88ComancheMitch Posted June 26, 2014 Share Posted June 26, 2014 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? Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 26, 2014 Share Posted June 26, 2014 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. Link to comment Share on other sites More sharing options...
88ComancheMitch Posted June 26, 2014 Author Share Posted June 26, 2014 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. Link to comment Share on other sites More sharing options...
88ComancheMitch Posted June 27, 2014 Author Share Posted June 27, 2014 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 Link to comment Share on other sites More sharing options...
cruiser54 Posted June 27, 2014 Share Posted June 27, 2014 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. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted June 28, 2014 Share Posted June 28, 2014 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. Link to comment Share on other sites More sharing options...
cruiser54 Posted June 28, 2014 Share Posted June 28, 2014 Yup. That's the starting point...... Link to comment Share on other sites More sharing options...
88ComancheMitch Posted June 28, 2014 Author Share Posted June 28, 2014 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 Link to comment Share on other sites More sharing options...
cruiser54 Posted June 28, 2014 Share Posted June 28, 2014 The Tips apply to your vehicle regardless of what tear engine it has now. Link to comment Share on other sites More sharing options...
88ComancheMitch Posted June 29, 2014 Author Share Posted June 29, 2014 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. Link to comment Share on other sites More sharing options...
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