[jimmyjimny]

Hi all, I've been in the process of doing a head gasket for weeks now onm y g13a Sierra and since putting it all back together the car hasn't been able to idle for more than a few seconds before stalling out.. but if I hold the revs up it will run and after a while of me doing this I can remove my foot and it will run by itself and gradually get better over time, but it still sounds like crap and is undriveable. I was in the process of trying to diagnose this as the problem wasn't existent until I took the head off so it's obviously something I've done.. but a giant oil leak from the crank seal has held me up since I stripped the crank bolts in the timing sprocket so I've had to wait for a new sprocket to come in on order.

There's a few things wrong with it that might be causing the idle issue but regarding the carb/vacuum hoses they all seem to be fine (and I left the carb on the manifold when doing the head anyhow) but I remember I was adjusting the timing on it and got zapped from the cap... so since I'm getting zapped would that mean spark is leaking and would be the reason it's now stalling and running poor? I also accidentally broke off that sensor on the front left of the rocker cover (on a bracket with 2 big 14mm bolts) so I've just bypassed besides that I can't think of why it would stall and run so poor.. When the head was blown the engine oil looked like a milkshake and still it was running far better then than it is now!!

I also tried a compression test and got 165psi-155psi in descending order on cylinders 1-3 but only managed 142psi on cylinder 4 which worried me a bit. All the timing marks are lined up perfect and everything I can't think of anything else that would cause it to stall and run so poor besides the dizzy as I did remove it when doing the head, maybe the leads gave way or something they look pretty old.

Any suggestions or advice would be greatly appreciated! Cheers

[shep]

Refit the dizzy following the fsm

[droverdave]

jimmyjimny wrote:

I also accidentally broke off that sensor on the front left of the rocker cover (on a bracket with 2 big 14mm bolts) so I've just bypassed besides that I can't think of why it would stall and run so poor..

What exactly are you refering too here?

And have you got a timing light?

[McBane]

just stick new leads rotor and cap on if they look old the probably are and if you got a boot off the dizzy its either cracked or has ingrained carbon tracking.

X2 on the timing light

[jimmyjimny]

cheers guys, this is the sensor I was referring too



I also put a timing light on it the other day and everything seems ok so I'm thinking carb/fuel issue now. I've started it every morning the past 3 days and it's always the same story. Engine won't fire up without pressing the throttle, once fires it dies unless revs are held up, then after a few minutes of revs being held up the car no longer dies once foot is off the throttle and then it finally runs ok all of a sudden or once a bit warm. I took a video it explains it a lot better http://www.youtube.com/watch?v=7njPylhG ... e=youtu.be

It sounds whiney to me I'm pretty sure it didn't before the head was pulled and it's idling high at like 1200rpm. The rev response is crap and it's running slightly rich not to mention it was missing and idling rough a few days back and somehow runs pretty smooth now lol. I attribute that to the carby cleaner but I can't remember exactly.

[droverdave]

With the timing light, you need to disconnect the vacuum advance on the distributer, and set it to about 10 degrees before top dead centre at idle. Did you do this?

It sounds to me like the timing is retarded quite a bit i think, its certainly out thats for sure.

The engine can run reasonably well with the timing miles out. I was 2 teeth out once and it still sounded ok when i got it running, but it it gave simliar symptoms to yours.

but yer i still think its partly a ignition timing issue, howeever if you find that the timing is correct.

I'd be putting that sensor thing back in, i dunno what it does, but the sierra carbies are so complicated that i suspect if it loses one of its widgets it doesnt know what to do.

and then start with the basics, cleaning the carby out with carby cleaner is a good start.