Engine power lag on take off.

ozzygus · 04-16-2015, 12:42 AM

Hi guys, recently my uncle pulled my engine apart & replaced all the seals & gaskets the engine ran perfectly fine except for the oil leaks, oil leaks are all gone now. but the problem is there seems to be A loss of power on take of & the idling is A bit rough occasionally coughs like its flooded, & sometimes stalls, He managed to get A scanner on it & he said it showing its running rich, he seems to think it might be something to do with the air mass censor. does this sound right? & is it possible to test or is there vacuum tubes that connect on to it? I'm trying to fix this my self as he's gone back to the bush & I don't want to hassle him anymore. Any help will be greatly appreciated
Thanks; Gus, Syd Australia

RedCoupe · 04-16-2015, 06:28 AM

You didn't tell us what model (964 or 993) but my experience with the 964 and its "barn door" air flow meter is that as the meter ages, the potentiometer can develop flat spots that you can feel at certain driving conditions. There are threads here on Pelican about repairing this. But, I don't think it would go bad all at once. Instead, I would look for everything that was disturbed during the engine reseal. One possibility is the valve timing. If it's off a couple of degrees on one or both sides, it would run but not well.

iamtheari · 04-16-2015, 07:27 AM

When the car is hot, where is the oil level when parked on a level surface at idle? Measure on the gauge and the dipstick. Overfilling oil, meaning adding oil to get anywhere near the top of the gauge when the car is hot, level, and idling, can cause oil to foul the various mechanisms that control the fuel-air mixture. Make sure your oil is not overfilled and then, either way, remove the idle stability valve (ISV) and clean it thoroughly with carburetor cleaner. I had this happen once after an oil change. The car had lots of trouble seeking an idle speed. It also died if I tried to increase throttle too quickly from idle (basically it was a difficult process to move my foot slowly enough not to kill the engine). Removing some oil and cleaning the ISV fixed these problems.

Wiring problems could also cause problems with the ISV and AFM (air flow meter, mentioned by RedCoupe above). Or they could just have been damaged in the process of taking the engine apart or by collecting dust while they were off the engine.

You are also supposed to check the valve adjustment somewhat frequently after the engine has been taken apart. Doing a valve adjustment may clue you in to problems with timing, although of course properly timing the cams is a precise thing that would require you to take the chain covers off the rear of the engine to diagnose. That can be done with the engine in the car but you have to remove a good part of the car to get to them (probably bumper, definitely air conditioner bracket, rear engine tin, and engine mount, which means you have to support the engine separately from the car).

Start with the oil level and ISV. If there is oil in that area, clean as much of the intake as you can, at least up to the throttle body, before moving on to more invasive procedures.

ozzygus · 04-16-2015, 07:32 PM

Quote:

Originally Posted by RedCoupe

You didn't tell us what model (964 or 993) but my experience with the 964 and its "barn door" air flow meter is that as the meter ages, the potentiometer can develop flat spots that you can feel at certain driving conditions. There are threads here on Pelican about repairing this. But, I don't think it would go bad all at once. Instead, I would look for everything that was disturbed during the engine reseal. One possibility is the valve timing. If it's off a couple of degrees on one or both sides, it would run but not well.

Thanks for your reply, yes you guessed right it's A 964. I'm going to take the air flow meter of now & have A look.

bazar01 · bazar01's Garage

Quote:

Originally Posted by ozzygus

Hi guys, recently my uncle pulled my engine apart & replaced all the seals & gaskets the engine ran perfectly fine except for the oil leaks, oil leaks are all gone now. but the problem is there seems to be A loss of power on take of & the idling is A bit rough occasionally coughs like its flooded, & sometimes stalls,

Can you tell us to what extent the engine was pulled apart to replace seals and gaskets?
Did you mark all the connectors?
Did you make sure all the connectors are properly seated?
What year model 964 is this?

ozzygus · 04-17-2015, 05:56 PM

Thanks guys, I've worked it out the air flow meter wasn't fitted correct uncle didn't tighten it up enough must of been sucking heaps of air before the air mass meter could do it's gob. now it's running fantastic, but now my rocker covers are leaking, seems like A never ending story.

iamtheari · 04-17-2015, 06:08 PM

Glad you got the air leak sorted out. Valve covers are a common source of oil leaks. Did you replace them or do anything to refinish them in the rebuild? Some people have luck with fine grit sandpaper laid down on a perfectly flat surface (like a granite countertop) and sand the valve cover so it is perfectly flat where it mounts to the cam tower. Or replace them with an aluminum version.

ozzygus · 04-17-2015, 11:10 PM

Not sure what he did but i think he would of maybe we'll have to rplace them, can't stand the smell of burning oil, this being A vert it gives me A head ache.

iamtheari · 04-18-2015, 05:51 AM

The normal oil leaks are the crankcase breather housing, crankcase through bolts, chain covers, chain tensioner covers, oil return pipes, the big oil line from the left side of the crankcase to the oil filter console, and valve covers. Of those, warped valve covers that do not sit perfectly flat are the only one that I can think of your rebuild might have missed. They're also the easiest of all those things to fix with the engine in the car, especially since you should be adjusting valves a couple of times in the first thousand miles or so after a rebuild. Drive with the windows down and heat turned off until then.