Just a quick question,
How much effect on my 1990 5.8L, If my Distributor was one tooth off ?

(She has about 165,000 miles on her, original owner, to date...always ran synthetic oil in her after the break-in oil came out of her.)
(she fires right up, sluggish on acceleration, with massive fuel consumption)

Okay..lol I lied...2 questions....whats the possibility of timing chain excessively worn?


I will be putting the timing light to her tomorrow sometime

Thanks

 

The timing chain could jumped a tooth. With 165K on the clock most chains DO need to be replaced… the engine will be much happier if all is timed properly.

One tip… don't go cheap on the chain. Buy a good quality timing set with a US or german chain… yes it makes a difference. Ask questions….better to buy it local and be able to see exactly what you are buying.

 

I rarely see a timing chain jump one tooth, except on install. usually when there worn they skip alot, but you will hear the chain slapping around the timing cover long before it gets to that point. Did you pull the distributor out recently? If not I doubt that jumped a tooth as well, did you check for plugged cats, low fuel pressure, dirty injectors, you need to scan this thing and make sure the O2's are switching properly, make sure there not stuck lean.
Semper Fidelis

 

None of it was still possible to set the base timing correctly. Check that first, get a timing light startup the motor and let it stabilize at idle, pull the spout plug to disable computer advance and you should see 10deg BTDC on the crank balancer. If you don't loosen the distributor and rotate it until you do.

 

In theory, it wouldn't matter if the distributor were any number of teeth "off". The problem is that the physical constraints of the engine/distributor prevent enough rotation to correct from being installed in the wrong orientation. For instance, if there were 12 teeth on the distributor gear, you would have to turn the distributor 30º to correct for being installed even one tooth off and maintain the same base timing.

Jason

 

Good advice, all these years, even when money was tight, i try very hard not to put junk parts on old "Greta" heheh
Thanks Krooser

 

Thanks Dave, and Semper-Fi -out in 73"
yes, before i drove 3200 miles with a full load on the back of her, I was tuning her up for the trip, I pulled the distributor out, new wires, O2 sensor,(only one on "Greta"T-God lol) cap n rotor, Checked..tps.map..and temp sensor, etc. (all in good range)
Even though I bench-marked the block/ dist....took me a few try's to get it back on the mark..I am not ruling out injectors /fuel, they are original as well

 

Thanks jason..makes sense..But now that you mention it, i didn't take notice of how many elliptical teeth were on the dist. does it have 12 ?
And..if in fact it was off 30 degree's,...could the computer correct sucha large error??

 

Will Do today Conanski, I had to work yesterday, But nothing short of the house burnin down will pull me away from this problem today!!
I will put the timing light to her today..then pull some codes....will report back tonight / tomorrow with my findings
Thanks fella's

 

I don't know how many teeth are there--it's been quite a few years since I pulled a dizzy, I didn't count then, and there's not room in my brain for that type of info anyway (that room is shrinking...).

No, the computer can't correct for a large error. What you're setting on the dizzy is base timing, then the computer advances it as necessary based on throttle position, oxygen sensors, and a whole host of other sensors for the best combustion based on its stored data tables. When you're setting timing, you'll find that you don't have to turn the dizzy very far in either direction for the engine to start running very badly. In fact, I've found that's a great way to temporarily set timing if there's not a timing light immediately available--turn the dizzy each direction until it runs rough, then leave it in the middle of those two points. Then get to a timing light soon to properly set it. The one plug that sticks out the side of the dizzy body keeps you from turning it very far as it physically interferes with other engine accessories. (I no longer have an F-series truck, so I can only vaguely picture it mentally.)

Jason