Hey Everyone, new to the forum. Read many of your posts regarding similar problems and fixes. Unfortunately they are still coming up short. Here is the issue.
87 with the AMC 258 4.2L. Carter 2 BBL Carb, (don't give me crap just yet). Does not have nutter bypass.
What I did:
Replaced the head gasket and all main gaskets there up - Valve Cover, Temp Gasket, Intake and Exhaust Gaskets. Cleaned up the head while I was in there. Removed valves and took the gunk off of the valves since what I saw was probably there since 1987. Installed new value seals and flushed everything out. New serpentine belt. New plugs.
Cleaned carburetor out of dirt and grime. Only thing I removed was the choke plate and the two screws directly below it to blew it out with cleaner. Ensure everything was in place to include the small ball bearing.
Reinstalled everything to spec. Started up on the 2nd turnover. Sounded fine. Checked timing, had to adjust a few degrees.
Instructions I got for the timing through the forum. Plugged vacuum advance from distributor. Set to 1600 RPM and adjust to 9-11 BTDC. Tighten and reconnect lines. Did not jump around at all. Seemed fine.
Drove the jeep to work for the day, seemed fine. Started up next day, didn't make it to the end of the street before it was stalling out. Thought nothing of it and continued, died again. Thought the idle was set to low. Had to start it 3 more times heading back to the house to get another vehicle to head to work.
I have adjusted timing over and over. Checked the carb. Blew it out again. I can get it to idle fine, but the second you push the throttle wide open it dies out. That is the problem.
Could not find any vacuum leak after spraying vacuum lines and intake. It is pulling around 23 inches. Seems normal.
All cylinders have good compression in normal operating ranges.
I am leaning towards the carb since that is all I hear about being the problem.
Prior to replacing the gaskets it ran fine, just leaked oil. Not from the head gasket as it turned out, but what the heck. It has a new one now. Rear Main seal is next.
Any help would be greatly appreciated.
before it dies, does it stumble or just go right to dead? If you increase the rpm's while stopped does it die or only when moving? I would double check the vac lines, and the carb... my CJ would die... unless I had it real high rpms it would die when coming to a stop.. vac line was not all the way hooked up... and fuel metering tubes(looks like two fangs) on the carter needed cleaned.
CJ.XJ.CJ. TJ. TJ.ZJ. TJ.TJ. ZJ.ZJ.YJ. XJ
I thought about that. If I hold the choke plate down I can open it up from idle with no problem.
I read some where to check the accelerator pump to press quickly on throttle when it is off to test and see if fuel comes out when it is off to feed more fuel. It did what test said to do. Unless that was something completely different.
If you are set on the carter I would check all hoses for leaks and check all vacum connections.
I am not set on the Carter, I will switch it fairly soon, but I am trying to ensure that the problem is actually the carb first. I don't want to end up ordering the carb and then still have the same problems.
The Weber I was looking at was the Weber 38 DGES along with the fuel regulator to solve the pressure inconsistencies.
I will problem grab some new vacuum hose and replace lines in the morning to eliminate leak issues. Shouldn't take long.
Timing is set at 9* +/- 2 as per what the manual says and what is under the hood at 1600 rpm with the vacuum advance plugged.
I am replacing all vacuum lines right now, just took a break for a few.
I took it out for a drive, and it drives fine at all RPMs. The only issue is the quick throttle response from idle makes it die. If you ease into it, it runs fine.
Here are my thoughts: (Not an any particular order)
1. The pump is not working properly.
When wide open from idle, it is either getting too much fuel and flooding itself out or it is not getting enough fuel and getting too much air when the carb opens up and killing itself.
I can look in the carb and see good healthy sprays when I hit the throttle and it runs fine at higher RPMS.
2. The carburetor is the problem. Do not know what exactly is wrong with it though.
I am pretty savvy when it comes to figuring out problems, but I cant get wrapped around this one. If someone needs something tested, let me know and I will do what I can. I need to get this back up and running correctly.
Just a heads up - California has very strict smog laws regard what is legal to put on what vehicle.
The only smog legal options for the 1987 4.2L YJ are:
Carter BBD in full factory setup (everything there and functional as it was from the factory)
Howell TBI (C.A.R.B. approved version)
Mopar MPFI (C.A.R.B. approved version)
Engine swap to a newer year fuel injected engine (like the 4.0L)
While the weber will do the trick for now to get you rolling again, it won't pass visual for the smog test (and probably wouldn't pass the sniffer either). If you are going to keep it carbed you'll have to put the carter back on for it to pass smog, and you'll have to figure out why the carter is behaving badly. Check out this site for details on the 4.2L setup: Adventures Under the Hood. It has plenty of diagnostic tips and tricks, as well as explains what does what - pretty much the best resource online that covers the factory setup on the 4.2L. The factory 4.2L is a Rube Goldberg dream.
I fought with the factory carter for a year before I finally caved in and went with Howell TBI.
Kinda sucks for us 4.2L owners here in California but that's the laws as they stand.