1991 Grand Wagoneer

[rpcar123]

Hi All,

I've been searching posts and threads for a problem I have with my newly acquired 1991 Grand Wagoneer. I've attached the vac diagram for 1991 because it seems to be a bit different than earlier models. Also, I'm scheduled for a smog test soon. So I can't bypass cto's and the like.

When approximately 7 inHG is reached at the distributor vac advance the jeep starts surging violently (barely keeps running). When I disconnect the vac advance no surging, but no advance either. Everything is connected as the diagram. Initial timing is set to about 15 degrees (sticker says 17 +- 2).
Manifold vacuum is about 18 in-Hg and steady, a bit low?. I think I have eliminated most vac leaks.
The jeep sat for over a year before I bought it.

Things I've already done so far:
Carb kit, the only issue found was leaking power valve.
new plugs, wires, cap, rotor,
One mile of vacuum line changed.
Compression is 132 - 145 psi on all cylinders.

Sorry, the attached pic is ultra-small. Attachment manger is rough!

Thanks,
rpcar

[babywag]

what elevation are you at?
sounds like you have a high altitude emissions sticker?
stock timing is 10*
high altitude(above 4000') are 17*
@7" the vacuum advance should be all done.

I'd lower initial timing and see how it runs

[wiley-moeracing]

Sounds like your distributer diaphragm is leaking causing a vacuum leak? You can leave it unplugged and it will run ok. If you need to you can plug the line and hook it up to the system so it does not leak and lets you get through emissions testing till you get it fixed.

[rpcar123]

I'm at 2800' elevation. I was wondering why the Haynes Manual didn't agree with the emissions sticker on the vehicle.

Is there an adjustment to stop the timing from advancing past 7"? I know about 1/8" allen adjustment, but I thought that just moved the initial operation of the distributor higher or lower.

The vacuum advance diaphragm is holding vacuum really well.

[babywag]

The only adjustment is the diaphragm screw.
As mentioned @ 7" the advance unit should be all done as in no more vacuum advance.
If stock carb & power valve it should be adjusted to be done ~10".

[Uberchin]

Search for threads talking about "Leaking vacuum" on the Charcoal Canister. You can remove yours and check if it still functions. If the diapham inside is broken, you will get a serious vacuum leak. Fix now is to by a canister made for an older chevy.

[rpcar123]

It is a stock Motorcraft 2150 Carb with a new kit in it. I didn't see adjustment instructions for the power valve (it is a 2-stage). I'll do some searching on a procedure.

I checked that the charcoal canister is holding vacuum at the purge valve. Is there a different check for it?

[rpcar123]

The only issue I found rebuilding the carb was a leaking power valve.

Babywag, which fuel-injection systems did you install on your GW's?

[wiley-moeracing]

I re -read your post, recheck for a vacuum leak in the system, carb base gasket, cto, etc. Check your distributer base plate and make sure the springs are there and the shaft springs back when rotated.

[redwoody]

temp switch for egr may allow vac to bypass. Test by unhooking vac to egr

[78 WIDETRAC]

If you are still looking for a vac leak, be sure to look close at the phenolic spacer for cracks.

[rpcar123]

Today is a day off so I've been working on the Wagoneer.

I do indeed have the "High altitude emission sticker" thanks babywag! I set the timing to 10 degrees and it seemed to help, but definitely didn't eliminate the surging. I put a vac pump on the vac advance canister and noticed the advance starts about 3 inHg and finishes at about 14 inHg. I also noticed the movement stutters. I pulled the vac advance canister off. The springs and linkages in the distributor feel smooth when I move it by hand. But, the canister feels like it has catch or bind (what's in there a diaphram and a spring). I tried to adjust the allen screw in the canister so that advance would be finished at 7 inHg, but the best I can do is about 10 inHg. I decided something is definitly wrong with the canister. After a bit (meaning a lot) of cleaning found that I have a Cardone 4891 distributor. I googled and Summit sell them, but not the canister. I called Cardone they gave me the part number for the remanufactured distributor 30-4891. WTF?