Jumpsoffrock

iTrader: (1)

Hesitation is a constant issue, the car is a '99 Z28 with the 6spd. For what seems to be over a year or more it has hesitated terribly. In gears at speeds it used to run smooth it now bogs terribly and slugs, car definitely doesn't perform as strong as before.
We have thrown every general maintenance at it.
I suggested checking engine vacuum after thinking not only myself but being told by at least 10 different people that "it sounds like a vac problem..."

So we go to hook up a gauge, and have no clue where to do so... Where to start?
Thanks a ton.

wrencher

iTrader: (2)

Manifold vacuum is mechanical engine health....
How about checking the fuel pressure?

Jumpsoffrock

iTrader: (1)

You don't think a vac leak could cause bogging or hesitation?

As for checking the fuel pressure, That's what I'll to next/first thing then, thanks!

wrencher

iTrader: (2)

The problem your describing doesnt sound like a vacuum leak.
Bogging hesitating & losing power/slugs?
Sound more like not enough fuel pressure, bad MAF etc SES light on?

Anthony Williams

iTrader: (3)

Yhea, I would look at sensors first. LSx really don't have vacuum issues like engines from the past. Fuel press, MAF,TPS and the speed sensor would be my first looks in that order, these are the main sensors that tell the PCM how to run the engine.

I-C5

iTrader: (1)

Its rare for them to have vacuum leaks....i tested mine then old way with started fluid. spray it around the intake and on hoses...it will rev up if its leaking from it

Jumpsoffrock

iTrader: (1)

Ok perfect, so far we'll try the fuel pressure and a new MAF sensor(he said he already cleaned it and it helped a tad which sounds similar to other people who have had bad MAF's).
Thanks again everyone.

great421

iTrader: (1)

The big question is what does your vacuum gauge read at idle, and what does your service manual state it should read?

If you've determined that you do indeed have low vacuum and want to test, there are a couple of methods my step-father (a ASE and State-certified Master Mechanic) uses:

1) A spray can of carb cleaner / brake clean / WD-40 sprayed in short bursts around each suspect area individually; if RPM changes then you have a leak in that area.

2) A doctor's stethoscope or single vacuum line from his ear to a suspect component or area - this method helps you 'hear' the leak.

Good luck!

garygnu

hook up a scanner and check for vacuum.you can check vacuum at the PCV port.

Jumpsoffrock

iTrader: (1)

The problem is we never got that far, we couldn't figure where to hook it up to!

Gary--After doing reading here I finally figured that out, thanks for the tip.



For what it's worth we replaced his MAF with a used unit from an LKQ parts yard(came with 6-month warranty). Cost $40 and didn't do a damn thing. The car bogs under load, bad. Only at low rpm's. The 1st-4th shift of the skip shift used to be smooth as normal according to him(long time ago), but now it bogs the crap out of the car. Similar reaction from any other gear when at low rpm and you step on it; 6th gear is basically impossible and useless, any slight incline and the engine bogs terribly.

Anyways, the used unit didn't help. I have a funny feeling that unit is just as much crap as what he's got under the hood in the first place and have tried to convince him to buy new... But on the flip side, the used one not producing any results makes me think, "what if it was good and that's not the problem, then I'm asking my friend to spend $100-140 on a brand new one for nothing."

If he were to spend that via my advice and his car still run like crap, I'd feel worse than his car runs!