Mechanics

SPEEDOMETER TROUBLE AFTER CHANGING INTAKE MANIFOLD GASKET

1999 GMC Jimmy

THE SPEEDOMETER WAS WORKING FINE UNTIL I CHANGED THE INTAKE MANIFOLD GASKET, CAP, ROTOR, PLUG, WIRES, FUEL INJECTORS, AND STATER. WHEN I START TO DRIVE THE SPEEDOMETER IMEDIATLEY JUMPS UP TO 29 MILES PER HOUR AS SOON AS I START TO STOP IT DROPS RIGHT BACK TO 0. TRIED REPLACING VSS BUT THAT HAD NO EFFECT. WOULD APPRECIATE ANY HELP THANKS GARY
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GARY KRUEGER
October 14, 2012.




Was the radio replaced or worked on? Try unplugging the radio connectors to see if the speedometer works.

KHLow2008
Oct 16, 2012.
THE RADIO WAS NOT WORKED ON I CAN CHECK CONNECTORS ANY WAY. I WAS TRACING THE WIRES FROM THE VSS UP INTO ENGINE COMPARTMENT AND I FOUND THAT THE GROUND STRAP FROM THE FIRE WALL TO THE ENGINE WAS BROKE BY THE ENGINE. COULD THIS BE MY PROMBLEM. I AM GOING TO TRY AND GET A NEW STRAP AND HOPEFULLY BY THIS WEEKEND I'LL GET A CHANCE TO INSTALL IT. THANK S GARY

Tiny
GARY KRUEGER
Oct 17, 2012.
A missing ground circuit an affect a lot of things and especially those that are sensitive.
AD

KHLow2008
Oct 17, 2012.
WELL I GOT A NEW STRAP AND INSTALLED IT BUT SPEEDOMETER STILL DOES NOT WORK. IT STILL READS ZERO UNTIL AROUND 13MPH THEN IT JUMPS UP TO READ 29MPH AT ABOUT 34MPH IT WILL JUMP FROM 29MPH TO 39 MPH AND STAY THERE UNTIL SLOW DOWN TO ABOUT 30 THEN IT DROPS BACK TO 29MPH UNTIL SLOW DOWN TO ABOUT 13 MPH THEN IT DROPS DOWN TO ZERO. I'M USING MY GPS TO KNOW HOW FAST I'M GOING
UN HOOKED RADIO SAME RESULTS

Tiny
GARY KRUEGER
Oct 19, 2012.
Either the VSS, the driven gear, wiring or meter cluster is faulty. Since you have replaced the VSS ( was it compared to the original to see if it is the correct part), checked the wiring the next thing you shoud be checking is the speedometer gauge itself.

SPEEDOMETER &/OR ODOMETER INACCURATE

1. Turn ignition off. Connect scan tool to Data Link Connector (DLC), located
under left side of dash. Raise and support vehicle. Start engine. Place shift lever
in Drive position (automatic) or third gear (manual) and allow drive wheels to
spin. Select VEHICLE SPEED parameter on scan tool. Compare vehicle speed
displayed on scan tool with expected speed at which vehicle is being driven. If
vehicle speed displayed on scan tool agrees with expected vehicle speed, go to
next step. If vehicle speed displayed on scan tool does not agree with expected
vehicle speed, go to step 4).

2. Compare vehicle speed displayed on scan tool with speed displayed on
speedometer. If vehicle speed displayed on scan tool is within 3 MPH of speed
displayed on speedometer, problem is intermittent. If vehicle speed displayed on scan tool is not within 3 MPH of speed displayed on speedometer, go to next step.

3. Replace IPC. Retest operation.

4. Turn ignition off. Disconnect IPC connector. Remove instrument cluster as
necessary for access to IPC connector. Remove IPC connector comb. Connect DVOM set to AC volts scale between ground and IPC connector terminal A4 (Dark Green wire). Start engine. Place shift lever in Drive position (automatic) or third gear (manual) and allow drive wheels to spin. If 3-5 volts AC exists, go to step 6). If 3-5 volts AC does not exist, go to next step.

5. Check for open, poor connection or short to voltage in Dark Green wire between
PCM/VCM and IPC connector terminal A4. Repair as necessary and retest system operation. If circuit checks okay, go to next step.

6. Go to SYMPTOMS (GASOLINE) in TROUBLE SHOOTING - NO CODES -
TRUCKS article in ENGINE PERFORMANCE.

KHLow2008
Oct 20, 2012.
MY COMPUTER WAS DOWN I FINALLY GOT IT BACK UP I WILL HAVE TO WAIT FOR THIS WEEK END TO CHECK WITH THE LAST INFO YOU GAVE. I DO HAVE ANOTHER QUESTION SINCE DRIVING I GOT A CODE PO171 AND PO 174 I DID A SMOKE TEST BY BLOWING SMOKE FROM A CIGAR INTO THE INTAKE THRU THE BRAKE BOOST VACUUM HOSE I DID NOT SEE ANY LEAKS. I HAD REPLACED THE OLD INJECTOR SPIDER UNIT WITH A REMANUFACTURED ONE WHICH CAME WITH A NEW FUEL REGULATOR, I ALSO REPLACED THE FUEL FILTER AND FUEL PUMP.I BELIEVE BY USING A MULTI METER WITH IT SET IN VOLTS HZ THAT THE MAF SENSOR WAS WORKING BASED ON WHEN THE ENGINE WAS REVED THE METER SHOWED AN INCREASE AND DROPPED BACK DOWN WHEN GAS WAS BACKED OFF. THE SERVICE ENGINE SOON LIGHT GOES OFF ON ITS OWN THEN WILL RETURN LATER WITH THE SAME CODES. IS THERE SOMETHING ELSE I SHOULD CHECK? THE CAR SEEMS TO DRIVE FINE EXCEPT WHEN I FIRST START IT UP AND TRY TO DRIVE THEN IT BOGS ALMOST STALLING BUT IF I WAIT AND LET IT WARM UP I CAN TAKE OF AND DRIVE. I DON'T THINK THAT THIS AND THE SPEEDOMETER ARE RELATED. ANY HELP WOULD BE GREATLY APPRECIATED THANKS FOR YOUR TIME GARY

Tiny
GARY KRUEGER
Nov 8, 2012.
If the MAF is not working, it should throw a code and the test indicates it is working but is it within range? This would need a more accurate test.

Any vacuum leakages between the MAF and throttle body would result in a lean running condition. Likewise it could be a rich running condition and the MAF is teling the computer to lean out the running conditions thus the lean code.

Check the air filter for clogging and PCV conditions.

KHLow2008
Nov 8, 2012.

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