question for the sensor gurus

[sandandsurf]

Ok, heres the lead-up

Its a 91 4.0 I6 .... its been sitting about 6 months because of a bad CPS and an owner too lazy to get under it (me).
I changed the CPS ...... ran, but really poorly, discovered a spider in the distributor. .... and a code for a bad pickup..... pulled the distributor,changed it out and now have what I thought were problems with timing.( hard start, breaks up on hard throttle, loss of power)

I thought i was a tooth off . I tried moving +/- 1 tooth, still was weird, i snapped off the tabs and tried rotating the distributor.

If I retard it I get a smooth start but breaks up badly on accel.

If I advance, barely starts and only runs marginally better.

Now my question. I'm now getting a code 13 for bad MAP sensor. Before I change it out (I hate to diagnose by dumping money) .........

Do you think the MAP is bad or would the other situation cause it to show bad on the computer. It just seems a little strange that they would all go bad in rapid succession. (I'm starting to think the local parts store has a remote control for my check engine light. They just press it on slow days to drum up business.

thanks
Tom

[87manche]

check for major vacuum leaks. That would trip a MAP sensor code, and it might explain your poor running condition.
I'd investigate and plug everything non essential, pay particular attention to the brake booster hose, it's large enough to cause a large leak. Also, check the torque on the manifolds.
It may even be a crack in the plastic line going to the MAP sensor.
It's quite possible that something even chewed through a line while it sat.

[sandandsurf]

I'll check for leaks in the morning... possible I hit something while I was working .. No booster line though ... it has the hydro-pump instead.(and thats another story)

[rickoregon]

Sitting for 6 months? Might be your gas is a little bad, now, as well. Did you put Stabil in it? Might want to drain tank and put some fresh in. Also consider replacing fuel filter. Probably not the problem, but a good idea if this hasn't been done for awhile. Old-man got me to using BG 44K and that cured a lot of my fuel-related problems on all our vehicles. You might give that a try, as well. Vacuum leaks should be found and fixed before you do much more, though. When I had problems awhile back with our '89 4.0 I ended up replacing just about every sensor before the problem was resolved (including the MAP), but they were all about due, anyway and autopartsgiant.com was a pretty reasonable source for oem parts. Good luck, Rick

[Saudade]

Here are the diagnostics for Code 13

Code 13
DRB-II displays SLOW CHANGE IN IDLE MAP SENSOR SIGNAL.
Condition is: Manifold Absolute Pressure (MAP) sensor output change
slower and/or smaller than expected.

Code 13
DRB-II displays NO CHANGE IN MAP FROM START TO RUN. Condition
is: no difference recognized between Manifold Absolute Pressure (MAP)
reading and barometric (atmospheric) pressure reading at start-up.

So check the wiring and connectors. Check the vacuum line from the manifold to the sensor and 87manche says.