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94 c1500 TBI Hesitation, Loss of Power and Running Rich

This is a discussion on 94 c1500 TBI Hesitation, Loss of Power and Running Rich within the Technical / Maintenance forums, part of the General Discussion category; Hi there, I've done some searching to see if I could find some answers to a notorious problem I've been ...

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    94 c1500 TBI Hesitation, Loss of Power and Running Rich


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    Hi there,

    I've done some searching to see if I could find some answers to a notorious problem I've been having with my truck, but with no luck. I was hoping y'all could help me out before I just give up. For about 2 months now I've been battling a bad case of Hesitation, running rich, stumble while idling, loss of power. I've had it at a shop multiple times and they seem to be stumped.

    It's not a persistent problem and its seems to vary when it decides to act up. It has progressively gotten worse however. I've had codes 13 and 45 pop after driving for awhile. It seems to stumble at an idle, just quick little drops and than idles fine. While driving it seems to be a gradual loss of power. I can keep a steady throttle and the engine will just die off and then catch or I can give it more throttle and power through it (most times). Tonight however is another story. It was running better then it has in awhile till the SES starting coming off and on. Was doing the usual power loss and hesitation with steady throttle, however, I could not power through it and was taking longer to catch to the point of stalling. If I went WOT it would down shift, but there was no power and it was just sputtering. I could barely keep it going 100km/h (canadian eh) When I got home it was doing the same RPM drop as when driving but at an idle. It was running below 500RPM and sounded like it was stock car, after awhile I could smell the overly rich exhaust, I put it in park and it revved up to 2000rpm and then slowly came down. After that I just shut her down. Also, it seemed when the SES light was on the truck ran some what normal. Only codes I've gotten were 13 and 45.

    I did a basic tune up, as well as replaced a bunch of parts that were bad or known to cause issues. So far I've replaced the following:
    Cap, rotor, wires, plugs, coil, EGR valve, TPS, MAP, CTS, o2 sensor (old one replaced was less then a year old, but wasnt reading correctly), fuel filter, throttle body gasket, PCV valve, timing checked and set at 0 degrees.

    All grounds were taken off and cleaned up to insure that could be ruled out, IAC was cleaned up, fuel pressure was also checked and ran consistently at 13psi even when it was hesitating and stumbling. One thing that wasn't right was the timing was set at 10 degrees when the shop checked it, I'm not sure who or why it was set to 10 but it was set back to 0 degrees.

    It's seriously got me stumped. Ole chev has got lots of life left in her. Please help!

  2. #2
    Registered User Mr_Shamrock's Avatar
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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    I think I would pull the throttle body and give it a good cleaning and put a rebuild kit in it. The kits come with a FPR and that just might be your culprit. I have found that even without a huge issue putting one of those kits just seems to make the motors happier and they will idle and accelerate smoother.
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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    I ordered a rebuild kit today that comes with everything and than some. Hopefully that gets my problems figured out.

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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    Did you replace the CTS that controls the gauge or the one that goes to PCM?
    1985 k-10 on 33's. Build in progress....

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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    The CTS on the top of the intake. Pretty sure that is the one for the computer. Truck is not drivable in its current state. Wondering if the actuator spring is pooched. Rebuild kit won't be in till Monday now. But if I dont need to rebuild it I don't want to open that sealed bag. Any other suggestions?

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    silverado96
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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    No I believe that is the one for the gauge. Replace the one on the drivers side head. I'm almost 100% sure that is the one that goes to PCM. The sensor is probably reading something like -40 degrees causing the engine to dump fuel into the engine. That would explain all your problems.
    1985 k-10 on 33's. Build in progress....

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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    ecm coolant temp sensor is on the intake. the one on the head is for the gauge.

    code 13 is an issue in the o2 sensor circuit. check the wiring with an ohm meter. ensure ground wire is grounded. ground should be by thermostat housing stud.
    if one wire o2 sensor purple wire ensure its not open.
    tan wire on thermostat housing stud is ecm ground for o2 sensor. ensure its not open. under 1 ohm is ideal.
    if heated add pink/black wire:
    ensure you have 12vdc ignition on engine stopped. if not check for an open and a blown fuze. unsure of which fuze it is.

    ensure egr valve is an exact oem replacement.
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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    cts test:
    here is the test for coolant temp sensor using multimeter set to ohms
    and ir temp gun.


    212f 177 ohms
    194f 241
    176f 332
    158f 467
    140f 667
    122f 973
    113f 1188 ohms
    104f 1459
    95f 1802
    86f 2238
    77f 2796
    68f 3520
    59f 4450
    50f 5670
    41f 7280
    32f 9420
    23f 12300 ohms
    14f 16180
    5f 21450
    -4f 28680
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    Both sensors tested good. Took cai off, injectors are spraying in a cone. Not sure how heavy the spray should be, let it run till it was nice and warm everything still looked good. Threw it all Back together. It's nice and warn today so I took it for a drive about a 100 km and it's been running fine. Think I'm still going to rebuild the tbi
    . So confusing

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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    Update: drove 100 km not a problem. Sat for a couple hours, drove fine for 5 mins and it started sputtering and losing power and hesitating.. Stopped again to fuel up and it drive home not a problem. Hmm..
    Last edited by jkorne; 04-22-2012 at 11:24 PM.

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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    I had a similar problem and it would run better above 1/2 tank turned out to be a pink wire that powers the ecu. I had to take my truck to an electrical shop to find out the problem.
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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    Quote Originally Posted by jkorne View Post
    Both sensors tested good. Took cai off, injectors are spraying in a cone. Not sure how heavy the spray should be, let it run till it was nice and warm everything still looked good. Threw it all Back together. It's nice and warn today so I took it for a drive about a 100 km and it's been running fine. Think I'm still going to rebuild the tbi
    . So confusing

    I am having very similar issue with my 1990 Suburban TBI which i've only owned 3 weeks. Same deal with powe loss and replaced almost all of the same sensors except CTS. No check engine light though but today was the worst..... idles fine, revs fine in park or neutral but as soon as i put it in drive and try to go it dies or lugs and serges.

    Keep me posted as to what you find works because I'm about to do the fuel pump as a start and maybe I'll do the rebuild kit for a second but rebuild kit sounds easier than a pump.

    thanks

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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    Quote Originally Posted by Burban Buddy View Post
    I am having very similar issue with my 1990 Suburban TBI which i've only owned 3 weeks. Same deal with powe loss and replaced almost all of the same sensors except CTS. No check engine light though but today was the worst..... idles fine, revs fine in park or neutral but as soon as i put it in drive and try to go it dies or lugs and serges.

    Keep me posted as to what you find works because I'm about to do the fuel pump as a start and maybe I'll do the rebuild kit for a second but rebuild kit sounds easier than a pump.

    thanks
    Mine has never actually stalled out completely. Idles fine usually, I notice a stumble here and there sometimes. Apparently mine is not a consistent problem which is even more aggravating. I'll keep y'all updated.

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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    Well.. turns out a new battery is all I needed... Guess the cold weather we had all winter finally did her in. Noticed the gauge dropping almost into the red with a little load on it (blower fan, lights), got a new one in there and she works amazing. No problems at all and ive put well over 500km on her already. Gauge never drops really far below 14V with full load.

    Its still idling wierd... still has almost what I would call a stumble, sometimes multiple times in a row. Only when cold tho. Anyone know what that could be??

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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    I have been having similar problems on a 93' GMC K1500. I have replaced the TPS and the IAC. It had new plugs, wires, cap and button. I need to replace the CTS. I am going to put a new one in it tomorrow and hope for the best. I am getting these codes: 15, 22, 35, 42 and 44. 15: Coolant sensor circuit (hopefully the CTS will fix). 22: TPS circuit 35: IAC (don't understand why it is giving me these because it has a new ones, and has had the relearn process) 42: Ignition Control Circuit (still trying to figure that out) 44: Lean exhaust (probably from the CTS malfunction). If anyone has anything to add, please do so. I am at a loss here.

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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    Well..... I did a lot of reading about the TBI system after i went on a long trip pulling a trailer. The truck ran extremely rich to the point that I could see the exhaust (9 mpg). Sometimes the truck pulled hard up hills at 1/2 throttle and other times the truck struggled to maintain hwy speeds on flat grounds at full throttle and kicking down into second gear.

    Since the symptoms were never consistent for more than a day I figured that the computer or TBI system had issues....ghost issues. To be honest I have even talked to other guys that have had similar issues and they have fixed the issue the same way I am going to do.......

    I Have purchased a 600 cfm carb, Performer intake, HEI vacuum advance distributor, and a fuel pressure regulator. I will install all the parts and leave the electrical harness alone. The fuel pressure regulator will drop my intake pump pressure down to 5 psi and the truck should run great..... All the time.

    I realize that some of you may think that this is a step backwards in technology an ideal fuel economy but in the same respect a person can spend a lot of money chasing a TBI issue (of this vintage) and still not solve the problem. I think that some of the minor issues are related to the actual wiring, others are a simple sensors, perhaps a new computer will help, but at the end of the day all we want is a good running vehicle.

    I vote for simple and reliable with minimal headaches.

    My total bill to swap over to a carb set up will be $300 for good used parts with a new regulator and carb kit.


    Good luck

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    Re: 94 c1500 TBI Hesitation, Loss of Power and Running Rich

    GM code 13
    OXYGEN SENSOR CIRCUIT OPEN
    Make sure the O2 is working before you tear into the TBI.

    Quote Originally Posted by jkorne View Post
    I ordered a rebuild kit today that comes with everything and than some. Hopefully that gets my problems figured out.
    04 K1500 Silverado EXT 3:73 gears, 5.3L 265/75-16,Pace Edwards tonneau,

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