why does my engine run rich?

Have codes read then post will advise this guide can help.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down this guide and report back.

po172 and po175 and po300

P0300 needs to be solved first Random Missfire try this clean MAF check for any cracked or disconnected vacumn hoses. Recent repairs?

it was the MAF sensor thank you so much

I have a S10 pick with a 4.3L runs rich on both banks does have service engine light on.

There may be a leak in the exaust near the oxygen sensors making it think it is running lean so it is dumping extra fuel cauising the rich situation. Look ofr exhaust leaks or the pressure regulator may be bad. Have the fuel pressure checked.

Hello,

I have a 95 S10 2.2L automatic. I've owend this truck for about 2 years and have sense done numerous amounts of work to it. Shortly after i purchased the truck i discovered it had a blown head gasket and had the head checked, milled, added new seals, etc... Ever since i've owned this truck it had odd idel problems or acceration problems. I've change the plugs/ wires/ vaccum hoses, etc... numerous times. I've also installed a new egr valve about 1 year ago. In the past the truck seemed to downshift sporadically at different speeds, however that seemed to clear up after i installed some new vaccum lines. I've also installed a new feul filter & feul pump. Now the truck is hard to start... it will take several seconds to crank and normally needs to be assited with pumping the throttle. Once it starts will will idel ok at times, then it will suddenly change its idel and accerate alittle higher with a low end bog... or a bog at and speed when accerating. To cure this problem i've attempted to replace the throttle position sensor (twice now) and also the crank sensor... with little results. Also, when i start the truck it will blow feul out the tailpipe. What could be the source of this truck running rich with a low end bog?

Any ideas or suggestions would be greatly apperciated. Thanks -Jimmy

chekc your fuel pressure, your regulator may be screwing up. it's condensation coming out your tailpipe, not fuel. It could also be the injectors, that's why you should have apro check it out to save yourself some cash on all the parts you've put in to try to fix it and it hasn't. don't go buying the store bought injector cleaner it doesn't work

Engine Performance problem
1994 Chevy S-10 6 cyl Four Wheel Drive Automatic

what can cause the pass,side 0f a 4.3 vortec to foul and it is only the passenger side and you can smell that it is runnig way to rich

hi sounds like leaky poppett valves this is the fuel injector unit under the plantum the orings go bad and cause eng flooding. cost about two hundred parts and a cpl hours labor..however codes should be pulled and exact cyl misfire idenified billymac good luck

my truck wont pass smog,and i was wondering what causes a 2.8L to run rich..please help

A bad O2 sensor, excessive fuel pressure (bad fuel pressure regulator or plugged return line), leaky fuel injectors, dirty air filter or restricted air inlet, or a defective coolant sensor that prevents the engine management system from going into closed loop mode

2.5 vin code E running very rich. I replaced the oxygen sensor, coolant temperature sensor, map sensor and air sensor in the intake manifold. I can unplug three sensors and make it go into open loop and it runs good, but fuel economy suffers. The tailpipe is shooting out black smoke indicating the running rich. Any help is appreciated.

Read your engine code to see what has messed up on it. But because you disconnected sensors you have to start over. Pull the ECM fuse for thirty seconds then start truck and let light come on. Shut engine off and take a paper clip and cross a and b at the aldl. Count the flashes then come to the site here and look under diagnostic codes OBD1. go from there.

Did you ever figure this out? I have the same truck and the same problem. I did not know you can unplug three sensors and make it go back to open loop. So I will try that. I know the OBD trick but no code to read just 1, 2 flash.

This sounds like a classic engine coolant temperature sensor that is causing he issue. Here is a guide to show you how to change the sensor out:

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Please run down this guide and report back.

Cheers, Ken

Truck runs for a few minutes fine the starts to stutter and shut off. You can smell the unburned fuel and it acts like it runs rich and stalls out. Can start right back up and do it again. Not sure if the timing is when the IACV closes or just the computer kicking into “closed loop” (if I got that right). Pretty much all sensors and distributor changed.

Hi Matt, were you able to see if it has any codes? I saw your other post and unplugging sensors usually does not reset codes, but disconnecting battery will.
And able to get fuel pressure?

No codes and yes fuel pressure.

Sorry Matt, I should have been more specific about fuel pressure and asked if a pressure gauge was ever installed to see how much pressure it has. Spec is 9-13lbs. higher pressure will make it run rich. It kind of sounds like the pump could be getting hot too.
And when you have a pressure gauge hooked up with the engine running, and the fuel pump is producing pressure within specification, let it run until the engine starts stuttering and stalling, to make sure the fuel pump pressure remains stable and within the 9-13lb. spec.,as it stutters and stalls.
And usually the check engine light turns on when they start running bad.
Also, it probably will have a code if you check it right after it stalls.
You need to make sure the vacuum lines are good. Did you guys change the MAP senor too?
https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

New fuel pump, good pressure and running rich.

Map tested fine and tried a spare but no original map is on.

No codes at all. Have not found any vacuum leaks.

4.3 TBI. v6, two wheel drive, automatic with 230,000 miles.

Here is my issue: I got the Blazer fairly cheap because the guy was not mechanically inclined and did not want to fool with it.

Anyhow, it starts only when you hold the pedal down. Once it does start it has a strong fuel odor and the ground is black from all of the carbon coming out of the tail pipe.

I replaced the coolant temperature sensor and rebuilt the fuel pressure regulator. Still the same issue. Today I took it to a shop I deal with from time to time and my buddy put a computer on it. Only code it came back with was MAP sensor or high voltage. I replaced the MAP sensor and it still has the same issue. I have checked the EGR valve by pushing in on the diaphragm and best I can tell it is fine. The truck will not run worth a bean with both injectors plugged because they are spraying so much fuel. With one injector, you can get it to putt down the street.

My next step is to just replace the computer, but I wanted to see if someone could shed some light on this issue or perhaps someone that has been through the same thing.


Latest progress:

Okay, I am back on this project now that the holidays are over. After testing voltages and hooking a computer up to the blazer, I was left with the computer being bad. I put a new computer in today and the car started up and ran like bad for a couple minutes and then cleared up. I turned it off for a couple minutes and tried to restart and nothing. I replaced all of the plugs using AcDelco. Once again, started up and ran fine. It would even sit there and purr like a kitten. This did not last long and it would try and stall out, and then clear up and run fine and then repeat the cycle. I was able to drive it home from the shop about ten minutes away and it ran good with the exception of the pinging and valve clatter. Not sure if it might have some water in the tank or not. I got home, turned it off and let it sit for about a hour. Went back outside to start it up, and would not start unless I held the pedal down. I am really not sure what direction to go at this point. Would the IAC cause this and OR the EGR valve?

Right after I put the new computer in, the truck started up and ran fine. It sat there and idled for about ten minutes with no issues. Today, I pulled all the plugs out and cleaned them, fired the truck back up and the injectors were once again dumping fuel. Just cranking the motor the injectors were dumping fuel like crazy. Keep in mind it did not do this after I put the new computer in at first, but it did the exact same thing with the old computer in. I had them order me another one and will pick it up in the morning. I am really confused at this point and I hope it was just a faulty computer.

Today's progress:

I put the new computer in and still the same. It will idle somewhat decent on 1 injector but is still dumping fuel. I ran the truck about 5 mins or so and could smell something funny and then seen smoke coming from underneath the truck. I looked underneath and it was REAL hot from the converter back...First time it's done this. I hope the converter is not bad now because the whole exhaust system was replaced last year.

Tonight I checked the map sensor using a voltmeter and a vacuum pump and it seems to be fine pressure and voltage wise. I have pulled the EGR off yet but I did apply pressure to it with the vacuum pump and I could see the diaphragm open and close and it seemed like it was moving pretty smooth.

Far as IAC, I could visually see the pintle moving in and out when I would bump the throttle. I havent checked the TPS yet, I will do that tomorrow.

Sorry for the long post, but I figured the more I could explain what I have done, the more it would help someone to be able to help me.

UPDATE today 1/21/2010

I spent nearly all day rechecking, back probing sensors, checking vacuum on the MAP, EGR solenoid, EGR valve seems to be working fine. All of the sensors are within specs far as voltages are concerned. The service engine soon light was out on the dash so I replaced that today. Put the new computer in and I still get the same result, dumping too much fuel out of the injectors. I am not getting a check engine light kicked on and it has been hooked back up on the computer at the shop and no codes are being kicked back.

I am really at a loss at this point. I am getting this computer replaced today just in case it is a computer issue seeing how the Blazer started up and ran as soon as I put the first new computer in. I have heard a couple say the proms (chips) were known to go bad. I am not sure if this is my issue or not.

I just cannot figure out what is going on since I am not getting any codes what so ever.

This is a good one. First, chances are the catylatic converter is toast. It sounds like it melted down. Remove it with the new computer to see if that makes a difference. Also, are you sure the injectors are good and they are not the problem? As far as the proms, they have been known to go bad.

If you are replacing the computer again, remove the converter to see if that changes anything. Also, recheck the temperature sensor to make sure it is not sending a reading to the computer telling it it is -40 degrees outside or something crazy.

Let me know what you find.

Joe

Yes gauge was used to check fuel pressure and checked in spec.

First off, thanks for taking the time to read through my problem.

Okay, buddy of mine came over after work with his computer. The MAP, TPS, IAC, are all showing fine. The 02 sensor goes rich to lean back to rich but that is because of the amount of fuel. We pulled the injector assembly out and checked the o-rings on the injectors and they are fine. I also pulled the regulator assembly apart and rechecked all of that, it was fine. We got it to run a little better by adjusting the distributor with the (ECT) wire I believe that is what it is called, unplugged. No codes are being kicked out. My buddy is thinking maybe at one point someone might have changed the injectors out with V8 injectors. He said he has seen it happen in the past. I am going to see if I can find a couple injectors tomorrow and see what happens then. I have not picked up the new computer, but I do not think at this point it is a computer issue. Unless the proms are bad which I am going to see if I can find some of those tomorrow also.

To me it sounds like the coolant sensor is pegged cold which would not trigger a code. Here is a guide to help you see what you are in for when changing it and the location on your car should be near the thermostat housing. You can test it against a new sensor.

185 ohms at 210 deg F
450 ohms at 160 deg F
1800 ohms at 100 deg F
3400 ohms at 70 deg F
7500 ohms at 40 deg F
13500 ohms at 20 deg F
25000 ohms at 0 deg F
100700 ohms at -40 deg F

https://www.2carpros.com/articles/how-to-use-a-voltmeter

and

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Check out the diagrams (below). Please let us know what happens.

Cheers, Ken

That would do it. I have seen it done before too. In-fact it was on a Corvette. The car ran really bad, and that is exactly what was wrong. Wrong injectors. Pick one up and compare it to what you have. If you can see a part number, compare it and if they are a different brand, ask the parts store if they can cross reference them.

Let me know what you find.

Joe

Today was another day wasted. I picked up two sets of injectors from the salvage yard. I tried both sets and got the same results, too much fuel. I also replaced the computer, nothing changed.

So, at this point myself as well as my buddies have ran out of ideas. No codes are being kicked back, the converter is fine, the injectors are fine. Only thing I have not done is check fuel pressure but I do not know how to place a tester on a TBI set up. I know on newer cars they have a port on the fuel rail. It has been suggested to me that it is possible the wrong pump could have been put in the tank and I am getting around 60 psi instead of 13 psi. I do not know if this is even possible because would not the pressure regulator not allow that much pressure, or would it bust the diaphragm?

The pressure regulator could be bad. To check it you just tap into the fuel line where it goes into the TBI. Yes, a bad regulator could cause this. For some reason I thought you checked it.

I said in the previous post I took the regulator back out and everything was fine.

Okay, I looked back through a couple but do not see it. Regardless, you removed the regulator and it is okay?

Yeah, it is fine.

Only two things I can think of myself, would be the proms or a wrong fuel pump. I am going to pick up a tester next week and see what kind of pressure I am getting.

You may want to check out a nationally recognized parts store to see if they will lend or rent one to you. Usually they lend them hoping to sell a fuel pump.

Well, I replaced the ECM chips and still the same result. Going to test the fuel pressure this weekend. I am determined to find the culprit.

Let me know what you find.

Joe

What kind of pressure should you have when you turn the key on? When I turn the key on, it jumps to 35 psi. With the injectors unplugged, it is jumping up to 50-55 psi when cranking the engine. I cannot get it started because the cylinders were so full of fuel.

Should the pressure be that high just on crank?

Let me know.