Skip the auto shop - Our mechanics make house calls

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?

A: Hi there, thanks for writing in about your ...

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?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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: Faulty gas gauge or sending unit?

This is a problem likely related to your fuel tank sending unit. This is a small float type component inside your fuel tank that measures the level of the fuel inside the tank. As the fuel level drops, the float...

Q: Engine unable to run as it should

This is most likely from the fuel filter is clogged or the fuel pump needs to be replaced. The fuel pump may loose pressure from a clogged fuel filter which causes the pump to not build up enough pressure to...

Q: How do I tune the radio station?

Tuning to the desired radio station is very easy. Simply press the Tune buttons to adjust the station to your liking.

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...