Howdy folks,

I have a customers car at the repair shop and the problem of it: 454BBC 1989
It wont pass emissions here in Germany, its running very rich, especially in cold start/open loop.

At first, I thought its running LEAN cause of its lack in power and light stumbling. So I hooked up a fuel gauge to check fuel pressure. Sadly, the gauge is not a quality piece and showed not exactly the pressure, I just came behind this after I hooked up a second gauge to adjust fuel pressure after changing fuel pump, fuel filter and pressure regulator diaghragm. It has the yellow tension spring in it, but changed to the other weaker spring in the regulator package wont change much. The regulator housing was plombed. I drilled that out and made it adjustable to correct the fuel pressure to 13 psi. The injectors has been changed some months ago since the problem exist a little longer already.

I hooked up tunerpro and made a datalog, I can post it here if its okay and somebody can help me. The async mode is on most of the time and it shows 300% (and more!) injector duty cycle. The sensor like o2 sensor, map, cts, tps act just fine. I double checked map and tps sensor with a DVM and it looked fine. I searched for vacuum leaks, everythings fine. Plugs and wires are new, rotor and cap looks fine to me. The BLM was 112 all the time, quite low. Its pulling fuel and dumping fuel at the same time?

When engine is coldstarted its stumbling bad! Nearly no vacuum, thats the cause it triggers the Code 33 Map high resistance, low vacuum for a sort of seconds that doesnt relate to rpm and TPS values.

Under load it drives OK, but not "nice" and no real power. In idle its way to rich.
Dont know what to check next, Im a little lost.

Could someone help me?
Greetings,

Chris

 

Is the timing at 4° BTDC with the EST wire disconnected? My buddies 91 dually was a bit retarded, bumped it to 8° BTDC and it never ran better. He never towed with it, so it was able to tolerate a bit more timing without knocking. Have to go fairly easy on the timing increase since the early 454s did not come with a knock sensor.

 

HOW is it failing? Excess CO probably means it's too rich. Excess HC probably indicates misfire. Excess NOx would relate to failed EGR/high combustion temperature.

If it's truly running rich in open-loop, creating a vacuum leak will make it run smoother, and at higher rpm.

Plomb is Latin for "lead". Pb is the chemical symbol for lead because of that. You're saying the regulator adjustment was soldered to make it non-adjustable. Yes, GM solders or welds the adjustment screw to make them "tamper-proof".

13 psi on an ACCURATE gauge is fine for that model year. Later TBI 454s used higher pressure. A common problem is folks using a guage intended for higher-pressure fuel injection, that perhaps reads to 80 or 100 psi, which is likely not accurate at 9--13 psi that the TBIs are specified for.

Changed...to WHAT? Stock replacements? Injectors with higher capacity? Finding this out could be crucial. Run the fuel pump without triggering the injectors. Is there fuel leakage past the O-rings or gasket that would enrichen the mixture?

I don't know Tunerpro. 300% duty cycle is not possible. Something is screwed-up.

Doesn't seem reasonable that the injectors are running "300%" duty cycle, but the O2 sensors are not showing rich exhaust.

The computer is indicating by the low BLM number that it's in lean-command. It's attempting to reduce the fuel delivery.

With no manifold vacuum, the computer will try to add fuel because it thinks the engine is under heavy load. TPS and perhaps O2 sensor would tend to counteract this. So the computer is getting sensor data saying it needs both more fuel, and less fuel.

I would connect a real scan tool, and verify ALL the sensors, in particular the coolant temp, MAP, and TPS; and assure that the vacuum hose and therefore the vacuum supply to the MAP sensor is good, and the coolant temp sensor is accurate. Make sure the charcoal canister is not flooded with gasoline.

 

Hey folks,

thanks for answering. I attach the. csv log file for you. Do you need the file for tunerpro also? Maybe you see something, that went wrong??
The fuel pressure was read by a gauge that have 0-4bar pressure scala with 0,1bar for a point on it so its pretty accurate. Thats the reason with the first gauge I thought it had not enough fuel. So fuel pressure is set to 13psi with help of the adjustable regulator now.

Its failing emissions testing cause of too much CO at idle, it has 7% CO and it should have no more than 0.5%.
When its on rpm, 2700 for example, it has good values, CO is very low and lambda is 1.02.

On cold start, it is worst, hard starting, long cranking and terrible smoking exhaust (smells rich).
Its stumbling bad and on rpm the engine slowly begin to fire on all 8 and then it starts to run ok with raising temperature.
As I said, I measured the MAP and TPS and they act good. Thats also what I saw on my datalog. The CTS is ok as far as I can see from my laptop data, but couldnt verify it yet cause the ac compressor is in the way. The injector duty cycle is unbelievable high as my data show, 300% is nothing, I believe 900% was shown on load and rpm. I also cant believe that since its running so rich! Im out of my mind. The vacuum hoses are new to MAP and so on. Charcoal canister was not checked yet but I can unplug the port to the TBI.
Next step is to check timing.

On cold start, it doesnt have vacuum, but the cranking pressure in the cylinders are ok. Thats just a problem with fuel delivery? How can an otherwise healthy engine doesnt produce vacuum?
With raising temperature or (of course) rpm, the vacuum increase and is OK when warm, like 20in/HG.

When driving, it feels like it has not that much power it should have and feels like something is throwing out and anchor, like "chewing gum effect" we would say here. But it drives ok! But not like it should.

The injectors where stock replacement SMP TJ11 with 90.77 lbs/HR.
Some advice guys?

Greetings,

Chris

 

I run the same TJ11 injectors on my 383 CF motor. Those are not rated at 13psi for flow rate of 90pph. I had mine tested and they are 80pph @13psi and 90.5pph @ 15psi.

 

As a rule, high HC is misfire, high CO is rich mixture.

You need guidance from someone else, but 300--900 percent duty cycle sounds like a measurement-tool incompatibility or outright defect to me. I've heard of slightly over 100%--like 103 or maybe 105 percent, It's an artifact that has to do with the response time of the injector--it doesn't shut off instantly when the power is removed, I guess. 300% seems to me to be completely unreasonable.

I think we have to assume that the catalytic converter is very unhappy; and probably defective by now.

 

Coolant temp sensor in front side of intake manifold.

 

Kinda thinking he got that message a year ago. Never bothered to tell us what he found, or whether it got fixed.