I just had a shop do some work on my car ('90 L98 Auto) and my SES light came on while driving - Brought it home and hooked up the ol' AutoXray to see what the code was... It was a code 33 - "MAP sensor too high" - What is this? And what is the fix?

Also, while I had the AutoXray connected I decided to look at the TPS voltage (the car idled a little too high IMO) What I found was .62v - I think this is ok.. is it?

The thing that really bothered me was the throttle blade shows to only open to 78% at WOT..... now that bothers me.

Would there be a reason it was set to this?

Another question is - Does the "Throttle Performance Switch" make any differance? According to what I have read about them, it makes the computer think the TPS is at 4.6v (WOT) when it's at 60%+ blade position.. delivering maximum fuel and timing for better performance.

 

ttt

 

hey coop, the specs call for .5 - .6 voltage at the tps. i try to set mine right at .6 and never had any problems. i can't see where a .02 over is going to cause a problem. never had a problem in this area.

 

The voltage really didn't concern me as much as the throttle blade angle - 78% seems a litlle low at WOT - what do you think?

 

For the most part, the TPS voltage doesn't affect the idle. The idle speed is burned int o the chip. I have been corrected when I have stated this before, and according to those that contradicted, a major voltage change will affect the idle, but not anything near the spec. Is the TPS adjustable on the '90? I keep losing track of exactly what changed, in which years. Same with the MAP. Does the '90 even have a MAP? High MAP voltages indicate high intake manifold pressure (low vacuum). A vacuum leak would cause low vacuum and a high idle. A disconnected MAP hose could cause both. Also make sure the TPS moves smoothly from the test reading all the way through to WOT. A bad TPS could cause the code 33.That 78% is the interpretation of the scanner. It may just mean that the voltage is 78% of the highest spec. Have someone in the car floor the throttle while you observe the throttle blades. Do they look like they're only 3/4 open? If they don't open wide enough, you may have to rearrange the carpeting under the pedal, or something similar.

RACE ON!!!

 

The '90 TPS is not adjustable. The '90 ECM has the ability to auto-zero the TPS if the (fully closed) voltage is between .36 and .96 volt. WOT should be about 4.6V. You probably already know that there are three wires on the TPS: the black is ground, the dk. blue is the TPS signal and the gray wire is the 5V reference. If you're concerned that you're not able to get WOT, determine that you can get about 4.6V at WOT. If you can, it is read as WOT.

Concerning you question re: code 33. Similar to the TPS, the MAP has three wires; Gray is the 5V reference; Lt Green is the MAP signal; Blk/Pink is the ground. Signal voltage varies from 1-1.5 v at idle to 4.0-4.8 V at WOT. You can use the auto-xray to read MAP voltage (I guess, I can do this with my Snap-on Scan Tool, anyway.) The code sets when:
* Signal voltage too high for > 1 second and
* TPS less than 2%.

A low or unstable idle can also set a code 33. You must correct any rough or unstable idle before diagnosing a MAP problem.

Test:

* Auto-xray in scan mode
* Ignition off. Disconnect MAP electrical connector.
* Ignition on. Does scan tool read a voltage of 1 V or less?
* YES: Probe sensor ground with a test light to battery voltage -- test light should light. If YES, vacuum leak, or faulty MAP. If NO open ground circuit.
* NO: MAP signal circuit (lt Green) shorted to voltage or reference circuit (gray) shorted. Or faulty ECM (unfortunately that's always there ) .

Jac