Q: Speedometer jumps up/down and van backfires. 1998 GMC Savana

asked by on

The speedometer in my van jumps up and down. The radio volume drops to almost nothing when it goes to 40 and then to 100. Plus, the van started backfiring when the engine is slightly cold and I’m pulling out. I took it to a professional auto shop and they worked on the temperature gauge, but it did not make any improvement in the speedometer problem. They even replaced it and the same thing is happening. Then they installed a Cam sensor and it stopped backfiring until today. Now it is backfiring again. Hundreds of dollars in repairs and the only thing working is the temperature guage! What will fix my van’s speedometer and backfiring problems?

Hi there, thanks for writing in about your 1998 GMC Savana 2500. The speedometer and radio may work together to adjust volume of the radio as the speed increases. The cluster or any of the affected modules may have a connector issue from fretting corrosion in the connectors. I would suggest disconnecting the battery and disconnecting the connectors to the engine control module, body control module, and the instrument cluster to look for corrosion and clean and apply dielectric lube to the pins and lightly seal and reinstall to make sure connections are secure. If you need further assistance, a certified technician from YourMechanic can come to your car’s location to inspect the speedometer and let you know what should be repaired.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Speedometer jumps up/down and van backfires. 1998 GMC Savana

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Speedometer jumps car moves slow

If your speedometer needle or gauge is jumping up and down while the vehicle is moving at a slower speed, two possible issues may have occurred. Either the whole instrument cluster has failed at some point preventing the speedometer from...

Q: Q: Warning light coming on

Are and of the gauges not acting like they normally do? On your vehicle a common failure is of the oil pressure sending unit. When this happens your gauge will display zero oil pressure and cause the check gauges light...

Q: Oil pressure dropped to zero

The engine would need to be diagnosed to find the reason for it to seize up. The oil pressure dropping to zero is an indication that the oil pump may have failed, and starved the engine bearings of oil. If...

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.