Map Sensor Help --- Is It Bad? (Voltage Fluxuations)

[88ComancheMitch]

I have a high-idle issue.

 

Symptoms-

 

In park/neutral idle is between 1900-2200. Sometimes surging high as 2500+ and as low as 1600.

In any gear (R, D, 1-2, 3) idle is about 1100-1300.

 

These idles are pretty much consistent. Every now and then, for a split second, idle will drop when in Neutral or Park to around 600-800 and sound like it's going to die/has a terrible miss.

 

I checked the voltages, and when the idle is at 2000+, the MAP sensor, wire "B" is between .07V and 1.1V. From what I'm reading it needs to be 1.2V-2.1V or something similar. I was lucky enough to catch the reading at the idle dropped, and when it dropped to ~900RPM in Park, the Voltage reading was ~1.5-1.8V.

 

Is my MAP sensor bad, or am I having another issue with vacuum somewhere?

[onlyinajeep726]

I'm assuming this is the '88 Comanche you have listed in your sig?

Tighten the manifold bolts.  It's a SAE 9/16th or 14mm wrench.  May not be it, but I guarantee if it's never been done, you'll have a handful of loose bolts.  It causes a huge vacuum leak.
 

[88ComancheMitch]

It is the 88. I have a exhaust manifold leak. I eliminated that as the problem thinking that if it was a leak there that it would fluxuate idle and not hold pretty much steady. I'll check them in the morning.

 

I thought my leak was a cracked manifold. Haven't checked to see exactly where its leaking because I'm just going to do I a 99+ intake and header.

[88ComancheMitch]

Well, one bolt was loose. Exhaust cracked at the rear collector. Going to replace the MAP sensor today hopefully and at least fix the high idle and 12mpg

[cruiser54]

After getting the intake bolts tight, check the integrity of the line from the throttle body to MAP.

 

Also, since it's an 88, I would click on the link in my signature below and do posts 1 through 5 before throwing any parts at it. 

[onlyinajeep726]

After getting the intake bolts tight, check the integrity of the line from the throttle body to MAP.

 

Also, since it's an 88, I would click on the link in my signature below and do posts 1 through 5 before throwing any parts at it. 

 

I second this.  Definitely improved MPG and running issues with my '88 XJ.

[cruiser54]

Yup. That's the starting point......

[88ComancheMitch]

I'll check those points. I did begin taking the intake/exhaust off last night. I'll take pics when I finish tomorrow afternoon/night. It's a 98' motor, do those tips still apply?

 

 

Mitch

[cruiser54]

The Tips apply to your vehicle regardless of what tear engine it has now.

[88ComancheMitch]

Roger that. I'll work on those tonight then. I have read through those tips more than once but never did them because I didn't think they applied.