Very hard start and running extremely rich.

Well I had a post about hard starts and high idles. I had a guy from a local 4x4 club come over and do some tests and so forth. He found my MAP was a goner due to reading 3-5 (I dont know if that is volts or not) but i should be around 15-19 he said. Well I picked one up and now my start is even WORSE!! Every time I start I need to floor it to start it and its running really rich, worse than a cold winter warm up. I dont know where else to look, he is coming back tomorrow to see if it is somehow installed wrong (dont see how that is possible). I checked and cleaned all my spark plugs but still nada. Its irritating me now

What year, might want to disconnect the battery for 30 min or so to reset the ECU's memory if it's an OBDII. Also get him back over to check it, it's not unheard of to get a bad one out of the box. We just had 2 bad external slaves out of the box, OEM too...

Sorry, I have a 1996. Its a midyear deal so every sensor is a 97+. After work today he is going to come back over to check this MAP and if it is bad head back to autozone. We didnt do any other checks on it, he did the MAP and the computer told him that it saw it but was very low or something similar and when you start it it made no difference.

He said that if my jeep backfired a few times real hard the pressure could have blown some little diaphragm inside the MAP.

check your vaccum lines. maybe the one going to your map sensor has a crack in it

Check the coolant temp sensor, the one for the computer (I think that's the one in the thermostat housing). What does that read?

If that's shot and it thinks the engine is always very cold, it could cause it to run really rich, start hard (especially when the engine isn't cold), and dump fuel resulting in really bad gas mileage.

Sounds like what my 96 was doing when the IAC was sticking. It didn't throw any codes by the key methode, but started hard, ran like the MAP was bad and would occasionally stall. I had to use the gas pedal and kind of coax it to life. Sometimes after it was warm, it would run just fine.
I took the IAC out of the TB once and cleaned the piston, the seat/well it sits in. Now when it begins to act up, I spray a liitle PB Blaster, down the IAC intake with the motor running, loosens it right back up again. I let the PB blaster kind of dribble in the opening, don't use too much. When I think of it (any time I have the air box off), I dribble a little blaster down the IAC intake opening, as a preventitive measure, to wash away/loosen the buildup before it becomes a problem.

I also believe it could be the coolant temp sensor fror the computer. Anony91xj was right on with his description. I had the same problem on my other car, an Aerostar with the same symptoms. Running real rich,black smoke at the tail pipe and poor milage. When I finally checked the resistance of the temp sensor it was either completely open or closed, I don't remember which, but the new one had a readable resistance value. Popped that in and it kicked over on the first crank, no more smoke and milage went way up. Good luck with this.

Steelghost said:

check your vaccum lines. maybe the one going to your map sensor has a crack in it

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I believe his 96 has the MAP sensor on the throttle body. No vac line going to it. Right?

Kyung

scca28 said:

I also believe it could be the coolant temp sensor fror the computer. Anony91xj was right on with his description. I had the same problem on my other car, an Aerostar with the same symptoms. Running real rich,black smoke at the tail pipe and poor milage. When I finally checked the resistance of the temp sensor it was either completely open or closed, I don't remember which, but the new one had a readable resistance value. Popped that in and it kicked over on the first crank, no more smoke and milage went way up. Good luck with this.

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Possible, sometimes they are not bad enough to trip the "Check Engine Light" but bad enough to cause problems. If my list is correct, either the MAP, the TPS (timing) or the engine temp. sensor should trip a constant "check engine light" if they are out of parameters.
I'd be tempted to look at something physical instead of a sensor. Stored computer codes, even intermittant codes (IMO) aren't to be relied on, but are an indicator, not difintive often enough..
Grounds and dirty connectors will mess with your sensor values, maybe not enough to trip a code, but wrong none the less.
The IAC is active mostly at throttle closed, but does keep right on doing fine air adjustments no matter what position the throttle plate is in.
Really poor ignition, will cause a fuel build up, that can make a motor run crappy. Anything from weak spark to bad fuel.
High (low) fuel pressure or a partially plugged return line (or in line/filter sock).
Things that would likely not throw a code, but cause the symtoms, are something to look at.
The IAC is fairly easy to service and probably needs it anyway, even if it's not the problem. Grounds need to be periodically checked anyway, connector cleaning is another (regular) service item after a certain age.
I know what my persent problem is, a plugged Cat. soon to be changed. My gas mileage has really gone south and the motor vacuum is way low at higher RPM's.