Hello. My mothers 95' Blazer 4x4 began running horribly over the last few days. It got as bad as not being able to accelerate over 25 mph. It's got a rough idle, and lacks power across the RPM range. It's undriveable to say the least. I should mention that I put in a fuel pump, and filter last summer. Yesterday I ran a fuel pressure check with a guage and everything was within the normal tolerances. So it's not anything behind the engine, it's in the engine. So today, I've pulled the plenum. I've also checked all other possbilites like the air intake system.

My "mechanic mentor" had told me when I pull the plenum, have someone turn the key on and watch for leaks. I've done this and saw nothing. However, upon inspection of the manifold, it was very dirty. There seemed to be a build-up of grease on the drivers side. There were also a few small puddles of what may be gas, surrounding some of the poppet nozzles.

How do I check the actual spider unit. There are multiple pieces to the fuel injection assembly, so how can I test them and find the weak link?

Also, I was just wondering, is there a way to clean all this grease and grime buildup lining the plenum feed pipes and the manifold? I'm sort of a neat-freak when it comes to engines. [&:]

Thanks.

 

I'll start by mentioning the basics... Plugs, wires, cap & rotor. When was the last time any of these components have been checked and/or replaced? You should probably pull the plugs and check their condition. If they have a lot of buildup on them, it's probably time to replace them. Check the wires with an old spray bottle of water at night with the engine running. Spray down the wires and watch for arcing. The cap and rotor should be pulled to check for cracks in the cap and carbon trails/buildup on the contacts on both the cap and rotor.

When you did the pressure check, did you do a leak down test? If the pressure drops more than 2-3 psi over 5 minutes, then you have a leak somewhere. Since you have eliminated the fuel pump, I would suspect a leaking injector (your '95 only has one electronic injector and 6 poppet valves).

I can speculate further, but I really need to know when the last time a basic tuneup was performed (consisting of plugs, wires, cap & rotor).

 

Thanks.
I performed a tune-up around spring/summer of 2004. I checked for arcing and correct plug gaps a few months ago as prevenative maintainence, and found nothing. But I'll check it all today I suppose.

When I did the pressure check I only experienced a 4 psi drop when I started the engine. It stayed steady for a good 10 minutes. It's definatley not the fuel system before the engne.

Thanks again.

 

Did you perform the leak down test with the engine and key off with the fuel system charged (ie. turn the key to 'ON' and pressurize the system, then turn the key off and watch the fuel pressure...

Also, how did the cap look when you replaced it?

 

Oh, yes, the leak tes I performed twice.....all was well.

I'm don't quite remeber. I'm removing the cap and checking the rotor and checking the plugs and wires now.

I'll post back with the results.

 

Everyone will find this funny!

Went to check the distrubutor housing. Noticed one of the spark plug wires at the distrubutor was unplugged. I though perhaps I had pulled it when removing the plenum. I search for the stray plug wire, find it, and notice the metal connector inside the boot is very corroded/oxidized. The female connector on the distrubutor is also oxidized. That leads me to believe it's been upplugged for some time. If only I had noticed it sooner!

Anyhow, I clean up the 2 contacts, continue with my ignition system check (visual) and find no verdicts. Replace the plenum and start eh car back up, runs much better. The car has almost all of its power back. The only problem I still feel is around 3k RPM, while rolling, the car will hesitate pretty bad. But it never gets close to dying. Even the brakes feel more responsive!

Now I'm thinking the Cat. converter may be clogged and/or damaged......or simply need replacing. Oh well.

Nothing like a hard-days work!

 

That sounds more like a MTV (manifold tuning valve) problem than a catalytic converter problem. How does the truck run above 3000rpm (say at 4000 rpm)?

 

Seems to be fine. When I say it's bad at 3 grand, it's only when accelerating around that speed. It's actually between 3k-4k range that it seems to crap out.

What can I do to check the MTV? Could a simple voltage test determine anything?

 

Well, here's some information on the MTV as I call it...
The MTV is controlled by a relay. It should be the relay closest to the drivers side in the row of 4 relays on the firewall.

 

There's only 3 relays on that mount.....does that matter?

Is there any possible way for me to test the relay? I don't feel like driving all the way to the local garage to have them tell me it's good!!

Or am I just better off replacing the relay with a brand new one?

BTW, what are the other relays for? I can't seem to find out.