is anyone aware of a map sensor test of any sorts? im having some problems with my 86 3.2(2.8) 5 speed izuzu. the car goes through good and bad times. which i why im leaning towards a sensor or electric part of some sort. sometimes when it starts, it takes a while to find its idle, and it rises slowly from 1000 rpm to 2000 or more. sometimes it idles perfect.

the more annoying part... most of the time when it is first started after a little sitting, driving the first mile or so is terrible. the gas pedal almost acts inversely, being if i step on it too quick or too hard, the motor bogs down and sputters, and i need to let off the gas and try again. really not fun when your late for work and in traffic. but it seems like after warming up some, it goes away. sometimes comes back, but not always.

also been having a situation where sometimes pulling up to a light or stop sign, clutch in, in nuetral, the as i slow down, my rpms drop, down to the almost stalling range, and then sputter and pop back up to either normal or running high for a little bit.

another feature, the car seems to sputter or buck with the gas pedal under light crusing conditions. under acceleration or a good take off, itll be fine. but cruising at oh say 40, in 4th, trying to hold steady, the car will sometimes act like it doesnt know if im on or off the gas pedal, and hiccup and buck and miss. but then if i stomp down on it, itll take off, but then trying to go back to holding a steady speed, it cant do it smoothly. really starting to get a little annoyed with this car. always seems like something is going wrong.

so any help would be greatly apprciated. thanks

a faulty map sensor would probably throw a code and your check engine light would come on

first thing I would do is check the fuel pressure and fuel filter, if all check out then I would consider changing the ignition module ..I have had similar symptoms with both systems on a 2.8 ..a bad coil could cause problems like that as well..even a clogged cat or vacuum leaks could cause some of the symtoms

[This message has been edited by Erik (edited 07-31-2006).]

fuel pressure is at 37-38 last time i checked. filter was good as well, recently replaced. it does have a newer msd coil in there. ive tried switching back and forth from the old ignition module to the new one with no definitive answer.

side question: i know people have mentioned using some computer thermal grease for the module. is this the $1.99 tube of stuff at radio shack?>

quote Originally posted by sublime922: fuel pressure is at 37-38 last time i checked. filter was good as well, recently replaced. it does have a newer msd coil in there. ive tried switching back and forth from the old ignition module to the new one with no definitive answer. side question: i know people have mentioned using some computer thermal grease for the module. is this the $1.99 tube of stuff at radio shack?>

Yes ..it is ..not sure if its a 1.99 though but it is the correct stuff to use..not the dielectric grease some autoparts places try to sell you

well, you want a quick and dirty test, unplug the map sensor and drive the car. you will definately pop a code, but if it acts similar, it could be the map.....

But it can also be the module itself, the TPS, and even the O2 sensor.... I just had a cold run issue I thought was the map, but it was in fact the new o2 sensor.

ah the terrible game of automotive electronics... ive basically replaced almost every electrical part on this thing in the last 2 years, but theres still no way of knowing if the new part is working any better or if they gave you a bad part..

ill be builing an ALDL cable tomorrow, been wanting it for a while, and it couldnt hurt now to help diagnose this.

quote Originally posted by sublime922: ah the terrible game of automotive electronics... ive basically replaced almost every electrical part on this thing in the last 2 years, but theres still no way of knowing if the new part is working any better or if they gave you a bad part.. ill be builing an ALDL cable tomorrow, been wanting it for a while, and it couldnt hurt now to help diagnose this.

Of course there are logical test procedures using a multimeter to detirmine wether an electrical part is good or bad ..its all a matter of wether you want to go through the steps ..an ALDL read can be very helpful and keeps ya from having to bend over so much ..usually

ah my favorite multimeter. thats basically what i was looking for in the first question about the map sensor. if there was any set procedure or known voltage values it should output to see if its working correcty. ive been going through and testing things here and there, but nothing had jumped out as being wrong yet. i know my o2 sensor is working, cuz i have an air/fuel gauge hooked up to it. i know, it means nothing, just a flashy light show. but i thought it was cool 2 years ago. so that aleast shows the sensor is reacting and working.. i think

Backprobe with a high impedance voltmeter at MAP sensor terminals A and C.
With the key ON and engine off, the voltmeter reading should be approximately 5.0 volts.
If the voltage is not as specified, either the wiring to the MAP sensor or the ECM may be faulty. Correct any wiring or ECM faults before continuing test.
Backprobe with the high impedance voltmeter at MAP sensor terminals B and A.
Verify that the sensor voltage is approximately 0.5 volts with the engine not running (at sea level).
Record MAP sensor voltage with the key ON and engine off.
Start the vehicle.
Verify that the sensor voltage is greater than 1.5 volts (above the recorded reading) at idle.
Verify that the sensor voltage increases to approximately 4.5. volts (above the recorded reading) at Wide Open Throttle (WOT).
If the sensor voltage is as specified, the sensor is functioning properly.
If the sensor voltage is not as specified, check the sensor and the sensor vacuum source for a leak or a restriction. If no leaks or restrictions are found, the sensor may be defective and should be replaced.

This is for a 92 Lumina 3.4 DOHC which is the same map as a Fiero

Definatley build or buy the aldl cable, sounds like the CTS --when cold, could be playing tricks with the ecm, also the mat sensor comes into play for air/fuel mix, if you haven`t done so yet, check the 02 sensor & wire connector. Try a leak down test on your fuel .
http://winaldl.joby.se/
http://aldlcable.com/

MAP sensors tend not to malfunction. They either work or go completley bad. In the event of failure a code will set. Your problem is most likely related to igniton or fueling.

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87GT 3.4 Turbo- 0-60 5.2 seconds -Best
Engine Controls, ECM goodies, Chip
re-programming & odd electronics stuff

Just out of curiosity, what engine mods have you done to your 3.2?

At one time my car acted the same way. What I did was unplug the map sensor....it seemed to smooth out. I started following the vaccum line for the map sensor and found a crack in the plastic line right under the plenum. There was a small clip that holds three lines together. It looked like one piece but it wasn't , it was cracked in half. Repaired that and it runs like new.

MAP tends to work or not. Official test is as follows...

Manifold Absolute Pressure Sensors: Messure voltage with ignition on and engine off. Start engine and apply 10 in./250 mm Hg to unit,
voltage should be 1.2-2.3 volts less.

This test can often set a code.

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