95 jimmy, 4.3 cpi. tranny or motor?

well i'll start from the beginning. about 5 years ago i was driving down the road and the torque converter came out of lock up and wouldn't go back no matter what i did. i came to a complete stop and then it returned to norm. then it has been fine until the past 8 months it started doing it again although this time it'd do it more often. it start by dropping out and then a few miles down the road it would come back in. it would do it 2 or 3 times and then be fine. then other days it would be fine and never happen at all. then i was driving it one day and i went to stop at a light after getting off the highway and the rpms were held around 1,600. it drove fine but the idle was being held high. drove about a mile to where i was going shut the truck off and came out a few hours later and it was fine. let the truck run for about 5 mins and then it went back up to1,800 or 2,000. shut it off and wiggled the connector at the tps. restarted truck and all was fine. the next day i replaced the tps. then everything was fine for a few weeks. now the newest thing is the converter issue is getting worse and will sometimes go in and out 10 times in a min and then be fine for awhile but then start back. if i come to a complete stop and wait 10 secs and then drive again it returns to normal. and normally it wont have anymore issues until the next trip. but now its also for the past month has been that i'll shift into drive and hit the gas and the truck will almost die but then recovers and i drive down my street. then i'll take off from a stop on throttle and then the truck starts surging. it does this though all gears and doesn't stop until about 5 miles down the road and then it runs great. although last weekend it stated doing it after coming to a stop and driving it for a hour. when it kicks in and runs right it feels like a boost of power.

no ses, tranny was flushed 2 months ago, tune up was 1 year ago, replaced plugs, wires, cap and rotor. cpi is about 4 years old with a regulator that was replaced 1.5 years ago. when it has problems with the torque converter my speed is at least 55 or better. any ideas?

Needs to be put on and checked oiut with a good engine/transmission capable scanner.
Read out shift and TCC data and codes
Post back any codes no's engine or transmission.

had it scanned today. it wasnt setting any codes but when looking the trans info we found it to be saying the tps was bad. took it for a test drive and sure enough it was. at 100% throttle it would read 60%. so we replaced that. then the torque converter started acting up and we found that the brake pedal switch to be telling the trans not to lock the converter up because i was applying the brake even though i wasnt. so this weekend i pan to replace that. it runs alot better but it still seems to have a little power loss from somewhere. was told also that it may be the computer going bad. i have a spare though.

Just a tip, computers almost never go bad. I'd be very careful swapping the computer on these trucks since they sometimes require a flash to make them work on a different vehicle.

well i swapped out the brake switch and i tried to map sensor also. still having issues. swapped out ecm and still the same issues. any ideas?

Proper testing.

hooked up scanner again to the truck and found out the abs light was coming on because it said the brake switch was shorted or stuck open. so i traced it out and i found 2 wires had came out of the plug on the brake switch. i plan to replace the connector today.

replaced connector and all is now well. converter now locks up properly.

well today i got it back from the shop. i needed tires balanced. and i'm still having issues with the motor. so while it was there they took a crack at it and found nothing. they also said everything looks fine but they can tell when they drive the truck it has no power. no one can figure it out. checked fuel pressure and its dead on. even driving it stays right where it needs to. put a vac gauge on it today and it was running 16.5hg at idle but if you brought it up to 2,000 rpm it'd pull 20hg. i dont know if it means anything. the other thing is that the idle is a little rough like you can tell theres a slight miss but if you unplug the vac line and make a vac leak then it smooths out and idles better then a sealed system. any ideas?

Out of curiosity, have you ever pulled and cleaned the EGR valve and the IAC valve?

the egr was replaced about 6 years ago. i cleaned the egr last year. iac i cleaned about 2 years ago. any other ideas?

Need to be put on a engine/transmission ca[pable scanner and road tested when it acts up.
Check all sensor readings and for present /past and history codes or and misfire codes.
If any codes post back codes no.
Also on that dead on fuel fuel pressure?
Was it tested on the road after it got hot and acting up.
What were the pressure readings?The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.
Your specs on a 96 code w is 55/61 you should see 57-60 running on road depending on engine load.
Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

Is it a code W or Z engine and does it have a PCM or VCM?

well today i got it back from the shop. i needed tires balanced. and i'm still having issues with the motor. so while it was there they took a crack at it and found nothing. they also said everything looks fine but they can tell when they drive the truck it has no power. no one can figure it out. checked fuel pressure and its dead on. even driving it stays right where it needs to. put a vac gauge on it today and it was running 16.5hg at idle but if you brought it up to 2,000 rpm it'd pull 20hg. i dont know if it means anything. the other thing is that the idle is a little rough like you can tell theres a slight miss but if you unplug the vac line and make a vac leak then it smooths out and idles better then a sealed system. any ideas?

That sounds like limp mode - 3rd gear only :confused:

Gauges bottoming out to 0 for no reason ever, then coming back up?

well the latest is that i've been playing it it and if i unplug the egr then the truck runs pretty good. idle is still off a little but performance is better. so i used a spare egr and plug it in while the current one was installed. i noticed that when i reved the motor the egr would open but then shut as soon as i let go of the throttle. as for fuel pressure the readings were taken with ignition on but motor off and pressure was 60-65psi. motor running was about 56psi. gave some throttle and shot right up to 63psi. took it down the road with tester still on and fuel pressure was always about 63-65 psi depending on load. i replaced the fuel pressure regulator this weekend just to be sure and still no luck. then thats when today i played with the egr. any ideas why its opening on load? gonna try to get a scanner soon and see what changes while driving. but 2 other mechanics looked at it and couldnt find anything even while it was fouling up. as for limp mode i know its running fine. shifts all gears and gauges read fine. and the computer is the vcm-a. its on top of the coolent bottle.

last night putting on the scanner we found the egr to be opening up to as much as 86% when the truck was under a load. less throttle and the less it was open. floor it and its 100%closed like it should be. any ideas why this is happening?

well the latest is that i hooked it up to another scanner. according to the computer its seeing a knock so its retarding the timing as well as opening the egr. even with the knock sensors unpluged it still sees a knock. i also swaped back in the old vcm just to make sure of things and no change. any ideas?

no ideas?