Original MAP doesn't hold vacuum

Tiny
ALEJO75
  • MEMBER
  • 1999 SATURN SL2
  • 140,000 MILES
Replaced with new. Both original & new MAP no volt decrease when testing for voltage drop w/ DVOM and handheld vacuum pump.

After seeing a detailed video and testing my MAP sensor on my '99 SL2 DOHC Vin#7. I saw no voltage drop when applying a vacuum on the MAP sensor both new and old. Voltage stayed steady at 5V. I tested the connector without the MAP connected and tested each metal probe to ground and got the proper readings. I was told to check the wiring back to the PCM. Where is the PCM and or how else can I check/diagnose and fix this issue?

Thanx in advance for your help.
Do you
have the same problem?
Yes
No
Tuesday, May 28th, 2013 AT 8:23 PM

20 Replies

Tiny
SATURNTECH9
  • EXPERT
On the scan tool what does the map sensor read at idle?Also any codes?
Was this
answer
helpful?
Yes
No
Tuesday, May 28th, 2013 AT 8:44 PM
Tiny
ALEJO75
  • MEMBER
I was hoping you'd see the video first.

I tested with a regular $20 digital volt/ohm multi meter with KOEO. (Key in RUN position engine off). No scan tool used.

The MAP sensor was removed from the intake manifold to test it. Engine running would have zero effect since no vacuum would be applied to the MAP from the intake manifold.

I back probed the MAP sensor connector and used a handheld vacuum pump and the multi meter to check just for curiosity. But there's no change in voltage. 5V steady reading.

Before any use of the DVOM, I checked the original MAP with the vacuum pump and saw that it wasn't holding a vacuum. I bought a new MAP and tested vacuum. The new MAP held 29in of vacuum no sweat.

I then tested that new MAP off the engine with the pump for voltage drop by back probing the connector to it with the DVOM and saw no voltage change.

OBDII scanner. No codes. Car runs great! Unfortunately I get about 22 city MPG and since I only drive at or slightly higher than the minimum legal speed limit on the freeways, I get 48 MPG.

Believe it or not, this Saturn is in mint condition. I've kept it perfect since it had 3 miles on it.

I'm at a loss. :-(

Any help would be greatly appreciated.
Was this
answer
helpful?
Yes
No
Tuesday, May 28th, 2013 AT 9:09 PM
Tiny
SATURNTECH9
  • EXPERT
I need the voltage readings that the scan tool is seeing?From that we can see which way were going to diagnose it. If there s no codes and it runs good I really want to see what the scan tool is seeing.
Was this
answer
helpful?
Yes
No
Tuesday, May 28th, 2013 AT 9:16 PM
Tiny
ALEJO75
  • MEMBER
I'll have to check tomorrow. I can check with engine running and off. I'm sure voltage will remain same and steady.

I remember seeing 19V from one of the connector probes to intake manifold as ground. But 19V is ridiculously impossible, right?

But just before I knock out for tonight, if all other readings are proper by testing with engine ON and engine OFF, other than the improper steady 5V reading under different vacuum testing of 5in, 10in, 15in, and 20in, would you recommend checking the wiring back to the PCM and if so, how would I do that and where is the PCM located?

Thanx in advance. I'll try the engine running tomorrow.
Was this
answer
helpful?
Yes
No
Tuesday, May 28th, 2013 AT 9:30 PM
Tiny
SATURNTECH9
  • EXPERT
Yeah I have never seen a Saturn run 19v the computer is on the drivers side under the dash top.I would ohms test the wires from the map sensor connector to the computer connector. You should see 2 ohms or less.
Was this
answer
helpful?
Yes
No
Tuesday, May 28th, 2013 AT 9:42 PM
Tiny
ALEJO75
  • MEMBER
Sorry for the delay.

I got 4.75v at zero vac. 3.88v at 5" vac. 2.97v at 10". 2.04v at 15". 1.20v at 20". 0.30v at 25".

Readings are with key in RUN engine OFF.

Now when I had the engine at idle, I got between 1.30v and 1.40v.

Voltage would decrease by about 0.25v for every 500 RPM increase after 1,000 up to 3,000 RPM.

But, when I rapidly press the accelerator to WOT for 1 second and release, the voltage would hit 4.00v and drop to about 1.20v to 1.30v at idle.

Engine was at normal operating temp.
Was this
answer
helpful?
Yes
No
Thursday, June 6th, 2013 AT 7:28 PM
Tiny
ALEJO75
  • MEMBER
I never disconnected the battery to reset the computer before I started my quest to figure this out.

After all my tests, I disconnected the + battery cable from the battery post, turned ON the headlight switch and also turned the ignition key to START to eliminate any residual electricity.

I did not perform any tests after the battery disconnect prep.

Should I have tried any tests with the battery cable disconnect prep?
Was this
answer
helpful?
Yes
No
Thursday, June 6th, 2013 AT 7:33 PM
Tiny
ALEJO75
  • MEMBER
I didn't check the wiring from the MAP connector to the PCM since I saw that there was voltage change when performing my tests.

I did drive the car after my initial inquiry thru this site and I guess the computer started communicating with the MAP. So, no need to check for ohms in the wiring.
Was this
answer
helpful?
Yes
No
Thursday, June 6th, 2013 AT 7:36 PM
Tiny
SATURNTECH9
  • EXPERT
The readings sound normal with it running with the meter. We need to see what it reads on a scan tool. You can get one on amazon that will read it for 50 something dollars.
Was this
answer
helpful?
Yes
No
Thursday, June 6th, 2013 AT 9:36 PM
Tiny
ALEJO75
  • MEMBER
Thanx for your help with my MAP questions.

I do have another minor but annoying issue.

Not sure if I was suppose to create another new question. But here it is.

The trans fluid has been flushed (not forced/no machines) I should say, just drained and refilled with the appropriate Castrol Dex/Merc ATF three times since I bought it in '99 with the most recent trans fluid drain May 2013.

I also replaced the exterior canister-type trans filter and also the TTS (Trans Temp Sensor).

Never has the trans been serviced other than what just mentioned.

Anywho, my issue is that REVERSE engages after a slight 2 to 3 second delay when the engine is warm/hot.

REVERSE never fails to engage immediately when cold. And it engages normally, no slams.

When warm/hot, I shift into reverse from Park, Neutral, Drive, etc. And it doesn't do anything for a few seconds. Sometimes I have to increase RPM's to about 1,500 to get it to engage in REVERSE.

By the way, all fluids on the car, other than the gasoline, have been drain/flushed out.

The ECT sensor was replaced I believe 2 to 3 yrs ago.

No delays/slippage occurs in any other gear.

This delay began about 2 yrs ago and since then, there have been numerous times where engaging into reverse resulted in heavy/hard slams from over-revving trying to get it to engage.

I disconnected the connector located on top of the trans valve cover and tested the probes protruding from the valve cover for ohms.

Both the probes and connector show no burnt signs/wear.

As far as resistance, each showed either 6.02 or 6.04 ohms.

I haven't taken the valve body cover off to check for resistance on the actual solenoids themselves.

What would be my next step? The solenoids?

Oh, before I forget, since I've let the reverse slam numerous times, has anything loosened up? All gears sound normal when they're engaged and vehicle is in motion, car/tranny handles very well in all gears any climate. Just the reverse engage delay when car is warm.

I ask that before I decide to dive into the trans.

Thanx again in advance for your help.

:-)
Was this
answer
helpful?
Yes
No
Friday, June 7th, 2013 AT 1:04 AM
Tiny
ALEJO75
  • MEMBER
. Climate temp extremes. Referring to Chicago weather.
Was this
answer
helpful?
Yes
No
Friday, June 7th, 2013 AT 1:05 AM
Tiny
ALEJO75
  • MEMBER
P.S.

Forgot to ask if I require draining the trans fluid before removing the valve cover and/or valve body top/cover to replace a solenoid should I have to.
Was this
answer
helpful?
Yes
No
Friday, June 7th, 2013 AT 6:48 AM
Tiny
SATURNTECH9
  • EXPERT
No need to drain the transmission to remove the valve body cover or valve body itself. To diagnose the reverse delay/slam we will need a transmission pressure tester gauge set.I can give you a recommendation of the one I have its 50 something on amazon. Its most likely going to be a worn out pressure regulator bore or a loose input shaft nut.
Was this
answer
helpful?
Yes
No
Friday, June 7th, 2013 AT 11:54 AM
Tiny
ALEJO75
  • MEMBER
Cool. What's the tool that I need to search for on Amazon?
Was this
answer
helpful?
Yes
No
Friday, June 7th, 2013 AT 5:39 PM
Tiny
SATURNTECH9
  • EXPERT
The OTC 5610 is the transmission pressure tester I have. The sonnax sure cure kit is the one I use to rebuild those valve bodies. Its a complete kit new regulator sleeve pressure regulator boost valve and and dampner spring.I have one in my 1999 Saturn sl2 its a great upgrade shifts better than the car shifted new.I should know I have driven tons of them brand new. The only problem is it takes a special tool kit made by sonnax to bore the upper valve pressure regulator to put in the sleeve. The tool kit isn't cheap to just do your valve body it isn't worth buying the kit.
Was this
answer
helpful?
Yes
No
Friday, June 7th, 2013 AT 8:43 PM
Tiny
ALEJO75
  • MEMBER
I have an exhaust question. What is the factory exhaust piping diameter?

I thought it was 2.25" but I was told it was under 2". My question is, how big can I go? No mods to the engine. Everything is stock. I'm not upgrading the exhaust for better sound/performance. I'm thinking that by putting a 2.25" or 2.5" piping I'll reduce exhaust back pressure restriction and increase fuel efficiency. I wanna squeeze as many MPG's as possible.

I'll be using the factory stock exhaust manifold and right after the O2 sensor right at the flex pipe I'll be using 18 gauge 304 grade stainless steel piping all thru out.

So, how what's the max diameter piping can I go with for the purpose of increasing fuel economy?

I don't race or anything like that, just normal day-to-day driving. The engine never sees over 2,500 RMP's.
Was this
answer
helpful?
Yes
No
Monday, June 10th, 2013 AT 6:00 PM
Tiny
SATURNTECH9
  • EXPERT
Inside diameter is 1.75" I wouldn't go any bigger then 2.25" you don't need that much flow for that engine.
Was this
answer
helpful?
Yes
No
Monday, June 10th, 2013 AT 6:18 PM
Tiny
ALEJO75
  • MEMBER
Thanx. :-)
Was this
answer
helpful?
Yes
No
Monday, June 10th, 2013 AT 6:23 PM
Tiny
SATURNTECH9
  • EXPERT
Your welcome anytime.
Was this
answer
helpful?
Yes
No
Monday, June 10th, 2013 AT 6:30 PM
Tiny
ALEJO75
  • MEMBER
Getting the exhaust installed tomorrow morning.

I bought the CAT, resonator/muffler and an 8.5' stainless steel 2" O.D. Pipe.

I only need to buy the flex pipe but I'm not sure what the specs/dimensions are.
What should I buy if going with the same size factory piece?

Length, O.D. Inlet/outlet, inside diameter center and the flange/gasket size?
Was this
answer
helpful?
Yes
No
Wednesday, June 12th, 2013 AT 4:10 PM

Please login or register to post a reply.

Recommended Guides