Huntershope

Hello, I've been lurking for awhile and have run into a bit of a situation. I have a '92 laredo and recently it has been hard to start and then it started running really rough and has a severe loss of power. After it starts and at idle, it will idle down to 500 rpms and feels like it is missing. Then it will idle up to 2000 rpms for about 5 seconds and then slowly idle back down to 1000 rpms and then about 1 min later it repeats. If i press the throttle at idle it bogs down for a second then the rpms rise but still sounds like its missing. If I try to drive it, the rpms just bog down and then it will start to go and will only go 10 mph and stay in 1st gear at about 3200 rpms. I've checked all visible vacuum lines and checked for clogged lines. Changed fuel filter and checked dist cap and rotor, all good. I unplugged the CPS and the engine died, unplugged the IAC and no change, I unplugged the MAP and the idle stabilized to 1000 rpms and held, but if I try to drive, it's the same issue as before, no power. So, I'm guessing it's the MAP sensor, But would like your opinions and knowledge before I buy one tomorrow. Thank you in advance.

Huntershope

Bump.

Jooman07

Is it throwing any codes at all? If so, obviously start there. Throttle position sensor, crank position sensor, cam position sensor, bad o2 sensor, numerous things could cause this issue. Start small and work your way up. Don't go throwing money at it when you don't know the issue. You'll wind up broke in no time.

If none of those small things are it, check your timing chain, could be loose and skipping a tooth. sounds similar to what mine has been doing for a while and turns out to be the timing chain needed replaced. If yours has never been replaced there's a good chance that could be it.

cruiser54

MAP sensor tube

There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor, behind the valve cover, higher up on the firewall. It has one vacuum line as already mentioned, with a 3-wire plug in the bottom.

CRUCIAL!! The MAP sensor will tell the ECU to dump fuel with little to no vacuum to the MAP. Any crack or blockage and it will be pig-rich. ( black smoke, fouled black plugs, must hold your foot to the floor to keep the engine running). You can pull the line off the MAP sensor and feel for vacuum with your finger. If it runs!

A visual inspection usually reveals any issues with the line from the throttle body to the MAP sensor.