sejamian

Hi all, happy to be a member here.

To start, I have done plenty of research before resorting to this thread....just looking for some pointers on things I may have missed..

Truck runs great..mostly...Has 105,000 miles (allegedly) and is super clean.

Upon cold start she runs strong and good. After she warms up, it goes through a moment of the idle dropping (not to the point I worry of it stalling) and then it comes back to life. There is no flickering of the lights....There is a faint whistling sound under light load....sounds exactly like an ecoboost (small turbo). I found a vacuum leak that got my vents working but cannot find another...I replaced the TPS, cleaned the entire carb and IAC.

Then (randomly) if I come to a stop and accelerate, it gets all hesitant for 10 seconds and then kicks back in......

I sprayed starter fluid along manifold and other vacuum lines and cannot find a leak...

My next thoughts are upstream 02 and Alternator...just not getting any of alternator issue symptoms except it does sound like it is making some noise...

Any feedback is appreciated. Thank you for reading!!

Bugout4x4

Master cylinder vacuum booster leak?

sejamian

Possible, but I don't see the whistle under load and the rpm drop after warming up being related to that. It does sound like the whistler is coming from passenger firewall...so hard to tell.

Bugout4x4

Then everything over there needs to be checked well. But if the whole system is low on vacuum because of a leak, it would affect the booster and create the drop in RPM's you describe when you are stopping.

sejamian

Interesting point! Does it matter that the drop isn't on stopping, it's on acceleration from a stop.....usually.

Bugout4x4

Well that was a polite way to explain I read it wrong. lol And I did... But if it is indeed a vacuum leak like you and I both suspect, When you accelerate it opens the butterfly valve in the throttle body and drops the vacuum like a rock. So if it is already low for some reason it will be exposed at that particular moment.

Have you chased down and checked the vacuum reservoir and lines for leaks, or the cruise control diaphragm if it has cruise? Main check would be the evap system area. But any "Whine or whistle" definitely sounds like a vacuum leak.

Sounds gross but it works... I always start at the intake it's self checking to see which system might have a leak. I pull one line off at a time and suck on it with my mouth and then put my tongue on the end. If it holds vacuum on my tongue then that system is good to go. If it doesn't then that is the direction and system to chase. lol

sejamian

I used a cigarette last night in several vacuum hoses and a little came out where the intake tube meets the TB, but spraying starter fluid there did not change the idle. I noticed something today...

When I started it this morning, when the idle dropped...a squeak became present towards the front of the vehicle. I am wondering if this could be an alternator issue? Those can whine/whistle and cause power issues. The ringer is a faint knocking behind the passenger dash...

97grand4.0

Try swapping out the IAC? Sounds like a bad one.

Bugout4x4

Is the vacuum reservoir behind the front bumper on these also? Mine did this onetime because the line to the reservoir was rotten. Think it could be the belt slipping because the alternator is dragging? or a bad bearing in the alternator? Time to loosen the belt and check it by hand?

Waynerd

A pulley with resistance due to a bad bearing or whatever will cause the belt to slip some as the bad pulley slows but the others continue to stay at a higher speed. Definitely need while excelerating.

Ticking near passenger firewall is likely the purge solenoid. And there is several vac lines on and around it. They are somewhat hidden but need to be checked thoroughly for leaks.

Waynerd

Also what's the status on the check engine light? If it's not on and you say Jeep is new to you then maybe it was cleared before the sale.

sejamian

Thank you for the feedback....some new developments...

Changed the plugs / wires / cap & rotor and changed oil....still acting up. Also seafoamed before oil change..

Noticed the temp gauge never really gets warm....not even the middle mark...also, the heat does not blow hot, just warm. The defroster does not work either...

I am thinking bad t-stat and or vacuum leak relating to the heating system (vent system).

All of this has to be related. When its not acting up it drives great....Also after cold start and running for 5 minutes the idle dies down and then kicks back up...like something to do with it warming up?