I have a 2000 chevy blazer that I just replaced the Lower intake manifold gaskets on. Just a side note, I did not pull the upper plenum or throttle body off the manifold as I just replaced those gaskets not long ago. Everything went smoothly except for me losing my timing, which I pulled the distributor back out and corrected per the timing marks on the balancer.

now for the problem:

Once the timing was right the truck fired right up, but It wouldn't rev without dying. It will idle smoothly so I let it idle for about 10 minutes and went back to it and it would only rev to about 1k rpm and start to die. So I tried driving it around a little and found that the more I drove it the more it started to come back around. After about a half hour of idling and driving, it would rev to about 2k somewhat smoothly and then just be totally dead on power after that. I also noticed that when cruising it at about 2k rpm on the street, when I pushed in the clutch the rpms would rise and fall multiple times between 1200-1800 rpm.

The only thing I have modified during the whole L.I.M. change is that when I pulled off the aftermarket accel distributor cap, I found a strange buildup on the brass contact points which I tried to clean up a little bit with sand paper. Also some sort of back buildup on the rotor contact which scrapped off rather easily

I've made sure all vacuum lines are connected and made sure all electrical is properly hooked up. I am stumped on whats next and hope for some input! Thanks in advance for your time!

quick edit: in the last 9 months ive replaced: fuel pump, fuel pressure regulator, cap, rotor, wires, plugs, MAF sensor, MAP sensor, TPS sensor.

 

The build up on the cap terminals is normal, (supposed to be there). When caps are installed, there should be a dab of silicone dielectric grease applied to each terminal, inside and out. Aluminum conducts electricity far better than brass. The problem is they both corrode, more so with brass terminals. The silicone dielectric helps keep corrosion to a minimum. When the spark jumps the gap between the rotor segment and the cap, the grease crystalizes. Might want to think about upgrading to an AC Delco cap & rotor, and use the grease


Does the service engine soon light come on with the bulb check?
Does the light remain on after the engine starts?
Are there any DTC's in memory?
If so, what are they?
Have you checked fuel pressure and leakdown at the service port and at the fuel filter outlet?
If so, what were all 4 readings?

 

Little update:

I realized something that may have contributed to my problem, one of the simpliest and most standard things to do when doing any work under the hood, I did not disconect the battery while doing the gasket swap

I did replace the distributor cap and rotor with ones with all aluminum contact points, no change in the way it runs, but was a good investment still.

I did also put the stock computer back in the truck,(pcm, ecu whatever you may call it) with no change. So no codes for right now

As for fuel pressure, I've never had great numbers with the AC Delco pump I installed,but the truck always ran flawlessly with it installed. Ill give a few numbers from the test port, but I dont think the fuel pump contributes to my problems im having now as it was not affected during this Intake manifold repair. Key on engine off- 53psi Key on engine on at idle 48psi.

As for updates on how it runs- Upon starting, i have to start it about 4 times for the idle to catch. It will rev up to about 1k rpm and then drop untill it shuts off. Once the idle catches it will idle a little rough for about 20 seconds and then idles perfect. If i hit the gas at all for about the first 2 minutes the truck bogs and tries to shut off. Once warms up a little bit, I can drive it pretty normally BUT if I hit the gas twice( like feather the clutch) it tries to bog. Then once it fully warms up I can hit it as much as I want and its not bad. But no matter what I cant push the gas past 5/8 throttle. As it gets warmer and warmer full throttle seems approachable in neutral, but not under load.

2 more symptoms im seeing is with an idle surge once fully warm, Ill be crusing at speed in 5th, and when I push and hold in the clutch for a stop. the idle rises and falls from 1200-1800 rpm and it seems like when I come to a complete stop, The idle settles down.

Also, The truck will not hot start, after bringing up to a temperature that allows driveability, I have to let it sit for 5 minutes before I can get it to studder start again.

Sorry for such a long post im just trying to include as many details as possible.

Today im going to get the ignition control module tested just to rule it out.

 

Low fuel pressure will cause most, if not all, of the symptoms you described. Fuel pressure is 10%+ below the minimum required.


Follow the link and post all 4 readings.
https://blazerforum.com/forum/2nd-ge...eakdown-88305/


On your 2000, use the pump prime terminal in the underhood fuse panel for activating the pump. Ignition switch in the OFF position for all tests.


We do not need "engine running" fuel pressure. All fuel pressure tests are done with the engine off.


Did you install an AC Delco cap & rotor?
Did you put silicone dielectric grease on each terminal of the cap?

 

Like the Capt. said, your fuel pressure is no good and you must use the AC Delco ignition parts. Just because your using parts that seem to be good quality does not mean they are correct. These engines are very sensitive to secondary ignition parts and they nearly demand original AC Delco or Delphi parts.

 

Check this out, so I was doing a little bit of trouble shooting again because of the fuel pressure. Was trying to confirm that it was and was pretty dead set on buying a new pump today. On a whim I changed out the MAP sensor with the old one which I changed only because the gasket material was rotted. Turns out the new Delphi MAP sensor I bought for the truck was faulty and threw the whole truck off. Put the gasket material from the new sensor on the old one, and the truck is 100% again. Although I need to keep an eye on that fuel pressure, the truck runs for now. I appreciate all of your help guys!

 

The MAP sensor has nothing to do with the fuel pressure. It's good that you found a problem with the MAP, but 53psi regulated fuel pressure is definitely an issue. Eventually it will refuse to start unless you add fuel to the throttle body. If the injector upgrade has not been done, the poppet nozzles will not squirt fuel if regulated pressure drops below ~40psi. If the upgrade has been done, the injectors will not squirt fuel if regulated pressure drops below ~43psi. If regulated fuel pressure drops below 60psi, it will cause driveability issues, guaranteed, whether you notice them or not