Erratic Idle when starting 98 Trooper

[zaqshore]

Hey everyone, this forum has helped me so much in the past with my Trooper burning excessive oil or when to replace my CV boots, so now that my Trooper has another problem I have another question.

The problem is that when I start my Trooper, sometimes (not ALL the time) I get a low idle that sometimes stalls the engine or sometimes will surge really low like it's going to stall, come back up to around 800 rpm, then go down again, then come back up and do that a couple times before leveling off at just under 1000 rpm idling. Other times the car will start with a HIGHER than normal idle, surging to 2100 rpm, then slowly coming down steadily (not surging) to around 1500 rpm. It stays at 1500 rpm, and I just drop it into D and go, then when I stop at a stoplight it will be idling normally.

This erratic idling only happens when I start the car, although about 6 months ago it WAS happening sometimes at inopportune moments while driving, like at a stoplight. Sometimes I would be sitting at a green light with a stalled motor. But it hasn't been doing that lately.

My engine has 170k miles and i've been using 15w40 rotella t from walmart for the past 6-8k miles. However, I was recently out of town for 2.5 months and my mom got the oil changed and they used 10w40, which I haven't switched back out yet. I used to have a dirty EGR and some problems with that, and after cleaning it didn't work I just bought a new EGR from Autozone for about $60 or $80 or something and that problem went away. I don't have a check engine light on. I have a K+N air filter and I've recently cleaned it.

What could be wrong with my car?

[amigo-2k]

If you have not ever replaced the intake manifold gasket that is the number one reason for your issues,

BUT

first I would clean the PVC and the EGR and EGR tube too.

Also since you have an oiled air filter you may want to clean your MAF too due to the age of your truck.

see the faq's for instructions on changing the intake manifold gasket?

[2eyefishclaw]