Hi Everyone.
This maybe a little longwinded, but I will try to make it as short as possible. My blazer was/is running rich and throwing a code. It also tends to hesitate when you punch the gas or take off from a stop. I was finally able to check the codes (cant remember what the #'s are atm) and it was pointing to the MAP sensor, O2 sensor, and the throttle possition sensor. I went ahead and replaced all three about a week ago and I am still having all the same problems. It is still throwing codes but I have not been able to catch them while the light is on. Any Ideas from anyone would be greatly appreciated.
Thanks, Kpiper
I forgot to mention in the post here that gas is getting in the oil. You can really smell it.
A buddy suggested replacing the FPR, which I did also. Still no luck.

 

The MAP and O2 sensor require no calibration but I'm pretty sure you need to calibrate the throttle position sensor. Any of you 4.3 guys know this for sure? As for the gas in the oil..do a compression test to make sure you've got no bad rings, could be getting in thru the piston.

 

I am going to jump on my "Check the coolant temp sensor for the ECM" wagon again...... If it is lying to the ecm, it will dump fuel, wash the oil off the cylinder walls, and ya end up with gas in the oil.... crummy gas mileage, possibly scored cylinder walls, and eventually, a no-start..... Need a scan tool to see what it has to say though.

 

Being an '89, a scan tool won't tell you much. You really need a scope to watch what is happening to the various sensor readings.

If you are getting fuel into the oil, then I would suspect that there is a problem with the throttlebody loosing fuel some way or another. If possible, unbolt the TB and place a shallow pan under it while leaving the fuel line connected, but disconnecting the injectors. Then energize the fuel pump to pressurize the fuel system and inspect for leaks with a flash light. If your injector(s) flow without power, the injector(s) need to be replaced. Cleaning at this point would take too long. If there is no fuel coming out of the injectors themselves, then I would look at all of the gaskets throughout the TB to make sure that there isn't a gasket blown out somewhere that is just dumping raw fuel into the engine.

If that doesn't do it, you may have some wiring trouble. Being that all of these components showed codes, yet replacing them did not help the problem, I would look into the wiring a bit. It is possible that a ground may be loose, corroded, or just plain disconnected. It is also possible that there may be a damaged section of the wiring harness that is causing some intermittent or constant shorting of wires together. Low voltage (such as these 3 sensors use) wiring shorts won't really show up readily. I would inspect the harnesses and look over all of the grounds.

The TPS does not need to be calibrated, but for best performance, it should be at around 0.5V with the throttle closed and around 4.5V with the throttle all the way open. If there is a slight adjustment, it should be checked. If there isn't an adjustment, just install it properly and move on to the next thing.

As far as the coolant temp goes, it is possible that it is telling the PCM that the engine is not warmed up yet and staying in the fuel enrichment mode, however, this shouldn't dump in enough fuel to wash the cylinder walls. With at TBI engine such as this, it would take something either seriously wrong with the throttlebody/injectors or something seriously wrong with the ECU for this to happen.

While you have the TB loose, now would be a good time to replace the base gasket. This has been known to be a point for a vacuum leak and could possibly result in the MAP & O2 codes. It doesn't explain the TPS code, but it is something to look into. And cheap to replace as well.

Hope this helps!

 

I will tell ya what....You guys have been a world of information and I cant tell ya how much I appreciate the help.
I will tare into the TB tonight. I have a gasket kit for it so I will go ahead and replace everything after inspection.
One thing that SUNSHINE COASTER brought up was bad rings. If this is a possibility, wouldnt I be noticing black smoke? If not, and say I do have a "stuck ring" isn't there an additive that can be added to the oil (or is it fuel) to help fix this?
One thing that I think I forgot to mention was that on cold weather start ups (after sitting overnight) it is next to imposible to get it to idel right. It idels very low to the point of dieing.
Don't know if that might help narrow things down any.
Any further suggestions please send them my way. I'll keep checking back.
Thanks again,
-Kpiper

 

Fuel problems can cause idle issues as well. Too much fuel can make idle unstable. I think it is best to try to eliminate some of the things that have been suggested before speculating further.

 

Ok, so the trucks check engine light came on this morning. I was finilly able to check the codes and here they are.




13
Open Oxygen Sensor Circuit




21
Throttle Position Sensor (Signal Voltage High)




22
Throttle Position Sensor (Signal Voltage Low)




32
Exhaust Gas Recirculation (EGR) Circuit




33
Manifold Absolute Pressure Sensor Circuit (High Sig.)




44
Oxygen Sensor Circuit (Lean Exhaust Indicated)

Any clues? I have not started working on the truck yet, plan on starting later this afternoon or tonight. *Thinks of a hundred things he'd rather be doing*
Just wondering where you guys think the best place to start would be.
Thanks for the help.
-Kpiper

 

Check for vacuum leaks......

 

Sounds like you have some wiring or ECU troubles... Don't quite know how else you can have both a HIGH and a LOW TPS code at the same time.

 

Ok so, I tested the throttle position sensor and it read fine. Then I did what Kyle mentioned and far as checking for leaks in the TB and checked the injectors. I did not see any leaks but I went ahead and took off the TB and stripped it down and replaced all the gaskets since I had a spare gasket set here on hand. After reassembling everything I fired it up and after a couple seconds it idled out and started running pretty good. It also respondes much better when you punch the gas although it still has a very slight hesitation to it and it still smells maybe a LITTLE rich, but nothing like it was. It has yet to throgh a code. I did not find any vacuum leaks. What and where should I start as far as looking for any wiring issues???
Thanks,
-Kpiper