89 454 tbi running like crap

[1track]

alright, just bought this thing last week and it runs like crap. It will miss, cough, stutter when accelerating, acts like it is running rich. It is through codes 33 and 44, the map and O2 sensors have been replaced, still throughing codes intermittent while driving. Now it is very hard to start. It will crank and crank but not fire, takes forever to get started when warm. If it is cold like first in the morning it fires right up. I haven't replaced egr due to cost and the coolant temp sensor seems to be reading okay, after running awhile I got around 1500 and figured about 100+ degrees. What now? Thinking of just junking the bbc and swaping in a cummins

[rfmaster]

1 track

TBI systems are some of simplest EFI systems around, but like any other piece of automotive electronics can fail due to neglect or mechanical issues.

Based on your code listing:

Code 33 MAP sensor voltage too high (> 4.0 V). Possible vacuum leak in the hose to sensor or faulty sensor. The MAP sensor requires a dedicated vacuum line - provided from the back side of TB between the two fuel lines. Make sure that you do not have cracks in the vacuum tubing!. Another source of TBI vacuum leaks is TB to intake manifold gasket. Over years of service this gasket gets soft and leaks. Another source of vacuum leaks on BBC is TB intake adapter pedestal. GM did not have a dedicated TBI BBC intake manifold, but they had plenty of BBC Q-jet intakes. Slapping TBI to Q-Jet adapter pedestal was an easy solution.

Code 44 - O2 sensor showed < 0.250 volt for over 20 seconds while operating closed loop - mixture is running lean; possible clogged fuel filter, fuel tank empty or sloshing, injectors dirty, fuel pump going bad, or bad sensor. Take off air cleaner assembly - take a look at a spray pattern that the two injectors are providing. At idle, it should be a fine mist hitting side walls - no big drops of fuel. Stock TBI system operates best with fuel pressure around 13 PSI and as low 9PSI. It is all too common for high millage vehicles to have weak fuel pumps!! Do a visual check first, verify fuel pressure. My bet is on dying Fuel Pump based on your description.

//RF

[1track]

I checked all the vacuum hoses going to the MAP sensor, a couple looked wore but no cracks. I replaced them anyways just to be sure. I have replaced the MAP as well. The O2 sensor has been replaced. I have done the visual to the injectors and they seem to be spraying a heavy spray at idle, not much more than a thick mist, no real big droplets. The top of the injectors are covered in some nasty looking gunk. I have not pulled the injectors yet so check inside housing for buildup. How can I check the fuel pressure? It is starting to act as if it is starving for fuel when you are around 1st-2nd gear change, unless you hammer the gas.

I pulled the ecm fuse to see if the codes would clear, and they did not. I havent owned a gas truck in years, much less a tbi system. Everything I have dealt with have been diesels.

[rfmaster]

Well It looks like you need to do a bit more troubleshooting to get that BBC running good again.

1) Fuel Pressure - TBI system does not have a specialized test port connection to measure fuel pressure. Most commercial FP gauge kits come with TBI adapter - which screws right at the TBI inlet port. Alternatively, fuel pressure can be checked at the fuel filter with a similar T (3/8") and appropriate length of 3/8 hose.

2) MAP sensor code - that one bothers me. With engine, ignition off - get a DVM and verify that Pin A of the MAP connector (black wire ) is tied to ground. If it is broken it will cause MAP sensor to always read high and cause drivability problems!

//RF

[f.monroe]

My 87 3/4 ton with a 5.7 had the same codes and it was a bad EGR . I think I unplugged the vac source from it and it ran better so I changed it . Problem solved . I bought mine at a dealership because I have heard that you can get bad rebuilt ones from the parts stores . No more codes and a great idle . It would also run OK when cold .
Frank

[1track]

I unplugged the egr with no change, I don't think it is the problem. I took the tbi apart yesterday and some of the gaskets around the right injecter where chewed up a bit, and that injector was rather dirty. However looking at the spray at idle it looks okay. Looking for a tbi repair kit as my O'reilly's is too incompetent to know how to look up parts. They ordered me a rebuild kit for a rochester carb off an 87 or something then wanted to argue with me that I even had a tbi 454 in my truck

[rfmaster]

Rebuilding TBI is allot simpler than rebuilding a Q-Jet! I would clean and inspect all components very closely. Verify that you do not have wobbly or out of round throttle shaft. Throttle shaft vacuum leaks are known for some odd ball behavior. Make sure that you have a correct TB to adapter gasket. Order your rebuild kit based on the part number stamped on the right front vertical boss edge.

Just follow kit instructions for the most part it is very straight forward.

//RF

[1track]

well I think I may have found the root cause. My tank selector valve I believe is sticking part way causing low fuel flow, which may be my lean mixture issue. Map seemed fine and I haven't been able to drive since I cleared the codes. How did I come up with this, well my LH tank didn't work (or so I was told) so I never used it, the switch on the dash seem to verify this. Well, I was under the truck today checking fuel lines and noticed my RH tank was leaking (badly) so I decided to swap the fuel pumps in both tanks and go to the LH till I can fix the other problems with this beast. I dropped the LH tank which to my surprise was full of fuel, clean somewhat fresh fuel. I decided to check some wiring first to see if by luck the fuel pump works. It is all new, tank and pump. I get a new dash switch and get something. The pump runs but no reading on guage and no start. I pull the feed hose off, it pumps a good stream on the ground. I put it back on and crank and crank, no start. The selector valve seems to be nonfunctioning. Hopefully I can get a new one or a used one at a junkyard as I am broke now buying stuff for this thing. I could not get a rebuild kit at all today, I tried everywhere so I willhave to order one online. I did swap injectors from side to side to see if there was any difference. It idles okay and fired right up, but until I get the tanks back in and the selector valve I am dead in the water, or driveway rather.

[1track]

well got the new selector valve installed today along with a new fuel filter. Truck runs smooth and purrs like a kitten. Now on to finding a replacement tank for the rh side.

[Cherub]

i love happy endings

[rfmaster]

Congratulations! - that 454 has a lot more miles to go on now. Tanks are relatively cheap and replacement can be had for about $120+. Good Luck with your truck!

//RF

[billnorman]

Hats off to RFMASTER for providing neat, detailed and accurate technical advice. I'm sure that I as well as many others learned a lot reading these posts.

[1track]

well I spoke too soon. It ran great for about an hour, then started idleing very low to where it would die when you come to a stop. SMoking black smoke too and giving the running rich code. Now what?

[f.monroe]

Post #5 , EGR valve .
Frank

[rfmaster]

Originally Posted by 1track

well I spoke too soon. It ran great for about an hour, then started idleing very low to where it would die when you come to a stop. SMoking black smoke too and giving the running rich code. Now what?

Reset your ECM - disconnect battery for about 30 seconds. This should clear all incorrectly learned fuel adaptation (BLM tables). Also, reset IAC. Rich code code could be due to higher fuel pressure (20PSI+) and ECM just does not have range to adapt. Re-verify your fuel pressure - also check your return line for restrictions (back pressure) (tank selector switch on return line)

//RF

[1track]

Originally Posted by f.monroe

Post #5 , EGR valve .
Frank

I unplugged it with no difference in running condition. I cleared the codes and it idles when cold, but blows black smoke like a diesel from running way to rich. How do I reset the IAC?

[1track]

okay, I pulled the IAC and the plunger, node, has a minor wear mark on it from ,I would say, being the original piece. I cleaned it really good and the chamber it bolts into with tbi/carb cleaner. I also rotated the cone some so the wear mark would be on the opposite side. I also pulled the egr valve and checked for diaphragm action and if the shaft seemed wore. It looked okay and while blackened, it wasn't plugged up any. If I replace the two I am looking at around $300 and I am already out that if not more with replacing tank selector, tank, pump, filter, map sensor, and whatever else I am forgetting. It will idle now but acts like it has a cam with a large lope, idles very low too, maybe 3-400 rpms (no tach), and smokes at idle from being rich but has the power when punched. Will flat get it when punched from a deadstop.

[suicide 63]

Originally Posted by 1track

well I think I may have found the root cause. My tank selector valve I believe is sticking part way causing low fuel flow, which may be my lean mixture issue. Map seemed fine and I haven't been able to drive since I cleared the codes. How did I come up with this, well my LH tank didn't work (or so I was told) so I never used it, the switch on the dash seem to verify this. Well, I was under the truck today checking fuel lines and noticed my RH tank was leaking (badly) so I decided to swap the fuel pumps in both tanks and go to the LH till I can fix the other problems with this beast. I dropped the LH tank which to my surprise was full of fuel, clean somewhat fresh fuel. I decided to check some wiring first to see if by luck the fuel pump works. It is all new, tank and pump. I get a new dash switch and get something. The pump runs but no reading on guage and no start. I pull the feed hose off, it pumps a good stream on the ground. I put it back on and crank and crank, no start. The selector valve seems to be nonfunctioning. Hopefully I can get a new one or a used one at a junkyard as I am broke now buying stuff for this thing. I could not get a rebuild kit at all today, I tried everywhere so I willhave to order one online. I did swap injectors from side to side to see if there was any difference. It idles okay and fired right up, but until I get the tanks back in and the selector valve I am dead in the water, or driveway rather.

Did the tank selector valve fix your fuel guage problem?I have the same issue.

[rfmaster]

Originally Posted by 1track

okay, I pulled the IAC and the plunger, node, has a minor wear mark on it from ,I would say, being the original piece. I cleaned it really good and the chamber it bolts into with tbi/carb cleaner. It will idle now but acts like it has a cam with a large lope, idles very low too, maybe 3-400 rpms (no tach), and smokes at idle from being rich but has the power when punched. Will flat get it when punched from a deadstop.

To reset IAC you need to go through the following steps (you'll need to get a hold of a tach):

1) Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' pins.

2) Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.

3) Start engine. You are now going to adjust "minimum air". There is a Torx screw on the front driver side of the throttle body. This set screw (only if absolutely necessary!) needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the minimum idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.

4) Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive for a stock engine.

5) If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait about 1 minute. This will clear the ECM of all trouble codes. Re-connect the battery and drive to allow the ECM to relearn your driving style.


A rich idle condition like you are describing could be due to a vacuum leak. Check your idle vacuum by inserting a T in the line that feeds MAP sensor. At idle stock engine should have 16 to 18 in-Hg and MAP sensor voltage should be between 1.0 and 1.5 Vdc Pin B measured to ground. I would also check TPS voltage Pin B to ground, at idle it should be 0.4 to 0.9 Vdc and >4.5 Vdc at WOT.

Re-verifying fuel pressure and making sure that base timing was set correctly.

For further troubleshooting a WinALDL program (free) running on a laptop with ALDL cable are the best tools to have unless you have access to OBD-1 scanner or GM TECH-1.

//RF

[1track]

Originally Posted by suicide 63

Did the tank selector valve fix your fuel guage problem?I have the same issue.

yes it did

[1track]

Originally Posted by rfmaster

To reset IAC you need to go through the following steps (you'll need to get a hold of a tach):

1) Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' pins.

2) Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.

3) Start engine. You are now going to adjust "minimum air". There is a Torx screw on the front driver side of the throttle body. This set screw (only if absolutely necessary!) needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the minimum idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.

4) Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive for a stock engine.

5) If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait about 1 minute. This will clear the ECM of all trouble codes. Re-connect the battery and drive to allow the ECM to relearn your driving style.


A rich idle condition like you are describing could be due to a vacuum leak. Check your idle vacuum by inserting a T in the line that feeds MAP sensor. At idle stock engine should have 16 to 18 in-Hg and MAP sensor voltage should be between 1.0 and 1.5 Vdc Pin B measured to ground. I would also check TPS voltage Pin B to ground, at idle it should be 0.4 to 0.9 Vdc and >4.5 Vdc at WOT.

Re-verifying fuel pressure and making sure that base timing was set correctly.

For further troubleshooting a WinALDL program (free) running on a laptop with ALDL cable are the best tools to have unless you have access to OBD-1 scanner or GM TECH-1.

//RF

I will see if the cap to the idle speed is there, if it is then I don't want to mess with factory settings. I will check the map sensor voltage and tps voltage. If the voltage is low of hi to the map, shouldn't it be throwing codes? Will let you know what happens

[f.monroe]

I say EGR because i have been through the same basic thing with two 87's . I spent money replacing all sorts of things until I went to the dealership and bought a GM EGR valve . Problem solved . Mine ran great sometimes and like you describe sometimes . If it was mine I would buy a GM EGR valve . I think mine was $75 at the dealer and that was 1 1/2 to 2 years ago .
Frank

[1track]

Originally Posted by f.monroe

I say EGR because i have been through the same basic thing with two 87's . I spent money replacing all sorts of things until I went to the dealership and bought a GM EGR valve . Problem solved . Mine ran great sometimes and like you describe sometimes . If it was mine I would buy a GM EGR valve . I think mine was $75 at the dealer and that was 1 1/2 to 2 years ago .
Frank

if all the above check out okay, then that will be my next purchase

[iwilkerson]

I kept getting those codes also, got the 33 fixed but the 44 kept comming back. I replaced the O2 sensor,Map,new plugs cap rotor button, all new Vac lines,dist moduel,ran carb cleaner around all areas no difference, rebuilt TBI, replaced 1 injector that looked bad,fuel filter, finally I dropped the tank the pickup screen was clogged so I replaced the pump and screen and that fixed the issue, now it runs like a 454 should
SO before you start doing all the replacment get a fuelpressure test