poor idle after a 90mi trip

[Mitsuzero]

hello all, i recently replaced the valve stem seals on my ram50 (G63B 2.0L) , i also removed the head and replaced the head gasket , valve cover gasket ect, as well as replacing the timing belt, spark plugs and lapping the valves. after i did this i set the timing (the truck seemed to idle best with about 11 degrees BTDC. i took it on two test drives of about 30 miles and it did great. today i took it on a 90 mile round trip (mostly highway) and when arrived at my destination the truck started to idle poorly and stalled out in the parking lot. i checked the nut on the distributor and it was tight and at higher RPMs the truck ran smoothly. i tightened up the throttle cable on the carb and had the truck stall out once after stopping at a light on my way home. i parked the truck at the house and threw the timing light on it and let it run while hot. the truck idled ok, but started to bog down a couple times before automatically advancing the timing. i loosened the nut on the distributor and wiggled it slightly. as i turned the distributor clockwise it idled very roughly and wanted to stall out, this became worse the closer i turned the distributor to 10 degrees BTDC. my truck has the stock mikuni carb with all the vacuum lines connected. does anyone have an idea why this happened or what i should look for next?

[xboxrox]

Mitsuzero <--- cool name

Try cleaning two electrical connectors (I used brake cleaner then WD40 then wipe off excess ~ it's all I had on hand at the time but it worked)

1) IAT Sensor connector near front of carburetor a brown round connector (Intake Air Temperature Sensor is inside the air cleaner)
2) Thermo-Valve Sensor screws into front of intake manifold (controls vacuum to operate the EGR valve)

Be very gentle with these old connectors & groom the wire looms if needed to remove any strain on the wires...
Make sure the vacuum hose (if so equipped) is removed from the distributor AND plugged off when setting ignition timing ~ it took me 10 years to figure out which screw on the Mikuni is to adjust idle (if your carb is stock with the rear choke tamper plate still in place then reaching that screw will be a chore even with the most appropriate screwdriver ~ also make sure you KNOW the engine RPM when setting timing ~ I have a Summit Racing cheap laser tach works good

Wish you the best

[Mitsuzero]

Thank you Xbox, I'll give that a shot although I think my truck is missing the IAT sensor as I was sold the truck without the air cleaner assembly. I also did not know about disconnecting the vacuum advance for the distributor during timing. As far the tamper plate goes I believe it is still intact, I can post a picture of the back of the carb if that will help

[xboxrox]

OK Mitsuzero

ALSO when setting ignition timing make sure the engine if fully up to operating temperature AND don't for get to cap off the end of the distributor vacuum hose or it will mess up the RPM which needs to be set before timing then once timed reset the idle speed ~ NEW IDEA maybe you should unplug every sensor connector clean with brass wire brush used can of keyboard compressed air to get all sensir connects 100% solid ?? IMPORTANT do NOT put di-electric grease on in or near any sensor connector IT WILL F-CK up everything TRUST ME ~ since you are running with the stock Mikuni carb you must have an air cleaner with IAT sensor or the engine will misfire MAYBE member LawDog has one he can provide ?? Make sure the O2 sensor is good AND that both catalytic converters are NOT PLUGGED

Hope to hear you got a success story soon
Aloha ~ George

[Mitsuzero]

i did adjust the timing with the vacuum line off of the distributor like you suggested and got the engine timed to about 10 degrees BTDC. I then compared the advance with the vacuum line connected. the distributor advanced the timing past 10 degrees BTDC but so far it isn't repeating it's poor idle behavior from yesterday. I'll have to hunt for a new air cleaner with the IAT sensor. i did make sure the connectors on the temp sensors were clean and tightly connected. i'll give it a test drive again and see if it's gotten better or i've got more work to do

[Fingers]

It would be a bit of money to ship the air cleaner just from the box size required. I would call around to salvage yards in your area that don't list on car-part.com and see if they have anything.
I have one laying around, but you are practically across the country from me. Same for LawDog.

[Mitsuzero]

Yeah I'll have to look locally, I do appreciate all the help.

[Mitsuzero]

I believe I have found the culprit, there was a vacuum line unplugged, I didn't see it and I probably caused it come loose as I've been going through the engine haha. It idles beautifully when it doesn't have a giant vacuum leak. I have some more fine tuning to do but it's running quite well now

[xboxrox]

Nice..!



HEY NEED AIR CLEANER to prevent

an AIT (Air Intake Temperature) sensor could be mounted into the bottom of just about any air cleaner case AND it will make your Mikuni ECU all Happy ~ hopefully the wire harness still has the connector still attached ~ a sensor is cheap to ship & a used one should be easy enuff to find...

Apologies for the lecture GOOD LUCK keeping Da Truck Running Well

[Mitsuzero]

No problem , if it'll help it run better I'm all for it. Would you happen to know where the connector would be located in the engine compartment? My truck is a 2nd gen if that helps

[xboxrox]

Help Please..!

Good question Mitsu; does it even exist..? Are you saying there are no unused connectors up by or near the carb..? On a Gen 1 it's a round connector that hangs right in front of the carb...

[Mitsuzero]

I'll compare my two trucks and see what's missing