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So I’ve got Little Blue  (87 4x4 4.0 auto) to run. Having some issue though. Truck idles fair, but does stumble (drop) occasionally. It has a new CPS, MAP, IAC and TPS. Upgraded 746 injectors and new plugs. Plug wires and distributor look fairly new also. 
 

When running it has good power in reverse, in forward gears it does not seem to have much power but will move. I ventured around the block today. Started out moving pretty good, then about 1/2 mile in it stumbled and seemed to lose power. Engine was stumbling and had some backfiring, limped it around the block about 10-15 mph after a couple of stalls. Engine starts right up after a stall. 
 

What are y’all’s thoughts? 

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3 hours ago, JustEmptyEveryPocket said:

Have you checked Fuel Pressure and Cylinder Compression numbers? That might be a good place to start looking at information.

Fuel system is all new except for rail and lines. New fuel pressure regulator, fuel line clip/connector, fuel pump and filter. I just repaired the splice for the fuel pump relay. Truck doesn’t smoke and has a fresh oil change. 

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So after a few more of @cruiser54s tips it seems I’ve got the idle better. She still wants to backfire and sputter if throttle is opened fast while parked, but that goes away after a moment or two and she revs fine to full throttle. Driving is a different story doesn’t want to accelerate at all under a load. Engine revs stay low and there is some sputtering and occasional backfire. 
 

I tried to recalibrate the new TPS from rock auto with no luck. Went back to the old TPS that came with the truck. It doesn’t want to calibrate either but it does at least show a reading. 
 

My base was 4.56 which means the out pit should be 3.78 all I can get out of the current TPS is 0.10. Ordered a Mopar TPS we shall see if that helps. 

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1 hour ago, BeatCJ said:

I think you're on the right track, but what's the condition of your catalytic converter? 

I haven’t looked at the guts of the car but it’s there. I am sure it’s an old one but probably not OEM unless it’s been gutted. Exhaust is on the list of things to do. Current muffler is beat up to say the least (has dents in it). I have a new muffler and tail pipe ready to put on soon.

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41 minutes ago, MiNi Beast said:

wrong/bad cps or out of alignment.  check and replace as needed. :thumbsup:

I recently replaced the CPS with one from rock auto. Also completed @cruiser54 Sensor ground fix #6 today.

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2 hours ago, cruiser54 said:

which Tips have you completed? 

 

Check fuel pressure with a gauge. 

Can’t remember all the specific numbers, but I’ve refreshed all the grounds. The splice for power to fuel pump relay, #6 just the other day and the idle got better. 
 

was just looking at the permeate fuel gauge install. Need to get the parts for that. I don’t have a fuel pressure gauge tester. I’ll be checking to see if I can rent one from a parts store.

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Tested CPS and I getting no reading at all. (So much for new being good). Have a new one ordered through NAPA. 
 

Tested sensor grounds no problems found. Tried again to set TPS (my reference is 4.56 x .83 = 3.78 output) all I can get out of the TPS is 1.26. So I also have a genuine Mopar TPS ordered. 
 

While trouble shooting I decided to pull the plugs and see how they looked. These were put in after I got the truck and maybe have an hour of mostly idle run time on them. Front three looked like this:

DB683CFA-79D5-42E9-BC16-B5F49ACCD0DE.jpeg.9d71d76b6424cca08be45d16f85239e5.jpeg


Cylinder # 4 looked like this:

72FF0186-FD22-4FAC-A781-E357C5348AC9.jpeg.38b3d47a7aa8577c8b28b844d33f294c.jpeg

 

5 and 6:47F45C7C-3C5B-4848-98A9-67646E88890E.jpeg.c7455a9526e392957c064f6f7fded48c.jpeg

 

Checked injector electrical connections and believe #4 was not making good contact. Reseated and idle seemed to smooth out. Checked all injector electrical connections and ensured they were seated good. 
 

Am I missing anything else? 

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18 minutes ago, CGCWO said:

Tried again to set TPS (my reference is 4.56 x .83 = 3.78 output) all I can get out of the TPS is 1.26.

 

862493237_C220TPS3pin.jpg.3d2000d3471924787a773a36c3bf25bf.jpg 1039320879_C259TPS4pin.jpg.730da11d8da78e524c6b0647f09c1b51.jpg

 

Which connector are you taking your measurement off of?

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The 4 plug square A and D 4.56, B and D 1.25. On the truck harness side. Good news is my backfire condition seems to have resolved. Thinking maybe that was some trash or bad/old gas. As I finally had to put some more new gas in today. 
 

Hope to get the REM from @NickInTimeFilmsin a day or so, received shipping info last night.

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http://cruiser54.com/?p=54

 

This is cruisers write up on the TPS.

4.56 seems low to me maybe just me. It is a 5V reference. I would definitely check the ground. Where the 3 intersect into 1 would be my guess. I skipped resoldering it the first time I went through my wiring. Went back and did it and was pleasantly surprised at the difference at the sensor.

http://cruiser54.com/?p=47

Here's the link to the wires I'm talking about.

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I did both the three prong flat and the square as not only do I have the idle issues but also the auto trans shifting issues. I will go back over it tomorrow and post my results. 
 

1 hour ago, cruiser54 said:

Use only the flat 3 wire connector. Have you read my write-up on setting the tPS?


I also have already tip #6, but I will go back and look at the connection again. 
 

 

44 minutes ago, JMO413 said:

http://cruiser54.com/?p=54

 

This is cruisers write up on the TPS.

4.56 seems low to me maybe just me. It is a 5V reference. I would definitely check the ground. Where the 3 intersect into 1 would be my guess. I skipped resoldering it the first time I went through my wiring. Went back and did it and was pleasantly surprised at the difference at the sensor.

http://cruiser54.com/?p=47

Here's the link to the wires I'm talking about.

 

On a happier note my electric fan works and comes on when the engine reaches temp. 
 

Still a long way to go, but moving forward. Get this sorted and then it’s on to brakes. 

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