Did you clean the throttle body oriface (hole) the IAC plunger fits into? Normally the IAC causes that kind of problem by its plunger not being able to move freely in/out of the hole in the throtte body. By the way, it is rare that the IAC actually needs replacing. It can normally be restored back to good functionality by just cleaning all the gunk off its solenoid actuated plunger and the hole it fit into.
Remember that having a different opinion doesn't also require one to be a jerk when expressing it.
Swapped in a known good MAP sensor - No change!
Also swapped in a known good canister purge solenoid -No change!
Cleaned all ground cables for PCM.
Inspected PCM connections for corrosion- looked good.
Seems to idle OK when in open loop but after being driven (in closed loop) begins to hang at various rpm's 950-1500+. Hot restart will usually give a normal idle (750) until I start driving.
Occasionally during a shift it hangs at 2000 for a fraction of a second before dropping to 1000-1200 or 1500.
Could the speed sensor have anything to do with this problem, how about a PCM problem?
I had a Camaro or something come in with symptoms similar. Turned out the vacuum line to the MAP had been replaced - but with normal rubber vacuum line rather than the stiff plastic. The rubber line was "sucked closed" from the high vacuum under deceleration, then it "trapped" the vacuum to the MAP.
That was a "hair puller" till we found it.
No exhaust leaks near the engine? The exhaust pulses don't just leak exhaust out, they can pull O2 in and affect the O2 sensors.
A fairly easy way to find a small inaudible exhaust leak (usually works) - a very dark garage, small but strong pencil beamed flashlight, rev it up and down while looking at the pencil beam light. You can usually see the beam of light distort from the heated air and pollution. Blowing cigarette smoke down there while doing it also helps.
It's no wonder the country is falling apart - stupidity abounds!
The MAP sensor bolts directly to the intake with a tiny L-shaped rubber elbow, tried one off my wife's G-Cherokee.(no difference) Elbow is solid, not deteriorated.
Exhaust system is tight, new manifold, cat, muffler,tailpipe only the headpipe is original. I did have several leaks with the original cracked manifold but not sure if I had the problem at that time, thought the TB was gummed up.
Ran a road test with a professional vacuum gauge, seemed pretty normal, 16.5" idle, 22" under decel and near zero under WOT.
Here's the real kicker, two days ago, took a 60 mile trip (in the rain) and it appeared to be almost normal dropping to 750 rpm's when completely stopped, as long as it was moving it would only drop to about 1000-1100.
(maybe the PCM is programmed that way?)
Today the problem returned, dropping to 1500-1600 (clutch depressed) but still rolling, once completely stopped it drops to 1000-1200.
I'm going to take a look at the speed sensor and any possible connections going to the PCM.
Well after reading numerous forums and 3 months of frustration it is fixed.
My specific problem was idle slow to return to normal when stopping, hard to restart once warm, running really rich, and terrible gas mileage.
93 Wrangler 4.0
In order of replacement:
1. Throttle body clean - no Change
2. IAC - no change
3. new vacuum lines - no change
4. Fuel injectors (four hole upgrade) - no change
5. Speed Sensor clean re-install - no change
6. TPS - no change
7. MAP - FIXED Running perfect!!!!
I had a bad dle when i was coming to stop lights- it would bog down but didnt cut off. I just changed my map sensor (new iac, tps beforehand). Just drove it around the block and it idles a lil lower than it used to, maybe like 100 or so rpms, just below the line, and it didnt really bob up and down when i pushed in the clutch to go to neutral and slow down for a light.
We shall see...
Hey guys. I'm new to this site and a jeep owner only for the second time in my 31 years of living. I have a 93 2.5 wrangler with bad idling and sputtering problems. It idles up and down in neutral and then when I wind whatever gear I'm in out, it stalls and sputters when the rpms are high until I change gears and lower the rpms. I have changed maps sensor, tps sensor, plugs, etc. and can't figure out the problem. Can anybody point me in the right direction? Thanks so much for your time.
I've been toying with this for about a year now. The first post described the symptoms perfectly. For me it is more noticeable when it is cold and/or wet outside.
So far I've cleaned the TB, replaced the TPS, replaced the IAC, replaced O2 sensors (all 4) with no luck. I'll check out my speed sensor connection and MAP sensor next.
I'm glad I've learned a bit about the fuel system trying to troubleshoot this issue but I'm ready to have it fixed. I'm worried that if I let the problem go, the high engine speed will wear my clutch much quicker. Anyone else notice the issue more in wet/cold conditions?
I'll check back in after looking at that MAP and speed sensor.
Thanks to everyone who posted their findings. This site is a great resource for guys like me who are a bit new to this stuff.