1988 jeep wrangler

[robdanmott]

I have a good one. I'm working on a 88 wrangler. I rebuilt the engine 2.5 4cyl TBI. Runs like crap. No power, runs rough, bogs down and blowing oil from God knows where all over the place. Seems to have quite a bit of oil mist and crank case pressure from the oil fill port in the valve cover. I verified systems to make sure I didn't screw the pooch. 152psi all cylinders. Mechanical timing is dead nuts. HOWEVER it's got some REALLY a soft vacuum line connectors that I've zip tied in place and done what I could to verify they're not leaking. The specks call for 7-11 deg BTDC on running timing. The idle speed surges and the timing mark is off the chart( maybe 20-24 BTDC) I've tried advancing and retarding the distributor a gear tooth at a time with no change in the timing mark. Vacuum gauge reads 13-14 in Hg steady at idle but falls steadily to 0 upon increasing RPMs. Plugs came out looking like they're gotten pretty hot prod restively front to rear. Crazy. Anyone have any suggestions.

 

[greg92jeepxj]

Welcome to jeeps.com . Have all the gallery plugs in the oiling system been replaced after the hot tanking and cleaning ? A good rebuild usually includes removing them for cleaning. I would like to suggest that distributor timing be rechecked . Make certain that distributor is installed correctly . It's very easy to improperly install the distributor wrong in 4.0 and 2.5 application whether it be the RENIX or Chrysler design.

 

[superj]

if its blowing oil, isn;t that a sign of too much pressure building up in the crank case? thats from rings not seating properly or something similar, right? or the head gasket not sealing properly? thats the only way i know of to introduce pressure the case. or a crank somewhere.

isn't it normal for vacuum to drop as you open the throttle? 13-14 is horrible for a vacuum reading though. maybe your distributor is hooked to the wrong vacuum source?

 

[greg92jeepxj]

Thanks SuperJ , I'll respect that. When I hear that someone rebuilt an engine , I wonder if the shop removed gallery plugs in the oiling system and didn't replace all . That's unlikely but shouldn't be overlooked. We don't know to what degree the rebuild was performed either . Were the cylinders just honed if they miked out ok and the block not even hot tanked is a possibility too. But I just have to question oil gallery plugs when I hear oil shooting out from God knows where. Wondering what oil pressure is registering ? Yes , it's seems clear there is blowby . Were all the rings ( compression and oil) checked for end gap and side clearance ? Normally , you can't even get a good fit and Pistons won't ride up and down the bore or starter crank right of end gaps at least were not done right. Side clearance is important if we want proper crank case venting . Got to question whether the rings were done right. Hate to tell someone to rip it all apart again if not but that's the only way unfortunately . If initial timing is dead nuts , then vacuum source may be wrong as you've said. An '88 is carbed so the proper source would be above throttle blades for distributor vacuum. Vacuum reading should improve when idle is set better but at least it's pulling that much. Can't hurt to recheck head torque and intake as well but at least cylinder head since its already got up to temperature and went one cooling cycle . Will have to get checked again after this problem is sorted out and got some miles on it anyway.

 

[superj]

Yup, I agree. It sounds weird to me for a fresh rebuild

 

[69jeepcj]

As to dist advance hose hook up, Yes yours should be above the throttle plate and I can tell you that if you are losing vac when you open the throttle you are on (full manifold vac) wrong vac port at the carb. On "full manifold" vac, you will begin to lose vac as the throttle Is opened. On ported vac (above throttle plate) vac will build as the throttle is opened up to a certain point, then start to drop out. On the crank case pressure, is your pcv,egr system hooked up and working?? I had similar problem on my 327, turned out I had no pcv (positive crankcase ventilation) system, once I installed the pcv and installed valve cover breathers, crank case pressure went away. I would seriously look for vac leak somewhere, you vac readings are pretty low for that engine unless you put a pretty decent cam in it upon the rebuild. Stock vac should be around 17-20"
NOTE: read your 1st post, your timing being off the chart at idle also verifies you are on full vac at carb or have massive vac leak.
NOTE: Your idle surge is either a vac leak OR>>> because you maybe on the wrong vac port for the dist. Running "full manifold" vac requires changing the amount of vac your dist "vac advance can" can pull. If not changed, your idle, and slow cruise speed will have a surge as the vac can dithers in and out because the can pulls more vac than the engine is producing.
so, I would make sure no vac leaks, get dist on the correct port, get a pcv and or valve cover breathers, recheck your timing and fire it up.