You didn't state the mileage so I'll assume 80,000.Sounds like low fuel pressure issues when problem is occuring.Have seen a lot of these earlier ones where the flex hose on the pump module wears through on the module spring.Could just be a bad pump.You have replaced the fuel filter?
Also if you have replaced the plugs you need to apply dielectric grease in the boots or they will arc.If this happened suddenly,may be a tank of bad gas.
Would think with all this going on you would have some codes.More info needed.

Lastly;if you have had work done to diag and repair this problem,you should not have been charged if it was not fixed.Russ
PS.The sensors involved in timing are the cam and crank sensors but they should be throwing codes big time. Have seen very few ecm problems on these but there is always a chance.

 

The mileage is 130000. Plugs, rotor and cap are new. Done by a mechanic. I am not seeing any check engine light, ever. If there were codes being thrown wouldn't I see that? Fuel pump was replaced at 100000 but it is whinning again(I hear a high pitched sound coming from the rear of the truck). Fuel filter was replaced. When the dealer replaced the regulator inside the engine, I was told the fuel pressure was 48 and should be 53(the numbers may not be correct but what I recall is the spread between the numbers seemed very small. I didn't believe an intermittent problem would be caused by such a small variation. But it was replaced.). This has been happening for 15 months so I have had a more than a few tanks of gas through the vehicle.
I have a software program(works with my laptop) from DIACOM for reading codes and monitoring the ECM on my previous suburban, 1988. But it does not work on this 2000 Tahoe. What do I need to get to obtain these codes?
I will change the fuel filter again when I get it back from the dealer next week.
Thanks for your reply.
PS The Diacom program is of no use to me. If someone wants it and will pay shipping, you can have it. It might as well be put to good use.

 

Bakfire issues, and the hot start problems you are displaying really sound like fuel delivery issues. If the timing is correct, and your distributor has been inspected (doesn't take much wear to really mess up timing), than you really need to look at fuel delivery. In response to your title, YES! Timing is critical. A broken centrifical weight will cause a lot of issues. A bad reluctor or even just a worn drive gear will cause a lot of issues, however, with the hot start vs. cold start, and the fact you say fuel pressure is low, I would look at fuel delivery. 5lbs low will cause a lot of problems. The computer is not delivering the amount of fuel it thinks it is. You really need to do a full avaluation of the fuel pressure under various conditions. The fact you are not getting any codes thrown is a bit disconcerting. As far as reading codes, you can get a handheld that will pull down the indstry codes, but you will not be able to get the amount of data the dealer can. The little readers are around 100-400 bucks, and can be usefull for getting into the right area. For really detailed analysis, the dealer is the best source, most people could never justify the cost of all the diagnostic equipment they have. Starting to wonder if you have a computer related issue? Sonoma? Shadams? Oh, and you can read the codes on the 88 using a paperclip...

 

Fuel pressure specs are 60-66psi key on engine off.You also need to check pressure on the road when condition is occurring.Normally should run on the higher side under full throttle.ALSO,CHECK THE DIST.CAM RETARD.Should be within 7* + - of 0.Need a scan tool for this.Anything more than 10* can make them run like crap and not kick a light.Need to check this above 1000 rpm.
Check in the dist cap for corrosion and deposits although that nomally causes cold problems..Russ

 

fuel pressure should be at 60-66 psi with key on engine off

i would do a fuel injector balance test. see if they fall lower than 12-13 psi
or if they dont fall at all then there is a likely chance there is a problem with a injector.


if your pressure is lower than 55 psi its likely that it could be a fuel pump.

 

I bet money that you have a bad ground. The same exact symptoms happend to me today with my company truck. Low power, stumbles backfires. And will only idle in gear. Are you having electrical probs? Like engine dies when you run radio, lights ,turn signals?

 

Is this a 5.7 or 5.3? I see you mentioned the cap and rotor have been replaced.

Check to see if the cats are clogged. Will cause those exact symptoms. Simply remove the EGR tube at the egr valve or remove the valve and restart engine. If it runs better, its a restricted exhaust. You can also use a vacuum gauge to diagnose this.

 

Just wondering if you ever got this problem taken care of. Sounds to me like you might have a problem with the check valve in the fuel pump. This might be causing a vapor lock issue in your fuel lines which causes all of your symptoms. Yes, you want to do the fuel pressure test with key on engine off then turn the car all the way off and see if the fuel pressure goes down quickly. It should retain pressure so there is pressure in the lines for start up and prevents vapor lock. There is a spec for this i just dont know it off the top of my head.

 

Double check your fuel presuure regulator.

Gary