I am a new member but have spent a long time here learning a lot of information. I guess I will get down to the nitty gritty... I have a 99 Blazer LT 4.3L. About four months ago during a -20 degree night I was driving home and my water pump apparently failed. Because of the failure my engine overheated and I didn't heed the warning causing some massive damage to the engine (I am not even close to a mechanic but the compression was really low on I think the 2nd and 4th cylinders). Anyway, it was under warranty so I took it to a Meineke shop (the only place that would cover the engine warranty) and they put in what I assume was a rebuilt engine as it didn't look very new. They didn't give me any details about the engine.

So about a month went by after I got the truck back and while I was traveling down the highway at 60mph the truck began to misfire. No check engine light just an occasional battery light. This happened while trying to maintain 60mph up a slight incline. Seemed the engine would drop about 500rpm and it seemed as though it should shift up and then it would just misfire.

I took the next exit so I could get off the road, thinking my truck was dying. When I slowed down it didn't misfire. I tried driving through town (25-30mph) it didn't seem to misfire. So I tried to keep my driving to in-town. Then after a week of babying the truck it started up again (about 70 degrees, sunny). Only this time it was through town going 30. I stopped at a red light on a slight incline (first in line) and it misfired and stalled as I tried to take off from a stop. Every other time it would start right back up but it didn't this time. Might have flooded it...? Luckily I had an alert driver behind me who cleared the road and "escorted" me into a parking lot. I waited 10 minutes and it started and I drove another 3 miles to my work and it misfired a couple of more times.

I began by changing the cap and rotor. In the process I found a vacuum line separated closest to the drivers side windshield, and what I think is one of the throttle cables (?) unhooked. Fixed those. Didn't help much other than it did seem to run a little smoother. The truck sat for about two weeks before I changed the fuel filter. It was clogged and I am not sure it had been changed at all during the 100k miles. So after the fuel filter was changed it seemed to have a bit more power and didn't misfire but it seemed to bog down when I tried to maintain a steady speed and seemed like the engine was doing the same thing it did when it would misfire (drop from about 2100rpm to 1400rpm).

This was the same for two days until this past friday night (running a bit rough but no misfire). We had a lot of rain and while driving it didn't misfire. When I was about to pull into my work there was a big puddle over half the road and my right side hit it pretty good. About five seconds later it began misfiring and stalled out. After a couple of minutes it started back up, but then took me ten minutes to get it 500 feet. Would start and idle but when I shifted into drive and began to press the pedal to move it would bog and stall. Thought it might be moisture in the cap so I let it dry out and also threw in some dry gas just in the off chance that some how water got in the tank... Let it pretty much sit till Sunday at midnight and it didn't make it 1000 feet without misfiring and stalling.

I have searched all over this site for misfire but everyone seems to get codes I had mine checked by a buddy with a really expensive diagnostic tool and it didn't show anything for codes tripped... I am at a loss for what to look at. Maybe something electrical? I am useless mechanic and that is why I love this site. It has helped me do work that I have never even seen or attempted to do. I appreciate ANY help or suggestions and will do what I can. Certainly I am better with electronics than the mechanic part but am willing to try.

 

One other possibility is plugged drains in the bottom of the distributor. There is a small screen in the bottom of the distributor that allows the distributor to breath up until it plugs. This can trap moisture up under the cap, causing a misfire.

Have you checked the condition of the wires? Cleaned the throttle body, EGR valve, and MAF sensor?

 

I've checked the wires and they appear to be good. Haven't been changed since I have had the truck (about 10,000 miles...?). I have just searched and printed the how-tos for the EGR valve and MAF sensor so I will try that either tonight if it stops raining or tomorrow morning. My truck is sitting at my work outside... I know I sound like a rookie but do I need to take the entire distributor out to get the screen (my knowledge of cars is comparable to my knowledge of the inners of my own body. I know if my heart is beating good and I am still moving I am doing okay, if anything goes wrong I am at a loss)? I will continue to search around the site and try these suggestions. I am so glad this site is here as it has certainly made me a blazer fanatic and also showed me how fun the misfire can be to diagnose...

 

Check the wires with a spray bottle, with some clean water inside, at night with as little light as possible and the engine running in park. Mist down the wires. If you see spark jumping out of the wires, replace them.

As far as the screen goes, you will have to remove the cap and rotor again, but the distributor can stay installed. I just went out to the garage to snap some pictures of the distributor I have from a 96 Astro Van, but it does not have the screen that my old 2000 Bravada had. Rather, it has two small holes that have a small slit in them. Looks like a much better idea to the problematic screen, but unfortunately does not help you out.

 

Okay, so after three weeks of rain in Maine, I finally have a warm sunny day to look at the blazer while on break at work. So I started it up and drove it a bit to see if the misfire/stall was as bad. It didn't seem to misfire, but then again I only drove it less than a mile. I took the cap and rotor off and looked at the distributor. There is a small round thing in the middle of the distributor. My guess is that this is the infamous EIP screen...?? It looks rusted so I am assuming that there has been some moisture there. How should I go about cleaning the thing? If this is not it could someone point me in some direction...? Thanks a bunch for the help in advance.

Sean


---------EDIT----------

So I drove the blazer home last night (20 miles) and it didn't misfire. I am still unsure if I cleaned the EIP screen right but I took a metal brush to it and wiped it down with a towel. I know this probably didn't help much but it must have dried during the warm day. Going to rain tonight so we'll see if it holds up. Misted the wires and I didn't see any sparks so I think I might be safe there.

Planning on doing the EGR valve and MAF sensor tonight while on break so I'll try to post later if I get some time.

 

hi my name is budda. and this sounds almost like my problem that i have been experiencing and well i have yet to find codes, etc. mine nly misses @ about 70 and every now and again when you stop and go to take off. i will try the screen thing. and will let you know how it goes. i will tell you this in my experience with other cars in the past, it doesnt sound like something really major. is probably the pump or the thing called the spider, it is inside the intake and houses the injectors and regulator is near it. those and the screen are the only things that i havent tried yet due to the economy. fuel pumps are the worlds worst for not showing signs of any sorts. atleast that is what i have found. and from what everyone says the pumps a autozone and advance only last bout a year. but dont know how true that is because is only that way for this vehicle from what i have heard. so me and you both my try to find out a good place to get a good fuel pump. well gotta go back to work.

 

I have been chasing the same problem in a 2001 Blazer for almost 2 years, and it's getting worse. Mine started as a intermittent sudden miss at road speeds, the tach would bounce up or peg, maybe once, sometimes every few seconds. Then it would run fine for day, weeks, even months. The frequencty of misses slowly increased untill the engine would actually quit. It would always restart.
As I was working for a high school that had a auto mechanics class, I let the teacher have his students check it out. No codes appeared, even though the check engine light was on.
I don't remember how many times the class and the teacher checked it, but no codes ever showed.
When it got to the point it was actually quiting altogether, I took it to a local mechanic. He read the code and immediatly diagnosed a bad crank sensor. I had him change it and it ran perfect for about 3 weeks. Mine you, it had become so unreliable, it was only being used one or 2 times a week.
The intermittent miss and quiting started again, and I took it back to the mechanic that changed the crank sensor, with the Service Engine Soon light on. Now, he says he can't find a code or anything wrong and wants me to come get it.
Any ideas?
Thanks for listening/reading my rant!

Chuck in E. Tn

 

i havent had a chance to try the cleaning of the screen. but i did notice that it does it worse when am low on gas, so am gonna try the pump and airfilter next. i didnt try the screen cleaning because i didnt see a screen in the distributor. could someone please explain to me fully how to do this step thnks.

 

I have a similar problem,my truck starts fine but when i accelerate it misfires
or you could say it st-udders. This seems to happen if i park it in the underground garage for a couple of days, possibly do to dampness. Ive had my spider fuel injection replaced and timing dune, but im still having trouble.
Any info to resolve this would be great.

 

theshave,
Rather than revive this old thread, please post a new thread in the appropriate section with your vehicle information in it and we will see what we can do to help.

*THREAD LOCKED*