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GMC Jimmy Car Repair Questions and Answers

Question: 2001 GMC JIMMY SLT mileage: 42,000. My Jimmy has automatic climate control. AC works great, but the heater only heats when the setting is 82 degrees, if I lower it to let's say 76 - 78 it's cold air. The Dealer can't find anything, but I know this not a unique problem. Any ideas? Thanks, Joe

Answer: The temperature sensor for the climate control or the control module itself may be faulty.

Question: 1998 S15 GMC Jimmy mileage: 92,000. The car wouldn't start the other night and it had to be towed home. Replaced the fuel pump twice and still no start. The fuel pressure would only go up to 30 and wouldn't hold. Replaced the fuel injection spider (very costly) but no luck. My husband finally replaced the fuel sending unit and it started, but only after he put some fuel in the intake (valve?). The car ran fine for a couple of days but today it would not start unless my son put some fuel in the intake again. That is the only way it will start. What can be the problem? We have a friend who is a GMC mechanic and he is stumped . . . then again, he told us to replace the fuel injection spider.

Answer: Since you did not mention it, we are assuming you did not have the computer scanned. If you haven't done so, do it now. It will tell you what is malfunctioning and causing the engine not to start.

Question: 1992 GMC Jimmy. I've read that the GMC Jimmy's are sort of prone to getting carbon build-up in the intake manifold. Is there any kind of carbon cleaner or cleaners that you could recommend that I could use to spray into the throttle body to clean it out, without harming the other components? I'm kind of new to having a fuel-injected truck. I've always had a carburetor in my cars. When I wanted to clean out the crud, I would just spray carburetor cleaner down the carburetor and that would take care of all the build up. But, with an injected vehicle, I feel a little lost. The problem that I've been having is that I keep getting carbon pieces flaking off and getting trapped in the EGR valve.

Answer: The intake manifold should be removed to properly clean the carbon buildup from the inside of the manifold. On engines with high mileage that are starting to use oil, the oil causes a carbon buildup to occur at an accelerated rate.

Question: 1995 GMC Jimmy  mileage: 101,000. The transmission in the "jimmy" seems to be operating correctly but each week when the fluid is checked a pint or so of fluid must be added. There is no evidence of a leak at the transmission pan or anywhere else on the case. The transfer case is also dry. If we park the vehicle on clean paper to detect a leak, there are no drops of oil present even after a long weekend. The engine seems to be running clean with no signs of fouling or blue-black smoke. Where can the transmission fluid be going?

Answer: Obviously you have a leak somewhere in your transmission. If the outside of the transmission is completely dry, the only other place it can leak is into the transfer case. If this is the case, the seal in between the two has failed. On older transmissions, the vacuum modulator diaphragm would fail allowing the transmission fluid to be drawn into the engine.

Question: 1996 GMC Jimmy mileage: 84,000. I have recently had problems with starting my 1996 GMC Jimmy. When I turn the ignition key sometimes it will turn over with no trouble and others will make a loud grinding noise and will sometimes hesitate to start. If I give it a little gas, it will help but the grinding noise continues. It sounds like when you leave the key turned for to long and the starter is still trying to start the engine but it is happening before the engine is even running. Once it is started there are no problems at all-knock on wood! This problem just started two days ago and would like to get it resolved before I get stuck somewhere.

Answer: Your problems may be caused by a faulty ignition switch or starter solenoid.

Question: 1996 GMC Jimmy 4 WD mileage: 70,000. In the overflow tank for the radiator I discovered that the antifreeze appeared black in color. It had the consistency of a black mud. This cooling system has been flushed three times by the car dealer, first telling me that I should not drive it and now they say that it's OK to drive. They changed the overflow tank for the radiator also. They also tell me that they checked for a head gasket leak or any other kind of oil leak but found nothing. I don't think they have a clue, would you have any idea on the problem or where to start to look?

Answer: If your truck is equipped with an engine oil cooler, it may be leaking internally into the radiator. Also, check the transmission fluid cooler as it may also be leaking.

Question: 1995 GMC Jimmy mileage: 95,000. I have recently been having trouble starting my truck. It is cranking but won't start. Eventually it will start, but when it does it usually backfires a couple of times and then settles down. After it is started, it runs great. I took it in to the shop and they ran some diagnostics. They said it had a lazy throttle so they replaced the TPS (Throttle Position Sensor). It didn't help. They also replaced the spark plugs. Since it runs great after it is started, I am wondering if it would have something to do with the choke. I'm not even sure how the choke works on a fuel injected vehicle, but I'm guessing there is something that functions like a choke. The shop mentioned something about a CPI unit. What is that? Thanks

Answer: Try replacing the fuel pump and the fuel filter.

Question:  1991 GMC mileage: 147,000.  I’ve been having problems with my 1991 GMC Jimmy lately.  First, I had a check engine soon light come on.  So, I had it put on a computer and found that the oxygen sensor needed to be replaced.  A few months after that the check engine soon light again came on and it also started to use an excessive amount of gasoline.  It also would run very rough at times and sometimes the whole vehicle would seem to shiver and shake.   I had someone put the check it out and he couldn't find anything.  No codes came up so we put new plugs and plug wires.  Well the check engine light continued to come and go off intermittently.  We thought maybe the catalytic converter might be plugged so we replaced and it still used gas excessively.  Last night our son was borrowing the jimmy and he said it started running very rough and then stalled and would not start back up.  Today we cleaned the egr valve and the pcv valve and still the vehicle will not start.  Any suggestions would be greatly appreciated.  We have run out of ideas.  Thank you.

Answer:  You might want to do a fuel pump pressure check and check the fuel pressure regulator.  The “check engine” light will “light” when there is a malfunction in the engine management system.  The fault code is then stored in the computer.  The computer must be scanned to retrieve these stored faults to pinpoint the malfunctioning component.   If you are sure there are no codes stored in the computer, it is possible that you have a faulty computer.

Question:  1995 GMC Jimmy 4WD  mileage: 126,000.  My truck has been experiencing many problem caused by carbon deposits in the EGR Valve.  We have replaced the valve and cleaned out the valve many times, including, most recently, three days ago.   However, the truck stalled again and when we checked the EGR valve, more carbon deposits had built up and had to be removed.  I understand that the GM Vortec engine has a history of carbon build up problems.  Is there anywhere else we should check for carbon buildup that's already in the system, or anything we can do to prevent the carbon buildup from occurring so frequently?  Thank you.

Answer:  The carbon buildup in the EGR passages is probably the result of excessive oil coming down the valve stems.  We've found similar problems with other cars usually at 60,000 or more miles.  Replacing valve stem seals reduces oil use.  The stems are made out of rubber and over time become hard and brittle and will no longer seal.

Question:  1995 GMC jimmy  mileage: 125,000.  Has been in the shop numerous times and they can't seem to find the problem.... service light goes on and when you start it up in the morning you can smell the fuel and it sounds like it wants to die out.  Also, when you are driving it, it seems like you do not go, like no gas.  And it spurts.  It’s been on the computer numerous times and it shows nothing wrong.

Answer:  Your stalling problem may be caused by the fuel pump.  Replacing it and the fuel filter should fix your problem.

Question:  1992 GMC Jimmy mileage: 94,000.  My digital dashboard is out.  For the last year, it would go off and on every few months.  Now it is off it seems for good how do I check for loose connection or replacement?

Answer:  From what you describe, your dash gauge cluster has failed and must be replaced.

Question:  1994 GMC Jimmy S-15 mileage: 100,000.  Can you tell me the firing order on a GMC V-6 and how the cylinders are numbered?

Answer: Firing order is 123456.  Number one cylinder is right front, number three middle right, number five last on right.  Number two left front etc.

Question:  1995 GMC Jimmy SLS mileage: 74,000.  I'm looking into a purchase of this 95 Jimmy from a private owner. One odd thing is that the electronic clock always stays lit.  The owner saws this has always been like that.  Is that true?   All my other GM vehicles the clock shuts off when the ignition is turned off.  If I buy the vehicle as is, should I plan on a visit to my local GMC dealer for a costly repair?

Answer: The light in the clock should go off with the key.  If the car is not driven for several days, the battery may go dead.

Question:  1988 GMC Jimmy mileage: 112,000. What would cause a new flywheel to break after only 4 weeks?

Answer: A flaw or hidden crack in the flywheel could have caused the failure. Check the transmission/bell housing for misalignment.

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