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1999 tahoe fuel gage eratic after warmup engine stumbles at

Sent to Car Experts May 31 2006 at 12:30 PM
   

1999 tahoe fuel gage eratic after warmup engine stumbles at this time.tac also jumps to 7500 rpm.

Edited by Customer (name blocked for privacy) on May 31 2006 at 1:53 PM

 

Optional Information:
1999 Chevrolet Tahoe 5.7

Already Tried:
I have a 99 Tahoe with a 5.7 engine. After driving a few minutes, the gas gauge starts moving up and down erratically. At the same time, the check engine light (P0339 ckp sensor) and ABS light (rear speed sensor) come on. The engine starts stumbling, no power, and missing. The rpm reading on the modis shows a spike to 5700 rpm, all other pids read normally. I have replaced the sending unit, the VCM, and crankshaft position sensor. I have also checked the grounds and powers for the VCM and sensors, and the battery ground to the engine body. I have disconnected the instrument panel while watching the readings on the modis with no improvement. It only seems to act up in gear when hot. I have checked all the electrical connectors to the ckp, sending unit, and VCM. Any ideas?? p.s. I have an alternate email at kennermechanic@aol.com, as my boss couldn't find the apostrophy for jr@jr'sautoparts.com/p>

Customer (name blocked for privacy)
Status:  Closed   Value: $50
Answer
May 31 2006 at 3:56 PM (3 hours and 25 minutes and 17 seconds later)
         
REPLIEDCheck Mark
first of all is the engine racing to 5700 rpm when you see it on the modis or is that a false reading.second what is the code for the abs?or is it a false light.i will start looking for answers and wait for your answers.craig

Craig
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craig swanson -- Auto Mechanic -- 100% Positive Feedback on 13 Car Accepts
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May 31 2006 at 4:06 PM (9 minutes and 57 seconds later)
         
REPLIEDCheck Mark
I want you to try and check the actual voltage during the failure on the ecm 1 fuse under the hood and the gauges fuse #4 inside the truck.It sounds like a bad ignition switch to me.They are kind of common on those and all of the things you are having problems with are powered by those two fuses.The power comes through the same buss bar in the underhood fuse box.I'll bet an ignition switch will fix it.

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1 Other Expert Agrees with this!
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Davo -- Master technician -- 99% Positive Feedback on 1964 Car Accepts
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June 1 2006 at 6:57 AM (14 hours and 51 minutes and 33 seconds later)
         
Reply to Davo/diablo666's Post: The voltage was normal-- no change on either fuse. We swapped ignition switches just in case to no effect.
Customer (name blocked for privacy)
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June 1 2006 at 7:06 AM (8 minutes and 55 seconds later)
         
Reply to craig swanson's Post: the reading is actually 7500 (mistyped earlier), and the engine is not racing...it is a spike on the modis graph (sharp up-and-down), in conjunction with engine stumble. The ABS code is rear speed sensor (C0237)... it is false, as there is no rear speed sensor on this vehicle (yes, checked on rear differential).
Customer (name blocked for privacy)
Answer
June 1 2006 at 12:44 PM (5 hours and 37 minutes and 49 seconds later)
         
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June 1 2006 at 12:44 PM (37 seconds later)
         
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June 1 2006 at 12:50 PM (5 minutes and 44 seconds later)
         
ACCEPTEDCheck Mark
Those are the VCM grounds.Make sure they are good with no corrosion or resistance back to the VCM.Check the one by the thermostat housing also.You have to have a bad ground,poor power feed to the VCM or a chaffed wire somewhere you are not seeing.If you swapped out the ignition switch you have good power to the fuses if you checked them with a meter and not a test light.

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December 6 2006 at 2:30 PM (188 days and 1 hour later)
         
Relist: I still need help.
1995 nissan maxima 3.0 engine. No power, idle ok. give gas hesitation, sthmbles, no power. i have 3 codes, cts, knock, crank sensor. check all that ok. check fuel presion ok.
Customer (name blocked for privacy)
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