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92 k1500 hesitation/power loss problem


hunter4ever12
10-08-2014, 08:33 AM
I have a 1992 k1500 5.0L. The pickup seems to run good, or at least better when it's cold and engine isn't to operating temp. But once it reaches temp it loses a noticeable amount of power, as well as has a "dead spot" in throttle response. From about 1/2 to 3/4 it's like nothing happens you push the pedal but no response. Only at about 3/4 once it down shifts then you get an increase in speed. So now back to power loss. It is bad enough that just to maintain a highway speed of 60mph it will downshift even on very small hills and on flat ground the pedal is about 3/4 of the way to the floor.

Some history:
It has a rebuilt transmission in it with a 2000 rpm stall converter instead of stock(so two questions one when I re installed the kick down cable could I have adjusted it wrong and could this cause my issue, and what's the proper way to adjust? Second could the 2000 rpm stall converter cause any issues?)
It has a new distributor, cap, rotor, along with plugs and wires. I recently installed: knock sensor, map sensor, coolant temperature control sensor, tps sensor, egr valve, pcv valve, ecm, rebuilt the throttle body, as well as a few other things I'm probably forgetting.
I suspect the engine is running rich because the exhaust tail pipe has a lot of soot(it has no cat was that way when I bought it but it has way more soot than it should even with no cat.) I just checked fuel pressure and it's right at 11 to 12 psi. I haven't pulled plugs yet to confirm rich condition, but last time I changed them they were all black as coal.

Any help to restore some power back to this old pickup would be greatly appreciated.

hunter4ever12
10-08-2014, 01:59 PM
Another thing I just thought of was, if my throttle cable from the pedal to the throttle body has stretched. Which would then cause it to never be at wot when pushing the pedal. Which in turn could cause issues with my kick down cable because when I set it I manually pushed the throttle to wot by pushing the arm on my throttle body. Could this possibly be a cause for my issue? If so my next question is how do you adjust the throttle cable? ..... I will check to see if this is even an issue when I get home. I will have my wife push the pedal to the floor and then I will see if I can press the arm for the butterfly back and open the throttle any more.

Schurkey
10-08-2014, 07:12 PM
I'd connect a scan tool, verify O2 sensor operation, verify O2 crosscounts, verify closed-loop operation. I'd check to see that the engine operating temperature seems normal, I'd look at the short- and long-term fuel trim numbers. I'd look to see if the knock sensor is retarding timing. I'd see whatever other data is presented.

Lastly, I'd look for whatever codes might be present.

Any chance the brakes are dragging? Tires inflated?

hunter4ever12
10-09-2014, 09:04 AM
I only have a code reader, I do have access to a scan tool but it's limited. It's my buddies and he is about 100 miles away, so I will try to get it asap. As far as codes none are preset. I did recently have a code 43 but that was taken care of I replaced the knock sensor, knock sensor wire harness as well as the esc module about a month ago, cleared the code and it hasn't been back since. Brakes aren't dragging just checked that last week. As far as tires, they are all inflated to proper pressure, but I will add, I am running 285's on it. So with that being said a little power loss is to be expected with the bigger tires but still not as much power loss as I'm experiencing. Also even when running 235's the power of the truck wasn't up to par so I know it's not the tires.

I checked the throttle and the kick down cable last night and pedal to the floor the throttle is wide open and the kick down was slightly out of adjustment, about an 8th of an inch from being all the way out at wot I adjusted correctly(all the way pulled out at wot.) I then noticed a slight improvement but the "dead spot" is still there, just less prominent, as well as it still is lacking the hp to easily drive at highway speeds. Also after adjusting the kick down cable, it does downshift sooner now and feels "like it's supposed to" far as down shifting when you get on the throttle but if you really get on it, it downshifts rpms go way up(by sound I don't have a tachometer) the Speedo doesn't go up much if at all, almost like all that happens is the engine revs way up, then as soon as it shifts again, it's like a "slingshot" it takes off like a bat out of hell and Speedo climbs up pretty fast. And if.doing on dirt tires break loose a little bit. When it shifts it's a hard shift and sits you back in your seat which if I understand correctly is good because that means there is no slippage correct? It has always had hard shifts since I rebuilt it(completely rebuilt it with all new parts all around including an entire new housing, 2000 rpm stall converter, sun shell, etc. etc) So I guess my question is, one will this do harm, and two what could cause this? The 2000 rpm stall converter possibly?

Also pulled a plug from each bank and inspected both plugs were a nice chocolate color so it is not running rich like I thought it was. I will say tho that after I adjusted the kick down cable last night it is running a little hot. It has a 195 deg thermostat and this morning the needle stayed right at about 205 to 210 deg. I suppose I could still be a little lean yet even tho my plugs looked good, just due to the fact that I have a Tbi spacer, injector pod spacer, high flow air filter, and the "salad bowl" on my intake. With those mods is 11ish psi an ok fuel pressure?

hunter4ever12
10-12-2014, 07:08 PM
Hey just to let everyone know I figured it out... thank you for all the help I couldn't have done it without you, I appreciate all your input(sarcasm for those of you that are intelligence challenged) :headshake

ASJT3
10-14-2014, 09:56 AM
Hey just to let everyone know I figured it out... thank you for all the help I couldn't have done it without you, I appreciate all your input(sarcasm for those of you that are intelligence challenged) :headshake

What was the issue in the end/how did you resolve it?

hunter4ever12
10-14-2014, 12:04 PM
Well first adjusted the kick down cable properly. I then put 2 and 2 together by realizing, if it runs good before the engine is to operating temp but bad afterwards it had to be lean because before engine reaches temp the coolant temperature sensor tells the computer the engine is cold still and delivers it with more fuel. So I took the fuel pressure regulator out of the throttle body, bumped up the pressure(i have an adjustable fuel pressure regulator) Re installed, checked pressure, it was right around 14-15 psi. I then test drove it, was better but still didn't like where it was at. I then adjusted base timing to about 3 degrees advanced. Tested again and it was night and day difference. Went from having the pedal to a little over half way to the floor just to maintain a speed of 60 mph to only having to have the pedal barely pressed down probably about an 8th of the way to the floor to maintain 60mph.

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