86'gn hesitation,sputter off idle

[SNAKE250R]

Just recently my gn started hesitating real bad cold,once warmed up ran better but still had a stumble off idle.the last code i had was 13 but after i cleared it,it never came back.i changed the o2 sensor anyway with a new denso and cleaned the iac,i also checked for vacuum leaks.the car seems to run better but still hesitates and will cough if you try to rev it fast.last year i had to replace my coil pack plus did a tune up.motor is mostly stock with poston thumbwheel,hot wired hp pump,LT1 MAF WITH MAF TRANSLATOR,9" k&n,gn1 exhaust,adjustable fuel reg.,boost gauge & 2.1 scan master.
Hot idle readings (o2's are not steady)
o2's 280 -800
af 05-06
l8 33-38
int 119-140
bl 155-160
iac 23
TPS .42

 

[TurboBuRick]

Looking at the sm #'s the blm's are high indicating a vacuum or exhaust leak.

 

[SNAKE250R]

thanks rick, i'll check harder for a vacuum leak,does a left side header crack cause problems like this.

 

[TurboBuRick]

Yea, that would prolly account for the high blm's. The stumble you may be able to adjust out by turning the cam sensor 1/8 to 1/4 counterclockwise. You will have to slightly loosen the hold down bolt to do so. This has worked for many. It's worth a shot.

 

[Mile Hi GN]

With this being a recent development with no other changes, odds are it's a vacuum leak. High BLM's would suggest the same.

Vacuum leaks can be pesty demons - smoke test is the most comprehenive means to find them. Don't be surprised if you uncover 2 or 3.

Don't overlook the hard lines coming from throttle body - they leak also, and if the crack is on the intake side, you'll never find it without the smoke.

 

[SNAKE250R]

Thanks,i'm going to lean on the vacuum leak being the problem.i started the car today cold and it wont idle at all untill it warms up.02's are all over the place on scan master.i'm thinking it's going to be the intake manifold.i was going to do the starting fluid test, what do i use to do the smoke test to find the leak or leaks.is there a common spot to check on the manifold.

 

[Mile Hi GN]

Smoke machine

The smoke machine is a powered device / canister used by auto repair shops - I understand it's expensive, and likely beyond the means of us lowly GN drivers.

In my example, we hung the device / canister from the hood, hooked it to the battery for power, then plug the smoke emitter it into a vacuum line. The machine pressurized the system with dark smoke.

Wherever the smoke escapes, you have a vacuum leak. There are other methods to find vacuum leaks, spraying starter fluid on all vacuum connections, etc.

I employed the other traditional methods to find my vacuum leaks repeatedly, couldn't solve it.

Hook up the smoke machine and within 30 minutes had found and fixed both my leaks.

It's the ONLY way to go....

 

[SNAKE250R]

thanks again,i'll try and find a smoke machine to use.i may try the old school methods first because i think my leak is large enough going by what "sounds like" a lifter tick or exhaust leak on the left bank.i will keep you guys posted.