I have a 99 Blazer four door, four wheel drive, 4.3 133,000 miles. I bought this as a project. The transmission went bad and was parked for a couple years, the guy had already taken the transmission out before I bought it.

The first thing I did was put the starter on and fire it up. It ran great for about 30 second then started to run a little rough. I figured the old gas was the reason for it running a little rough. I had to cut a piece out of the exhaust to get the new tranny in, so after it was in I took the Blazer to an exhaust shop to weld the piece back in. I had them check the ses light and one code came up for the tps.

I thought that was the problem but I replaced it and no luck. I let the Blazer sit for a couple days then went to move it and it wouldn't start. The fuel pump went out. So I replaced the fuel pump and then it ran a lot better! It seems to run great except at idle. It has a slight miss at idle. When you give it gas it has a hesitation then comes right out of it and revs up like it should. So this is real noticable at stop signs and especially when you back up and then put it into drive it will actually die sometimes.

When I did the fuel pump I noticed the gas was getting to the point it was real yellow and foggy, on its way to varnish. I did drain the tank, and when it was done I filled it with 93 octane and used techron fuel system cleaner.

Sorry this is so long but I wanted to give you guys the full scoop and hoping some one has advice. Thanks!

 

Is there anyone that can give me some advice on this issue? I want to sell this Blazer, but this hesitation issue may scare off potenetial buyers.

I have noticed that when the Blazer is first started and is cold, that it has no problem at all. When it gets to operating temp it will hesitate from idle. The blazer seems to run perfect when driving around, but as soon as you stop at a stop sign and hit the gas to take off, there is about a half second delay before it takes off like it should.

I have checked for vacuum leak and cleaned the maf. Can the tps be adjusted?

 

Despite the fact you use a Ford reference you may not know or recall that one good way of defining your driveability problem is to unplug the MAF once the engine warms and see if it runs better or worse.

If it runs better, the MAF has a problem. If it runs worse, something else is bad.. possibly the MAP.

You've replaced the TPS.. like Fords since early 90's, there's no adjustment. Hesitiation across rpm/throttle angle at tip-in says it's probably good anyway.

EGR, the system is good at picking those up and like Fords have to be pretty serious to affect driveability. However, EGR pintle leaks result in false rich condition reflected in long term fuel trims. Once in closed loop, PCM runs engine leaner than it should.

You didnt say HOW you checked for Vacuum leaks. Is there any idle problem at all.. cold or warm?

Once you check the MAF, With engine warm, disconnect ALL vacuum lines from manifold, and plug the ports. Drive slow speed and local cause you got next to no brakes. If better hook up brake vacuum and drive it more with everything else disconnected. If gets worse again.. small leak in booster valve or line to it.

If no change, THEN remove fan or take off belt, disconnect the IAC, {shim throttle stop if necessary to keep engine running} and use an unlit propane torch around all intake gasket surfaces and around fuel line bulkhead at rear. If RPM changes, then you've found the leak spot. Note: NOT disconnecting IAC, you have to have a damn good ear for 'engine tone'.

dont forget PCV and both PCV lines for cracks
You can do this cold engine. You dont want to run it long w/o water pump.

 

Hi Juicey

I have had the same problem with one of my other cars which is an acura, but it sounds exactly like the problem I had

1) Have you done a complete tune-up, it may be best to change plugs wires and distrib.
2) The problem with my car was the rear o2 censor. I needed to get a new one.


Also for some reason, doing something to the exhaust could screw up the o2 censor. My buddy took his blazer in to get some exhaust work on since his older one was rusting, and they screwed up his o2 censor while doing so. They put a new one on for him free of charge.

 

Thanks a lot guys for the advice, I really appreciate it!
Petty I'm going to print out what you said to do and take it with me to the shop today, hopefully I can get this figured out.
The way I checked for vacuum leaks was visually and I also sprayed carb cleaner around the intake.
Thanks again I will keep you guys informed.

 

Everything but #2 is true in one way or another..
Not going to speak for how Honda does things but .. no it wasn't the rear sensor in a Blazer.. or a Ford, for that matter.
A bad after-cat sensor is a messenger only and sets a code for emissions. It only reports on the catalytic converter. Does not affect engine performance in any way.
It's a good idea to get the codes, of course.. but replacing the rear sensor itself will do nothing to fix what ails the engine.

 

Sorry I took so long to get back with you guys, I just wanted to let you know that I sold the Blazer and never did figure out what the problem was. I did hook a scan tool to it and the code was for an o2 sensor.
When I put the tranny in it was real tight to the drivers side and was rubbing on the 02 sensor, and actually cut through the wires. So I ended up taking the sensor out to gain more room and I repaired the wires to the sensor. I wonder if my patch job wasn't sufficient? Anyway, the Blazer is gone now and on to the next project! I really appreciate your guy's help!