Jeep Enthusiast Forums banner

1990 Wrangler 4.2L Timing Help

20K views 41 replies 14 participants last post by  hubb6666 
#1 ·
I just purchased a 1990 Jeep Wrangler with the 4.2L 258 engine. It has the Offenhauser Intake Manifold with the Holley 390CFM 4 barrel carburetor and headers. I also noticed that the "Nutter" bypass has also been done. My problem is the jeep runs terrible and had to tow it from the persons house that I bought it from. I tried checking the timing but either my timing light is reading wrong or maybe the timing chain is off. I disconnected the vacuum advance and plug it. When I take a reading my timing light is not showing the mark at all. I have to advance my timing light to 45 degrees to see mark at 0 degrees. I tried contacting the guy that sold me the jeep to see if it has ever run after he put all this stuff on and to see if he has messed with the timing chain but no luck. I looked at the timing chain cover and there is a new gasket on it. Can anyone lead me in the right direction on what steps to take next? Thanks
 
#3 ·
I set the #1 cylinder to TDC at the compression stroke. Distributor is dead on. I just put plugs in yesterday and looked at them this morning and they are black as the ace of spades. I also think the carb is a tad big. I ordered the Webber conversion kit (WK551-34) and should be here today but this timing thing really has me confused.
 
#5 · (Edited)
Try doing the Team Rush mod as well. I had done the nutter bypass and timed it with a timing light and it was missfiring a lot. Just yesterday I did this mod and it's a whole other beast. Carb may be a factor as well, but it goes in hand with the Team Rush. Seriously do this mod and add a hotter coil and you'll be golden, it's just $70 if you look around carefully
 
#9 ·
Would be worth inspecting the timing chain, the carb is definitely too big and you won't be able to tune it properly unless you have a different cam. 300 CFM is around the area for a 4.2 engine, 390 seems too much for me...

Make sure you find TDC and check the marks, I know you said you already did but make sure you are on the compression stroke.
 
#15 ·
Look at this site... Coolant Temperature Override Valve (CTO)

That'll tell you what the ports on the CTO valve are. Any of the ports that aren't used can just be capped off with vacuum caps. You could also just plate off the EGR, although if it's still there, I'd go ahead and run it.
 
#18 ·
You may have to create your own linkage--I did. Also, I was having the exact same problem on my timing. I manually found TDC using the ol' screw driver in the spark plug hole. My timing mark wasn't even close. I then drew a new mark, and rechecked timing. Now neither mark was on the scale. Took it to the shop to get it checked out, and I sold it while it was sitting in the parking lot waiting to get pulled into a bay. In the end I have no advice, but I feel your pain.
 
#20 ·
Okay that was embarrassing. I was wrapping things up for the day and I said to myself. Self why don't you at least put that pretty air cleaner on. I opened the filter package and there was the throttle bracket. :laugh: Anyway going to Lowes and Advanced Auto to get a few more parts and I will try starting it tomorrow. If I still have a problem then I will be doing what Fernando suggested and check the timing chain. Thanks everyone for all your help. :thumbsup:
 
#26 ·
Big vacuum leak or timing is way off. Which manifold are you using now? If you have the stock manifold check the manifold heater. There's a gasket and an o ring that seal it off. You'll have to pull the manifold to get to it. You are checking manifold vac below the carb or right on the manifold correct?
 
#27 ·
High manifold pressure at idle indicates very retarded ignition. You can try advancing the timing and backing off the carb idle screw till you hit 20 - 21 in on your vac gauge.

If you static timed it and still have this problem, pull the timing cover off and see what the deal is.Proper installation of the timing chain and gears isn't rocket science, but there are opportunities to get it wrong.
 
#28 ·
I just put the stock manifold on today and plan on starting it tomorrow. I'm checking manifold vacuum not port. I will have to see what your talking about tomorrow on the manifold heater. When I had the Offenhauser intake on I sprayed carb cleaner all around the intake and never found any leaks. I swear it looks like everything is leaning towards the timing chain or cam. At idle (rough) the best I can get my timing light to read is 45 degrees and the spark plugs are very black.
 
#29 ·
On the timing issue.. If is the original balancer it could have slipped. It obviously sounds like you have other issues with low vacuum not running right. However, I had a problem with not being able to set the timing with a light. When I tried the mark was about 60 degrees off. I just set it by ear and it ran great. Come to find out the outside of the balancer had walked. A new balancer was installed and the timing marks are now where they should be.
 
#34 ·
Just wanted to say thanks to everyone. After installing the Stock Intake, Weber Conversion Kit and Holley Regulator my Jeep now runs good, vacuum is at 20 and my timing is dead on 9 degrees. I guess there must have been some sort of vacuum problem causing my timing to be way off. As you can see in the pics I didn't hook up the heater hoses going to the intake because Advanced Auto said they don't show any heater hoses going to the intake. :)
 

Attachments

#35 ·
As you can see in the pics I didn't hook up the heater hoses going to the intake because Advanced Auto said they don't show any heater hoses going to the intake. :)
They're wrong, but you probably won't notice any issues throughout summer, but it could be an issue in winter. You don't have to have any preformed hoses there, just standard old heater hose will work.

Glad to see that you've got it all going. :thumbsup:
 
#36 ·
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top