So I just finished replacing my IAC and all of my vacuum lines. (previously cleaned throttle body and adjusted TPS based off of Cruiser's recommendations) I have also replaced the fuel filter, spark plugs, spark plug wires, distrib cap and rotor.

Jeep runs great while driving, idles at about 1250 while in park and idles around 900 when in drive and brake is pressed down. Much better then before, but now it seems even though it idles fine once I come to a stop sign, once I press down on the gas it immediately wants to stall. If I slowly press on the gas then it doesn't want to stall as bad but if I were to press on the gas without easing into it, it just dies. Any ideas? I've searched around the forum and seems like maybe it could be my fuel pump or map sensor. I replaced the map sensor line but it was a very snug fit, should I try putting the old line back in place?

Much thanks!

 

The high idle speaks of a vac leak either the throttle body gasket or the intake gasket(at least in my experience). When braking the loss of vac to the power booster will starve the engine and can cause a stall. Your idle should be between 400 to 700 at the most. I would re-check the vac lines before going further. The intake likes to leak at the back by the #6, unless the gasket is oil soaked it may be okay to just tighten it back down.

 

I had the exact same problem, but on my wifes 2008 sonata. It turned out to be the MAF sensor and the airbox gasket, from the idiot at valvoline that decided to force the air filter on upside down, which destroyed the gasket and fouled the MAF sensor. I don't even know if this applies to cherokees, because I haven't touched the motor on mine yet, still replacing floors!

 

1250 is WAY too high an idle. Did you test the TPS o the flat 3 wire connector? Did you remove the TPS at all?

 

Double checked the vac lines, everything looks secure. As for the gaskets I replaced the throttle body gasket when I cleaned the throttle body I havent looked at intake gasket though.

I dont believe that the cherokees, or at least my particular model have the MAF sensor..

Cruiser, when I removed and cleaned the throttle body I also removed the TPS and IAC and cleaned both, when I reinstalled the throttle body and reinstalled the TPS I adjusted it using the square connector.

So I just starred it up again, here are some more details..

Start jeep up, idles at 1000 for ~5 secs then drops to ~600-700 and stays for abot 5 secs, then it drops to about 400 and starts shaking like it wants to die, I press on the gas a little to get the rpms up again and the cycle repeats from 1000 to 600-700 then back tp 400, then I gotta rev it again. This process repeats a few times, maybe 4-6 times (I think maybe it does this just because its cold engine) it finally settles between 1100-1250 and stays there indefinitely, once I put it in drive or reverse the rpms drop to 600-700 and stays there, as long as I keep my foot on the brake, but as soon as I give it gas it wants to stall, if I get passed the initial stall it drives no problem, but once I come to another stop I have to worry about the stall again. If the jeep stays in park or neutral idle is high at 1100-1250, in drive or reverse it is ideal (I believe) at 600-700.

 

Alright, I just tested the flat three wire, I didnt understand what was meant by pulling it parallel and over the map sensor so these figures could be skewed. My ohm resistance was 2.1and I know it said not to go any further if it was over 1 but for S&G I proceeded and input was 4.93 output was .69 when it should have been .83

 

Coupla things could be at play here. First off, you originally didn't adjust the tPS on the correct connector.

Secondly, did you get the tang of the TPS on the correct side of the linkage so it moves when the throttle is actuated?

Thirdly, TPSs wear out and don't take kindly to cleaning as a rule.

 

1. So should I readjust the TPS using the flat three wire instead of the square one?
2. Yes to the tang, when throttle is pressed tps moves with it.
3. If readjustment based off three wire flat doesnt work should I just buy a new TPS?

Edit: adjusted TPS using flat connector instead of square one. Fixed one problem, still has a high park idle.

Jeep now idles at ~1300 while in park or neutral. But while in drive or reverse idles at 600-700 and has NO stall when pressing gas, yay!!! Now, where to start to fix the high park/neutral idle...

 

Vacuum leaks suck. I go around with short little shots of starting fluid, if you hit one the sound of the engine will change. Small little shots! You don't want that stuff to accumulate. It's a fire hazard, but It evaporates right away. Also with a tube, or a section of hose you can listen for it. Don't forget the lower O rings on the injectors need to seal as well. (uppers would leak fuel).
The manifold bolts have a habit of loosening, especially that rear one. On anything like that you never want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I go over about three times. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension. For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep.


ALSO, there is a large line coming off the intake, rear of the TB that goes back to the firewall, across, then forward down to the vacuum ball behind your right front bumper. You can pinch that off or unplug it and cap the nipple to test if you have a leak there.

 

1. Yes
2. Good
3. Yes

Maybe someone screwed with the throttle butterfly stop screw at one time?