# Extremely rich fuel mixture



## OKCSpitfire (Jan 16, 2008)

Hello, I have a 89 HB D21 2WD pickup with a Z24i engine. Most times it runs great, smooth idle easy starting. Have had the truck since March of 07 only changes thus far is replacing the fuel pump in the tank. However, over the last two month the truck will suddenly run rough and starts blowing black smoke out the exhaust. One day I'll have to hold my foot on the brake and keep pressure on the gas peddle to keep it running. Next day the truck runs fine again like there never was a problem. It usually starts doing this when I start the truck, no set time morning or afternoon it's does not appear to be related to internal or external temps. Totally random but when it does it drinks gas like it knows there is a shortage and it wants all it can get. Anyone have any ideas that might help me determine what needs to be done to fix it?

Thanks
J Stasysezn


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## SE-R Redline (Dec 12, 2007)

o2 sensors control the mixture of the gas, maybe start there. it could even be the sending unit on the fuel pump


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## dvdswanson (Nov 6, 2005)

check for codes


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## bkea (Feb 4, 2005)

Check for codes first. I had a similar problem and it was the airflow meter (similar to MAF or MAP sensor).


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## OKCSpitfire (Jan 16, 2008)

*Thanks for replying*

I found a link on this forum that give instruction on how and where to find the codes so I;ll give that a try. I asked an autoparts store here in Oklahoma about an O2 sensor and they said it didn't have one. I haven't found one either, if it had one it was remove by the PO, the exhaust system is not exactly a grade a upgrade. The airflow meter is something to look into I knew it didn't have a MAF sensor like on newer cars and trucks but it would make sense if it has one. Something is causing the truck to dump more than normal amounts of fuel into the cylinders which is causing it to run extremely rich, an airflow meter could be the cause.

Thanks


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## bkea (Feb 4, 2005)

A z-24i definitely SHOULD have an O2 sensor. It is on the exhaust manifold. It should be rather cheap. O2 sensors mainly work at idle though, not so much for faster speeds. 

The AFM mounts on the throttle body. I bought one from an online wholesale dealer for around $125.


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## zanegrey (Dec 5, 2005)

read the codes..

the injectors are firing continuiously..

1. the injectors are bad or u have lost the control signal from the ecm to the injectors..2.

3. the fuel pressure regulater is bad ..so the injectors just bleed ..

but i am really drunk right now so read the cod4s..


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## 88pathoffroad (Jun 6, 2004)

A bad coolant temp sensor can also make it run rich if it's telling the ECU that the engine is cold when it's not.


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