other system in?

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Pi-eyed Piper wrote:

Reply to
Mike Romain

The system has no computer, it's gone when we changed the carb and installed the header. The carb is from a 77 CJ, NO emissions stuff at all.

I am using the electric choke from my old carb. The choke is set to 1800 rpm, then the second stage is set to 1200RPM. Thats where it sticks. It will kick off from 1800RPM to 1000-1200 no problem. then I have to pop the hood and manually take to choke off the last "tick" so it idles at 700RPM (which is does fine).

This is a brand new refurbished carb, using the OLD electric choke. I sprayed the linkage when we installed it and thought it would "work itself out" but it's been almost a week.

Reply to
Pi-eyed Piper

also, when we were setting the carb up it would idle as low as 400rpm...

Reply to
Pi-eyed Piper

Mine is running a little rough right now, but I am still getting close to

20mpg. I recently rebuilt the carb, just needs a plugs, wires, cap tune up and I should back to 24ish.

Reply to
Rusted

Reply to
L.W.( ßill ) Hughes III

You have a dirt issue or the connecting rod isn't installed correctly. Not a very encouraging thing to see on a 'new' carb. That counter weighted idle stepper should flop open on it's own easily. If the connecting rod is on backward it might bind or it just needs a good clean on the shaft. The shafts do get corroded/pitted and can need to be polished up with emery paper. That should have been done when the carb was made 'new', but having one dead out of the box seems to be par for today's poor excuses for rebuild techs.

I personally have seen 2 'new' ones dead out of the box and have heard of lots others.

Mike

Pi-eyed Piper wrote:

Reply to
Mike Romain
20MPG in the city? That's pretty damn good. I was getting 21 on the highway last summer with stock tires..something is definitely amiss in my setup.
Reply to
Pi-eyed Piper

I was TRYING to behave, but come on! 10.50MPG, something is fooked.

Reply to
Pi-eyed Piper

I'll play with it this weekend. I would have rebuilt the carb, but I liked the idea of having no emissions crap there, I know it can just be unplugged but I got it cheap.

besides the idle...there is no evidence of anything else being fooked. It's running nice, not rich ot lean...I dont know what else to check.

Reply to
Pi-eyed Piper

Then I would just undo the one screw and pull the fast idle cam off to see if it is pitted or corroded under there and polish it up anyway. The linkage arm coming down should be pointing out at the bottom bend where the clip goes on. I believe it is best left dry with no lube at all. Like carb cleaner sprayed.

Mike

Pi-eyed Piper wrote:

Reply to
Mike Romain

I just checked last week; 16.5 city driving. 2004 tj w/35's and 3.73 gears.

Reply to
LowBFlat

Reply to
Pi-eyed Piper

If the choke is staying on, then besides a high idle, it's gonna be rich. The choke pull off will be enough to get it off the high step of the fast idle cam, but no more.

Possible choke heater problem. Take your test light and clamp it to the battery negative post, then see if it'll light up when you probe the choke heater wire (engine running for this test). If it doesn't light, check for power into the oil pressure switch (two wires) near the sending unit. If you have power there, you need a switch. If you don't you need to find out why.

If you're getting power to the choke heater, then the heater needs testing. Engine off, clamp your test light to the battery positive. Unplug the choke heater wire and probe the terminal on the choke cap. It should light. If not, probe the metal part of the choke cap. If that lights it, you need a new choke heater (cap). If not, check to make sure the choke retaining ring is clamped against the metal part of the choke cap (this is where it gets it's ground). If that's okay, probe the carb body it's self. If that doesn't light it, your carb's not grounded. I've never seen this happen, but I don't like leaving things to chance, so I'd check it anyway.

Reply to
bllsht

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