Ok it's time to troubleshoot...

bowtie_pasta · December 21, 2002

This motor is in an 85' S10 Blazer. This vehicle is my daily driver, which is imperitive why it keeps going (do not need to part w/ any cash for another ride right now).

Ok on to the problem:

Recently it has started becoming excessivly sluggish. Forcing me to push the petal farther to the floor to get up to speed. Just prior to this it was really running good. I know this motor is basically a dog, but it has always done better than this. Sometimes it hesitates (cuts out), and just has a very hard time pulling overdrive on the freeway/highway. Also, my check engine light will come on for a couple minutes then disappear (this only happens when running above 60mph on the freeway/highway). I've been keeping track of mileage lately too and it's been getting worse.

Per my maintenance records the basic tune up stuff like plugs, wires, dist. cap, and rotor are not quite due. I don't like to replace stuff that isn't at the mileage mark (however this is about what I'm ready to do). I change the oil every 3000 and try to keep it in good running shape.

I can't give an exact mileage on the engine because when we bought it (~7 years ago) the previous owner had the engine overhauled. So based on my best guess this rebuild has ~100,000 miles on it, maybe more.

Another note; I had the carb rebuilt ~2 years ago too.

So I'm looking for suggestions/tips to help me. I'm going to be pulling the plugs soon and reading them. I have a feeling that the trouble may be ignition related.

Sorry for writing a book, but I wanted to give as much info as possible so maybe someone can help me keep this truck running.

Thx

Colorado Kid · December 23, 2002

Pretty good description I'd say.

It leaves me with only a couple prime suspects.

You didn't mention Oxygen Sensor. It could cause these symptoms.

Somewhere in the hundres of miles of hoses you may have a vacuum leak...this would usually result in a ragged idle, which you probably would have mentioned.

It's also a slight possibility that there's a problem with the (mechnical) fuel pump or fuel filter.

Finally the EGR Valve could be sticking partially open.

Hope this helps.

bowtie_pasta · December 24, 2002

Well, here's what I did this weekend: pulled the plugs, they were sparkling clean, burning nice. Checked distributor cap, same thing, not a speck of carbon. While I had the cap off I was looking over the vacuum hoses toward the back of the motor and I found a 3 way 'T' type fitting busted in half. Bingo! Can you say vacuum leak? I found a suitable replacement at the parts store. Also replaced a section or two of old vacuum hose while I was at it. Runs much better know, got some power back, better idle, have yet to see a check engine light. Still acting a little sluggish though.

I've thought of the oxygen sensor. Do you happen to know where they are located on this truck? I know the shop changed it several years ago, I've never changed it myself. I will reference the Haynes guide for this.

Fuel pump and filter have been changed recently, the pump should be working good.

EGR, is that the valve mounted on top of the drivers side valve cover? Heck, if that's it I'll just go change it.

Anyway, thanks for the help Colorado! *runs off to grab the book*

BlueRado · December 24, 2002

Another one you might check into, if that particular model had one, is the knock sensor(s). If it's running smoothly, but sluggish, the knock sensor could be bottoming out everything if a) it's faulty, or b) sensed a knock situation with the vacuum leak.

If it's idling and accelerating smoothly now, the EGR is probably OK, but that's my 2 cents opinion.

Oxygen sensor(s) are in the exhaust stream, usually in the head pipe before the CAT.

bowtie_pasta · December 25, 2002

Ok, here's the latest:

Driving home on the freeway last night I had a lot more power. Still got the check engine light for about 3 minutes. It always goes out once I bring the mph down under 60. Sometimes it will just go out regardless.

So today I located the EGR and oxygen sensor. I know the oxygen sensor is fairly new (and I can't find any type of maintenance interval specified for changing one) I went ahead and disconnected the connector and cleaned it (covered with oil/muck), put it back together.

Glad to hear the feedback on the EGR Rado, because it does idle good and I don't want to have to change the EGR anytime soon. I looked it up and it's around a $60 part. Plus the fact that it's in a poor working location to change. It mounts to the intake manifold and looks like a PITA to change.

I replaced several more pieces of old vacuum tubing today as well though. Also placed a zip tie or two on some of the larger vacuum hose connections to prevent leakage.

Drove to work today and it's idling good and most of the power is back. I'm gonna keep tweaking on it and hope I can really get it dialed in. What I want to do is change the EEC canister filter, but I can't find replacement filters. The dealer didn't even have any, but they sell the whole canister for around $90 (ouch) .

Anyway thanks again and feel free to drop anymore knowledge, it all helps. :thumb: