I have an 88.5 Sammie. With a stock carb it was getting 24 mpg.  After the carb went T.U., I installed an EFI from a 92.  It runs weaker than before and very rich, so rich that there is smelly, black smoke at idle.  I've put in new plugs, wires, cap rotor, K&N filter from TT, Thorley header, O2 sensor, 2" exhaust and new muffler with cat, new fuel pump and filter, checked my vacuum line routing, adjusted valves and set timing at 10* BTDC.  I failed emissions and I'm pulling my hair out, what's left that is!!  

The idle seems to be at the proper speed, but it can be rough.  My fuel mileage has dropped in half as well.  What can be wrong?    

The motor only has 65k on it and is the original engine.  I have a new timing belt, that is my next step.  Does anyone have any ideas?  How do I check the MAF sensor?

I really need to get this fixed.  My p/u has a 383 stroker in it....and it needs 93 octane!!!   $48.00 to fill the other day!!!

Thanks everyone!!

Nobody who knows anything is answering here, so I'll say something. It seems obvious to me that you are running really rich. That is almost certainly a result of the fuel injection system either having a defect or being told by a component (computer? mass air flow sensor?) to add fuel. It may be that the fuel injection is in a limp-home mode because it is not receiving the correct information, or it may be that the computer is in limp-home mode because the MAF or some other component is either defective or missing. Have you thoroughly checked a stock fuel injection installation to make sure you have everything you need?

Yea this is Wilds department and he is being led through the Golden Spike trail at this very moment by Hagen i'm sure they will be back on line no later than monday braging about the trip, and will respond.
Zig

Nobody who knows anything is answering here, so I'll say something. It seems obvious to me that you are running really rich. That is almost certainly a result of the fuel injection system either having a defect or being told by a component (computer? mass air flow sensor?) to add fuel. It may be that the fuel injection is in a limp-home mode because it is not receiving the correct information, or it may be that the computer is in limp-home mode because the MAF or some other component is either defective or missing. Have you thoroughly checked a stock fuel injection installation to make sure you have everything you need?

  I had NO idea that older models using a carburator even had a fuel injector. I would say (and I'm really guessing) that the engine is running rich and the mixture screw on the carburator needs adjusting. It could also be a simple problem with the carburator float. Sometimes they absorb fuel and sink.

Longrod, he replaced his carb with a fuel injection unit from a later-model car. I'm sure it's been done before, but I also suspect there are traps for the unwary. That's why I suggested he check a stock fuel injection unit to make sure he has every single piece he needs.

i dont know much about this..but dont losse hope alot of the more well informed zuki people are at MOAB or on there way back right now..so im sure when they gat back someone will be able to help u

I did the timing belt and it runs much stronger, but now I have a code 44, TPS. I don't have a vacuum pump or the right feeler gauge to test it. It has black soot inside my new exhaust from running so rich. Has anyone had any luck with troubleshooting the TPS code?

Check the water temp sensor, disconnect it and see if it is running rich like before or not. If there is slight inprovement compare to when it is connected then it may be a fauty water temp sensor.

If the water temp sender was bad, wouldn't it keep the idle up high all of the time?  I'm going to check all of my grounds tomorrow and if that doesn't fix it I'll have to take it to a shop.  In WA state, if you fail emissions, they can make you spend up to $150 to fix it.  The only problem is it has to be at a state certified repair shop.  It doesn't count towards the $150 if I buy tuneup parts and do my own work.  It has to be documented and then you can get a waiver.  I don't really want a waiver, I want it fixed!!

Faulty water temp sensor won't keep the idle high, it just cause the engine to run rich. Some time too rich that the engine is hard to start, it just faul up the sparkplug.
I have the same problem on a 2.0L V6. Tested everything ECU, TPS, AFS and it turn out to be a cheap water temp sensor. I had wasted 2 weeks of spare time.

mtntoy,

I'm going to assume you have also replaced the distributor, ECM, wiring harness and added all the other components such as the electric fuel pump when you did this TBI conversion.  There are many differences between a carb'd system and EFI. For one, there is a Crank Angle Sensor (CAS) in the disty that sends engine speed info to the ECM, which in turn manipulates fuel mixture.

BTW, found my FSMs last night and did some reading....there's tons of diag stuff in there for running rich and poor fuel mileage.  You really need to get the 1990-1994 supplement (p/n 99501-83350-33E), it covers all of the stuff you're interested in.

Ronzuki, he said he has a code for the TPS - is that the throttle position sensor? It makes some sense if the TPS is bad (or not present?) that the engine might run rich.

There are 2 codes pertaining to the TPS: 21, 22 and 2 for the Idle Switch of TPS:44,45. Yes, TPS is throttle position sensor.

Somebody give PM me a fax # and I'll fax the troubleshooting pages for those error codes.

I installed the entire wiring harness, bumper to bumper, new ECM, Electric fuel pump, manifold, etc.  I got pics of stock EFI Sammies to double check my vac hose routing, I had one wrong.  With the carb running poorly as it died it was backfiring and when I changed the timing belt yesterday, I discovered it was off by a tooth.  I believe it was the original timing belt, it was stamped "89" and the truck only has 64k on it, so it was definately time.  It starts up right away, settles down to a good idle, but it will put out lots of smoke at times, especially at idle.  It's bad enough to makke your eyes water.  

On the good side, when I changed the belt yesterday, I had an excuse to change the front seals as well.  I put on a new gasket on the pan and new o-rings on the disty a while back and no longer have the oil leak called a mechanical fuel pump either.  I'm considering using some engine cleaner on it today, but I'm not sure I'd be able to work on the engine without all it's lovely oil deposits everywhere!!

With the EFI it definately has more pop at acceleration now.  I'm sure part of it is the headers and exhaust, but I was accelerating to 70 mph yesterday, not struggling to get to 60.  i t has a noticable power surge at 4000 rpm when accelerating.  I'm running 235s with stock gearing, so wheen I put in my transfer gears I am hoping to be able to run on the interstate at 70 at will.

Thanks for your help guys.  Wish me luck today!!