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Setting timing on 350 TBI...set to 0 deg but surging, wont run **UPDATE**

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90K5

1/2 ton status
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Lubbock, TX
does a 350 tBI have vacuum advance? Im trying to set timing, but cant find any vacuum lines to the dist...its a 90 model does it have mechanical or vacuum advance? as it is, the timing is set to 0 degrees on the tiing gauge, but nothing is unplugged except the tan wire by the firewall. Engine surges, acts like it will dies, then revs up, idles back down, just keeps surging like that...any ideas? thanks
 
Re: Setting timing on 350 TBI...need to unplug vacuum advance?

It sounds like you set the timing correctly. There is only that one wire to disconnect. There is vacuum advance, but it goes through the computer.
 
Re: Setting timing on 350 TBI...need to unplug vacuum advance?

I'm thinking the EGR is good though....i have traced this problem back to decemeber 01, when the truck was in the shop for some distributor problems...ever since then it hasnt wanted to pass inspection....it always did real well before that, and today the timing was off by about 35 degrees when i checked it...unless it gradually got off thats what happened i think. Not that that really matters now though. I switched the plug wires CCW ons space in case that was the problem, and its sort of closer, but the coil to igniotion module wires hardly reach, which makes me think its wrong. Even wehn it seems to be running well it surges......any ideas on this? thanks
 
Re: Setting timing on 350 TBI...need to unplug vacuum advance?

just went out and checked the EGR valve...it holds a vacuum, operation isnt exactly smooth, but not too bad. Had it running great with the timing set correctly for about 10 minutes, then it started surging. This was during its inspection today...when it was running right, it was well on its way to passing but the surging started...what would cause this? It was throwing a code 42, but i think thats because i had the tan/black wire unplugged for setting the timing. With that wire unplugged, the timing still jumps around a little bit, like maybe a degree or two, but stays in the right general area.
 
Re: Setting timing on 350 TBI...need to unplug vacuum advance?

90K5,
I've been reading about timing on the site b/c my 91K5 had a loose disb. holddown bolt and thus needed retime. After reading through the board I found out that after you time it(making sure to unplug the tan/white connector b/n master cylinder and wiper motor) that you had to disconnect the battery to allow computer to clear memory. I don't really know if this will help or not but just relaying some info on what I read. Good luck.
Tom
 
Re: Setting timing on 350 TBI...need to unplug vacuum advance?

90k5,
I've just finished checking out your blazer pics. Looks great. If you dont mind my asking, what is the thin box located beside the brake cylinder on your truck? ABS system? I'm curious b/c mine doesn't have one. Its a 91 that I've recently bought four months ago from some idiot who molested the truck. I'm a bigger idiot for buying but have wanted one since 1988. Anyway I have a plug and wire set up that just hangs from underneath the master cylinder that I'm sure went to something. There have been numerous wires on my truck that were broken, unconnected, and dangling around that I've fixed via soldering etc. Too numerous too even mention. Anyway tks in advance.
tom
 
Re: Setting timing on 350 TBI...need to unplug vacuum advance?

It's the ABS computer. Does you ABS work?
 
Re: Setting timing on 350 TBI...set to 0 deg but surging, wont run

IMO, one of a couple of things.

1) EGR control solenoid is being strobed for some reason. Problem with the ECM, bad EGR, bad valve, or bad vacume. Disconnect the EGR vacume and plug the line. Better?

2) Fuel pressure is not sufficient. This is my bet. It happened to me when I got a pin hole in the rubber line from pump to sending unit in the tank. Check pressure at the TB.
 
Re: Setting timing on 350 TBI...set to 0 deg but surging, wont run

I have been thinking i have a valve messed up...i had it running great for a few minutes the first time that i timed it, and then it sounded horrible, lots of noise from the engine, like an internal problem...then i timed it again, got it running great, but it started surging 10 minutes later...how do i check for a valve problem? compression test?
 
Re: Setting timing on 350 TBI...set to 0 deg but surging, wont run

had it running great a minute ago, but the timing is way off...the timing mark is way up on the balancer though, at the 12 o'clock position, pretty far from the timing marks. It runs great here, this is where is was running before, but it will never pass inspection here.
 
Re: Setting timing on 350 TBI...set to 0 deg but surging, wont run

Internal engine noise and timing jumping around?
Sounds like maby the timing chain to me. Is the noise coming from the front of the engine? Could possibly also be a bad Dist gear or the dist not installed in its seat all the way.
You also should clear the codes as said in previous post. After cleared start it up again Run it. Then check codes again. If you still get a 42. The problem may be a bad module or pickup coil. Also check all the connections and connectors That are related to the distributor.
 
Re: Setting timing on 350 TBI...set to 0 deg but surging, wont run

Ive seen a few dist at work that wore out the upper bushing for shaft. Truck would run great cold ,warm timing was all over the place. Best way to check is to warm it up and pull cap real fast ,check for play at rotor button.When it cools down the slop is gone.As for the noise if its real sloppy rotor may hit cap /forums/images/graemlins/shocked.gif
 
Re: Setting timing on 350 TBI...set to 0 deg but surging, wont run

the distributor isnt worn out, its been recently rebuilt. the timing isnt all over the place either, its just about 30 degrees off, but staying there...still have no idea.
 
Re: Setting timing on 350 TBI...set to 0 deg but surging, wont run

Mine used to do that until I fixed the advance springs. If it is rebuilt perhaps the wrong advance springs were installed or installed improperly.

John
 
Re: Setting timing on 350 TBI...set to 0 deg but surging, wont run

I was thinking that might have been it, but it was rebuilt back in decemeber of 01, so ite been a while...its out getting diagnosed right now, i dont have time to try and troubleshoot all this myself
 
Re: Setting timing on 350 TBI...set to 0 deg but surging, wont run

got it back today, timing was set to about 10 BTDC....truck runs great when cold and if i floor it, but cuts out when its warmed up. I was thinking i had a plugged cat, so i chopped it off, but it didnt help...plugs brand new, new cap and rotor, O2 sensor...does need new injectors, acts like its running out of gas, but like i said, only when warm...what could it be? thahks
 
Re: Setting timing on 350 TBI...set to 0 deg but surging, wont run

sounds like you need to find a shop with people that aren't in the mood to deal with inspections, and hand out stickers. then register it in Lubbock next year. Good luck dude.
 
Re: Setting timing on 350 TBI...set to 0 deg but surging, wont run

yeah, or an inspection man with a magic wand that fixes unknown and stupid problems - but that would be too easy!!!!!!!!!!!!
 
Re: Setting timing on 350 TBI...set to 0 deg but surging, wont run

yea a magic wand would be nice. need a magic wand welder and cutter too.
 
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