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Matt, Engineer
Category: Jeep
Satisfied Customers: 21995
Experience:  Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.
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I'm a bit stumped as after forking out over £400 at two

Customer Question

Hi... I'm a bit stumped as after forking out over £400 at two garages they still don't know what's going on! My Jeep revs really high before changing gears and I keep getting the error codes P0702, P0700 and P0836
JA: Are you hoping to fix this yourself?
Customer: No but need to get a quote and 3 garages can't agree what might've the problen
JA: OK! The Jeep Mechanic will help you with the diagnostics so you are sure to get this fixed right. Is there anything else the Jeep Mechanic should be aware of about your Jeep?
Customer: I've already had them change the transmission fluid and also clean out filter etc (which apparently was clean inside)...
JA: Our top Jeep Mechanic is ready to take your case. Just pay the $5 fully refundable deposit and I'll fill the Jeep Mechanic in on everything we've discussed. You can go back and forth with the Jeep Mechanic until you're 100% satisfied. We guarantee it.
Submitted: 1 year ago.
Category: Jeep
Expert:  Matt replied 1 year ago.


to have those codes I'd say its very likely that the issue is with the control board of the shifter mechanisim

these do fail to the extent that an aftermarket option has sprung up at greatly reduced cost of the replacement part

see here

Customer: replied 1 year ago.
Hi Matt. Yeah I've been reading about that!However Jeep garage making out its an internal (mechanical problem) not electric. From researching error codes myself I wondered if that part but further reading the drivers having that problem don't have sticking/over revving before changing gears like mine?
Customer: replied 1 year ago.
In fact following your link I've already looked at that exact page :)
Expert:  Matt replied 1 year ago.


Its possible that its not a single fault?

as the shift error codes are very likely to be the circuit board

but its possible the over-revving is an engine issue?

as this could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.

the airflow sensor is the main load input into the ECU and so used to judge gearshifts.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattenedpiece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

Expert:  Matt replied 1 year ago.


do you still need help?

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