This is not one of those HELP ME PLESE!!!!!!! posts. I spent four afternoons working on this and did all my homework. I wish more people would do the same. I love having these forums available, but hate how cluttered they get with people posting "my car makes a funny noise when i hit pot holes at 70mph. my brothers friends father whos neighbor is a mechanic says it is either a balljoint or my front driveshaft. is there any cheap way to fix it? i am so broke cause i like to spend money on stupid stuff rather than fix my car. plz help me."



I feel better now.


This is a tricky one:

My '01 Blazer with 105k was running perfectly fine before I replaced the intake gasket. The job went well. I took my time with it and did it right. There were no indications that I would have any problems once completed. And please don't ask me if I am sure I didn't forget to connect a wire somewhere. I am overly organized and have a wife who nagged at me until I triple checked everything. The MIL is off and there are no codes. A full tune-up was performed less than 5000 miles ago.

It will not run on its own. It cranks fine and kicks over like it is about to start but will not. It will run off a can of intake cleaner indefinitely.

Fuel pressure at the Intake is 62psi when the pump initially turns on/cranks and then drops to between 53 and 55psi. It holds to 50psi after 10 minutes and 46psi after 20. I believe all of this to be within specs. The pump is loud, but I have seen pumps right out of the box be just as loud. It has also never given me any indication of being weak.

I checked all the fuses.

I unplugged the MAF. No change.

I checked the TPS. It had no dead spots.

I found the IAC to be noisy and sticking. My gorilla hands broke it while I tried cleaning it so it has been replaced.

I did the passlock relearn. No change.

I ohmed out the injector harness wires for both the ECM-1 fuse and ground. No problems.

I confirmed voltage at the injector harness. And though I could not confirm pulse, the voltage readings changed when the engine was cranked.

I verified that oil pressure is being registered on the dash.

so what have I missed?

I am now leaning towards three things.

the idea that wire carrying the signal from the oil pressure sending unit to the pcm got damaged during gasket removal or intake installation. This would of course require that this signal is carried on a different wire than the signal to the dash.

A bad fuel pressure regulator. Which should not have suddenly blown since it ran fine prior to the intake gasket job and I never split the lower and upper intakes apart. But i have seen stranger things happen. And cars are subject to all sorts of voodoo.

a fuel pump replacement. even though it is within specs, with 105k on it and it being loud, it might not be a bad idea to change it out now as preventative maintenance and to rule out the possibility. Though that is costly.

any ideas as to what I have overlooked are most welcomed and appreciated.

 

Do you have a remote starter on this, the bypass module could be bad. I would start by redoing the pass lock relearn. If you can grub a capable scanner you can force it.

 

Can you give us a summary of your distributor timing procedure?

 

Thank you for the ideas.

It does not have a remote start. Good idea though.

I thought about re-relearning the passlock. Including doing the scanner force relearn. I have not done it because no passlock issue "symptoms" are present. The security light is not acting in a passlocked manner.

As for distributor timing procedure, I did not think I had to time it. I marked the distributor and rotor when I pulled them. I also did not rotate the cam or oil pump when removed so it should have only been able to go back in perfectly timed or 180 degrees away from perfectly timed. And I do not think the distributor can go in more than one way. Besides, if it were timed wrong, would it run off of a can of intake cleaner? I actually kept it running for a few minutes by routing the pressure relief hose from my fuel pump pressure tester, into the throttle body. I pressed the button whenever it needed fuel. It ran great. Surprisingly, it didn't trigger a code. I thought it would throw a MAF or TPS code.

Please note that this method of running an engine is dangerous. I do not suggest anyone try this. Especially without a fire extinguisher handy.

 

I have had a distributor installed wrong and it still ran, lol. Hated to start but it ran.
Have you pulled the plugs to see if they are soaked in fuel or bone dry after trying to start? Sounds like your injectors are not squirting any fuel or your distributor is out a few teeth. Does it ever kick back when trying to start? You have good enough fuel pressure to start.

 

This is the EXACT scenario I am currently dealing with. Intake manifold gasket replacement. It ran just fine prior to the repairs. Everything was meticulously re-assembled. After re-assembly it wouldn't start.

My thoughts have always centered around the distributor being installed incorrectly. I've spent hours messing with it, trying to get the thing started. I am to the point now to where it starts and runs, but it idles extremely rough and the RPMs surge from around 200 - 800 as if someone is repeatedly pressing and releasing the accelerator.

 

Even when I don't disturb the engine, I have limited success in marking the distributor position and dropping it back down in there. Sometimes it works, sometimes it doesn't. I've gotten to the point where I don't bother marking it at all anymore. I just start over with the #3 cylinder TDC procedure and it usually runs fine.

 

Is there a special procedure that you can outline for getting the distributor in properly?

What I did:

1) Turn motor over with breaker bar and line up the first timing marker on the crank pully.
2) Drop the distributor in 90° out
3) Turn motor over and line up the second timing marker
4) Confirm that the rotor is pointing to the #1 contact on the distributor cap.

No idea how sound this method is, but it's the only way I could even get my Blazer started.

 

I figured out the problem.

I am a good enough mechanic to think I know what I am doing. Which is worse than someone who admits they know nothing.

Come to find out, there are multiple problems. I amalgamated them into one problem. It would not start because the fuel pressure regulator was junk. I have no idea why it decided to become lazy at the exact moment of intake gasket replacement.

Secondly, I can hear a small vacuum leak somewhere. I shall track it down in time.

Third, I do believe that the distributor is off a tooth or two. It starts great now, but runs real rough. I plugged my scanner into it and can see that at idle, it is 12-18 degrees before.

The second ant third problem may be the same problem. I will look into it more as I find time. I sure am glad I have three other cars to drive. And I am also glad to have a resource such as these forums and its members.

For BB15:
Surging is difficult to diagnose. If i were to guess, it would be a timing issue that the pcm is trying to correct. I would put carb cleaner or propane to the engine to check for vacuum leaks. If none are located, I would do as aa21830 suggested. Vacuum leaks can cause idle issues but usually not surging.

A leaking fuel pressure regulator possibly could.