4.0L OHV Cam Synchronize fix

[Fossiljager]

Hi guys,

I had a problem with my 4.0L OHV surging. I had people tell me it was probably a vacuum leak or bad intake manifold gasket or fuel pump, dirty fuel filter, clogged IAC, clogged injectors dirty throttle body, ect... You get my drift, the diagnoses was all over the map. So where to start? Because I built the engine 50K miles ago, I had wondered for sometime whether I properly stabbed the Cam synchronizer correctly? So yesterday, out of frustration, I covered the engine with with pads so I could comfortably lay on top to reach the cam sychro buried at the back of the engine. I put the timing on 34mm BTDC, unscrewed and removed the hall effect sensor, cleaned that with electrical contact cleaner. Noted the synchronize position was dead nuts, cleaned the plug contacts, reinstalled the cap, reconnected the ATX vacuum line and went for a drive.... holly snappen, the hesitation and surging was gone. Even the built A4LD that was shifting strange in OD was now cleared up. I just returned from a 70mph tour down the highway, but first I did a slow creep up a moderately steep hill (that's where the surge was worst) and nothing, no surge, just gobs of torque and smooth power. Just thought I would share this with you guys. Who knows, it might alleviate your surging issue. If you have one that is... Cheers

 

[410Fortune]

So?? The problem was the disconnected vacuum line or?
Glad you got it sorted out!

 

[Fossiljager]

So?? The problem was the disconnected vacuum line or?

No, the ATX vacuum line was fine. The solution was to thoroughly clean the hall effect sensor. The sensor was so covered with black muck it could hardly detect the signal.

 

[smegun]

So?? The problem was the disconnected vacuum line or?
Glad you got it sorted out!

i have the wrench and have been at that sensor before i dont have surging but i have no power like im stuck in batch mode or am not getting the right timing and fuel mix i know the routine i was going to go for the vacuum modulator

 

[Fossiljager]

Guys,

Let me clarify, My problem had nothing to do with the vacuum line to the trans. I disconnected the vacuum line to get at the Cam sensor, then reconnected it once I was finished. My vacuum lines are fine. I have a new sensor coming, it should be here in a day or two. I'm pretty sure that is the issue, the cam synchronizer is a common failure in these engine. The original I have in there now only has 320K on it. How can it be possibly worn out. lol

Thanks for your in put.

 

[410Fortune]

Heck yeah! When you replace your old 320K sensor and have it in your hands let us know how it feels, see if it has looseness or shows signs of wear

 

[Kesp4.0]

I have my old window style cam synchro out of my 93 (CA) engine and it has 270K on it. I compared it to the new OEM 1996 cam synchro that I'm replacing it with. The old one honestly doesn't look that bad. The sensor cap is loose on it but the rotating gears at the bottom don't show too much wear. Even the o-ring doesn't appear to be damaged at all

 

[Fossiljager]

I have my old window style cam synchro out of my 93 (CA) engine and it has 270K on it. I compared it to the new OEM 1996 cam synchro that I'm replacing it with. The old one honestly doesn't look that bad. The sensor cap is loose on it but the rotating gears at the bottom don't show too much wear. Even the o-ring doesn't appear to be damaged at all

I did not know you could swap them? I guess as long as they both are three (3) wire, why not.

 

[Kesp4.0]

I didn't, either until it was suggested here on EF. I just need to add the correct connector to my old harness, which I'm totally lost on which wire goes where, but I'll ask when I get to stabbing it into the new engine. Thanks for posting this thread, btw. It's good to know how important it is to have it installed correctly.

 

[Fossiljager]

Admittedly I am still confused on the procedure of timing the synchro. I've hear you first need to find TDC on the crank pulley, then measure back 34mm BTDC. Set the timing needle on the 34mm mark. Now go back and stab the synchro at 60 degrees off center line to the passenger side, that should give 15 degrees off center line when the camshaft synchronizer is seated. All the while making sure you joined the oil pump rod. Does that sound right, or is it TDC only? I'm going to try it at 34mm BTDC. Sounds about right for the injectors to fire. Thoughts?

 

[Fossiljager]

I installed a new Dorman Camshaft Synchronizer PN: 689-110. I did not install the base, only the top sensor. The reason being, the shaft attached to the oil pump had zero play in it. The problems I had were, surging at low RPM at Low speed, At cruise in OD (50mph+), the engine seemed to cut out like it had an electric short. It seem to go away if I shifted from OD to drive. Sometimes a rough idle, poor fuel economy. I did several things to try to correct the problems, including O gauge ground straps from body to the frame, engine to the frame. New coil pack, new 8.1 gauge wires. Checked all vacuum lines. Replaced IAC, replaced EGR, Cleaned throttle body and intake manifold, Checked timing. (I completely rebuilt the engine 60K ago). As for timing the cam sychro, I set the engine to TDC, backed it off to 34mm BTDC. pulled the old sychro sensor off and found the interrupter wheel was exactly where it was meant to be according to spec. So I would recommend the 34mm setting when timing your Cam synchro. Finally the engine runs as it should, the loping and surging is gone. No more misses in OD at speed. The engine starts and runs well. I hope this helps people looking to set their sychro timing. Sorry no pictures......

Be well