shifts from 3rd to od after warming up

[gmc junky]

need some help.. not shifting from 3rd to overdrive until motor has warmed up... and after awhile feels like a loss of power...installed new pmd and extension cable outside of engine compartment., also changed new coolant sensor and switch ..,, yeah the one on top of engine and the one on the side of engine/head.. and new iat sensor sensor on top of upper intake..i have been gettig codes.P0113 IAT Sensor Circuit High Voltage.., P0118 ECT Sensor Circuit High Voltage.., P0236 Turbocharger Boost System.. installed turbo master and 3" exhaust from crossover.. did away with catalytic converter also some time back before these symptons..i"m not sure but it seems like the fan kicks on and stays on longer than it did before.. even though its pretty hot here in the panhandle of texas..i"ve been in hotter places this time of year... i could just be imagining the fan...??.. temp gauge has been running pretty normal.. oh yeah.. i also cleaned all grounds.. i'm now lost..any suggestions.. thanks..

 

[ak diesel driver]

4l80s won't lock up the torque convertor until the engine reaches 170*. Are you sure it's not shifting from 3 to 4? How much boost you running? Sounds like your overboosting and the stock pcm doesn't like it. Also are you an s engine or and f? If s it could be your egr acting up

 

[540s10]

4l80 will lock up the converter at any engine temp, as longs as the ATF in the pan is over 80 degrees (yes there is a temp sensor in there).

 

[buddy]

It may be that you just notice the torque converter locking up after the tranny is warm. Everyones does that.

What year and type of truck is this?

Do you still have the codes? Did you think maybe you had a broken or shorted wires if all the sensors were reporting bad. they share common 5V sources and such.

 

[THEFERMANATOR]

4l80 will lock up the converter at any engine temp, as longs as the ATF in the pan is over 80 degrees (yes there is a temp sensor in there).

Beg to differ with you on this one. GM programmed the PCM to not lock the converter until the engine is up to 170 degrees to aid in warm-up of the engine. There is certain criteria that can be met to over-ride this function, but for the most part it will not lock-up until 170 engine temp AND roughly 100 trans temp.

 

[Detroit Dan]

When I was having tranny issues, one place told me to replace the engine coolant temp sensor as thats where the tranny got its info, however I later learned that by my year they had changed it and put a temp sensor in the pan. So changing my ECT did nothing for the tranny because it no longer (in 97) was controlling OD in the 4l80e. But apparently older 4l80es did. So it looks like you are both right.

 

[gmc junky]

1998 gmc 4-dr 2wd,, boost 8-12 at times..f engine.. left work this morning.. and yep did not want to shift into od/4th until apx 180-190 degrees..seems to have normal power until it reaches 200/210 degrees..then seems to feel bogged down..and yes still have the codes..and what i'm reading is the temp sensor in the tranny pan could be the problem..???.. i'm still thinking it may be the pcm.. i have had some overboost times.. what about a boost fooler.. where can i get one..????

 

[625fireman]

Prolly defueling due to the "active" codes in the ECM. You gotta get them cleared out before your truck would not feel sick.

 

[JiFaire]

Welcome to The Truck Stop, gmc_junky! This here is the best place on the web for you to learn about your truck and meet up with the best people around (some of whom you've already been talking to ... :thumbsup

1] Help us out a bit, before we start helping you; fill out your signature with details of your truck and what you've done to it so far. Click on the signature link (in my signature) and it will take you to yours. We need to know what modifications you have already made - it helps with diagnosis.

2] When you have a minute, click on the Diagnostic Checklist in my signature; when it comes up, highlight and copy it, then come back to this thread and paste it into a new post. Fill in as many details as you can, answer as many questions as you know how to... it will let us see and hear through your eyes. Diagnosing truck problems over the internet requires some really good information.

3] The 6.5 Technical Library in my signature has some great information in it; you might want to read through there when you get the chance, so you can learn more about your truck.

The guys here will help you figure out what's going on, that's a fact!

Jim

 

[ak diesel driver]

you need a scan tool to read the sensors. My guess is you have a faulty ect sensor (the one in the crossover)

 

[gmc junky]

Problem: Explain your problem in concise language (ie: Cranks but won’t fire). _will not shift from 3rd to 4th until warms up to apx 190 degrees___________________________

Demographics: tell us about your truck and your ambient conditions:

- Year: 1998______
- Truck model and class (ie: c2500) _GMC 3500________
- Automatic or Standard _automatic_________
- Mileage: (indicate miles or km) ___196000______
- Replaced parts and mods (IP, PMD, chip/PCM, TM, injectors etc) PMD, TM, 3" EXHAUST, W/ONLY MUFFLER___________
- Model: ‘S’ or ‘F’ engine, NA or Turbo, EGR? ____F__________
- Ambient outside temp: (indicate *C or *F) _98 F_________
- What fuel are you using? (#1 Diesel, #2 Diesel, Bio, VO, WVO, etc) _#2 DIESEL________
- What fuel additives are you using? _NONE__________
- Where are you located? __TEXAS PANHANDLE FOR NOW___________

General maintenance: inspect and evaluate the condition of each. When were they last changed?
- Air filter ___less than 3 mths______
- Fuel filter ___less than 3 mths______
- CDR Valve? __haven't changed since purchase 2 yrs_______
- Coolant – last flushed/replaced at __3 mths___________
- Oil – synthetic/regular, changed at ___rotella________
- Batteries – state of charge, (matched set) replaced at __2yrs good condition___________
- Battery cables and grounds (removed, cleaned and tightened): __cleaned ____________
- Glow Plugs - how many miles on them? ____?_____ What type? ___?__________
- Injectors - last changed at _______?________


History: (Describe how the problem first appeared.)
- What were you doing when it happened? _driving normal conditions_____________
- How was the truck running fine before this problem appeared? __only hint was rpm fluctuation of 100-200 on occasion before codes and shifting problem

_________
- Has this problem ever happened before? ____________no___________
- Describe any related factors that might be part of the problem. ____?__________
- Have you checked for DTC (Diagnostic Trouble Codes)? (Y.N) ___y_ And? __p-113 p-118 p236______


Diagnostics:

1] Starting:
1a] Does the engine start? ___yes______
1b] Does the engine crank over? _yes_______
1c] Are your batteries fully charged? yes_________
1d] Have you removed, cleaned, and tightened all battery connections? __yes______
1e] Does your Wait to Start light come on for a time? How long? __apx 60 seconds_______
1f] Does your glow plug light come on? ___n______ For how long? _________
1g] Do you see smoke from the exhaust while cranking? What color? __light color______
1h] Does the Service Engine Light Glow during Start/bulb check? _____n___

2] Fuel Issues (if not running):
2a] Can you hear your lift pump working? _____y_______
2b] Do you get a steady flow of fuel from the water drain (T-handle) ? ____?_____
2c] Loosen the inlet line from the IP – is fuel coming out (Lift Pump on)? ____?_______
2d] Loosen an injector line and crank the engine - does fuel come out? ______?___
2e] Do you hear a vacuum (hiss) when you remove the fuel cap? ____yes_______

3] PMD / IP Issues
3a] Location of PMD (on pump, on intake, remote mounted) __outside remote mounted_________
3b] Condition of Extension harness (if used) Vendor or Homemade? ___new vendor______
3c] Condition of grounds / ground wires to IP / PMD. Check Harness. __cleaned_______
3d] PMD Make: ____?_______
3e] PMD Age: ______new 1 month_______

4] Stalling Issues
4a] Do you experience stalling only when hot? ___no_________
4b] Does it stall under particular circumstances? (ie hit bump, or on accel) __no____
4c] Does pouring cool water over the IP seem to help with restarting? _?____?____
4d] Is stalling momentary (engine recovers)? ___no______
4e] Does SES light come on when engine hiccups? __no_______
4f] Does cruise control quit working when engine hiccups? ___no________
4g] Does re-starting seem to reset engine, restoring cruise and power? __?_______
4h] Changes to dash lights or instruments during stalling events? ______no_____

5] Running Issues
5a] On cold start, does upper rad hose get hard before engine warms up? _?______
5b] Any bubbles or oil film in coolant overflow tank? ____?___
5c] Any white slime on oil surfaces (dipstick, CDR, oil Fill cap)? __no________
5d] Excessive white smoke from exhaust on cold start? ____not a lot_____
5e] Excessive black smoke from exhaust under hard acceleration? __yes alot________

6] Performance Issues
6a] Do you have gauges (boost, EGT) ? ______boost_____
6b] Maximum boost under load? ______12-14______
6c] Have you added a performance PCM (reflash) or Chip? __no____________
6d] Have you changed exhaust / downpipe / crossover? ______same crossover 3" exhaust with only muffler__________
6e] Wastegate – mechanical or vacuum (OEM)? ____TM __________

7] Temperature-related Issues:
7a] Single or dual thermostats? _______?_____
7b] Have you replaced them lately? Manufacturer of replacements? __no_______
7c] Have you pulled and cleaned Radiator and coolers lately? ________no____
7d] Have you replaced the fan clutch? Manufacturer of replacement? ___no_____
7e] (winter) Have you tested your antifreeze? Good to what temp? ____?______
7f] (winter) Are you using a winter grille cover? ___no________

List and describe any other factors which are not addressed in this checklist. We can’t see, hear, smell, or touch your truck, so the more descriptive information you can give, the more likely it is that somebody can assist you

truck ran ok had vacum wastegate issues,, installed tm and 3" exhaust.. lots of power after,, ran like a beast..rpms started fluctuating 100-200 a few months ago..and then tranny started "not shifting into 4th until engine warm up to apx 190 degrees.. installed new pmd and extension cable in bumper, changed coolant sensor, switch, and iat snesor.

 

[buddy]

Are you absolutely sure its not shifting into 4th, or its just not locking the torque converter? A lot of people mistake the two. When the torque converter locks its like upshifting and RPMs will drop like 300rpm. This will not happen until the transmission is warm.

 

[JiFaire]

You need to clear your codes with a scantool. Then see which (if any) come back. The PCM misreading engine and IAT temps will mess with things...

I notice you have no dash lights (glow-plug light, WTS light, etc). Are your glow-plugs all working? Is it a hard-starter?

P0113 IAT Sensor Circuit High Voltage
P0118 ECT Sensor Circuit High Voltage
P0226 APP Sensor 3 Circuit Performance

Have you cleaned all of your Grounds (especially the engine-body straps)?

As for the shifting, try shifting manually, just to see that you get... You should have 4th gear regardless of temperature, but the Torque-converter definitely won't lock until temperature is reached.

 

[gmc junky]

yeah its shifting, its a good rpm change when it does... like it use to do,, i plan to clear codes next few days,, and its a good starter..really quick now that i have cleaned all connections including the batteries..i kina think the boost is messing with it,, the pmd maybe..

 

[gmc junky]

ok,, cleared the codes twice and same ones still coming back.. i've changed both coolant sensor and switch and iat sensor..????

P0113 IAT Sensor Circuit High Voltage
P0118 ECT Sensor Circuit High Voltage
P0226 APP Sensor 3 Circuit Performance

 

[buddy]

The sensors are probably not the problem. You need to make sure the wires going to them are in tact. unplug them and check that the voltage on the harnesses with the key on. Pin B of both should be ground they share one ground. So checking voltage across the pins with ign on should have around 5V. the voltage should be on pin A, so if you dont get 5V across the harness pins check pin A to battery/engine ground.

 

[ak diesel driver]

you need to get a scanner that will let you read the sensors so you know what the pcm is seeing. ie Carcode

 

[gmc junky]

Ok,, finally broke down and bought a nice scan tool...on drive mode noticed coolant temp and iat temp were not reading...turns out the problem was loose connections at the coolant sensor and plug in front and on top of engine,, and the iat sensor and plug on top of upper intake...messed with plugs,, now truck runs great...and shifts great just like it use to...thanks for all the suggestions and help..hope this post can help someone ...sometimes its the simple things...p.s....pmd in the bumper and no problems there so far..will put it to the test in a few weeks when i make a nearly 900 mile trip pulling my camper...