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Running Rich, Code 45, TBI 454 ***FIXED***

MTBLAZER89

MTBLAZER89

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My TBI 454 has been running rough.

History: It used to only do it when it got real warm like 200*ish then it would miss and sputter really bad with small throttle inputs but seemed ok if you got on it. The cap had a crack in it so I suspected it may get worse with heat and I changed it.

Seemed to have been good up until a couple weeks ago it started running rough except all the time now. As soon as i start it in the morning it seems to have an intermittent miss. This does not go away when it warms up or with throttle input. The exhaust is very rich and today it finally threw a code. 45 for O2 rich condition. Tips, troubleshooting, what worked for you?
 
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Without more info i can only guess.
First try unplugging the electrical connector at the MAP sensor. If it runs better unplugged. Replace the MAP sensor.

Could also be a leaky injector. Check the spray pattern. Also look for drips when the engine is shut off.

Check EGR valve function. Make sure it is not stuck open.

How are the plug wires/plugs, Rotor ?
 
I've got one thats been doing the same thing. You can change the plugs, wires, cap, and button and it runs decent for a few weeks. Then it all goes to crap, with a miss and sucking fuel like nobody's buisness. I was wondering if it could be the gear on the distributor worn, causing bad timing issues.
 
Thunder said:
Without more info i can only guess.
First try unplugging the electrical connector at the MAP sensor. If it runs better unplugged. Replace the MAP sensor.

Could also be a leaky injector. Check the spray pattern. Also look for drips when the engine is shut off.

Check EGR valve function. Make sure it is not stuck open.

How are the plug wires/plugs, Rotor ?
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Not sure how the plugs are I may pull them this weekend and check them out. Wires look ok and the cap and rotor are fairly new. The whole motor was rebuilt less than 7000 miles ago.
 
EGR functions normally. Engine idles down when diaphram is pressed up. Diaphram moves freely.

No trace of fuel in the lines or canister.

Wires look good and are all secure.

Spray looks ok from the injectors..looks like a LOT of fuel LOL eh 454 I guess

I unplugged the MAP sensor and let it warm up. Took it for a drive and it didn't miss at all. I got a little bit of black smoke when I started it without the MAP. May have been from messing with EGR before I turned it off though..:dunno:

Also I am assuming the Check Engine light is normal with the MAP unplugged?

Does this point to the MAP? What else can I check?

Can I drive without causing problems this way? I will let it sit overnight and drive to work (7 Miles) to see how it runs.

Hopefully Dorian will see this.
 
If it smoothed out and ran better with the MAP unplugged. The Map sensor is most likely the problem.
When you unplug the MAP sensor it puts the ECM in bypass or limp home mode. It runs off a pre set program stored in the MEM Cal pac. ECM ignores input from most sensors except TPS and CTS.You can drive it with the MAP unplugged for a while with no harm. The CEL will light will be on, it may run a little rich and get poor mpg. I would not run it for a long distance that way. The rich condition will soot up the 02 sensor and you may have to get a new one.
 
Ok cool. IMO it is running less rich than it was with the MAP unplugged. Before i could smell the gas at idle. Now its not so bad.
 
Update:

This morning on the way to work. It seemed to idle fine, but there was a small miss still when the engine was cold. Nothing like before I could just hear it in the exhaust. The small miss seemed to go away when the engine was up to normal temp.
 
Same thing this morning as yesterday except maybe a little more pronounced. Had a slight miss while driving before engine at operating temp. Seemed to smooth out once it went open loop. Is this because the MAP is unplugged or could it be something else along with it?
 
Done a good visual on the engine bay? You mentioned plugs, wires, cap rotor, but have you looked at all connectors, visible wiring, vacuum hoses, and checked the TBI itself for vacuum leaks with something like propane? Did you inspect the wiring/components inside the distributor under the rotor?

Got an autozone around?

I'd also want to look at what the coolant temp sensor is saying engine temp is. They can do that for free.

If it's missing at idle, you can also pull plug wires individually while it's running to see if any one cylinder being disconnected doesn't change how the engine runs.

I'd hook the MAP sensor back up though. If it's doing it disconnected, it's not the issue, or at least not the sole issue. Hook it back up, remove the ECM fuse for at most 10 seconds, and then start your diagnostics after having done the visual inspection.
 
Yeah when I unplugged the MAP the other day I looked over all my vacuum lines and plugs. They look ok. The only thing broken is the hose from the PCV to the air cleaner housing is cracked right at the PCV.

I am not sure if it makes a difference but this truck has AIR crap on it.

The miss is much worse with the MAP hoooked up it seems so it may be more than one problem I think.

With checking the temp sensor should i just be verifying it against the gauge to make sure they are similar? Should i do it hot or cold?
 
It would be nice to do it cold, and watch it climb, but unless you own a scantool, that is pretty much impossible. However, if it runs bad at operating temperature, if the scantool says anything other than pretty close to your thermostat temp, your CTS is likely bad.

If the PCV is disconnected or leaking it can cause problems. If possible, have you plugged the leak to see what kind of difference you see? Regardless, if it's broken, it's something that needs fixed.
 
Ok I will see what I can find out at autozone tonight with the coolant sensor. It definetly runs better at operating temp than cold, but it runs better either way with the MAP disconnected.

On second thought there is no PCV on that line it is just a hose from the valve cover to the factory air cleaner that is cracked. Need the new hardline there. The other side has the PCV valve in it.

I think I am also gonna try plugs and wires just to see and I don't know the condition of these so it can't hurt.

Which Delco plugs are reccomended factory ignition? I have a box at home i think CR43 something? Wire reccomendations?
 
I *personally* don't think wire is that critical. It needs to hold up, that's where cheap wires fail, longevity. People have told me Accel's are junk, mine have held up for years, and the cheapest wires I've got from Schucks have also held up fine, as long as I don't get them too near the exhaust. :)

I don't know what your engine requires for plugs, I think that may be on the emissions sticker underhood?

If there is a definite transition in how it runs warm/cold, with it running better warm, it would indicate the CTS COULD be a problem. Because CTS is so critical however, it's tied into just about everything, and a problem with another component that the ECM uses CTS for calculations could mislead us into believing its the CTS.

Leaky injector(s) would be a prime example...the ECM runs the injectors off of pre-programmed "cold" (imagine a choke) values when just starting out, and if the injectors are dumping more fuel than normal, the ECM has no way to know, so it would run richer than normal. When the system goes "closed loop", the ECM will try to reduce the amount of fuel the injectors deliver. That can also be seen with a scanner, but man, I can't recall what the 128/128 (ideal) numbers are called...as the numbers go up or down, it indicates the ECM trying to richen or lean the mix...if something like a leaky injector, it would consistently show it trying to lean the mix.
 
Ok I'll have to search round on here for the Delco # for a TBI big block. I know the plugs I have will work in my 350, but not sure if they are the same. Wires I'm just gonna spring for some 8MM wires whatever brand.

As far as the transition between warm and cold the more I have driven it the less I notice any difference at all when it gets to operating temp. It may just be more pronounced when its cold because the engine is cold.

I am going to hook the MAP back up tonight and pick up some plugs and wires and see if I can scan this tonight.
 
Here's another couple things to look at. 454 are notorious for vacuum leaks at the TBI base. Just replace it, don't over tighten.

Is it a stock 454 TBI engine with the CTS in the stock location?

Use a timing light to look at the spray pattern of the injectors. You will see a little drip here and there but mostly should be nice even pattern. You'll notice a leak or plugged area.

I know people say to use propane with a hose but I have never seen that work. Something that does always work and can be very dangerous is starting fluid in small, little direct squirts at the area being checked. Remember this can find spark leaks too (not good)!!!

Take a vacuum reading. Very cheap tool to have. Idle reading has to be steady. Any shaking of the needle shows a mechanical issue. Accelerate while watching the reading, it'll drop but again if you see it shake at the same time as your problem it may be mechanical (engine not EFI).

If you have a laptop you can get a cable for about $30. and use WinALDL a free software program (scan tool about $300 I think..) and read just about everything a scan tool does.
 
I was reading in another thread here somewhere about the hose that goes from the driver valve cover to the air cleaner. I discovered mine was broken. Fixed that and I threw some some new AC Delco plugs and some 8.8 Accels on it today. Runs smooth as silk:laugh:

I don't know where to buy that new plastic tube from, but I just repaired mine with some rubber hose which seems better to me as it allows some flex when I remove the air cleaner.

I looked at my Blazer which has the TBI 350. It has a short (2") spacer under the air cleaner that this hose goes to. Anybody know were to get that from? That seems like the best fix then you never have to mess with that hose.

TTT for any similar problems.
 
MTBLAZER89 said:
I was reading in another thread here somewhere about the hose that goes from the driver valve cover to the air cleaner. I discovered mine was broken. Fixed that and I threw some some new AC Delco plugs and some 8.8 Accels on it today. Runs smooth as silk:laugh:

I don't know where to buy that new plastic tube from, but I just repaired mine with some rubber hose which seems better to me as it allows some flex when I remove the air cleaner.

I looked at my Blazer which has the TBI 350. It has a short (2") spacer under the air cleaner that this hose goes to. Anybody know were to get that from? That seems like the best fix then you never have to mess with that hose.

TTT for any similar problems.
Click to expand...

Get the hose or the spacer? If you need just that plastic hose i think i still have the one i took off my blazer. I'll have to go check but i'm about 99.9% sure i still have it.

Do yourself a big favor and buy this. Makes for alot better air flow into the TBI. http://marine-performance-parts.com/hypertechpowerchargerforfullsizetruckgmtbi5057.aspx

This is also a good thing to have since it will increase air flow past the injectors as well. http://marine-performance-parts.com/cfmtechinjectorspacerforgmtbi435057.aspx
 
MTBLAZER89 said:
I was reading in another thread here somewhere about the hose that goes from the driver valve cover to the air cleaner. I discovered mine was broken. Fixed that and I threw some some new AC Delco plugs and some 8.8 Accels on it today. Runs smooth as silk:laugh:
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The hose your describing sounds like the vent for the PVC. It has no vacuum and even off it won't affect the way your engine runs. So I'm guessing the plugs and wires helped. How did the plugs look?
 
eagle mark said:
The hose your describing sounds like the vent for the PVC. It has no vacuum and even off it won't affect the way your engine runs. So I'm guessing the plugs and wires helped. How did the plugs look?
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No its the hose opposite of the PCV valve. The PCV is on the passenger side valve cover.
 
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