MAP Sensor

Bought an '87 S15 Jimmy with the 2.8L v6 (approx. 174,000 miles)it has a low idle speed and a rough idle I can't get to go away. Codes said MAP sensor ,changed that, still got the code, decided to do a tune up i.e. plugs,wires,cap,rotor, still got MAP sensor code, tried to adjust TPS no change in idle speed, changed the O2 sensor and still no change. While changing plug wires I noticed the distributor was loose so I grabbed my timing light and set the timing the best I could, now when I run the codes I get a TPS code , a MAP sensor code , And An O2 sensor rich code. Could this be a vacuum leak , EGR , or timing problem? or maybe all three?

It sounds like an egr problem. try taking it off and cleaning the carbon deposits out of it. Take air filter grabv a spray bottle of water and shot in the intake through the throtle body slowly take your time this will clean any carbon deposits out of the engine do this before you take your egr off. Trust me on this it my sound shady but trust me it will work just take your time. Also when your engine is running look down at your 2 injector spray patters.

Bought an '87 S15 Jimmy with the 2.8L v6 (approx. 174,000 miles)it has a low idle speed and a rough idle I can't get to go away. Codes said MAP sensor ,changed that, still got the code, decided to do a tune up i.e. plugs,wires,cap,rotor, still got MAP sensor code, tried to adjust TPS no change in idle speed, changed the O2 sensor and still no change. While changing plug wires I noticed the distributor was loose so I grabbed my timing light and set the timing the best I could, now when I run the codes I get a TPS code , a MAP sensor code , And An O2 sensor rich code. Could this be a vacuum leak , EGR , or timing problem? or maybe all three?

Did you set the timing with the timing wire unhooked from the PCM?

Your pcm will retaurd and advance your timing all you need to do is put it in and lock it down right where it was before or just keep it in the center. You do not adjust timing on this vechicle

Your pcm will retaurd and advance your timing all you need to do is put it in and lock it down right where it was before or just keep it in the center. You do not adjust timing on this vechicle

Please know what your talking about before you post answers like that.

You are wrong, he just can't throw it in there and have the computer auto adjust it!

He does have to set his base timing on that truck. All trucks that are OBDI have base timing that needs to be set properly with the timing wire unattached from the PCM.

I did not unhook timimg wire- I think I'll let a pro set the timing and then start from there. thanx for all the help

Your more than half way there setting the timing....just disconnect the timing wire, LT gave you the picture, its the only thing there to unplug. Unplug it and start it, the Service Engine light will come don't worry, adjust your timing to the degrees specified on the VECI label under the hood, I think its 0 degrees if im not mistaken. Reconnect the timing wire, reset the computer by unplugging the fueses or the easiest unplugging the battery and your done. As for the MAP, make sure it is getting vaccuum from the manifold and that the vaccuum l;ine is not plugged. Get a vaccuum tester and make sure it is a good source of vaccuum. If it isn't it will not be sensing anything for the computer, setting the code.

Thanx for the pic and all the help. I'll give it another go.

if you are getting good vaccuum (14 in hg with accumulator unplugged) check signal voltage there should be 3 wires ground, 5v ref, and signal, should be 4.5v with ign off and wot and about .5v at idle volts should rise as vaccuum falls (as you give it throttle)

The sticker under the hood was unreadable but a website told me what the timing is (10 degs.) I reset timing(this time with timing wire unhooked) Still no change but I unhooked vac line to EGR and now it idles smooth . As soon as I can I'll replace the EGR and it's gasket. this may be a dumb question but the manual I have doesn't tell me . Anyone know what the idle speed should be ?

The timing should be set to ZERO with the timing wire off.